U.S. patent application number 11/416723 was filed with the patent office on 2007-01-18 for oral hygiene devices employing an acoustic waveguide.
This patent application is currently assigned to Second Act Partners, Inc.. Invention is credited to David A. Ballard, George A. Barrett, Daniel Bayeh, Frederick Jay Bennett, Gerald K. Brewer, James Christopher McInnes, Richard K. Taylor.
Application Number | 20070011836 11/416723 |
Document ID | / |
Family ID | 37308681 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070011836 |
Kind Code |
A1 |
Brewer; Gerald K. ; et
al. |
January 18, 2007 |
Oral hygiene devices employing an acoustic waveguide
Abstract
An oral hygiene device having an ultrasound transducer 22 and an
acoustic waveguide 24 facilitating the transmission of ultrasonic
acoustic energy to fluids in the oral cavity is disclosed.
Preferred ultrasound operating parameters for operation in aqueous
environments and in dental slurries are disclosed. Devices may
incorporate a drive motor 16 for oscillating a device head 23,
acoustic waveguide 24 and one or more bristle tuft(s) 26 at sonic
frequencies, and preferred sonic operating parameters are also
provided. Multi-element piezoelectric transducer assemblies 30, 40,
and various control and communications features are disclosed. Oral
hygiene devices disclosed herein achieve improved plaque and stain
removal from the teeth as well as interproximal and subgingival
regions, while enhancing the user experience, massaging the gums,
stimulating dental tissue, and disrupting biofilm.
Inventors: |
Brewer; Gerald K.; (Redmond,
WA) ; McInnes; James Christopher; (Seattle, WA)
; Bayeh; Daniel; (Seattle, WA) ; Bennett;
Frederick Jay; (Kirkland, WA) ; Taylor; Richard
K.; (Fall City, WA) ; Ballard; David A.;
(Sammamish, WA) ; Barrett; George A.; (Shoreline,
WA) |
Correspondence
Address: |
SPECKMAN LAW GROUP PLLC
1201 THIRD AVENUE, SUITE 330
SEATTLE
WA
98101
US
|
Assignee: |
Second Act Partners, Inc.
Redmond
WA
|
Family ID: |
37308681 |
Appl. No.: |
11/416723 |
Filed: |
May 3, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60677577 |
May 3, 2005 |
|
|
|
Current U.S.
Class: |
15/220.1 |
Current CPC
Class: |
A61C 17/3481 20130101;
A61C 17/20 20130101; A46B 15/0002 20130101; A46B 15/0028
20130101 |
Class at
Publication: |
015/220.1 |
International
Class: |
A47L 1/00 20060101
A47L001/00 |
Goverment Interests
REFERENCE TO GOVERNMENT SUPPORT
[0002] One or more of the inventions disclosed herein were made
with Government support under SBIR Contract No. 1-R43-DEO16761-01.
The Government may have certain rights in one or more of those
inventions.
Claims
1. An oral hygiene device that is user-activatable to initiate an
operating cycle comprising: a device head support structure having
an acoustic waveguide and at least one bristle tuft projecting from
the support structure; an ultrasound transducer acoustically
coupled to the acoustic waveguide that operates, during the
operating cycle, to produce ultrasonic energy at frequencies of
less than 1500 kHz; and a motor mechanically coupled to the support
structure that operates, during the operating cycle, to produce
oscillation at sonic frequencies of less than 1000 Hz and to
produce oscillation of the bristle tips at a velocity of less than
1.5 m/sec.
2. The device of claim 1, wherein the ultrasound transducer
comprises multiple piezoelectric elements.
3. The device of claim 1, wherein the ultrasound transducer
comprises multiple piezoelectric elements connected mechanically in
series and electrically in parallel.
4. The device of claim 1, additionally comprising an impedance
matching layer contacting the ultrasound transducer.
5. The device of claim 1 comprising a plurality of bristle tufts,
wherein at least one bristle tuft has an exposed length that is
greater than the exposed length of at least one other bristle
tuft.
6. The device of claim 1 comprising a plurality of bristle tufts,
wherein at least one bristle tuft has a stiffness that is greater
than the stiffness of at least one other bristle tuft.
7. The device of claim 1, wherein at least one bristle tuft has an
angle of orientation that is different from the angle of
orientation of at least one other bristle tuft.
8. The device of claim 1, wherein the motor operates, during an
operating cycle, to produce oscillation at the bristle tips of a
peak amplitude of less than 2.2 mm.
9. The device of claim 1, wherein the motor comprises a limited
angle torque motor.
10. An oral hygiene device that is user-activatable to commence an
operating cycle comprising: a motor mechanically coupled to a
support structure that operates, during the operating cycle, to
produce vibration at sonic frequencies of less than 2000 Hz; an
ultrasound transducer that operates, during the operating cycle, to
produce ultrasonic energy at frequencies of less than 1500 kHz; and
at least one controller that controls operation of the ultrasound
transducer and the motor during the operating cycle; wherein the
output of the ultrasound transducer and motor are variable during
an operating cycle.
11. The device of claim 10, wherein the output of the ultrasound
transducer and motor are varied synchronously during an operating
cycle.
12. The device of claim 10, wherein the ultrasound transducer
operates at a duty cycle of less than 100% during an operating
cycle and the output of the motor is reduced when the ultrasound
transducer is active during an operating cycle.
13. The device of claim 10, wherein the output of the motor is
modulated by modulating the current supplied to the drive
motor.
14. The device of claim 10, wherein the current drawn by the drive
motor is monitored.
15. The device of claim 10, wherein the drive frequency of the
motor is monitored.
17. The device of claim 10, additionally comprising an ultrasound
drive circuit and a transformer assembly that inductively couples
and transfers power from the ultrasound drive circuit to the
ultrasound transducer.
18. An oral hygiene device comprising: a support structure having
an acoustic waveguide and at least one bristle tuft comprising a
plurality of bristles projecting from the support structure; an
ultrasound transducer acoustically coupled to the acoustic
waveguide that operates, during the operating cycle, to produce
ultrasonic energy at frequencies of less than 1500 kHz; and a motor
mechanically coupled to the support structure that operates, during
an operating cycle, to vibrate the bristle tips at a peak bristle
tip velocity of less than 1.5 m/sec and at a peak bristle amplitude
of less than 2.2 mm.
19. An oral hygiene device of claim 18, wherein the motor comprises
a stepper motor.
20. An oral hygiene device of claim 18, wherein the motor comprises
a limited angle torque motor.
21. An oral hygiene device of claim 18, wherein the motor produces
an oscillating motion at an included angle of less than about
12.degree. during an operating cycle.
22. An oral hygiene device of claim 18, wherein the motor produces
an oscillating motion at an included angle of between about
3.degree. and 7.degree. during an operating cycle.
23. An oral hygiene device of claim 18, additionally comprising an
ultrasound drive circuit and a transformer assembly that
inductively couples and transfers power from the ultrasound drive
circuit to the ultrasound transducer.
24. An oral hygiene device of claim 18, additionally comprising a
detection feature that allows initiation of an operating cycle only
when the ultrasound transducer is determined to be operational.
25. An oral hygiene device of claim 18, additionally comprising a
controller that provides a timing function that separates a device
operating cycle into a plurality of operating subcycles.
26. An oral hygiene device of claim 18, additionally comprising a
controller that monitors the resonant operating conditions of the
motor.
27. An oral hygiene device of claim 18, additionally comprising a
controller that modulates the ultrasound drive frequency and/or
amplitude during an operating cycle.
28. An oral hygiene device of claim 18, additionally comprising a
controller that provides frequency sweeping of the ultrasound
transducer drive frequency within a predetermined frequency range
at one or more predetermined modulating frequencies.
29. An oral hygiene device of claim 18, additionally comprising a
controller that monitors current drawn by the ultrasound power
supply circuit and ultrasound transducer during an operating
cycle.
30. An oral hygiene device of claim 18, additionally comprising a
controller that is programmed to count the number of device
operating cycles.
31. An oral hygiene device of claim 18, additionally comprising a
controller that is programmed to monitor the function of the
ultrasound transducer.
32. An oral hygiene device of claim 18, additionally comprising a
controller that is programmed to monitor conditions of the fluid
environment during operation and modify operating parameters of the
device based on the detected conditions of the fluid
environment.
33. An oral hygiene device comprising: a support structure having
at least one implement projecting from the support structure; an
ultrasound transducer assembly acoustically coupled to the
implement and an ultrasound drive circuit and power supply in
operative communication with the ultrasound transducer assembly to
drive the transducer assembly to produce ultrasonic energy during
an operating cycle; and a transformer assembly that inductively
couples and transfers power from the ultrasound drive circuit to
the ultrasound transducer.
34. The device of claim 33, wherein the transformer assembly
comprises a primary coil and core in operative communication with
the ultrasound drive circuit and a secondary coil and core in
operative communication with the ultrasound transducer
assembly.
35. The device of claim 33, wherein the transformer assembly
additionally comprises an additional transformer component that
enables the exchange of electrical information between the primary
coil and core and the secondary coil and core.
36. A device head adapted for detachable attachment to a device
handle having a power source, comprising: an implement projecting
from a device head support structure; and an ultrasound transducer
having multiple piezoelectric elements connected mechanically in
series and electrically in parallel acoustically coupled to the
implement.
37. A device head adapted for detachable attachment to a device
handle having a power source, comprising an implement projecting
from a device head support structure, the implement adapted to be
powered by a power source; and a transformer coil and core mounted
in the device head and adapted to cooperate with a transformer coil
and core mounted in the device handle to inductively couple power
from the device handle to the device head.
38. An ultrasound transducer assembly comprising: at least two
piezoelectric elements arranged in a cooperating configuration in
which the elements are arranged mechanically in series, each
piezoelectric element having electrically conductive material
associated with one or more surfaces and each piezoelectric element
being electrically connected to another piezoelectric element in
parallel.
39. The ultrasound transducer assembly of claim 38, additionally
comprising at least one acoustic impedance matching element mounted
in proximity to the piezoelectric elements.
40. The ultrasound transducer assembly of claim 39, wherein the
acoustic impedance matching element comprises graphite.
41. The ultrasound transducer assembly of claim 38, wherein the
piezoelectric elements are bonded and arranged in a stacked
arrangement with an electrically conductive layer provided on at
least a portion of the element surfaces.
42. The ultrasound transducer assembly of claim 38, wherein the at
least two piezoelectric elements form a transducer array.
43. An ultrasound module comprising an ultrasound transducer
assembly of claim 38 in combination with an acoustic waveguide that
contacts a substantial portion of the transducer assembly.
44. An ultrasound module of claim 43, wherein the acoustic
waveguide is acoustically transmissive and comprises a material
having a hardness less than 80 Shore A.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Patent Application
60/677,577 filed May 3, 2005.
BACKGROUND OF THE INVENTION
[0003] 1. Technical Field of the Invention
[0004] The present invention relates generally to the field of oral
hygiene devices and, more specifically, to the field of oral
hygiene devices such as toothbrushes that employ sonic and/or
ultrasonic acoustic mechanisms.
[0005] 2. Brief Description of the Related Art
[0006] Even the most effective existing power toothbrushes leave
clinically significant plaque at tooth-to-tooth contact surfaces,
at the gingival-tooth contact points, below the gingiva and beyond
the direct reach of the bristles or other toothbrush components.
Many oral hygiene devices employing sonic and/or ultrasonic
mechanisms are known in the art. Previous attempts to take
advantage of ultrasound acoustic energy in toothbrushes failed to
exploit microbubble formation in dental fluid for purposes of
facilitating plaque removal, or failed to consider microbubbles and
macrobubbles as a potential impediment to ultrasound propagation
beyond the bristle tips.
[0007] Some toothbrushes that employed ultrasound technology
attempted to achieve the propagation of ultrasound waves from the
base of the bristles either through the bristles themselves or
through the bubbly dental fluid that fills the spaces between the
bristles. For example, U.S. Pat. Nos. 5,138,733 and 5,546,624 to
Bock disclose an ultrasonic toothbrush having a handle, a battery
pack, an electronics driving module, a piezoelectric member, and a
removable brush head. U.S. Pat. Nos. 5,247,716 and 5,369,831 to
Bock disclose a removable brush head for an ultrasonic toothbrush
having a plurality of bristle clusters, a substantially tubular
body constructed of a flexible material, and tensioning means
securing the brush head to the ultrasonic device, providing for the
efficient transmission of ultrasonic frequency oscillations from
the device via the brush head. Because conventional toothbrush
bristles and bubbly dental fluid can reduce rather than facilitate
the propagation of ultrasound waves, the toothbrushes disclosed in
these references would not achieve efficient ultrasound wave
propagation. Also, the ultrasound systems in prior art toothbrushes
did not take advantage of the specific bubble structure within
dental fluid.
[0008] U.S. Pat. No. 3,335,443 to Parisi discloses a brush that is
coupled to an ultrasonic, vibratory handheld dental instrument that
is capable of being oscillated at high sonic and ultrasonic
frequencies. U.S. Pat. No. 4,071,956 to Andress discloses a device
that is not a toothbrush, for removing dental plaque by ultrasonic
oscillations.
[0009] U.S. Pat. No. 3,809,977 to Balamuth et al., which reissued
as U.S. Pat. No. RE 28,752, discloses ultrasonic kits, ultrasonic
motor constructions, and ultrasonic converter designs for use alone
or in combination. The ultrasonic motor may be of piezoelectric
material having a removable tip and is contained in a housing
having an electrical contact means adapted to be plugged into an
adapter that is connected to a converter. U.S. Pat. No. 3,840,932
and U.S. Pat. No. 3,941,424 to Balamuth et al. disclose an
ultrasonic toothbrush applicator in a configuration to be
ultrasonically oscillated to transmit mechanical oscillations from
one end to a bristle element positioned at the other end.
[0010] U.S. Pat. No. 3,828,770 to Kuris et al. discloses a method
for cleaning teeth employing bursts of ultrasonic mechanical
oscillation at an applicator repeated at a sonic frequency to
produce both ultrasonic and sonic vibratory motion during use.
[0011] U.S. Pat. No. 4,192,035 to Kuris discloses an apparatus
comprising an elongated member formed of a piezoelectric member
with a pair of contacting surfaces with a brush member adapted to
be received within the mouth. A casing adapted into a handle is
configured to receive the piezoelectric member. U.S. Pat. No.
4,333,197 to Kuris discloses an ultrasonic toothbrush that includes
an elongated handle member in the form of a hollow housing having a
low voltage coil and cooperating ferrite core that is driven at
ultrasonic frequencies. A brush member is affixed to the core and
is adhesively affixed to an impedance transfer device that is
adhesively affixed to the core material. The impedance transfer
device insures maximum transfer of ultrasonic energy from the core
material to the brush.
[0012] U.S. Pat. No. 4,991,249 and U.S. Pat. No. 5,150,492 to
Suroff disclose an ultrasonic toothbrush having an exchangeable
toothbrush member that is removably attached to an ultrasonic power
member.
[0013] U.S. Pat. No. 5,311,632 to Center discloses a device for
removing plaque from teeth comprising a toothbrush having a thick,
cylindrical, hollow handle encompassing an electric motor that is
actuable to cause rotation of an eccentrically mounted member and
oscillation of the entire device and an ultrasonic transducer
actuable to produce high frequency sound waves along the brush.
[0014] Japan Application No. P1996-358359, Pat. Laid Open
1998-165228, discloses a toothbrush utilizing ultrasonic waves in
which an ultrasonic wave generator is provided in the handle of a
manual or electrically powered toothbrush and an ultrasonic wave
vibrator is mounted in the brush and wired to the wave
generator.
[0015] Japan Application No. P2002-353110, Pat. Laid Open
2004-148079, discloses an ultrasonic toothbrush wherein ultrasonic
oscillation is radiated from a piezoelectric vibrator arranged
inside a brush head and transmitted to the teeth via a rubber
projection group.
[0016] U.S. Pat. No. 6,203,320 to Williams et al. discloses an
electrically operated toothbrush and method for cleaning teeth. The
toothbrush includes a handle, a brush head connected to the handle
having a plurality of hollow filament bristles, passageways through
the handle and brush head for transporting fluid into and through
the hollow filament bristles, an electrical energy source in the
handle, and a vibratory element for imparting a pulsation to the
fluid being transported.
[0017] U.S. Patent Publication No. 2003/0079305 to Takahata et al.
discloses an electric toothbrush in which a brush body is
simultaneously oscillated and reciprocated. The electric toothbrush
comprises a casing main body, an arm extending above the casing
main body, a brush body arranged in a top end of the arm, and an
ultrasonic motor arranged in a top end inside of the arm for
driving the brush body.
[0018] U.S. Pat. No. RE 35,712, which is a reissue of U.S. Pat. No.
5,343,883 to Murayama, discloses an electric device (i.e. a
flosser) for removal of plaque from interproximal surfaces. The
device employs sonic energy and dental floss secured between two
tines of a flexible fork removably attached to a powered handle.
The electric motor revolves at sonic frequencies to generate sonic
energy that is transmitted to the flexible fork.
[0019] U.S. Pat. No. 6,619,957 to Mosch et al. discloses an
ultrasonic scaler comprising a scaler tip, actuator material, a
coil, a handpiece housing, and an air-driven electrical current
generator. The actuator material, coil, and air-driven electrical
current generator are all encompassed within the handpiece
housing.
[0020] U.S. Pat. No. 6,190,167 to Sharp discloses an ultrasonic
dental scaler for use with a dental scaler insert having a resonant
frequency. The dental scaler insert is removably attached to a
handpiece having an energizing coil coupled to a selectively
tunable oscillator circuit to generate a control signal having an
oscillation frequency for vibrating the dental scaler.
[0021] U.S. Pat. No. 4,731,019 to Martin discloses a dental
instrument for scaling by ultrasonic operation. The instrument of
the dental instrument has a distal end with a hook-like
configuration with a conical pointed end and comprising abrasive
particles, typically diamond particles.
[0022] U.S. Pat. No. 5,378,153 to Giuliani discloses a dental
hygiene apparatus having a body portion and an extended resonator
arm. The apparatus employs an electromagnet in its body that acts
in combination with two permanent magnets to achieve an oscillating
action about a torsion pin. The arm is driven such that the
bristle-tips operate within ranges of amplitude and frequency to
produce a bristle tip velocity greater than 1.5 meters per second
to achieve cleansing beyond the tips of the bristles.
[0023] U.S. Patent Publication No. 2005/0091770 A1 discloses a
toothbrush employing an acoustic waveguide that facilitates the
transmission of acoustic energy into the dental fluid. The acoustic
waveguide may be used in combination with a sonic component and/or
an ultrasonic transducer. The disclosure of this publication is
incorporated herein by reference in its entirety.
[0024] There remains a need in the art for devices that provide
improved oral hygiene, and particularly that improve cleaning
between the teeth and gums, at points of contact between the teeth,
and beyond the direct action of the bristles.
SUMMARY OF THE INVENTION
[0025] Oral hygiene devices having an acoustic waveguide, an
ultrasound transducer assembly and/or a drive motor for generating
oscillations at sonic frequencies are provided herein. The device
head typically comprises a support structure having an acoustic
waveguide, an ultrasound transducer assembly, and one or more
bristle tufts mounted therein. A handle structure typically houses
a rechargeable power supply, a motor generating oscillations at
sonic frequencies, an ultrasound drive circuit, and a controller.
The device head may be detachably mounted to the handle and
replaceable. The device may also include a battery charging station
that is connectable to an external power supply for recharging the
batteries. A user interface comprising at least an on/off control
is provided and, upon activation of the device by the user, an
operating cycle is initiated. Suitable ultrasound operating
parameters and sonic oscillating parameters and protocols are
described in detail below.
[0026] Within various embodiments, the present invention provides
oral hygiene devices, such as toothbrushes, including manual
(non-motorized) toothbrushes incorporating an ultrasound transducer
and an acoustic waveguide structure, power (motorized) toothbrushes
incorporating an acoustic waveguide structure, and power
(motorized) toothbrushes incorporating both an ultrasound
transducer and an acoustic waveguide structure. The acoustic
waveguide structure, in combination with an ultrasound transducer
and/or motor for generating oscillation at sonic frequencies, and
optionally in combination with one or more bristle tufts, acts upon
the microscopic bubbly flow within fluid in the operating
environment to induce cavitation, acoustic streaming and/or
acoustic microstreaming within the fluid. Oscillation of the brush
head at sonic frequencies, in combination with emission of acoustic
energy from the acoustic waveguide at ultrasound frequencies,
and/or in combination with the oscillation of one or more bristle
tufts, furthermore generates a favorable mouth feel, stimulates and
massages the gums and other dental tissue and, in general, provides
an improved dental cleaning experience.
[0027] An oral hygiene device such as a toothbrush, employing an
acoustic waveguide in combination with an ultrasound transducer
and/or a motor generating oscillations at sonic frequencies under
the conditions described herein, provides improved cleaning
properties and disruption of biofilm. As described in detail
herein, oral hygiene devices according to the present invention are
effective in increasing bubbly fluid flow by motion, including
sonic motion, of the acoustic waveguide and promoting bubble
formation by movement of the waveguide and/or one or more bristle
tufts. Oscillation of the brush head at sonic frequencies moves and
activates the bristle tips so that they cleanse tooth surfaces by
means of direct bristle contact and also generates bubbles within
the dental fluid surrounding the waveguide that, when exposed to
acoustic energy at ultrasound frequencies, provide improved plaque
and biofilm removal.
[0028] In embodiments employing an ultrasound transducer, devices
of the present invention are effective in transmitting ultrasound
waves generated by the ultrasound transducer and propagating those
waves through an acoustic waveguide into;the oral cavity and the
dental fluid to achieve improved plaque disruption and removal, as
well as biofilm reduction. Devices of the present invention
employing an ultrasound transducer operating in accordance with the
parameters described herein in combination with a sonic component
are also effective in facilitating bubbly fluid flow and
transmitting ultrasound to produce cleaning effects at and beyond
the bristles, e.g., from about 0.5 mm to about 7 mm beyond the
bristle tips, more typically at least about 1 mm and up to about 5
mm beyond the bristle tips.
[0029] Oscillation of bristle tufts and an acoustic waveguide at
sonic frequencies generates bubbly flow and improves cleaning, even
absent the action of an ultrasound transducer and transmission of
acoustic energy through the acoustic waveguide at ultrasound
frequencies. It is, however, the combination of the ultrasonic
transducer, acoustic waveguide, and sonic component that together
achieve the most effective power toothbrush embodiment of the
present invention and yield synergistic cleaning effects that are
substantially superior to the additive effects of the sonic and
ultrasonic components in isolation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Various aspects and advantages of this invention will become
more readily appreciated and may be better understood by reference
to the following detailed description, taken in conjunction with
the accompanying drawings, wherein:
[0031] FIG. 1 is a schematic, partially cross sectional diagram
depicting an exemplary toothbrush of the present invention
incorporating an acoustic waveguide, a plurality of bristle tufts,
an ultrasound transducer, and a motor for producing oscillation at
sonic frequencies;
[0032] FIG. 2A is an enlarged schematic perspective view of an
exemplary ultrasound transducer assembly and associated matching
layer and electrical contacts suitable for use in devices of the
present invention;
[0033] FIG. 2B is an enlarged schematic perspective view of another
exemplary ultrasound transducer assembly and associated matching
layer incorporating electrical contacts suitable for use in devices
of the present invention;
[0034] FIG. 3 is an enlarged perspective schematic view, partially
broken away, illustrating an ultrasound module of the present
invention incorporating an ultrasound transducer assembly with an
associated matching layer and electrical contacts mounted in a
support structure with an acoustic waveguide mounted over and
around the transducer assembly;
[0035] FIG. 4 shows an enlarged side cross-sectional view of a
brush head assembly of the present invention incorporating an
ultrasound module and electrodes providing power to the transducer
assembly but omitting bristle tufts;
[0036] FIG. 5 shows an enlarged side view of a brush head of the
present invention having a plurality of bristle tufts;
[0037] FIG. 6 shows an exploded view of a device handle and the
components typically mounted in the handle; and
[0038] FIG. 7 shows an enlarged exploded view of a device head and
the components typically mounted in the head.
DETAILED DESCRIPTION OF THE INVENTION
[0039] As used herein, the terms "ultrasound" and "ultrasonic"
refer to acoustic energy having a frequency greater than the normal
audible range of the human ear--generally a frequency greater than
approximately 20 kHz. The term "sonic" refers to acoustic energy,
or sound, having a frequency that is within the normal audible
range of the human ear--generally less than about 20 kHZ--for
example, between 20 Hz and 20 kHz.
[0040] As used herein, the term "cavitation" refers to the
generation and/or stimulation of bubbles by sound. By "generation"
is meant the creation of bubbles; by "stimulation" is meant the
action that causes the bubbles to become dynamically active--that
is, to move, to get bigger or smaller, to grow, to dissipate, all
with associated mechanical and/or chemical effects in and around
the fluid surrounding the bubbles and within the gas inside the
bubbles. The term "cavitation" refers to the interaction between an
ultrasonic field in a liquid and in gaseous inclusions (e.g.,
microbubbles) within the insonated medium.
[0041] Cavitation of existing microbubbles may be subdivided, to a
first approximation, into two general categories--"stable
cavitation" and "inertial cavitation." "Stable cavitation" is the
induction of stable, low-amplitude, resonant oscillations of
preexisting microbubbles by low-intensity ultrasound energy, which,
in turn generates local shear forces within the fluid flow
(referred to herein as acoustic microstreaming) near and adjacent
to the microbubbles. As the ultrasound intensity is increased, the
amplitude of oscillation also increases until the bubble becomes
unstable and collapses due to the inertia of the inrushing fluid,
giving rise to "inertial cavitation." Generally, microbubbles that
undergo cavitation under the ultrasonic conditions used in devices
of the present invention are between about 1 .mu.m and about 150
.mu.m in diameter. Clusters of microbubbles may also be induced to
cavitate.
[0042] Oral hygiene devices of the present invention incorporating
an ultrasound transducer and an acoustic waveguide typically
promote at least stable cavitation--that is, simple volumetric
changes in bubbles, where factors in addition to and/or instead of
the inertia in the surrounding fluid govern the bubble behavior.
Low levels of ultrasonic acoustic energy induce temporal variations
in bubble volume, both within an acoustic cycle and over many
acoustic cycles, that generate movement within the fluid in
proximity to the bubble, whose mechanical effects promote removal
of plaque and disruption of biofilm.
[0043] "Microbubbles" refer to microscopic bubbles present in the
oral cavity, for example, in the dental fluid or plaque.
Microbubbles may be endogenous to the fluid--that is, they may be
introduced, such as in a fluid or dentifrice containing
microbubbles; they may be generated by the movement of toothbrush
bristles during manual brushing; and/or they may be generated by
the oscillation of bristles and/or an acoustic waveguide at sonic
frequencies. "Microbubbles" are acted upon by acoustic energy at
ultrasound frequencies transmitted by an ultrasonic transducer and
propagated by an acoustic waveguide. "Microbubbles" resonate at or
near a specific frequency depending upon the microbubbles'
diameter.
[0044] "Acoustic streaming" refers to the bulk or coherent flow of
fluid that occurs due to momentum transfer from an acoustic wave to
a fluid as a result of attenuation of an ultrasound beam.
Ultrasound propagating into fluid, with or without bubbles, can
generate "acoustic streaming," which can be quite significant in
size and extent. Acoustic streaming effects may be even greater
with bubbles than without bubbles in a fluid. Acoustic streaming
generally requires higher frequencies than are required for
stimulating the bubbles and, in general, the higher the ultrasonic
frequency, the greater the acoustic streaming effect.
[0045] "Microstreaming" and "acoustic microstreaming" refer to the
movement of fluid near and adjacent to microbubbles that occurs as
a result of the action of mechanical pressure changes within the
ultrasonic field on the microbubbles. In the context of the present
invention, shear forces are associated with cavitating microbubbles
within dental fluid that are distributed along the surfaces of the
gums and teeth, as well as in interproximal and subgingival spaces.
Microstreaming induced by the ultrasonic acoustic energies used in
devices of the present invention produces shear stresses of between
about 0.1 Pa and about 1000 Pa. Devices of the present invention
preferably operate at acoustic operating parameters to produce
shear stresses of between about 0.2 Pa and about 500 Pa and, in
some embodiments, produce shear stresses of from about 0.3 Pa to
about 150 Pa In yet other embodiments, shear stresses produced by
devices of the present invention are from about 1 Pa to about 30
Pa. These shear stresses remove plaque and/or stains on the
surfaces of teeth and other structures in the oral cavity and
disrupt biofilm.
[0046] Oral hygiene devices of the present invention are capable of
generating fluid flows within a fluid operating environment at a
range of from about 0.5 cm/sec to about 50 cm/sec at a distance of
between about 1 mm and 10 mm beyond the toothbrush bristle tips
and/or acoustic waveguide. More typically, toothbrushes of the
present invention are capable of generating fluid flows within a
fluid operating environment at a range of about 1 cm/sec to about
30 cm/sec at a distance of between about 1 mm and 10 mm beyond the
toothbrush bristle tips and/or acoustic waveguide. Oral hygiene
devices are preferably capable of generating fluid flows of between
2 and 10 cm/sec at a distance of between about 1 mm and 10 mm
beyond the toothbrush bristle tips and/or acoustic waveguide.
[0047] An Exemplary Device
[0048] FIG. 1 schematically illustrates an exemplary oral hygiene
device of the present invention, a toothbrush, comprising an
ultrasound transducer, an acoustic waveguide, and a motor for
generating oscillations at sonic frequencies in a toothbrush.
Toothbrush 10 comprises a handle 15 constructed from a rigid or
semirigid material, which typically houses at least one
rechargeable battery 12 that is preferably adapted to be induction
charged using a charging device powered by an external power source
(not shown); electrical circuitry, including an ultrasonic module
drive circuit 14; a motor 16 for generating oscillation at sonic
frequencies, preferably a DC motor for driving toothbrush head 20
at sonic frequencies; and controller 18 that provides timing, motor
control and various other control functions. Suitable motors,
ultrasonic drive circuits, rechargeable batteries, and controllers
are well known in the art and may be used in devices of the present
invention. Ultrasonic module drive circuit 14 is coupled to an
ultrasound transducer for producing acoustic energy at ultrasonic
frequencies at the brush head and motor 16 is coupled to the brush
head to produce acoustic energy at sonic frequencies at the brush
head.
[0049] Toothbrush head 20 is mounted on handle 15 and includes a
stem portion 21 and brush head portion 23. Stem portion 21 may
provide a channel or other means for facilitating transmission of
ultrasound drive instructions, power and sonic oscillations to the
brush head portion. Brush head portion 23 comprises an ultrasound
transducer 22 and an acoustic waveguide 24 in operable proximity
and acoustically coupled to the ultrasound transducer. In the
toothbrush embodiment illustrated schematically in FIG. 1, an
optional ultrasound reflecting element 28 is shown behind, and
extending around each side of, the ultrasound transducer 22 that
reflects the ultrasound through the acoustic waveguide 24 and into
the dental fluid. The toothbrush head 20 may be either detachably
or fixedly attached to the handle 15 and, in preferred embodiments,
is detachably mountable to handle 15. The brush head portion may
then be provided as a separate, replaceable component.
[0050] In general, toothbrush head 20 includes a plurality of
bristle tufts 26 disposed adjacent to and generally surrounding
acoustic waveguide 24. The toothbrush head 20 may optionally
include an impedance matching layer 29 mounted between ultrasound
transducer 22 and acoustic waveguide 24. Impedance matching layer
29 may improve the efficiency of the device, as discussed below.
All of these components are described in greater detail below with
reference to specific embodiments.
[0051] Alternating current supplied by the ultrasonic module drive
circuit 14 (from a rechargeable power source) drives ultrasonic
transducer 22 such that the transducer 22 expands and contracts
primarily along one axis at or near resonance with the frequency
supplied by the ultrasonic module drive circuit 14, thereby
converting electrical energy into acoustic energy at ultrasound
frequencies. The resulting ultrasonic acoustic waves are conducted
into, propagated through, and radiated out of acoustic waveguide
24. The transmitted ultrasonic acoustic energy acts on microbubbles
within fluid in the oral cavity (typically a mix of saliva, water
and dentifrice) to induce cavitation, thereby loosening plaque
deposited on the teeth and in interproximal regions.
[0052] The device of FIG. 1 illustrates an exemplary oral hygiene
device of the present invention in the form of a power toothbrush.
Additional and preferred embodiments including various ultrasound
and/or sonic operating parameters, device components, control
features, and the like, are described in greater detail below. It
will be appreciated that while certain combinations of operating
parameters and features may be preferred for use in certain
applications and in particular environments, the device components,
operating parameters, control features, and the like, may be
combined in many different ways in oral hygiene devices of the
present invention.
[0053] It will also be appreciated that these features may be used
in various types of oral hygiene devices and, indeed, in other
types of devices, and the inventions described herein are not
limited to oral hygiene and toothbrush embodiments. In alternative
embodiments, for example, devices may have a support structure,
such as a handle and/or a device head, having at least one
implement projecting from the support structure. The projecting
implement may be an acoustic waveguide, a bristle tuft, a prong, a
holder for a detachable implement or material, or the like. In
preferred embodiments, the projecting implement is acoustically
coupled to an ultrasound transducer. The device may additionally
incorporate one or more bristle tuft(s) and one or more motor(s)
for producing oscillation of the device head and/or projecting
implement at sonic frequencies.
[0054] Ultrasound Operating Parameters
[0055] Ultrasound operating parameters for oral hygiene devices of
the present invention incorporating an ultrasound transducer
assembly include: the ultrasound frequency; the pulse repetition
frequency (PRF); the number of cycles per burst; the duty cycle;
the power of the ultrasound transducer; the peak negative acoustic
pressure generated by the ultrasound transducer; and the
environment in which the device is operated.
[0056] Ultrasound transducer assemblies incorporated in oral
hygiene devices of the present invention generally operate at a
carrier frequency (i.e., the frequency of the individual ultrasound
waves) greater than about 20 kHz; typically between about 30 kHz
and about 3 MHz; typically less than 1.5 MHz; and more typically
less than 1.0 MHz, which is lower than the operating frequency of
many ultrasonic toothbrushes. In many embodiments, the preferred
ultrasound carrier frequency is between about 100 kHz and about 750
kHz; in some embodiments between about 100 kHz and about 600 kHz;
in still other embodiments between about 150 kHz and about 500 kHz;
and, in yet other embodiments, between about 250 kHz and about 500
kHz. It will be understood that the optimal range of the carrier
frequency for different applications may vary depending upon the
available bubble population, the size and power of the ultrasound
transducer employed, and the conditions prevalent in the operating
environment--e.g., the composition of fluids, and the like.
[0057] Ultrasound may be applied continuously or may be pulsed in a
regular or irregular pattern of on/off periods. For many
applications, ultrasound is pulsed to produce a predetermined
number of waves within a packet or burst (cycles/burst) at a
predetermined pulse repetition frequency (PRF). The duty cycle
(i.e., the percentage of time that the ultrasound is activated) is
related to the PRF and the number of bursts per cycle. A 100% duty
cycle represents continuous ultrasound application. Ultrasound duty
cycles of less than 100% may be achieved in many ways. For example,
ultrasound may be "packaged" into bursts wherein the number of
cycles per pulse and the pulse (burst) repetition frequency is
varied to achieve a desired duty cycle. A 10% duty cycle of a
100,000 Hz (100,000 cycles per second) ultrasound signal yields
10,000 cycles. These 10,000 cycles may be delivered in a single
burst of 0.1 second duration, followed by a 0.9 second off state
(burst length=10,000, pulse repetition frequency=1 Hz).
Alternately, 10,000 cycles may be delivered in 10 bursts of 1,000
cycles each (burst length=1,000, pulse repetition frequency=10 Hz)
for a total ultrasound on time of 0.1 s (i.e. 10*0.01 sec. pulses)
and 0.9 sec. (i.e. 10*0.09 sec pulse) of off time.
[0058] In general, dental plaque and biofilm removal increases with
increasing duty cycle. Practical levels of ultrasound duty cycle
may, however, be limited by factors such as transducer operating
characteristics (power consumption, internal heating, etc.), safety
to tissue (thermal index, tissue heating, etc.), user feel and
preference, and the like. For oral hygiene applications where the
device is operating in a typical dental slurry, ultrasound duty
cycles of from about 1 to 30% are typical, with duty cycles of
about 4 to 20% being most common, and duty cycles of from about 4
to 15% being preferred. Higher duty cycles may be preferred for use
in particular applications.
[0059] The desired ultrasound PRF may depend upon the ultrasound
frequency, the number of cycles per burst, and the environment in
which the toothbrush is operating, including the composition and
physical properties of the fluid medium into which the ultrasonic
energy is being transmitted. Typically, though not exclusively, in
oral hygiene devices of the present invention, the PRF ranges from
about 0.5 Hz and about 10,000 Hz; more typically between about 0.5
Hz and about 2,500 Hz, and still more typically between about 1 Hz
and about 500 Hz. In toothpaste, for example, a preferred PRF at a
10% duty cycle .is generally less than about 20 Hz and may be less
than about 10 Hz. In an aqueous environment, though, a higher PRF
may be used, typically over 40 Hz and often in the range of between
40 to 200 Hz. In some embodiments of oral hygiene devices of the
present invention that use ultrasound frequencies in combination
with sonic frequencies, the PRF is a small multiple (generally two
or greater, more typically four or greater) of the sonic frequency
(i.e., the frequency of movement of the bristles and/or acoustic
waveguide driven by a sonic component of a toothbrush of the
present invention).
[0060] The number of individual ultrasound waves within a packet or
burst of ultrasound (cycles per burst) is another ultrasound
operating variable and, in oral hygiene devices of the present
invention, is typically between about 10 and about 10,000
cycles/burst and, for many embodiments, between about 500 and
10,000 cycles/burst. The desired number of cycles per burst may
depend, for example, upon the ultrasound frequency, the PRF, and
the environment in which the toothbrush is operating. For promoting
acoustic microstreaming in the context of devices of the present
invention, relatively long bursts and relatively low PRF are
suitable.
[0061] Generally, less frequent pulses of a greater number of
cycles is preferred to more frequent pulses of a lesser number of
cycles. Operating in the environment of a dentifrice slurry
generally requires more cycles per pulse than a 100% water medium
requires to achieve comparable biofilm removal. In a dental slurry,
100 to 10,000 cycles per pulse is common, with 500 to 5000 pulses
being even more typical. The pulse repetition frequency can be
calculated based upon the desired duty cycle. For example, for a
250,000 kHz ultrasound signal, a 10% duty cycle, and an ultrasound
package of 1000 cycles per burst, the pulse repetition frequency is
25 Hz (i.e. 250,000 kHz.times.0.10/1000 cycles/burst=25 Hz).
[0062] The ultrasound operating parameters preferred to provide
optimal cleaning and user experience vary depending, for example,
on the composition and character of the fluid environment in which
the device is operated. Toothbrushes are operated in the oral
cavity where fluids such as saliva and water are typically mixed
with toothpaste or another cleaning agent to form a slurry. A
typical dental slurry is more viscous than water and may be more or
less acoustically transmissive than a water/saliva mix. For
toothbrush and other oral hygiene devices operating in a typical
toothpaste dental slurry environment, the combinations of operating
parameters described in the table below are suitable.
TABLE-US-00001 Ultrasound Frequency Range Duty Cycle Cycles/Burst
PRF (Hz) 100-750 kHz 5% 500-10,000 0.5-75 100-750 kHz 10%
500-10,000 1.0-150 100-750 kHz 15% 500-10,000 1.5-225 250-500 kHz
5% 500-10,000 1.3-50 250-500 kHz 10% 500-10,000 2.5-100 250-500 kHz
15% 500-10,000 3.8-150 300 kHz 5% 500-10,000 1.5-30 300 kHz 10%
500-10,000 3.0-60 300 kHz 15% 500-10,000 4.5-90
[0063] Other types of devices may be used in a substantially
aqueous (water) environment, and the operating parameters may be
adjusted accordingly. For oral hygiene devices operating in a
substantially aqueous environment, the combinations of operating
parameters described in the table below are suitable.
TABLE-US-00002 Ultrasound Frequency Range Duty Cycle Cycles/Burst
PRF (Hz) 100-750 kHz 5% 50-1,000 5-750 100-750 kHz 10% 50-1,000
10-1500 100-750 kHz 15% 50-1,000 15-2250 250-500 kHz 5% 50-1,000
12.5-500 250-500 kHz 10% 50-1,000 25-1000 250-500 kHz 15% 50-1,000
37.5-1500 300 kHz 5% 50-1,000 15-300 300 kHz 10% 50-1,000 30-600
300 kHz 15% 50-1,000 45-900
[0064] In yet another embodiment, oral hygiene devices of the
present invention having an ultrasound transducer, such as a
toothbrush, operate at an ultrasound frequency of greater than
about 250 and less than about 350 kHz, at a duty cycle of about 10%
with about 5,000 cycles per burst at a pulse repetition frequency
of about 6 Hz. In yet another embodiment, an oral hygiene device of
the present invention having an ultrasound transducer, such as a
toothbrush, operates at an ultrasound frequency of greater than
about 250 and less than about 350 kHz, at a duty cycle of about 10%
with about 500 cycles per burst at a pulse repetition frequency of
about 60 Hz.
[0065] Various combinations of ultrasound operating parameters may
also be used to promote acoustic streaming. For oral hygiene
applications in which it's desired to promote acoustic streaming,
the following ranges of ultrasound parameters are generally
employed: (1) the carrier frequency is typically greater than about
20 kHz; more typically, between about 500 kHz and about 5,000 kHz
or more, to enhance acoustic absorption; (2) the pulse repetition
frequency (PRF) is typically, though not exclusively, between about
1 Hz and about 10,000 Hz; more typically between about 10 Hz and
about 10,000 Hz; still more typically between about 100 Hz and
about 10,000 Hz; and yet more typically, greater than about 1000 Hz
and less than about 10,000 Hz; and (3) the number of individual
ultrasound waves within a packet or burst of ultrasound is
typically between 1 and 5,000; more typically between about 5 and
about 100 waves. For oral hygiene applications in which it's
desired to promote acoustic streaming, longer duty cycles are
typical, such as, for example, at least about 10%; more typically
at least about 25%; still more typically at least about 50% or at
least about 75% and, in some embodiments, up to 100%. Longer
bursts, e.g., greater than about 100 waves at a frequency of about
1 MHz, with a PRF of at least 1000 Hz, are exemplified herein. It
will be apparent that different burst lengths, frequencies, and PRF
values may be suitably employed in oral hygiene devices of the
present invention.
[0066] The magnitude of the acoustic output of the ultrasound
transducer assembly and the acoustic waveguide affects the
disruption of dental plaque biofilm, as does the composition of the
fluid media. In general, higher acoustic output yields greater
bubble activation and improved cleaning, plaque removal and biofilm
disruption. One measure of acoustic output from an ultrasound
transducer is the peak negative acoustic pressure measured during
an operating cycle. Suitable operating peak negative acoustic
pressure parameters in oral hygiene devices of the present
invention are generally in the range of from about 0.01 to 10 MPa;
more typically in the range of from 0.1 to 5 MPa; for many
embodiments in the range of from 0.1 to 1 MPa; for many embodiments
in the range of from 0.25 to 0.6 MPa; and in yet other embodiments
in the range of from 0.3 to 0.5 MPa.
[0067] "Mechanical index" refers to a measure of the onset of
cavitation of a preexisting bubble subjected to one cycle of
applied acoustic pressure. The mechanical index is defined as the
square root of the ratio of peak negative pressure (in MPa) to the
ultrasound frequency (in MHz) and provides a means to quantify the
acoustic output of an ultrasonic transducer. To produce a specific
cleaning effect, a device operating in a fluid medium that is
substantially aqueous (e.g., 100% water) requires a lower
mechanical index than a device operating in a more viscous fluid
medium, such as a saliva/water/dentifrice fluid. In a typical
dental slurry fluid environment, a mechanical index of at least
about 0.25 is generally required to achieve plaque removal. In a
relatively low viscosity aqueous (water) environment, a mechanical
index of at least 0.1 is generally required to achieve plaque
removal. If the mechanical index is reduced below these threshold
levels, the removal of significant dental plaque biofilm is
generally not achieved even if the ultrasound duty cycle is
increased. Conversely, once the mechanical index exceeds the
threshold level and is sufficient to produce a significant effect,
the ultrasound duty cycle may be reduced without significant loss
of plaque removal efficiency. Thus, for example, at a 10% duty
cycle reducing the mechanical index by 50% (e.g., from 1.0 to 0.5)
has a substantial effect on biofilm removal. Holding mechanical
index at 1.0 while reducing duty cycle by 50% (e.g., from 10% to
5%), however, yields a substantially smaller effect on biofilm
removal.
[0068] The mechanical indices delivered by devices of the present
invention are generally in the range of about 0.001 to about 1000.
More typically, mechanical indices are in the range of about 0.01
to about 20, still more typically in the range of about 0.02 to
about 10, and even more typically in the range of about 0.1 to
about 5, or between about 0.1 and about 1.9. Devices intended for
operation in substantially aqueous environments preferably exhibit
a mechanical index of greater than 0.1. In devices of the present
invention intended for operation using a dentifrice or another
relatively viscous composition in the oral cavity, the mechanical
index is preferably greater than about 0.25 and less than 1.9 and,
in other embodiments, the mechanical index is greater than about
0.25 and less than 1.5. Devices of the present invention, according
to some embodiments, operate with a mechanical index of between
about 0.5 and 1.5 and in yet other embodiments, between about 0.8
and 1.4.
[0069] Sonic Operating Parameters
[0070] Within certain embodiments, oral hygiene devices of the
present invention incorporate a drive motor that generates
oscillation at sonic frequencies in combination with an acoustic
waveguide and/or an ultrasound transducer. A motor assembly that,
when the device is activated, generates oscillations at sonic
frequencies is typically mounted in a device handle and the
oscillations are transmitted to the device head, thereby producing
oscillation of the acoustic waveguide and/or bristle tufts. The
motor may alternatively be mounted in a portion of the device
head.
[0071] The acoustic waveform of sonic oscillations, as generated in
devices of the present invention, is generally sinusoidal, but
other waveforms may be used--additionally or alternatively. Sonic
oscillations may be driven in non-sinusoidal waveform-s, for
example trapezoidal, triangular, square, purely rotational, and
other waveforms. Additionally, the frequency and/or amplitude may
be modulated. The frequency of sonic oscillation influences the
effectiveness of cleaning produced by both the sonic and ultrasonic
components, and may additionally influence user comfort and the
user's perception of cleaning effectiveness.
[0072] In a device incorporating one or more bristle tufts,
generation of oscillations at sonic frequencies at the brush head
produces bristle tip motion. Bristle tip motion may be
characterized by bristle tip velocity, amplitude, frequency,
acceleration, and other metrics. Devices of the present invention
employing a motor generating oscillations at sonic frequencies
preferably operate to produce bristle tip frequencies of greater
than 20 Hz and less than 20,000 Hz. High bristle tip frequencies
are irritating to many users and may create an undesirable tickling
sensation in the oral cavity. For this reason, bristle tip
frequencies of less than about 2,000 Hz are preferred. A desired
sonic operating frequency may be a note on the musical scale, most
typically those have a frequency greater than about 54 Hz and less
than about 1662 Hz. According to some embodiments, operating
parameters producing bristle tip frequencies of less than about
1500 Hz are preferred; bristle tip frequencies of less than about
1000 Hz are preferred for many applications; bristle tip
frequencies of less than about 500 Hz are preferred for yet other
embodiments. In still other embodiments, bristle tip frequencies of
greater than about 20 and less than about 500 Hz are preferred; in
yet other embodiments, between 100 and 300 Hz.
[0073] To maintain a generally constant bristle tip velocity as the
frequency increases, the bristle tip amplitude decreases.
Similarly, to maintain a substantially constant bristle tip
velocity as the amplitude increases, the frequency decreases. Both
frequency and amplitude of bristle tip movement may affect cleaning
and user comfort. Oral hygiene devices of the present invention,
intended for use in the environment of a common dentifrice slurry
and employing sinusoidal sonic motion, generally operate to produce
a desired peak bristle tip velocity during an operating cycle, of
from 0 to 10 m/s, more typically from 0.2 to 5 m/s, more typically
from 0.4 to 1.5 m/s and generally less than 1.5 m/s. For many
embodiments, the bristle tip velocity during operation is less than
about 1.0 m/s, often less than 0.8 m/s, and in some embodiments
between about 0.4 and 0.8 m/s. These bristle tip velocities are
generally lower than the bristle tip velocities produced by many
power toothbrushes that operate by oscillating bristle tufts at
sonic frequencies. Bristle tip velocity measurements are taken with
the bristles dry, in air, without an applied load to the bristle
tips. Actual bristle tip velocity is generally reduced during
operation as a result of loading associated with frictional contact
of the bristles against teeth and drag associated with moving
bristles through a fluid environment.
[0074] The bristle tip amplitude produced by sonic oscillation also
influences the cleaning effectiveness provided by both sonic and
ultrasonic components. The peak amplitude of bristle tip motion
during an operating cycle or subcycle may range from about 0.01 to
10 mm. A preferred range of peak bristle tip amplitude (as wetted
and typically loaded in the oral cavity) is in the range of 0.1 to
6 mm, and is generally less than 4.0 mm. According to further
embodiments, the peak bristle tip amplitude is less than 3.0 mm and
may be in the range of from 0.2 to 3.0 mm or from 0.4 to 2.2 mm.
This is lower than the peak bristle tip amplitudes of many power
toothbrushes that operate by moving bristles at sonic frequencies.
Bristle tip amplitude measurements are taken with the bristles dry,
in air, without an applied load to the bristle tips.
[0075] The Acoustic Waveguide
[0076] As indicated above, oral hygiene devices of the present
invention incorporate an acoustic waveguide projecting from the
device head support structure in combination with an ultrasound
transducer and/or a motor oscillating at sonic frequencies. The
acoustic waveguide provides a conduit for the transmission of
ultrasound waves from the ultrasound transducer, where they are
generated, through an (optional) impedance matching layer, to fluid
in the oral cavity and is substantially more efficient and
effective than the bristle tufts in transmitting the ultrasound
acoustic energy to fluids in the oral cavity. Thus, devices of the
present invention direct ultrasound through a waveguide structure
and substantially isolate it from the bristle tufts. The dental
fluid into which the acoustic waveguide is immersed during use of
the device in the oral cavity is typically a saliva and toothpaste
emulsion that is acoustically absorptive and, in the absence of an
acoustic waveguide, the fluid would attenuate significant amounts
of the ultrasound before the wave front reached the tooth and gum
surfaces. Impedance mismatches are also a significant barrier to
sound transmission from an ultrasound transducer to the tooth and
gum surfaces. The acoustic waveguide serves as a bridge across the
acoustic mismatch by transmitting acoustic energy at ultrasound
frequencies into the saliva and toothpaste emulsion near the tooth
surface.
[0077] Typically, as shown in FIG. 1, the acoustic waveguide is
positioned at the base of a brush head portion of the device in
proximity to one or more bristle tufts. According to preferred
embodiments, the acoustic waveguide is in operable proximity and
acoustically coupled to an ultrasound transducer and transmits
acoustic energy at ultrasound frequencies to the fluids in the oral
cavity. The acoustic waveguide, as described previously, may
additionally be oscillated at sonic frequencies.
[0078] A variety of acoustic waveguide designs are contemplated for
use in devices of the present invention. Two parameters
substantially affect the transmission of ultrasonic waves through
an acoustic waveguide: (1) the material(s) from which the waveguide
is fabricated; and (2) the geometry of the waveguide. Each of these
parameters is described in further detail herein. In addition, the
acoustic waveguide must have a pleasant mouth feel and must present
a surface that is soft enough to be appealing when it is oscillated
at sonic frequencies and contacts the oral cavity and teeth.
Acoustic waveguides having an appealing texture and softness are
designed to efficiently receive, conduct, coherently focus,
incoherently compress, and transmit out the acoustic energy at
ultrasound frequencies. Acoustic waveguides may also be designed to
channel acoustic energy along the waveguide, and transmit or "leak"
acoustic energy into the surrounding medium before it has
propagated to the end of the waveguide. One way to promote this
acoustic leakage is to fabricate the waveguide from a material
having a sound speed substantially lower than that of the
surrounding fluid and/or to provide a waveguide having tapered side
walls.
[0079] The acoustic waveguide, in general, has a solid, block-like
structure with at least one dimension that is substantially larger
than that of an individual bristle tuft. The dimensions of the
acoustic waveguide are determined by design parameters such as the
ultrasound transducer face area, mounting considerations, the feel
of the waveguide in the user's mouth, and the arrangement of
bristle tufts. The acoustic waveguide is in operable proximity and
acoustically coupled to the ultrasonic transducer and adjacent to
and flanking, on one or more sides, bristle tufts. The size and
configuration of the base of the acoustic waveguide, in the
embodiment illustrated in FIG. 1, generally matches the size and
configuration of the exposed surface of the ultrasound transducer
and/or an associated impedance matching layer and is mounted
contacting an exposed surface of the ultrasound transducer and/or
an associated matching layer. The body of the acoustic waveguide
may form a generally rectangular solid or may have one or more
curved profiles, as shown in FIG. 1.
[0080] In some embodiments, at least one of the waveguide walls is
tapered so that the tip, or distal face, of the acoustic waveguide
distal from the ultrasonic transducer has a smaller cross-sectional
area than that of the base of the acoustic waveguide in proximity
to the ultrasound transducer. In general, the acoustic waveguide
has a length, often oriented generally along the longitudinal axis
of the brush head, that is greater than the diameter of a bristle
tuft and, more preferably, has a length that is greater than the
(side-to-side) combined diameters of at least two bristle tufts. In
another embodiment, the length of the acoustic waveguide is greater
than the (side-to-side) combined diameters of at least five bristle
tufts. In another dimension, the width of the acoustic waveguide,
often oriented generally transverse to the longitudinal axis of the
brush head, at its base, is generally greater than the diameter of
a bristle tuft and, in some embodiments, is generally greater than
the (side-to-side) combined diameters of at least two bristle
tufts. The structure and composition of many alternative acoustic
waveguides that are suitable for use in devices of the present
invention are described in detail in U.S. Patent Publication
2005/0091770 A1, which is incorporated herein by reference in its
entirety.
[0081] In general, acoustic waveguides are constructed from a
material that is somewhat "soft" and "rubbery," such as a silicone
rubber, or other types of biocompatible materials, such as other
types of rubbers, thermoplastic elastomers, and closed or open cell
foams having good ultrasound transmission properties and a pleasing
feel and surface texture. The hardness of the material is generally
less than about 80 Shore A, and more often is from approximately 10
to 65 Shore A. A hardness of approximately 40 Shore A or less may
be employed in order to achieve improved oral comfort. In some
embodiments, acoustic waveguides may have a composite structure in
which a relatively harder material is provided in proximity to the
ultrasound transducer and a relatively softer material is provided
in proximity to the distal face of the waveguide. The hardness of
the waveguide in proximity to the ultrasound transducer may be
greater than about 40 Shore A, for example, while the hardness of
the waveguide in proximity to the distal face may be less than
about 40 Shore A, for example. The waveguide material properties
may be isotropic or anisotropic.
[0082] In one embodiment, the height of the acoustic waveguide
exposed when the waveguide is mounted in the brush head is less
than the exposed height of at least one bristle tuft and, in
another embodiment, the height of the acoustic waveguide exposed
when the waveguide is mounted in the brush head is less than the
exposed height of each of the bristle tufts mounted in the brush
head. In another embodiment, the height of the exposed acoustic
waveguide portion is greater than at least one bristle tuft
provided in the brush head. In general, the exposed height of the
acoustic waveguide is greater than about 30% and less than about
90% of the exposed height of the bristle tufts. In yet another
embodiment, the exposed height of the acoustic waveguide is greater
than about 40% and less than about 80% of the exposed height of the
bristle tufts.
[0083] The distal face of the waveguide may be curved or flat. In
some embodiments, the cross-sectional area of the waveguide at its
distal face is at least five times greater than that of a bristle
tuft; in another embodiment, the cross-sectional area of the
waveguide at its distal face is at least ten times greater than
that of a bristle tuft; and in another embodiment, the
cross-sectional area of the waveguide at its distal face is at
least twenty times greater than that of a bristle tuft. The surface
of the acoustic waveguide is substantially smooth in many
embodiments; in alternative embodiments it may be textured in a
regular or irregular pattern.
[0084] Materials having suitable ultrasound transmission
properties, desired hardness and feel, and the like, are well known
in the art. Silicone rubber and other types of rubbers, silicone
materials such as castable/moldable RTV, liquid injection-molded
(LIM) silicone, thermoplastic elastomers, thermal plastic elastomer
(TPE) injection-molded processes, and closed or open cell foams may
all be used. Polymers have an advantage over other waveguide
materials, owing to their relatively low shear wave velocity.
However, because of their viscoelasticity, cross-linking of
polymeric materials may be necessary to avoid excessive acoustic
loss and provide equilibrium elastic stress, thus providing a more
stable waveguide composition.
[0085] The acoustic waveguide may optionally incorporate an
acoustic impedance matching device, such as a matching layer of
graphite, mineral, or metal-filled epoxy. Various dielectric
materials, such as silicon dioxide (SiO.sub.2), silicon nitride
(Si.sub.3N.sub.4), and many other polymers may also be used as or
incorporated in an acoustic impedance matching device. The matching
layer may be embedded or incorporated in the waveguide and
positioned to contact an exposed face of the ultrasound transducer.
In another embodiment, the functions of a matching layer and
waveguide may be combined by fabricating a stratified waveguide
component with varying acoustical impedance in the direction of
wave propagation. Thus, within certain embodiments, acoustic
waveguides of the present invention may comprise two or more layers
comprising different, acoustically transmissive materials. For
example, acoustic waveguides comprising three, four, and/or five
acoustically transmissive layers are contemplated for certain
applications. Multiple layers may be provided in a symmetrical
laminar structure; regular or irregular areas composed of different
materials may also be provided. Acoustic waveguides may further
comprise one or more inserted or embedded elements for shaping the
acoustic properties, promoting acoustic propagation and optimizing
sonic properties. A waveguide assembly may include, for example, a
graphite core portion or similar component that may be inserted
into an injection mold, and an elastomeric outer portion molded
around it using an insert molding process. Alternatively, a
multishot molding approach may be used to create a gradient of
materials with different acoustic and/or elastomeric
properties.
[0086] In preferred embodiments, acoustic waveguides of the present
invention are substantially free from unfilled or gas-filled voids.
To the extent that multiple materials or elements are used to form
a waveguide, those materials and elements generally contact each
other closely without allowing the formation of air gaps between
surfaces. In some embodiments, however, it may be desirable to form
one or more voids in the acoustic waveguide and substantially fill
the voids with a material that has desirable acoustic transmission
properties at the ultrasound operating parameters described
herein.
[0087] The acoustic waveguide may also be fabricated, or mounted in
the device head structure, to provide direct contact removal of
plaque. In such an embodiment, the distal face of the waveguide may
project beyond the ends of one or more bristle tuft(s). Auxiliary
elements may be incorporated on the surface of the waveguide
structure such as embedded bristle filaments, squeegee-type shapes,
molded or shaped protrusions similar to bristles, and the like, and
such auxiliary elements may be provided in an ordered or random
pattern. These features may, optionally, be exploited to ensure
that a specified separation distance is maintained between the
tooth surface and the bulk surface of the acoustic waveguide. This
optional feature may be incorporated in those applications wherein
it is desired to minimize direct transmission of ultrasound into
the tooth structure and/or if bubble activation occurs at a
distance from the end of the acoustic waveguide and a spacing
device is needed to maintain this distance.
[0088] According to yet further embodiments, the acoustic waveguide
may be provided with a coating, or an outer layer, that is
continuous or discontinuous, of a uniform or variable thickness,
and that comprises a material providing additional functionality.
In one embodiment, for example, the acoustic waveguide may be
fabricated from a material that is coated or impregnated with an
antimicrobial or antifungal agent that is biocompatible, such as a
metal ion such as silver or another antimicrobial agent. In another
embodiment, the acoustic waveguide may be coated or overlaid with a
substance that wears away with use to indicate:that the acoustic
waveguide and toothbrush head has reached the end of its useful
life. Suitable indicators may include, for example, substances that
produce a change in a property, such as color, flavor, texture,
and/or odor over periods of extended use. In yet another
embodiment, the waveguide may incorporate a thermally activated
color changing agent, such as a dye, that senses heat generated by
a functional piezoelectric transducer. This feature may be used,
for example, in combination with a charging function that allows
the ultrasonic generator to add heat to the acoustic waveguide and
thereby change its color during the time that the batteries are
also being charged.
[0089] The waveguide may be positioned generally aligned with the
longitudinal axis of the toothbrush head, as shown in FIG. 1. In
this configuration, the waveguide may be structured to
approximately match the contour of tooth surfaces throughout the
mouth. The efficacy of the cleaning operation may depend less on
user brushing technique/style with the waveguide in this
longitudinal orientation, which allows the user to brush as he/she
would without concern about waveguide location. Alternatively, the
longitudinal axis of the waveguide may be aligned generally
transverse to longitudinal axis of the toothbrush head. In this
orientation, the waveguide may be designed to drop into the
interproximal space and provide tactile feedback to the user such
that the user may index movement from one interproximal space to
the next, thus providing cleaning induced by the ultrasound
interproximally--where it is needed most beyond the bristles.
Alternatively, the waveguide may be positioned at the distal end of
the brush head without bristle tufts being located more distally,
such that it can be effectively used either on the facial or
lingual surfaces, as well as on the posterior surfaces of the molar
teeth.
[0090] The waveguide, in any of these orientations may act as a
standoff to prevent the user from using too much force when
applying the bristles against the teeth, thereby reducing the
incidence of gingival damage from excessive force during brushing.
It may also act as a scrubbing agent, thus cleansing the tooth
surface, and as such may contain a surface texture to enhance the
scrubbing action. It may also act as a gum massaging agent, thus
stimulating the gums (as often recommended by the dental
profession) to reduce swelling and to help contour the tissue. It
may additionally function to stimulate saliva flow, which is
particularly of interest to individuals with xerostomia.
[0091] The structure and composition of the waveguide may be
designed to increase the acoustic intensity delivered by
compressing the acoustic field, and/or to coherently focus energy
into the surrounding media beyond the tip of the waveguide. This
may be accomplished, for example, by shaping the end of the
acoustic waveguide to produce an acoustic lens effect that focuses
the waves from the waveguide into a higher intensity field beyond
the waveguide. This focusing effect may be achieved with one or
multiple waveguide materials combined together and shaped to create
a focused field. For instance, a low attenuation, higher sound
speed material may be used at the end of the waveguide to continue
propagating and focusing the wave front before the wave front
emerges into the higher attenuation fluid environment of the oral
cavity. As with the acoustic field compression described above, the
increased acoustic intensity achieved with the focusing effect
improves the device efficiency.
[0092] The Ultrasound Transducer
[0093] As described above, certain embodiments of the present
invention provide an oral hygiene device employing an ultrasound
transducer to generate ultrasonic energy in combination with an
acoustic waveguide to efficiently propagate ultrasonic energy into
the dental fluid. Microbubbles, present in the dental fluid as a
result of the movement of bristle tufts and/or formed by sonic
oscillation of bristle tufts and/or an acoustic waveguide, are
stimulated, through ultrasound energy-induced cavitation, to
produce "scrubbing bubbles" that are effective in loosening and
removing plaque from exposed tooth surfaces and at interproximal
regions at a distance from the toothbrush head. The ultrasonic
transducer disclosed herein causes these microbubbles to pulsate,
thereby generating local fluid motion around the individual bubbles
and producing microstreaming that, in combination with the
ultrasonic cavitation effects, achieves shear stresses that are
sufficient to disrupt plaque.
[0094] The ultrasound transducer is generally mounted in a device
head or brush head portion of an oral hygiene device of the present
invention in proximity to the location of ultrasound emission to
fluids in the oral cavity. An ultrasound transducer may,
alternatively, be placed within the toothbrush handle and
communicate with the device head to produce ultrasound emissions at
or near the device head. By utilizing an extended coupler
fabricated out of a low loss material such as titanium and/or steel
protruding into a device head portion, acoustic energy may be
coupled into a waveguide on the toothbrush head as described above.
Acoustic coupling between the handle and an acoustic waveguide in
the toothbrush head may, for example, be achieved using a solid or
liquid material that turns the acoustic energy. 90-degrees with
respect to the longitudinal axis of the handle and toothbrush
plastic. Such a coupling mechanism preferably employs a functional
interface that permits the brushing portion of the toothbrush to be
removed and replaced.
[0095] Ultrasound transducers that may be suitably employed in the
oral hygiene devices of the present invention are readily
available. See, e.g., ultrasound transducers disclosed in U.S. Pat.
Nos. 5,938,612 and 6,500,121, each of which is incorporated herein
by reference in its entirety. Ultrasound transducers suitable for
use in devices of the present invention generally operate either by
the piezoelectric or magnetostrictive effect. Magnetostrictive
transducers, for example, produce high intensity ultrasound energy
in the 20-40 kHz range. Alternatively, ultrasound may be produced
by applying the output of an electronic oscillator to a wafer of
piezoelectric material, such as lead zirconate titanate (PdZrTi or
PZT). Numerous piezoelectric PZT ceramic blends are known in the
art and may be used to fabricate ultrasonic transducers suitable
for use in devices of the present invention. Other piezoelectric
materials, such as piezopolymers, single or multilayer
polyvinylidene fluoride (PVDF), or crystalline piezoelectric
materials, such as lithium niobate (LiNbO.sub.3), quartz, and
barium titanites, may also be used.
[0096] In addition to piezoelectric materials, capacitive
micromachined ultrasonic transducer (cMUT) materials or
electrostatic polymer foams may also be used in ultrasound
transducers of the present invention. Many of these materials can
be used in a variety of oscillational modes, such as radial,
longitudinal, shear, etc., to generate the acoustic waves. In
addition, single-crystal piezoelectric materials may be used to
reduce the lead content of the piezoelectric element(s). Materials
such as Pb(Mg.sub.1/3Nb.sub.1/3)O.sub.3--PbTi0.sub.3 (PMN-PT),
K.sub.1/2Na.sub.1/2NbO.sub.3--LiTaO.sub.3--LiSbO.sub.3 (KNN-LT-LS)
and others may be used to reduce voltage/transmit level ratios by
as much as an order of magnitude, as described in Lead-free
piezoelectric ceramic in the K.sub.1/2Na.sub.1/2NbO.sub.3 solid
solution system, N. Marandian Hagh, E. Ashbahian, and A. Safari
presented at the UIA symposium March 2006.
[0097] Ultrasound transducer assemblies used in devices of the
present invention may comprise single piezoelectric elements that
have a generally block-like form and generally rectangular
configuration, as shown in FIG. 1. Such single element transducer
assemblies may be provided in a variety of other configurations,
such as cylindrical, elliptical, polygonal, annular, or the like
and may have configurations that are symmetrical or asymmetrical. A
single element ultrasound transducer may have a generally uniform
cross-sectional configuration and dimension along its thickness, or
it may taper or have another varied cross-sectional
configuration.
[0098] Piezoelectric ultrasound transducer materials generally
require a drive voltage that is proportional to the thickness of
the piezoelectric element. A single piezoelectric element having a
substantial thickness requires a high drive voltage. Thus, in
alternative embodiments, devices of the present invention
incorporate multi-layer ultrasound transducer elements, or
multi-element transducers, to reduce the drive voltage required for
a given acoustic output. Multiple piezoelectric element transducer
assemblies are preferably constructed with the piezoelectric
elements arranged mechanically in series and connected electrically
in parallel. This arrangement reduces the drive voltage required
for a given transducer output.
[0099] FIGS. 2A and 2B illustrate exemplary ultrasound transducer
assemblies suitable for use in oral hygiene devices of the present
invention. In the embodiment illustrated in FIG. 2A, an ultrasound
transducer assembly suitable for use in toothbrushes of the present
invention comprises two or more piezoelectric elements arranged in
a cooperating configuration, such as a stacked configuration, and
bonded to one another. Ultrasound transducer assembly 30 has an
overall generally rectangular or trapezoidal profile and comprises
at least two piezoelectric elements 32 and 34 having electrically
conductive material associated with one or more surfaces and one or
more electrical contact(s) 36 contacting a conductive surface of
each of the piezoelectric elements and in electrical contact with
an ultrasonic module drive circuit located in the brush head or in
the handle. Electrical contact(s) 36 in this embodiment are
provided as an electrically conductive framework structure that
tightly contacts the transducer assembly at contact points and
additionally provides mechanical integrity to the transducer
assembly structure. Contact points of an electrically conductive
framework structure with one or more piezoelectric element(s) are
preferably arranged at or near nodal points of the piezoelectric
elements where the amplitude of movement of the element(s) is
reduced. The conductive framework structure may be spring loaded to
provide pressure connections and/or soldered, welded, or conductive
epoxy to make a more robust electrical connection.
[0100] In the embodiment illustrated in FIG. 2A, the piezoelectric
elements are notched or grooved along at least a portion of their
perimeter, indicated at notched region(s) 33. Notched region(s) 33
are electrically conductive to provide contact points for
electrical contact(s) 36 at or near the location where multiple
piezoelectric elements are bonded to one another. Electrical
contact(s) 36 include prong-like contact extensions 38 for
providing electrical contact to electrodes in communication with
the ultrasound drive circuit. In the embodiment illustrated in FIG.
2A, contact extensions 38 extend from the transducer assembly
structure and may be flexible or spring-loaded to provide positive
contact with electrodes. Ultrasound transducer assembly 30 may also
incorporate an impedance matching element 37.
[0101] There are a variety of ways to make electrical connections
between the piezoelectric elements and the electrodes in contact
with the ultrasound drive circuitry. Electrically conductive
surfaces may be provided, for example, using various techniques
such as plating, sputtering or soldering conductive materials, or
applying conductive epoxy or another conductive material. FIG. 2B
illustrates an alternative embodiment of a multi-element ultrasound
transducer assembly 40 suitable for use in oral hygiene devices of
the present invention. In this assembly, piezoelectric elements 42
and 44 and impedance matching element 47 are bonded in a stacked
arrangement with an electrically conductive coating or layer
provided on at least a portion of the element surfaces.
Electrically conductive "pads" 45 are provided on external surfaces
of the transducer assembly for connection to electrodes
communicating with the ultrasound drive circuitry. This type of
electrical connection is commonly used, for example, in multilayer
PCBA interconnects. An exterior lead frame may also be employed for
ease of construction of transducer module and ease of assembly of
the module into the brush head.
[0102] In preferred embodiments, multiple piezoelectric elements
are stacked in series mechanically, and connected electrically in
parallel. Mechanical stacking of the elements in series provides
that the displacements associated with the individual piezoelectric
elements are additive. Electrically connecting the piezoelectric
elements in parallel provides that the capacitances associated with
the individual piezoelectric elements are also additive. This
arrangement provides a greater range of electronics driving
possibilities.
[0103] In addition to the transducer elements, one or more
impedance matching element(s) may be provided in association with
the ultrasound transducer assembly to improve the efficiency and/or
bandwidth when transmitting acoustic energy from the generally
high-impedance transducer elements into the lower impedance
acoustic waveguide materials. Generally, a matching material is
chosen having a thickness that supports a quarter wave of the
desired frequency and having acoustic impedance properties
intermediate those of the two impedances to be matched. Appropriate
impedance matching elements may comprise materials such as epoxy
and metal particulate composites, graphite, and a host of other
candidate materials known by and readily available to the skilled
artisan. The configuration and cross-sectional area of the
impedance matching element generally matches that of the distal
face of the ultrasound transducer and the impedance matching layer
is generally in close contact with an exposed, distal face of the
transducer.
[0104] Within alternative embodiments, ultrasound transducer
assemblies used in devices of the present invention may employ a
flextensional transducer that comprises an active piezoelectric
drive element and a mechanical shell structure. Such a shell or
"cymbal" structure is used as a mechanical transformer, which
transforms the high impedance, small extensional motion of the
piezoelectric drive element into a low impedance, large flexural
motion of the shell. Suitable flextensional transducers are known
in the art. Using a flextensional transducer may eliminate the need
for a matching layer.
[0105] Still further embodiments of devices of the present
invention employ a transducer assembly comprising a transducer
array. In one embodiment, a piezocomposite transducer array
comprises a plurality of posts. These posts may be fabricated, for
example, by dicing a block of piezocomposite material into many
smaller sub-elements or by injection molding an array of these
elements to shape. Depending upon the precise application
contemplated, the piezocomposite material and arrays fabricated
from such materials may offer improved properties for ultrasound
transduction compared to bulk transducers, due to reduced acoustic
impedance and a high coupling factor. Many types of piezocomposite
materials are known; exemplary materials are described in "The role
of piezocomposites in ultrasonic transducers," Wallace Arden Smith,
1989 IEEE Ultrasonics Symposium. The sensitivity of a composite
transducer is primarily in the normal direction, thus decoupling
transverse mechanical oscillational modes and the interference they
cause. The net result is greater acoustic output with lower drive
voltage.
[0106] The Ultrasound Module
[0107] The ultrasound transducer assembly may be incorporated in an
ultrasound module that additionally comprises a transducer
supporting structure, an optional matching layer(s), and an
acoustic waveguide. One exemplary ultrasound module 50
incorporating the transducer assembly shown in FIG. 2A is
illustrated in FIG. 3. In this ultrasound module, transducer
assembly 30 comprising piezoelectric elements 32 and 34 and
impedance matching element 37, with electrical contact structure 36
with electrical leads 38 is mechanically mounted in a substantially
rigid supporting structure 52 that provides mechanical support for
the transducer assembly and also serves to direct ultrasonic wave
propagation through the optional matching layer(s) 37 and acoustic
waveguide structure 55. Good mechanical connection and acoustical
properties may be accomplished, for example, by positioning the
supporting structure coupling features 53, 54 to coincide with
areas of minimal motion (nodal mounting) on the piezoelectric
ceramic, matching layer, and waveguide. Acoustic waveguide 55 is
then mounted or molded onto the transducer assembly and support
structure to provide close contact between the internal surfaces of
the waveguide and the external surfaces of the transducer assembly
and support structure.
[0108] The acoustic waveguide may be mounted to and contacting an
upper surface of the transducer assembly, as illustrated in FIG. 1
or, in alternative embodiments, acoustic waveguide 55 may be
mounted to and contacting the upper surface of the transducer
assembly and at least a portion, and preferably a substantial
portion, of the side walls of the transducer assembly and support
structure, as illustrated in FIG. 3. The waveguide structure 55
comprises a base structure 56 sized to (at least partially) cover
ultrasound transducer assembly 30 and having a configuration
generally matching that of the ultrasound transducer assembly. Base
structure 56 is generally mounted and anchored in a toothbrush head
with distal waveguide portion 58 projecting outwardly from the
brush head structure. Waveguide structure 55 is preferably provided
as a unitary structure having a generally block-like,
three-dimensional configuration and having multiple faces. In-the
embodiment illustrated in FIG. 3, the cross-sectional area of base
structure 56 is generally larger than the cross-sectional area of
distal waveguide portion 58 and opposing side walls 57 and end
walls 59 terminate distally in a distal waveguide face 60.
[0109] Distal waveguide face 60 may be curved in a generally convex
configuration, as illustrated in FIG. 3. In alternative
embodiments, distal waveguide face 60 may be generally flat, curved
in a generally concave configuration, or curved in a more complex
configuration. The intersections of one or more of the waveguide
faces may be rounded or chamfered, as shown, or they may form
angular corners. Any of the acoustic waveguide materials and
structures described herein or in U.S. Patent Publication
2005/0091770A1 may be used in connection with ultrasound modules
incorporated in devices of the present invention.
[0110] The acoustic waveguide module is generally mounted in the
head of an oral hygiene device, such as a toothbrush head, so that
the acoustic waveguide projects from the support structure of the
device head. Additional waveguide supporting structures may also be
provided as structural features of the transducer module or the
brush head structure. A waveguide support flange may be provided
extending from the brush head support base or bristle plate, for
example, in proximity to the perimeter of the waveguide structure
to provide a rigid structure supporting the base of the
waveguide.
[0111] Regardless of the precise configuration of the individual
elements that comprise the ultrasound module, the piezoelectric
element, matching layer and/or the acoustic waveguide are generally
designed to transmit, and optionally focus, the acoustic energy at
a desired location relative to the emanating surface(s) or to
disperse the acoustic energy in a specific pattern. The ultrasound
energy may, for example, radiate directly from a generating source
such as a piezoelectric ceramic element directly into the oral
cavity fluid without an intervening matching layer or waveguide.
Alternatively, an acoustic waveguide may be placed directly on the
piezoelectric ceramic. In still further alternative embodiments,
the entire ultrasonic module, including the acoustic waveguide, may
be fabricated from a piezoelectric polymer.
[0112] The Device Head Assembly
[0113] The device head assembly is preferably detachable from the
handle assembly and replaceable. A toothbrush head assembly
comprises a substantially rigid housing structure adapted to
receive and support an ultrasound module, one or more bristle
tufts, and components for transmitting power to the ultrasound
module and for coupling oscillatory motion to the acoustic
waveguide and bristle tufts. Electrical power may be provided to
the ultrasound transducer by hardwired electrical connections
established by positive contact of complementary electrical
contacts mounted in the handle and brush head upon attachment of
the brush head to the handle. Alternatively, a transformer assembly
may be implemented to provide coupling and power transfer between
the device head assembly and the handle.
[0114] One embodiment of a toothbrush head assembly is illustrated
in FIG. 4. The housing structure of toothbrush head assembly 80
comprises a base portion 82 for attachment to a mating attachment
region on the handle, a smaller cross-section stem portion 84 and a
brush head support structure 86 in which an ultrasound module 50
and/or toothbrush tufts are mounted. In this embodiment, power is
provided to the ultrasound module by means of a transformer having
a primary coil and core mounted in the handle (described below) and
a secondary transformer core 87 and transformer coil (and
associated bobbin) 88 mounted in the base portion 82 of head
assembly 80. Operation of the transformer to deliver power to the
toothbrush head without requiring hardwired connections is
described below.
[0115] Electrical connection between the secondary coil 88 mounted
in the toothbrush head assembly and the ultrasound transducer
assembly in the ultrasound module 50 is accomplished by means of
(one or more) conductive electrodes 89 that contact the transducer
assembly contact(s) and contacts provided at the secondary coil.
One or more conductive electrode(s) 89 may be provided as
conductive metal strips retained in channel(s) in the brush head
assembly and may be molded into the brush head structure.
Alternatively, flexible electrical connections (e.g., jumper-type
connections) may be used between the transducer assembly contacts
and the coil contacts. In an alternative embodiment, the electrical
contacts attach mechanically to the non-moving part of the brush
head housing so that the contact provides a spring force to return
the brush head to a center position or another desired
position.
[0116] The bristle tufts are mounted on a support plate 90 in
proximity to ultrasound module 50. The support plate may have a
variety of configurations, including rectangular, generally
circular, generally oval or elliptical. The support plate may also
function as an acoustic matching layer. This plate can be
ultrasonically welded to the brush neck to provide a seal around
the ultrasound module or may be integrally formed with support
structure 86. The brush neck assembly is attached to the housing
with coil and core.
[0117] The device head, including the bristle filaments, the
bristle filament and/or tuft spacing and orientation, the bristle
and/or tuft trim, the waveguide configuration and placement, and
the support structure of the device head are generally designed to
promote holding, trapping, and otherwise encumbering fluid. The
device head may also be designed to actively pass the ultrasound
through the bristle filaments and/or tufts. This may be
accomplished by mounting the ultrasound transducer assembly
immediately below one or more individual tuft(s) and/or filament(s)
and eliminating the coupling of the ultrasound through the
toothbrush base plastic, as done in prior art toothbrushes.
[0118] Device heads of the present invention, and particularly
toothbrush heads, typically incorporate assemblages of one or more
bristle tufts, each tuft comprising a bundle of one or more bristle
filaments. Many types of bristle filaments are available and may be
used in device heads of the present invention. In general, bristle
filaments, and tufts, may be characterized by the material of the
filaments, the diameter, cross-sectional configuration and exposed
length of each filament and tuft, the stiffness or flexibility of
filaments and tufts, and the like. The filaments within each tuft
may comprise the same material and have the same dimensional
properties, or more than one bristle type, shape or size may be
incorporated in a single bristle tuft. Likewise, multiple bristle
tufts forming the assemblage may comprise the same dimensional
and/or physical properties, or bristle tufts having different
dimensional properties, lengths, stiffnesses, and the like, may be
provided in various arrangements on the brush head. The tufts may
comprise bristle filaments of a particular shape and/or size to
facilitate both cleaning and user experience. Bristles of a
particular shape may be positioned and oriented to complement the
presence of a waveguide in the brush head. For example, stiffer
bristles and bristle tufts (having a generally greater filament
cross section and/or shorter bristle length) may be positioned to
facilitate orientation of the waveguide at a particular position
with respect to the teeth, and softer bristles (having a generally
smaller filament cross-section and/or longer bristle length) may be
positioned to facilitate waveguide penetration at interproximal
spaces.
[0119] Nylon bristle filaments are suitable for use in devices of
the present invention. In many embodiments, each bristle tuft
comprises from about 25 to 40 filaments; in further embodiments,
each bristle tuft comprises from about 28 to 30 filaments. The
diameter of each filament strand is generally from about
0.005-0.009 inch and, in embodiments preferred for some
applications, the diameter of each filament strand is from about
0.005-0.007 inch. Each tuft is approximately 0.03-0.12'' in
diameter; preferably about 0.05-0.08'' in diameter. Other types of
oral hygiene devices of the present invention may comprise more or
fewer tufts and tufts having different properties.
[0120] Individual bristle filaments may be solid or, alternatively,
the filaments may be hollow. Hollow bristle filaments may serve as
sources of gas that becomes entrapped and forms bubbles within the
dental fluid. Gas may be passively channeled through the bristles
or actively pumped through the bristles. In one embodiment, the
center diameter of hollow filaments may be designed to promote
formation of bubbles having a diameter that is resonant with the
frequency of the applied ultrasound, i.e. bubbles whose diameter is
roughly in the range from 13 to 65 .mu.m. Alternatively, hollow
bristle filaments may be filled with an acoustically transmissive
material that conducts ultrasound. The filler material may form a
permanent part of the filament, or it may be dispensable through
the filament. Dispensable filler material may contain a dentifrice
or other bubble promoting material. The ultrasound may be
conducted, for example, through a fluid absorbing material such as
a sponge that sufficiently absorbs fluid when wetted to efficiently
couple the ultrasound from the transducer to the tooth surface.
[0121] Bristle filaments used in oral hygiene devices generally
have a cylindrical cross-sectional configuration and are often
trimmed to present a blunt exposed end surface. Devices of the
present invention may employ bristle filaments having a
non-cylindrical configuration that have a longer dimension along
one axis than the other. Filaments having a non-circular
cross-sectional configuration, such as a diamond-shaped,
rectangular or oval cross-sectional configuration, may be trimmed
on an angle and oriented such that the longer axis is perpendicular
to the direction of bristle tip motion, thus acting as
"mini-paddles" to increase fluid flow in the desired direction.
Bristle filaments that are longer in one axis than the other may
also be oriented with the longer axis generally perpendicular to
the direction of bristle tip motion to provide a softer motion and
feel, or with the longer axis generally parallel to the direction
of bristle tip motion to provide a stiffer motion and feel.
[0122] Bristle filaments and tufts suitable for use with devices
disclosed herein may be trimmed to promote bristle contact with the
surfaces of the teeth, e.g., to promote bristle contact with both
the facial and lingual tooth surfaces as well as reaching into the
interproximal spaces. In devices incorporating an acoustic
waveguide, bristle filaments may also be trimmed to preferentially
orient the acoustic waveguide to a desired position along the
surface of the teeth and/or to orient the waveguide toward a
location that enhances interproximal penetration of the
ultrasound.
[0123] According to one embodiment, illustrated in FIG. 5, brush
head 86 incorporates a plurality of bristle tufts 93, including a
combination of longer and shorter bristle tufts. Typically, bristle
trim is dependent upon the orientation of the sonic bristle motion.
In one embodiment, a local peak 94 of longer bristle tufts is
positioned generally aligned with (as viewed from the side of the
brush head) a location on acoustic waveguide 95 where the
ultrasound output is maximum--generally at the longitudinal
midpoint of the waveguide. When the acoustic waveguide incorporates
a distal face having a peak or apex, a local peak 94 of longer
bristle tufts is generally aligned with the peak of the distal
waveguide face.
[0124] The tuft spacing and arrangement on brush head 86 is
generally designed to promote contact of bristle tufts with tooth
surfaces and to facilitate cleaning by means of the sonic
oscillation and ultrasound effects. Tuft spacing is generally
irregular, with tufts being arranged at a higher density in
particular areas of the brush head. Preferred tuft spacing on the
sides of the brush head in proximity to the side walls of acoustic
waveguide 95, for example, may be less dense than the preferred
tuft spacing at either end 96, 97 of the brush head in proximity to
the end walls of acoustic waveguide 95 (with the waveguide 95
oriented generally along a longitudinal axis of brush head 86). In
one embodiment, a relatively dense cluster of bristle tufts is
provided at the distal end of the brush head 96 and another
relatively dense cluster of bristle tufts is provided at the
proximal end of the brush head 97, with bristle tufts arranged on
either side of the longitudinal face of waveguide 95 in a less
dense arrangement. Bristle tufts at either end 96, 97 of the brush
head may also be stiffer than bristle tufts in a central portion of
the brush head. Additionally or alternatively, tuft spacing may be
arranged to create passages that allow fluid surrounding the brush
head to enter the region adjacent to the brush head. In many
embodiments, these passages are located near the corners of the
waveguide and/or at the ends of the long axis of the waveguide.
Passages 1 to 3 mm in width (space between adjacent tufts) are
preferred.
[0125] The bristle tufts may be positioned and oriented to
complement the action of a waveguide mounted on the brush head. In
one embodiment, tufts are spaced relatively densely in proximity to
the longitudinal sides of the waveguide to couple fluid to the
waveguide, allowing fluid passage towards the brush head tip. The
tufts, bristle filaments, waveguide and/or toothbrush head
components may additionally be oriented to promote generation and
transfer of bubbles having a desired size to be activated by the
frequency of the applied ultrasound, i.e. bubbles whose diameter is
roughly in the range from 13 to 65 micrometers. The desired
orientation may depend on the surface tension, viscosity, density,
and/or other property of the surrounding fluid and the wetability
of the filaments, waveguide and/or other brush head components,
i.e. fluids with a high surface tension and tufts and/or filaments
too close to each other may prevent bubbles from forming and/or
traveling towards the waveguide tip.
[0126] Bristle tufts may be oriented at an angle to perpendicular
to the surface of the support plate. In one embodiment, for
example, one or more bristle tuft(s) may be angled inwardly toward
the waveguide at an angle of from about 1-15.degree. to promote
coupling of the fluid to the waveguide and to enhance user feel and
comfort. In another embodiment, one or more tufts are oriented at
an angle away from the surface of the waveguide. In another
embodiment, a portion of the bristle tufts are oriented so that
they're aligned generally parallel to the surface of the waveguide.
The waveguide itself may be shaped to enhance this coupling,
containing ridges, fins, flutes and/or other structures that may
parallel the bristles. Devices of the present invention may
comprise bristle tufts provided in a variety of orientations.
[0127] The bristle tufts may be arranged and/or oriented to direct
the waveguide toward interproximal locations. A denser region of
tufts may be provided in certain areas, for example in proximity to
either end of the brush head, that tends to drop more naturally
into the interproximal space. A sparser region of tufts may be
provided in other areas, such as a central area of the brush head,
to conform to and bend around the facial and/or lingual aspects of
the teeth. Tuft positioning and orientation may also be used to
prevent the waveguide from deforming and/or contacting the
teeth.
[0128] Spaces between bristle tufts may be filled with another
material and/or object to complement the presence of a waveguide
within the brush head. This material may be open or closed cell
foam, elastomeric elements/projections, or other materials that
provide one or more of the following functions: effectively fill
space; enhance fluid and/or bubble properties; act as a reservoir
of fluid; or enhance user comfort and perception of cleaning.
[0129] The Handle Assembly and Components
[0130] An exemplary device handle housing and an exploded view of
components typically mounted mounted in the handle housing is
illustrated in FIG. 6. Handle 100 is generally rigid and has a
generally cylindrical profile, with an internal cavity and
associated internal mechanical structures for retaining the
components shown. Handle 100 may also incorporate one or more user
interface(s), such as on/off button 102, battery charge level
indicator 104 and brush head replacement indicator 106.
[0131] A charge coil 110 and charge core 112 are generally provided
in the base of the handle assembly for inductive charging from a
separate charging station accessing a power supply (not shown).
Charge coil 110 is electrically connected to one or more
rechargeable batteries 114 that supply the power requirements for
the device. Suitable rechargeable batteries include, for example,
Nickel Cadmium (NiCad) batteries and NiMH (Nickel metal hydride)
batteries. In the embodiment shown in FIG. 6, batteries 114 are
mounted in a mechanical carrier structure 116 that provides
mechanical support for the batteries and also supports a controller
or circuit board assembly 118. The batteries are preferably located
near the center axis of the handle assembly to provide a desirable
weight balance to the handle and allow the housing to taper to a
smaller size at the top and bottom. The housing may comprise an
integral cylindrical component or it may be formed in one or more
pieces, such as an upper and lower part, that are joined during
handle assembly. This housing design allows the shape to be large
in the center and taper down at the top and bottom. Different
designs of the lower section may be used for different versions of
the handle assembly.
[0132] In the embodiment illustrated in FIG. 6, a single circuit
board is provided and all control and monitoring functions, as well
as the ultrasound drive circuitry, is provided on the single
circuit board. It will be appreciated that these functionalities
may be provided on separate circuit boards located in separate
locations within the handle, and that additional circuit boards
providing additional functionality may also be provided.
[0133] It will be appreciated by those having skill in the art that
ultrasound transducer drive circuits may take many forms and that
various drive circuits are suitable for use in devices of the
present invention. The ultrasound drive signal is typically sent
from the controller to a signal conditioning and pre-amp circuit
and from there is conducted to a signal amplifier. There is
typically a matching network for the ultrasound transducer, which
may range from quite simple to quite complex, depending upon the
transducer to be matched. The purpose of the matching network is to
achieve a resonance at or near that of the resonance transducer
drive circuit, producing generally efficient, generally high power
ultrasound acoustic output. Within certain embodiments, described
in detail below, a gapped ferrite core transformer forms part of
the matching network and is employed to drive the piezoelectric
ultrasound transducer. "Solid-state" switches including, for
example, transistors, may be employed in the ultrasound transducer
drive circuitry and controlled by a microcontroller that connects
the battery voltage to the primary(s) of a transformer located
within the handle. Electrically efficient circuit designs
frequently utilize reactive components (such as, for example,
inductors and/or capacitors) in a resonant or tank circuit
topology.
[0134] Exemplary ultrasound power supply (USPS) circuits may
comprise one or more of the following elements: a resonant tank;
resonant power; a resonant converter; a parallel resonant
converter; a series resonant converter, a DC-to-AC inverter; a
square wave converter; a modified sine-wave converter; and a
flyback transformer. Within still further embodiments of the
present invention, the USPS may employ a high voltage supply and
electrical connector as a substitute for or in addition to the
transformer architecture described herein. The ultrasound power
supply circuit may also incorporate a high capacity capacitor to
achieve an increase in battery life. Pre-charging of this capacitor
while in the charger base may reduce the initial battery reliance
by using the line power to supply its initial charge.
[0135] Drive motor 120 is electrically connected to the controller
and incorporates a drive shaft 122 for delivering motor output,
e.g. oscillation, to the device head to oscillate the toothbrush
head, the acoustic waveguide and bristle tips at sonic frequencies.
Drive shaft 122 typically projects from the handle assembly and is
mechanically coupled to a structure in the brush head upon
attachment of the brush head to the handle.
[0136] Many different types of drive motors may be used to produce
oscillation at sonic frequencies in devices of the present
invention. In one embodiment, a stepper motor is used to provide
oscillating rotary motion of the motor drive shaft that is coupled
to the toothbrush head. Stepper motors are generally controllable
to provide precise manipulation of the amplitude of oscillation and
toothbrush head position and may thus be suitable for use in
devices in which the oscillation is varied during an operating
cycle. Limited angle torque (LAT) motors may also be used as drive
motors in the present invention to provide oscillating motion at an
included angle of less than about 12.degree., preferably less than
about 10.degree., and in yet additional embodiments at an included
angle of between about 3.degree. and 7.degree..
[0137] Wobble weight motors, conventional rotary motors, and
piezoelectric motors or actuators may alternatively be used as
drive motors for producing oscillations at sonic frequencies in
devices of the present invention. In one embodiment, the motor
incorporates a centering or return spring in the handle, or the
portion of the motor shaft positioned in the device head assembly
during operation incorporates a centering or return spring. The
motor is preferably of a compact and lightweight design that fits
conveniently in a generally cylindrical device handle. Preferred
motor dimensions are typically between about 0.60 inch and about
1.0 inch in diameter and between about 0.5 inch and about 1.0 inch
long. Pancake style motors may be employed.
[0138] Devices of the present invention may use conventional
electrical or magnetic contacts to transfer power to components,
such as an ultrasound transducer, that operate in the device head.
In preferred embodiments, however, devices of the present invention
employ a transformer to inductively couple and transfer power from
the ultrasound drive circuitry and power source in the handle to
the transducer assembly in the device head. The transformer
assembly may additionally provide a step-up of voltage from the
ultrasound power supply circuitry to the ultrasound transducer and
desirably provides a physical separation of the transformer primary
and secondary side components when the head assembly is detached
from the handle. The transformer assembly also desirably provides
electrical isolation between the power supply circuit in the handle
and the ultrasound transducer circuit in the toothbrush head
assembly.
[0139] Suitable transformers typically employ a primary and
secondary split between the handle and toothbrush head assembly. In
one embodiment, the ultrasound power supply circuit and primary
side coil and core of the transformer are mounted in the device
handle, and electrical contacts extend from the transformer primary
coil into the main handle compartment for connection to the
ultrasound power supply. As illustrated in FIG. 6, the transformer
primary coil 128 and core 126 components are generally provided in
a sealed enclosure in the device handle that is isolated from the
other components mounted in the handle by means of sealed spacer
124 and sealed plug 130. The ultrasound transducer and secondary
side coil 132 and core 134 of the transformer are mounted in the
device head assembly 80 and sealed by cover 136, as illustrated in
FIG. 7. The transformer assembly, in this embodiment, delivers the
impedance-matched voltage required by the piezoelectric transducer
to produce the desired ultrasound output intensity. The secondary
coil and core, mounted in the device head, may be mounted in a
stationary fashion to the housing, for example, while other
portions of the device head, such as a brush head stem, remain free
to oscillate. Alternatively, the secondary coil and core may be
mounted in the device head for movement with other portions of the
device head to achieve a moment of inertia for the toothbrush
head.
[0140] The transformer coil assemblies are typically wound on a
bobbin in a circular or elliptical path and sealed. Annular cores
having an aperture in the center that permits the motor drive shaft
to pass through the transformer assembly and couple to the
toothbrush head are preferred for many applications. A small air
gap (typically from about 0.010 to 0.150 inch, more typically less
than 0.010 inch and, in some embodiments, between 0.040 and 0.080
inch) between the cores mounted in the handle and head is desirably
maintained during operating cycles for efficient operation of the
transformer. Within certain embodiments, the air gap between the
cores may be achieved by using sealed coil assemblies and having
the cores mounted outside these sealed assemblies. In an
alternative embodiment, a ferroelectric fluid or ferro-filled
elastomer may be used as a filler composition between the cores to
improve transformer efficiency.
[0141] Alternative transformer designs are also contemplated. These
include, without limitation, the use of torrid wound core or
lamination stacks to form the core. Regardless of the precise
transformer assembly adopted, it may be desirable to have the
primary and secondary portions of the transformer split between the
handle and toothbrush head assembly.
[0142] Within certain embodiments of the present invention, the
transformer assembly used for power coupling between the device
head assembly and the handle may provide power to other devices
requiring power in the device head, and may further provide for the
exchange of electrical information between the device head and the
handle. This may, for example, be achieved by adding a coil, or an
additional coil winding(s), to the primary side of the transformer
assembly, or by using a center taped coil, that inductively couples
signals to the coil (or coils) in the device head (i.e. the
secondary side of the transformer). Thus, a signal may be sent from
the handle to the toothbrush head assembly and a corresponding
response provided by the toothbrush head assembly components.
Alternatively, signals between the primary and secondary sides of
the transformer may be coupled to induce a voltage on top of the
ultrasonic drive waveform. This may, for example, provide an
amplitude modulation signal riding on top of the ultrasound
waveform. Alternatively, the signal frequency may be modulated to
provide frequency modulation or a combination of frequency
modulation and amplitude modulation.
[0143] This additional transformer component may, optionally, be
employed to provide a feedback signal for monitoring transducer
performance. Such feedback may, for example, control a voltage
controlled oscillator (VCO) and/or a phase locked loop (PLL) for a
self-tuning oscillator frequency to the transducer, to monitor
operation of the ultrasound transducer at the initiation of, or
during, an operating cycle or subcycle.
[0144] Devices of the present invention comprising transformers
with one or more extra coil(s), or additional coil winding(s), may
incorporate additional device functionality. In one embodiment, for
example, the additional coil, or coil winding(s), is primarily used
for interaction with the ultrasound transducer power supply
circuit. In another embodiment, an additional coil, or coil
winding(s), is employed to monitor the performance of the
ultrasound transducer. In another embodiment, an additional coil,
or coil winding(s), actuates the ultrasound transducer assembly and
monitors the performance of the transducer. In yet another
embodiment, an additional coil, or coil winding(s), is used for
testing and/or calibration of components mounted in the handle
and/or device head assembly. In still another embodiment, an
additional coil and/or coil winding(s) is used to sense the
environment in which the device is used, such as properties in a
user's mouth and/or on a user's teeth, and communicate that
information to a controller. In another embodiment, an additional
coil and/or winding(s) is used to determine and/or signal the
acceptable or unacceptable performance of the ultrasound transducer
and/or the end of the useful life of a device head. In yet another
embodiment, an extra coil and/or winding(s) may be used to monitor
the transducer for a unique signature, thereby identifying a
toothbrush head assembly.
[0145] Device Operating and Control Features.
[0146] Devices of the present invention generally incorporate Power
On and Power Off control mechanism(s) that are operable by the
user. In one embodiment, a mechanical actuator is provided that,
upon application of pressure, activates the device to initiate an
operating cycle. Initiation of the operating cycle generally
involves activation of the motor drive and/or ultrasound transducer
and may incorporate a delay feature that delays initiation of the
operating cycle for a predetermined period. The same mechanical
actuator may be used to inactivate the device and terminate an
operating cycle, or the device may be programmed to automatically
shut off after termination of an operating cycle or following a
predetermined delay period after termination of an operating cycle.
An indication that the device has been activated may be provided by
illuminating a Power On button, for example, using LEDs. In
addition to Power On and/or Power Off controls, devices of the
present invention may have one or more predetermined programmed
operating cycles that are selectable by a user. Alternatively,
devices of the present invention may be programmable by the user to
provide one or more operating cycles selectable by one or more
users. Devices of the present invention may additionally
incorporate detection features, for example, that allow initiation
of an operating cycle only when a device head is appropriately
coupled to a device handle, or only when a device head is
determined to be operational. In the event a non-functional device
head is mounted or a device head is mounted improperly, a user
interface may signal the user to make an appropriate
correction.
[0147] Additional user interfaces may be provided. The level of the
battery charge may be enunciated to a user, for example, by
illuminating a display visible to the user using LEDs. Variations
in the level of charge may be communicated and visualized, for
example, by illuminating different quantities or patterns of
signals. A user interface may also be provided to indicate that the
device head is functioning properly, or that the device head is not
functioning. Any type of user interface may be implemented
including illumination of an indicator using one or more LED
display(s), one or more LCD display(s), an audible tone(s), a pause
or change in the operation of the drive motor, or the like. Such
indicators may be incorporated variously and in different positions
on the device, such as on the handle, on an accessory charging
device, on a device head, or on an accessory control device.
[0148] A device head, and a device handle, may incorporate an
identifier that distinguishes a head or handle from others. Such an
identifier may take the form of a color or pattern coded band,
light, or other identifying indicia, or may be provided as an
electronic identifier detectable upon mounting of the device head
in the handle, or by means of an accessory device. Multiple device
heads and/or multiple types of device heads may be used with a
common handle and may be distinguishable by the user and/or by the
controller upon mounting of the device head on the handle. In one
embodiment, a device head identifier may be associated with one or
more operating protocols such that upon initiation of an operating
cycle, the device identifies the device head and runs an operating
protocol associated with that device head. Alternatively, if any
device head is associated with more than one operating protocol,
the device may prompt a user to select a protocol upon or prior to
initiation of an operating cycle. The device may similarly detect
different types of device heads and initiate appropriate operating
cycles depending on the detection and identification of the
operating head.
[0149] The device controller generally provides a timing function
that separates a device operating cycle into a plurality of
operating subcycles. A plurality of pre-programmed operating
periods may be provided, for example, with an audible tone and/or a
momentary pause or change in operating conditions producing a
user-perceptible division of subcycles. In one embodiment, for
example, four generally equal operating subcycles may be provided
in a toothbrush of the present invention, providing convenient
operation in the four brushing quadrants in the oral cavity. In
another embodiment, four generally equal operating subcycles may be
provided, followed by a fifth subcycle that is equal or unequal in
time to the four previous subcycles. The duration of the operating
cycle, for toothbrush applications, may be from about 1 min to 3
min, with operating subcycles generally having a duration of from
about 10 sec-45 sec. It will be recognized that any number and
combination of subcycles, periods and/or routines may be provided
and may be preprogrammed in the device or may be programmable by
the user. If multiple preprogrammed subcycle routines are provided,
a user interface is provided to allow user selection.
[0150] In some device embodiments, the sonic and/or ultrasonic
operating parameters are programmed and controlled to provide a
substantially constant level of sonic and/or ultrasonic output
during an operating cycle and/or during operating subcycles. In
alternative embodiments, the sonic and/or ultrasonic operating
parameters are programmed and controlled to provide a variable
level of output or to vary certain sonic and/or ultrasonic
operating parameters during an operating cycle, or during one or
more operating subcycles.
[0151] For some oral hygiene applications, the oscillatory motion
(bristle tip velocity, amplitude and/or frequency) is desirably
greater during some periods of an operating cycle and/or an
operating subcycle than at others. In some embodiments, therefore,
the motor drive output producing oscillatory motion is variable
over an operating cycle of the device. The motor drive and
oscillatory output may, for example, operate synchronously with the
ultrasound transducer and be controlled to provide higher output
(greater bristle tip velocity and/or amplitude) or lower output
(lesser bristle tip velocity and/or amplitude) before, during, or
after the initiation or termination of an ultrasound burst. In
general, when oscillatory motion is employed in combination with an
ultrasound transducer and acoustic waveguide, it is preferable to
vary the sonic output over an operating cycle or subcycle such that
the motor drive output and oscillation is reduced during periods of
ultrasound bursts and the motor drive output and oscillation is
increased during periods when the ultrasound is not operating.
[0152] In one embodiment, the motor drive is controlled, for
example, to reduce oscillation at sonic frequencies (bristle tip
amplitude and/or velocity) during ultrasound transducer operation
and to increase oscillation at sonic frequencies (bristle tip
amplitude and/or velocity) when the ultrasound transducer is not
operating. Thus, within certain embodiments, the timing and output
of the ultrasound transducer and drive motor is synchronized. The
motor drive output may be reduced by controlling one or more of the
following parameters: the frequency of the motor drive output; the
duty cycle of the motor drive output; the amplitude of the motor
drive output; and the current supplied to the drive motor.
[0153] In another embodiment, devices of the present invention
employing a drive motor are capable of determining and controlling
the desired motor drive operating frequency by monitoring the
resonant operating conditions of the motor. The controller may, for
example, monitor both the current drawn by the drive motor and the
drive frequency of the motor on a continuous or intermittent basis.
The resonant frequency of the motor is detectable by monitoring the
current, since the current required is lower when the motor
operates at its resonant frequency. The controller may then set the
drive motor operating frequency to a desired offset from the
determined resonant frequency, or vary the drive motor operating
frequency to achieve a desired resonant frequency under different
operating conditions.
[0154] Alternatively, the motor operation may be monitored on a
continuous or intermittent basis and the electromotive force (EMF)
detected from the motor may be used to determine the natural
resonant frequency of the motor and/or its driven system, including
the brush head. Since the resonant frequency is different with and
without the brush head installed, this system may be used to
determine if a brush head is attached to the handle. Multiple brush
heads having different inertia properties may also be detected and
identified using this system, thereby identifying different users
and, optionally, matching different protocols or programmed
features to the different users and/or brush heads. This system may
also be used in conjunction with a brush head replacement feature,
to detect and identify replacement brush heads and thereby trigger
a reset operation.
[0155] An accessory device may also be used, in conjunction with
the controller monitoring the drive motor frequency, to monitor the
angular amplitude for each frequency. The resonant frequency of the
motor is detectable by monitoring the angular amplitude for each
frequency. The angular amplitude measurements may be communicated
to the controller, which then sets the drive motor operating
frequency based on the determined resonant frequency, as above.
[0156] In some device embodiments, the ultrasound transducer is
operated only as needed in certain regions of the oral cavity. It
may be desirable, for example, to pulse the ultrasound only into
interproximal locations and not on the lingual or facial surfaces
of teeth, or vice versa. Thus, an inventive toothbrush is designed
such that it can sense the interproximal location and pulse the
ultrasound only when the waveguide is optimally located relative to
that interproximal location. Various technologies may be employed
to achieve interproximal localization. For example, a means of
detection may be mechanical, e.g., by employing a spring motion to
sense the three-dimensional contours of the tooth, or electrical,
e.g., by detecting variances in the tooth's electrical
conductivity. Preferentially the detection methodology may utilize
the ultrasonic transducer as a means of sensing a force applied
from the waveguide against the tooth surface. Such a force, whether
intermittent or constant, may be sensed by either an electrical
signal output of the transducer, a change in the acoustic impedance
as viewed by the transducer/electronic circuitry, or any other
similar technology available in the art. Alternatively, the
ultrasound may be shut-off when the waveguide is in direct contact
with the teeth and turned on when a fluid interface forms between
the tooth and waveguide tip.
[0157] According to yet further embodiments, the ultrasound drive
frequency is modulated, continuously or intermittently, over an
ultrasound burst and/or over multiple ultrasound bursts within an
operating cycle or subcycle. Continuous frequency sweeping of the
ultrasound drive frequency may be provided, for example, within a
predetermined frequency range and at one or more predetermined
modulating frequencies. Thus, if the center frequency is Fc, the
frequency may be swept from Fc-.DELTA.F to Fc+.DELTA.F. The rate at
which the frequency is swept, Fm, is selected for desired optimum
operation under operating conditions and may be variable within an
operating cycle. The transducer may be operated at one or more
harmonics of the resonant frequency.
[0158] Operation of an ultrasound transducer at or near its
resonant frequency is preferred. Operation of the transducer using
an appropriate sweep mode ensures that, under any given brushing
conditions, the ultrasound module is driven at its resonant
frequency for a portion of the operating time. Operation of the
transducer using an appropriate sweep mode may also be used to
drive ultrasound elements having varying resonant frequencies,
since the sweeping action ensures the transducer will be at its
resonant frequency for at least a portion of its operating cycle.
This results in peak acoustic output, which typically occurs at
resonance.
[0159] Modulation of the transducer drive frequency using a sweep
mode, as described above, may also be implemented to adjust and
improve operation of the ultrasound transducer in response to
sensed environmental conditions. In one embodiment, for example,
real time ultrasound drive frequency optimization is achieved by
monitoring one or more characteristic(s) of the ultrasound drive
circuit, such as drive current, and adjusting or tuning the drive
frequency based on a comparison of the sensed current draw and a
standard or desired current draw pattern or adjusted to compensate
for changes in transducer parameters (e.g. transducer operating
temperatures). In another embodiment, ultrasound drive frequency is
swept while monitoring one or more characteristic(s) of the
ultrasound drive circuit, such as drive current at the initiation
of an operating cycle or following a reset command, or the
like.
[0160] Within certain embodiments, devices of the present invention
employ a feedback function that allows monitoring of the ultrasound
transducer operation and performance at the initiation of, or
during, an operating cycle or subcycle by comparison, for example,
to a standard or standard ranges of transducer operating
parameters. This monitoring function may be used to confirm, for
example, that the device head is correctly installed and/or the
ultrasound transducer element is operational. When the monitoring
function indicates that the device head is not properly
functioning, the controller may fail to initiate an operating
cycle. Alternatively, a pacer function may be activated to prompt
the user to reposition the device head. Such a pacer function may
be announced to a user, for example, by means of an illuminated
user interface incorporating one or more LED or LCD, by the
generation of a sound, such as one or more beeps, by using a
buzzer, or by pausing or changing the operation of the motor
drive.
[0161] Still further embodiments of the present invention include
monitoring functions that indicate the useful life and/or
functionality of the ultrasound transducer element and/or device
head. Exemplary feedback indicators may, for example, indicate one
or more of the following: when an ultrasound system and/or device
head is missing; when an ultrasound system and/or device head is
present but inoperative or operating erratically; when an
ultrasound system is operating but not in a desired mode of
operation (e.g., out of frequency and/or an undesired mode of
oscillation); and when an ultrasound system is operating normally.
In one embodiment, for example, the operation of the ultrasound
transducer and/or device head is monitored upon initiation of an
operating cycle, and/or operable electrical connection to the
ultrasound transducer is confirmed, to determine whether the device
head is mounted properly.
[0162] In another embodiment, operation of the ultrasound
transducer is monitored continuously or at intervals during the
operating cycle or subcycle, and the sensed operating parameters
are compared to one or more predetermined standards or ranges of
standards to determine whether the ultrasound transducer and/or
device head is operating within acceptable ranges. A user interface
indicating normal operation may be activated when the device head
and/or ultrasound transducer is operating within acceptable ranges.
Upon detection of unacceptable operating during or at initiation of
an operating cycle, a user interface may be activated to advise the
user of the malfunction or advise the user to replace the device
head.
[0163] Detection of unacceptable transducer or device head function
may be monitored, for example, by monitoring the current drawn by
the ultrasound power supply circuit and ultrasound transducer. An
ultrasound transducer or device head that is not functioning
properly exhibits a different current signature than one that is
functioning properly. The current signature of a functioning
transducer in "normal" use, for example, is characterized by sudden
variations in the current. The current signature of a
non-functioning device head (in which the waveguide has
delaminated, for example, or electrical contact is not being made
with the transducer) is characterized by constant current that
doesn't exhibit substantial variation. In one control scheme,
therefore, a running current "delta" (min-max) is acquired during
each operating cycle or subcycle. If the min-max delta detected
over the operating cycle or subcycle is large, the brush head is
functioning properly. If the min-max delta detected over the
operating cycle or subcycle is small, one or more failures have
occurred and an appropriate user interface is activated.
[0164] Within yet further embodiments, the controller may be
programmed to count the number of device operating cycles. The
number of operating cycles for a particular device head may be
displayed in a user interface. The controller may also be
programmed to count the number of operating cycles and to monitor
the functionality of the device head simultaneously. Following a
predetermined number of uses (typically 2 uses per day for 6 months
or 180 uses), the microprocessor is set to monitor the electrical
current flowing through a current sense element located in the
handle and detect unacceptable device head operation, as described
above. In yet another embodiment, the controller may be programmed
to monitor the function of the device head at predetermined
intervals, e.g., following a predetermined number of device head
operations or activations. For example, the controller may be
programmed to monitor twenty consecutive device head uses and make
an assessment of how many different device heads are being used
with that handle. Depending on the pattern of uses and proportion
of "good" to "bad" responses during an operating cycle or subcycle,
or the proportion of "good" to "bad" operating cycles or subcycles,
the microprocessor may be programmed to activate a user
interface.
[0165] Certain reset functions may be programmed in the controller
and initiated by a user through a user interface. Following
replacement of a defective device head, for example, a user may
provide input to a user interface on the device or an accessory
unit and effectively reset the controller and its device head
detection, counting and/or monitoring functions. The reset function
may instruct the controller to initiate a new monitoring and
control cycle that may be the same as or different from a previous
monitoring and control cycle. It will be appreciated that many
different monitoring and control algorithms may be programmed into
the controller.
[0166] Alternatively, separate test protocols may be implemented to
monitor the performance of a device assembly. In one such test
protocol, the device head and ultrasound transducer may be immersed
in a vessel containing an embedded transducer sense element. The
vessel may, for example, be filled with water and the ultrasound
signal transmitted by the toothbrush head detected by the sense
element and the acoustic output measured by a system within the
vessel. The strength of the signal may be converted to a signal to
the user that indicates the performance of the ultrasound element.
Within various embodiments of the present invention, the test
vessel may be provided as a stand-alone unit or may be incorporated
into an accessory device charger or control unit.
[0167] Within other embodiments of the present invention,
toothbrushes may employ one or more mechanisms, including
bactericidal ultrasound-based mechanisms, to achieve the
antimicrobial treatment of the toothbrush head thereby reducing the
level of live bacteria remaining within the toothbrush
elements.
[0168] Adaptive Feedback Mechanisms
[0169] Within certain embodiments, toothbrushes of the present
invention comprise electronic circuitry that permits both the
transmission and detection of ultrasonic signals for real-time
modulation of ultrasound characteristics to achieve enhanced bubble
oscillation and, hence, dental plaque removal. Transmission
characteristics are monitored electronically and the resulting
feedback is fed into a detection circuit and/or microprocessor. The
individual characteristics of the ultrasound protocol (such as, for
example, PRF, CPS, duty cycle, Mechanical Index factors, etc.)
and/or sonic motor drive parameters (such as, for example, drive
voltage, frequency, duty cycle, pulse width, etc.) can be modified
to permit improved ultrasonic output for improved plaque removal.
Such "smart ultrasonic" power toothbrushes optimize bubble size and
density to produce superior plaque removal as compared to a fixed
drive ultrasonic transducer and sonic motor.
[0170] Ultrasound does not travel efficiently through air. It does,
however, transmit quite efficiently in aqueous environments, so
long as the ultrasonic transducer is designed to emit in an aqueous
(water) medium. As discussed above in reference to microbubbles,
acoustic streaming, and acoustic microstreaming, when bubbles are
encountered in a relatively small bubble population (i.e. 1% to
20%) and when their size matches the ultrasound transducer drive
frequency, the bubbles are excited to vibrate and this increases
the cleaning effect compared to the cleaning provided by a
convention, sonic motor driven toothbrush. When ultrasound is used
in combination with sonic frequencies, the ultrasound waves become
attenuated when the bubble size and population is too large. This
phenomenon is characterized by a large void fraction (e.g., more
than 30% void fraction or trapped air bubbles). When the sonic
parameters are held constant, the void fraction primarily depends
upon fluid properties. Furthermore, void fraction is significantly
higher in a dentifrice medium than in water. Thus, the capacity of
"smart" ultrasonic power toothbrushes of the present invention to
control bubble characteristics and/or to control operation of the
device to take advantage of the operating (fluid) environment is of
significant benefit to plaque removal efficacy. Several different
protocols are described below and may be used to detect and control
bubble characteristics and modulate operating parameters during
operation of a device of the present invention.
[0171] Process A--A transmit transducer emits ultrasound into the
bubbly fluid and a receiver transducer detects ultrasound
scattering and variation. Big bubbles or dense populations of
bubbles are more reflective and tend to scatter the ultrasound. The
receiver transducer provides input to a detection circuit and/or
microprocessor based algorithm, which is capable of detecting and
defining the fluid acoustic properties of the operating environment
based on the detected ultrasound scattering and variation. Based on
the determined fluid properties, the sonic drive motor and/or the
ultrasound protocol is adjusted automatically and optimized for the
fluid properties detected in the operating environment.
[0172] Process B--Following the emission of ultrasound transmit
signals, ultrasound reflections are detected by the same
transducer, or by another separate (receive) transducer. The
received reflection signals are input to the microprocessor, which
detects and defines the acoustic properties of the fluid operating
environment based on the ultrasound reflections. The controller may
then adjust either the sonic motor frequency or duty cycle, or the
ultrasound operating parameters, to "tune" the operation of the
device to the fluid operating environment.
[0173] It should be noted that there are several conditions that
provide distinct differences in operation and performance of the
waveguide. When the waveguide is fully immersed in water,
ultrasound is emitted in a low impedance environment and easily
exits the waveguide. When the operating environment has a higher
impedance as a result, for example, of the presence of air or large
population(s) of bubbles, the ultrasound is emitted in a higher
impedance environment and exits the waveguide differently. This
effect can be detected and input to the microprocessor for control
of sonic motor or ultrasound protocol(s).
[0174] Process C--The same transducer may be used for both
ultrasound transmit and ultrasound Receive functions. Echo
ultrasound data is collected between Pulse Repetition Frequency
(PRF) bursts and analyzed to detect changes in reflection due to
bubble population and size. Motor speed and/or ultrasound burst
length and/or PRF may be adjusted during use based on features
extracted from this reflected signal.
[0175] Process D--Forward and reverse power, impedance or other
characteristics of variance delivered to the transducer are
monitored. The bubbly fluid characteristics change the coupling of
ultrasound into the fluid. Increasing reverse power indicates
decreasing coupling under these conditions, and the motor speed
and/or ultrasound burst length and/or PRF maybe adjusted to
decrease the reverse power. Sense turns on the matching transformer
can reflect magnetic flux variations which represent variations in
the transducer load, which can then be decoded through a
microprocessor algorithm to assess the transducer life condition.
Various enunciators (sound, light, brush motion, oscillation,
musical note, etc.) can then be engaged to advise an operator to
replace the brush head or transducer element.
[0176] All of the processes disclosed herein above comprise the
step of monitoring conditions within the toothbrush, circuit,
and/or user's mouth. Monitoring signals may be routed to a
comparative or computing device, such as a microprocessor,
differential amplifier, and/or A-D converter, to detect electrical
changes and convert them into control modifications affecting: (1)
the ultrasonic protocol (i.e. voltage, frequency, burst conditions,
etc.) which defines the transducer output and (2) the sonic
protocol (i.e. motor drive voltage, current, duty cycle, pulse
width, etc.) that defines the motor characteristics controlling the
sonic brushing characteristics (i.e. bristle tip velocity,
acceleration, and/or cavitation within the dental slurry).
[0177] Fluid characteristics may also be controlled by modulating
the sonic and/or ultrasonic operating protocol(s) (i.e. viscosity,
bubble size, bubble density, color, etc.). The amount and location
of fluid in the operating environment may be modified by
introducing fluid or withdrawing fluid from the operating
environment. Fluid present in the operating environment, e.g. the
oral cavity, may be withdrawn to a reservoir when it is in excess,
and additional fluid may be introduced when the fluid quantity is
insufficient or to modify the fluid properties, thereby enhancing
the ultrasonic effects.
[0178] In those embodiments of the present invention wherein the
toothbrush head is equipped with a mechanism to dispense a powder
or some other material that alters the bubble forming properties of
the dental fluid, the feedback and controls previously disclosed
may be employed as well. For example, dispensing baking soda will
modify the pH of the dental fluid, dispensing other additives can
reduce surface tension and reduce excessive bubbling effects of the
surfactants commonly found in toothpaste.
[0179] The control and/or dispensing of a topical fluid or powder,
when combined with the ultrasound, enhances cleaning, stain
removal, and whitening, and changes the properties of the dental
fluid to result in improved in dental cleaning and general oral
health (i.e. reduced gingivitis, toughened gums, reduced carries,
plaque, bad breath, dry mouth, etc.).
[0180] The toothbrush sensor and controls described above may be
employed in order to control the angular position of a stepper
motor (potentially 360 degree rotation). The motor, once in a new
position, will resume its oscillating brushing motion. This type of
control of toothbrush head movement allows the toothbrush head to
move to a position in which it senses the interface of soft and
hard tissue (gums and teeth). When air is detected, the toothbrush
head position is redirected to a position where the tooth gum
interface is again present. Such an embodiment reduces user control
of the toothbrush head such that the toothbrush head automatically
tracks to the optimal brushing position.
[0181] Alternative or additional technologies that may be employed
to achieve a suitable feedback function that may be used in
toothbrushes of the present invention include, but are not limited
to light-emitting diodes, photodiodes, phototransistors, and/or
opto-couplers that sense light beam attenuation. Since light can
pass through air bubbles with only some refraction, the light
transmission may not be directly proportional to acoustic
transmission. Ultrasonic transmission will either be reflected or
absorbed by a bubble population, which will be at different
wavelengths than light sources. An opto-coupler, however, installed
in a toothbrush head, typically within the acoustic waveguide,
sends light across a notch in the waveguide and is received on the
other side of the notch. The fluid density, according to the light
transmission, is representative of the fluid presence and condition
in the direct vicinity of the waveguide. Light may be transmitted
into or from the nylon bristles and variations in transmission
detected that are correlative of fluid properties. These variations
can then be fed into a microprocessor algorithm to aid in control
of the sonic and ultrasonic protocols similar to the other methods
described herein. Still further embodiments of the present
invention exploit the beneficial microbiological effects,
especially when coupled with the other ultrasound and sonic
protocols.
[0182] Brushing power may also be adjusted based on how hard the
user is pressing against the teeth. The force applied may be
determined by employing load sensing transducers and/or by
measuring the current through the motor. Depending upon the force
applied, the power applied to the motor may be reduced to reduce
the risk of abrasion from too much mechanical scrubbing.
Alternatively or additionally, the brush may be operated in an
optimized mode using the feedback signal by continuously adjusting
the sonic drive power level based on the feedback.
[0183] Design, Shape, and Features of Exemplary Toothbrushes
[0184] The general shape and size of oral hygiene devices of the
present invention having a handle and a device head, take into
account both ergonomic functionality and aesthetic appearance. Two
distinct grip areas may be provided that differ in size and
positioning, and are designed for different tasks. One grip section
is for general handling (i.e. transfer into and out of a charger
and holding by the user while applying dentifrice). This grip
section is generally grasped by a full grip in the palm of the
hand. This area is located in the middle and lower portion of the
device handle and has a generally oval or elliptical cross
sectional configuration. A second grip area is located in the upper
portion of the toothbrush handle and is optimized for holding the
device while operating it (e.g., brushing the teeth). This grip
section is generally grasped with the finger tips and may employ a
surface texture and/or a soft material to help prevent slipping in
the hand. The on/off switch is generally located at the interface
between the upper grip area and the device head. The on/off switch
may be provided as a mechanical switch activated, for example, by
modest pressure.
[0185] Devices of the present invention may have a general
configuration and profile having a larger section in the middle,
tapering to smaller sections near the top and bottom An oval,
elliptical, or triangular cross sectional shape typically feels
smaller in the hand and is easier for small hands to grasp. An oval
shaped toothbrush handle may be advantageous in those applications
in which it is important to determine, by feel, the orientation of
the toothbrush head.
[0186] Features and shape of the grip areas may be employed to
achieve one or more of the following functionalities: (a) an aid in
determining proper orientation of the brush bristles; (b) the shape
at a handle to toothbrush head interface may provide a visual aid
for proper alignment; (c) the general shape may communicate product
functions and/or technology such as a sonic wave and/or bubbles;
(d) a power (on/off) switch may be located above the upper grip
area; (e) a display (e.g., battery charge indication) may be
located near the center of the handle.
[0187] Fluid Control and Fluid Dispensing
[0188] Fluid is required at the tip of the waveguide to couple
ultrasound emanating from the waveguide tip to the oral cavity and
tooth surfaces. Absent the addition of significant fluid to the
oral cavity at the beginning of an operating cycle, the
availability of fluid may vary from the beginning of the operating
cycle to the end. Typically, saliva is generated by the user at a
rate of approximately 2 ml/min. Dentifrice, which is typically
applied to the device as a paste and/or gel at the beginning of an
operating cycle, breaks down and integrates within the saliva
and/or water added to form the dental slurry. As a result of the
nature of the dentifrice and variation of fluid availability, the
dental slurry may be relatively thick at the beginning of a
brushing event and relatively thin at the end. To reduce the
variation of fluid availability and composition during an operating
cycle, the device may incorporate a component that (a) introduces
fluid at the beginning of an operating cycle, (b) withdraws fluid
toward the end of an operating cycle, or (c) both introduces and
withdraws fluid during an operating cycle. The addition and/or
withdrawal of fluid may be either active (e.g., by providing a pump
and/or vacuum mechanism) or passive (e.g., by providing fluid
absorbing material in proximity to the brush head and oral cavity
environment).
[0189] During a typical operating cycle, fluid naturally migrates
to the bottom of the oral cavity, surrounding the lower
(mandibular) teeth. Less fluid surrounds the upper (maxillary)
teeth. It is desirable to carry fluid with the brush head and
provide it such that it is available to couple between the
waveguide and the teeth, both while brushing the lower and upper
teeth. The toothbrush head may, additionally, provide a component
that absorbs or collects fluid during brushing the upper teeth
dispenses or emits fluid (the same and/or replacement fluid). This
addition or subtraction of fluid may be active (e.g., pump/vacuum)
or passive (e.g., fluid absorbing material).
[0190] Within certain embodiments, oral hygiene devices of the
present invention may further employ a mechanism for dispensing
fluid and/or other media (including, but not limited to water,
pre-formed bubbles, a paste, a gel, and/or a powder), thereby
enhancing the performance of the device. For example, it may be
advantageous to improve the acoustic properties of the fluid in the
mouth and/or induce a chemical or physical reaction by application
of the ultrasound. Typically, a reservoir of fluid (or other media)
is provided in the toothbrush head assembly, or in the handle
assembly with passages for moving fluid from a remote reservoir to
a dispensing area at the device head. A pump or flow control valve
may be used to dispense the fluid from the reservoir.
[0191] The fluid may exit the toothbrush head through the acoustic
waveguide and/or through a port or valve or nozzle in the area of
the bristles. In some embodiments, the pumping action or actuation
of a flow control valve may be produced by the transducer element
contained within the toothbrush head. Alternatively, an
electromechanical device may be provided in the toothbrush head
assembly to facilitate pumping action or flow control. Electrical
coupling of the dispensing device within the toothbrush head
assembly may be achieved with a control circuit in the handle
assembly that is provided through the transformer assembly.
[0192] Alternative embodiments of the present invention provide a
small length of filament from the wave guide (or bristle area) that
aids in the transmission of the ultrasound and/or action of the
bristles. As the filament wears, an additional amount (small
length) is dispensed from the toothbrush head to maintain the
placement of an optimal length.
[0193] Still further embodiments of the fluid storage devices used
in combination with the toothbrushes of the present invention
include a sponge that stores fluid when full and releases fluid
when squeezed thereby increasing the amount of fluid in the mouth.
The squeezing force on the sponge may be achieved by the ultrasound
transducer and/or other electromechanical device within the
toothbrush head. When filled, the sponge is also an effective
medium for transmitting ultrasound and, thereby, performs in a
manner similar to an acoustic waveguide, as described herein
above.
[0194] Regardless of the precise reservoir configuration, it will
be appreciated that the amount of stored fluid (or other media) may
depend upon the specific function contemplated. If a large volume
of fluid is to be dispensed during brushing, then a mechanism for
refilling the reservoir may be employed. Thus, a reservoir may be
adapted to permit refilling prior to each use or, alternatively,
the reservoir may hold sufficient fluid to permit several
brushings. If only a very small volume of fluid is needed for
brushing, then a reservoir in the toothbrush head assembly may
contain sufficient fluid to last the life of the toothbrush head
assembly. The latter option may be further exploited in order to
determine the end of the useful life of a toothbrush head
assembly.
[0195] In those embodiments wherein a fluid reservoir is attached
to and/or contained within a toothbrush handle assembly, a fluid
path carries the fluid from the reservoir to the brush head. This
fluid path may be a flexible tube and/or may be routed through the
motor shaft into a hollow bush neck to the bristle area of the
toothbrush head. A pump or flow control valve may, for example, be
located in either the toothbrush head assembly or the handle. The
pump or flow control valve may, alternatively, be actuated directly
by the user (a mechanical pump or valve) or may be controlled
(electrically) by the handle electronics.
[0196] Thus, depending upon the precise toothbrush configuration
contemplated, the fluid dispensing system may comprise one or more
specific characteristics and/or attributes including, but not
limited to, (a) fluid dispensed through the acoustic waveguide; (b)
motion from the ultrasound transducer may be used to provide a
pumping action; (c) a pressurized reservoir may employ the
ultrasound transducer to actuate a flow control valve; (d) fluid
may travel from a handle through a drive shaft to a toothbrush
head; (e) fluid may be contained within the toothbrush head
assembly; (f) fluid may be used to alter the acoustic properties of
fluid in a user's mouth; (g) fluid may interact with ultrasound to
improve efficiency of the toothbrush; (h) fluid may be used to add
to fluid in mouth in order to ensure sufficient volume of fluid in
mouth; (i) dispensing of fluid may be based on acoustic properties
in a user's mouth as measured by an ultrasound transducer; (j) a
fluid supply in a toothbrush head assembly may be sufficient to
last the life of the toothbrush head thereby obviating the need for
refilling and enabling its use to indicate end of a toothbrush
head's useful life; (k) a change in taste of a stored fluid may be
employed to indicate end of a toothbrush head's useful life; (l)
dispensing a gel, paste or powder in place of fluid; (m) dispensing
a filament or other stranded material that acts as an acoustic
waveguide and/or similar device to transmit ultrasound; (n)
dispensing a fluid and/or other media to coat the teeth prior to
brushing; (o) dispensing a fluid, such as fluoride, to enhance
after-brushing protection; and (p) synchronizing fluid dispensing,
ultrasonic burst, and brush motion/positions.
[0197] Dentifrice Design and Compositions
[0198] Within certain related embodiments, it is contemplated to
provide a dentifrice that is particularly suitable for use with the
inventive power toothbrush described herein. For example, it is
herein contemplated that such a dentifrice will facilitate the
creation of a desirable bubble population that may be acted upon by
the ultrasonic transducer and acoustic waveguide disclosed
herein.
[0199] The natural bubble population within a dental fluid may be
assayed by the tendency of that fluid to absorb ultrasonic energy
that is transmitted through it. The higher the absorption, the more
bubbles that are present at the relevant size (given heuristically
by the resonance formula, developed originally for bubbles in pure
water at 37 degrees Celsius, although applicable as an
approximation for more general conditions F.sub.0R.sub.0=3.26,
where the frequency F.sub.0 is given in MHz and the radius R.sub.0
of the bubble is given in microns), although many bubbles
off-resonance would also create desired plaque and stain removal
effects.
[0200] Typically, for example, dentifrices according to the present
invention facilitate the formation of bubbles within the dental
fluid having a diameter of between about 1 .mu.m and about 150
.mu.m that resonate when ultrasound is applied in the 20 kHz to 3
MHz frequency range. More typically, dentifrices according to the
present invention facilitate the formation of bubbles within the
dental fluid having a diameter of between about 1 .mu.m and about
100 .mu.m that resonate when ultrasound is applied in the 30 kHz to
3 MHz frequency range. Still more typically, dentifrices according
to the present invention facilitate the formation of bubbles within
the dental fluid having a diameter of between about 5 .mu.m and
about 30 .mu.m that resonate when ultrasound is applied in the 100
kHz to 600 kHz frequency range. In an exemplary dentifrice
presented herein, bubbles are formed in the dental fluid that have
a diameter of between about 12 .mu.m and about 26 .mu.m that
resonate when ultrasound is applied to those bubbles with an
ultrasound transducer operating in the 250 kHz to 500 kHz
range.
[0201] Dentifrices suitable for use with the toothbrushes disclosed
herein comprise a surfactant that produces surface tension values
that facilitate production and stabilization of bubbles in a
suitable size range for stimulation by the ultrasonic transducer in
combination with an acoustic waveguide. Typically, surfactants
employed in the dentifrices disclosed herein produce surface
tensions in the range of about 0.1 Pa to about 500 Pa, more
typically in the range of about 0.2 Pa to 250 Pa, and still more
typically in the range of about 0.5 Pa to about 50 Pa.
[0202] Alternatively, or in addition to providing a dentifrice as
described above that promotes bubble formation, bubbles having a
desired size range may be incorporated in a dentifrice or another
composition and introduced directly into the oral cavity by
application of the composition on a toothbrush or by introduction
of the composition into the oral cavity. Bubbles having a diameter
of between about 1 .mu.m and about 150 .mu.m, more typically
between about 1 .mu.m and about 100 .mu.m, in some embodiments
between about 5 .mu.m and about 30 .mu.m, and in yet other
embodiments between about 12 .mu.m and about 26 .mu.m may be
incorporated directly in a dentifrice composition or in another
composition, such as a mouthwash or another generally liquid,
gel-like or semi-solid carrier for delivery to the oral cavity.
[0203] Bubbles in the carrier material may be present as voids in
the composition itself, or as microspheres or other microstructures
forming gas-filled voids in the carrier material. The OPTISON.TM.
ultrasound contrast enhancing composition, for example, comprises a
suspension of microspheres having a mean diameter of 2.0-4.5 .mu.m,
the microspheres being formed from human serum albumin and being
filled with an octafluoropropane gas. A population of microspheres
of the desired size range (as described above), formed using a
material that's safe for human consumption and generally inert and
filled with a gas that's safe for human consumption and generally
inert may be incorporated in a suitable carrier material and used,
in conjunction with toothbrushes of the present invention, to
promote effective cleaning.
[0204] All references to ranges of parameters described in this
specification are understood to include reference to a range equal
to and greater than the lower value of each range, as well as
ranges equal to and less than the higher value of each range. Thus,
for example, the recitation of a carrier frequency of between about
250 and about 500 kHz in this specification is interpreted to
include carrier frequencies of 250 kHz and greater; carrier
frequencies of 500 kHz and less; as well as carrier frequencies
within the stated range.
[0205] It will be appreciated that the combination of an acoustic
waveguide with an ultrasound transducer and/or motor generating
acoustic energy at sonic frequencies may be used in other types of
oral hygiene devices and, indeed, in other types of devices for
cleaning surfaces, and the inventions described herein are not
limited to toothbrush embodiments, which are described in
detail.
[0206] All U.S. and foreign patents and patent applications and all
other references are hereby incorporated by reference in their
entireties.
* * * * *