U.S. patent number 3,731,384 [Application Number 05/136,518] was granted by the patent office on 1973-05-08 for medical instrument.
This patent grant is currently assigned to Electro-Dent, Inc.. Invention is credited to Bernard Brooks, Jerome Farber, Theodore Roseman.
United States Patent |
3,731,384 |
Brooks , et al. |
May 8, 1973 |
MEDICAL INSTRUMENT
Abstract
A medical device is disclosed, which employs a form of electric
desensitization in connection with the use of pain-producing
medical tools. The device is particularly useful in connection with
dental drilling operations and includes, in the preferred
embodiment, a coil mounted within a dental handpiece and a rotating
permanent magnet mounted so that its magnetic flux overlaps the
coil windings. Rotation of the magnet induces an electric current
in the coil which flows through the drill and into the tooth to
desensitize the nervous system of the tooth upon contact.
Inventors: |
Brooks; Bernard (Belle Harbor,
NY), Farber; Jerome (Cherry Hill, NJ), Roseman;
Theodore (Westmont, NJ) |
Assignee: |
Electro-Dent, Inc. (Cherry
Hill, NJ)
|
Family
ID: |
22473183 |
Appl.
No.: |
05/136,518 |
Filed: |
April 22, 1971 |
Current U.S.
Class: |
433/32; 433/129;
433/132 |
Current CPC
Class: |
A61C
1/081 (20130101); A61N 1/36021 (20130101) |
Current International
Class: |
A61C
1/08 (20060101); A61N 1/32 (20060101); A61N
1/34 (20060101); A61c 001/10 () |
Field of
Search: |
;128/409
;32/27,26,48 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
535905 |
March 1895 |
Horton et al. |
26388 |
December 1859 |
Washburn |
|
Foreign Patent Documents
Primary Examiner: Peshock; Robert
Claims
What is claimed is:
1. Dental drilling apparatus, comprising:
a handpiece including a high-speed fluid turbine assembly and a
source of alternating electrical potential mounted within said
handpiece and adapted to be actuated by energization of said fluid
turbine, said fluid turbine having an elongated rotary hub with
inner and outer ends, said inner end protruding axially inwardly of
said turbine assembly, said outer end forming part of a rotary
chuck assembly adapted for securing to said turbine an electrically
conductive dental drilling bur, said source including a stator
element mounted inwardly of said fluid turbine and a rotor element
secured to said hub for rotation therewith adjacent said inner end
and substantially in alignment with said stator element; and
means substantially concentric with said rotary hub for
electrically connecting said source to said bur, whereby upon
actuation of said turbine, the electrical potential generated by
said source passes to said bur to effect the flow of an electric
current upon contact between the bur and a patient's tooth.
2. The device as recited in claim 1, wherein said rotor element
comprises a substantially annular sleeve of magnetic material
mounted concentrically with said hub and having permanent magnetic
pole areas of alternating polarity spaced around its
circumference.
3. The device as recited in claim 2, wherein said stator element
comprises at least one coil element having a predetermined number
of windings and being secured to the interior wall of said
hand-piece.
4. The device as recited in claim 3, wherein the rotational axis of
said rotor is substantially perpendicular to the longitudinal axis
of said coil.
5. The device as recited in claim 1, wherein said electrically
connecting means comprises:
first electrical contact means mounted on the inner end of said hub
and electrically connected to said bur; and
second electrical contact means electrically connected to said
source and biased against said first contact means to form an
electrical connection therebetween.
6. The device as recited in claim 5, wherein said first and second
contact means comprise first and second contact buttons, each of
said buttons having a contact surface.
7. The device as recited in claim 6, wherein said second contact
means comprises in addition:
a support member movable longitudinally relative to said first
button, said second button being mounted at one end of said support
member; and
biasing means engaging the other end of said support member for
continuously urging said contact surfaces together as said bur
rotates.
8. The device as recited in claim 7, wherein at least one of said
first and second contact buttons is formed of silver graphite
material.
9. The apparatus of claim 5 in which said second contact is adapted
to engage said first contact at a point lying substantially along
the rotational axis of said hub.
Description
BACKGROUND OF THE INVENTION
The invention relates to pain producing dental and medical tools,
and more particularly to apparatus for relieving pain from the use
of such tools by a form of electric desensitization which is
administered through the tool directly at its point of contact with
the patient.
Heretofore, electric analgesia in dental drilling operations,
particularly as disclosed in the U.S. Pat. No. 3,083,463 to B.
Brooks et al., has been achieved by placing an external
unidirectional magnetic field across the affected area of the
tooth. The drilling operation is then performed so that the bur
rotates in the field. Current is thereby generated in the bur, and
this current works directly on the nervous system of the affected
tooth. Somewhat better results have been obtained by utilizing a
special bur embedded with an insulated coil of fine wire. One of
the leads of the coil is connected to the bur tip, and the other to
the bur shank. The additional conductor embedded in the bur shank
can generate higher currents in lower strength fields for more
effective analgesic action on the dentinal nerves.
Certain attendant disadvantages, however, have rendered the prior
devices impracticable, and significantly reduce their
effectiveness. One such disadvantage is the observed variation in
the level of desensitizing current, depending upon the orientation
of the drilling bur with respect to the magnetic flux crossing the
affected area of the patient. Dependable current levels have been
difficult to maintain owing to the natural field distribution of
the magnetic flux density.
Earlier devices have been found to be impractical because of the
large size of the permanent magnet and the large size of the coil
wound on the drilling bur. In addition, the operation of such
devices depended upon the use of special drilling burs embedded
with the appropriate turns of wire. This necessitated replacement
or doubling of an operator's entire stock of plain drilling burs.
Furthermore, lack of concentricity between the drilling bur and the
coil embedded therein tended to effect uneven rotation of the bur.
Such irregularity becomes especially apparent at relatively high
turbine drive rotational speeds and resulted in undue vibration and
other operational difficulties which significantly shortened the
life of such prior apparatus. It has also been necessary to take
special precaution to obviate side effects of the powerful magnetic
field, for example eyeglasses with metal frames and patient's
wristwatches had to be removed. Occasionally, serious psychological
aversion to the unusual equipment set up around the patient's head
has been observed.
Another disadvantage of prior dental drilling apparatus is that
upon deactivation of the drive means, usually a high speed turbine,
the drilling bur continues to rotate under its momentum. It is
necessary therefore, that the operator exercise extreme caution in
removing the still rotating bur from the tooth to avoid inadvertent
contact with otherwise healthy portions of the tooth or the mouth
of the patient.
Servicing of prior drilling apparatus has heretofore been costly
and time consuming. Transmittal of the defective device to the
manufacturer for repair is often required which results in a
substantial loss in operating time and other expenses.
Accordingly, the present invention provides a self-contained and
compact unit which requires none of the complicated preparation and
maintenance of the prior apparatus. The invention discloses
preferably at least one coil mounted within a handpiece, one lead
being electrically connected to the handpiece casing, or circuit
common, and the other being electrically connected to a
pain-producing tool such as a dental drilling bur. It will be
understood however that other forms of conductors, such as a wire
grid or the like, may be used in place of the coil, as desired,
without departing from the scope of the invention. A magnet,
preferably a permanent magnet, is also mounted within the handpiece
in the vicinity of the coil. The usual fluid-operated
turbine-bearing assembly may be provided, preferably for rotating
the magnet relative to the coil, although the coil may be rotated
without departing from the scope of the invention. Rotation of the
permanent magnet causes its magnetic flux lines to move across the
coil thereby inducing a predetermined electric potential at the
tool. Upon contact between the tool and the patient's body, current
flows through the patient to the common, thereby desensitizing the
contacted area.
For dental drilling operations, the invention provides a plurality
of component units, or modules, which may be easily removed from
the apparatus for replacing or other servicing. One such unit
contains the electrical system for connecting the preferably fixed
conductor, or coil for example, to the rotating drilling bur.
Another unit may contain the turbine bearings, collet and magnet.
Worn bearings or electrical contacts may therefore be easily
serviced on location by simply replacing the deficient unit with a
new one.
A further advantage of the present dental handpiece is that it does
not require the use of special drilling burs. Accordingly, there is
no necessity for costly replacement or doubling of an entire supply
of such burs, as was required by the prior apparatus. The present
device may be easily assimilated into otherwise standard dental
systems.
The invention also provides for braking means to act upon the
rotating drilling bur, whereby upon deactivation of the turbine
drive, the bur will be rapidly decelerated to its stop mode. This
arrangement serves to minimize the danger of inadvertent injury to
the patient upon removal of the bur from the affected tooth.
It is one object of the present invention to provide a readily
usable and highly effective medical apparatus for producing an
electric analgesic effect simultaneously with the use of
pain-producing medical tools.
Another object of the present invention is to provide a dental
drilling apparatus which produces an electric analgesic effect
simultaneously with its use.
Still another object of the present invention is to provide a self
contained dental drilling apparatus for producing electric
analgesia.
A further object of the present invention is to provide a dental
drilling apparatus for producing electric analgesia which is simple
to use and minimizes any adverse psychological reaction in
patients.
A still further object of the present invention is to provide a
dental drilling apparatus which generates a predetermined
subliminal current in the dental drilling bur by the movement of a
magnetic field across a coil having a predetermined number of
windings.
A yet further object of the present invention is to provide a
dental drilling apparatus for producing electric-analgesia which
utilizes the usual type of dental drilling bur.
Another object of the present invention is to provide a dental
drilling apparatus having braking means rapidly to decelerate the
rotating drilling bur to its stop mode upon deactivation of the
turbine.
Still another object of the present invention is to provide a
modular dental drilling apparatus which may be readily serviced at
its operating location.
Yet another object of the present invention is to provide a simple
and inexpensive apparatus for manipulating a rotatable chuck such
as may be used in connection with a dental drilling handpiece.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, reference may
be had to the accompanying drawings, in which:
FIG. 1 is a side elevation, partially cut away, of a preferred
dentl handpiece embodying the principles of the invention;
FIG. 2 is an enlarged, fragmentary, vertical sectional view of the
head of the handpiece shown in FIG. 1;
FIG. 3 is a view taken along the line 3--3 of FIG. 2;
FIG. 4 is an enlarged, fragmentary, vertical sectional view of the
head of an alternate embodiment of the present invention.
FIG. 5 is a view taken along the line 5--5 of FIG. 4;
FIG. 6 is a fragmentary side elevational view of a wrench implement
to aid in replacement of dental tools in the handpiece;
FIG. 7 is a view taken along the line 7--7 of FIG. 6; and
FIG. 8 is a view taken along the line 8--8 of FIG. 6.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and in particular to FIGS. 1 and 2,
there is shown, by way of example, a dental handpiece, generally
indicated by reference numeral 10, having an elongated handle 11
with knurled gripping portions 12, and a head 13. A pain-producing
tool 14, which in the present embodiment is a dental drilling bur,
protrudes from the head 13 for operating upon a tooth 16. It should
be understood, however, that the invention may be used in
connection with different types of medical pain-producing tools,
and is not to be limited to dental drilling apparatus.
FIG. 1 is, by way of example, a schematic illustration of the
electrical circuit for producing electric desensitization during a
dental drilling operation. As will be described below, current is
generated within the head 13 during the drilling procedure. Upon
contact between the tooth 16 and the drilling bur 14, such current
will flow into the tooth provided that the tooth is effectively
connected to a circuit common, which is preferably the casing 17 of
the handpiece 10. It has been observed that a current of
approximately 2 microamps is sufficient to desensitize the nervous
system of the tooth. The effect of such desensitization is limited
to the specific tooth involved and only for such a duration of time
as that tooth is in contact with the drilling bur 14.
The handpiece 10 may also contain a conventional cooling system,
including a tube 15 for directing a water spray against the tooth
while the drilling is being carried out. Fiber optic techniques,
embodied in a light-conducting tube 20, for illuminating the
drilling area may also be contained within the handpiece.
As shown in FIG. 2, the head 13 is preferably composed of a
plurality of interconnecting housing portions, each of which may be
formed from stainless steel, or other electrically conductive
materials suitably rigid to form a proper housing structure. A cap
19 forms an enclosure for the open end of the turbine casing 18 and
may be connected thereto by means of cooperating threaded portion
21. The removable cap 19 provides easy access to the internal
components of the device to simplify assembly and repair.
The cap 19 is also provided with a central bore 22 having a reduced
diameter portion 23 and a larger diameter portion 24. An insert cap
26, preferably having a threaded engagement with the larger
diameter portion 24 of the bore 22, may be provided to allow easy
access to, and replacement of, certain component parts subject to
frictional erosion, as will be described in detail below.
Since the head of a dental handpiece is intended for use within a
patient's mouth, the outer surface area must be smooth and free
from edges which might cause inadvertent injury. Accordingly, the
insert 26 fits within the bore 22 so that its upper surface is
flush with the outer edge of the cap 19. Under such circumstances,
it has been found convenient to provide the insert 26 with a pair
of recesses 27 and 27a, which may be used to apply the necessary
rotational torque.
Located within the turbine casing 18 is a fluid turbine 28 which is
mounted on upper and lower bearings 29 and 29a. A conventional feed
tube 30 carries the driving fluid, usually air or water, to the
turbine from a remote source. In operation, the fluid is directed
over drive blades 31, thereby forcing them to rotate. An exhaust
tube (not shown) or other exhaust means, such as vents (not shown)
for evacuating from the head fluid which has passed over the blades
31, may also be provided in the handpiece. In the present
embodiment, such residual fluid, especially air, has proved to be a
useful coolant for components subject to high frictional
temperatures during operation.
A preferably elongated rotor shaft, or hub, 32 is connected to the
turbine blades 31 so as to be driven thereby, and contains a
central bore 33 which extends inward from its lower or external end
almost to the top thereof so that the hub is, in effect,
substantially tubular. The upper end of the bore is threaded, as
indicated by reference numeral 40, so as to connect with a
correspondingly threaded collet member 34. The rotor shaft 32 and
collet 34 have external extensions 35 and 36 respectively, each
with a preferably hexagonal outer surface. The rotor shaft and
collet function together as a rotary chuck, generally indicated by
reference numeral 60, for gripping the drilling bur 14. As
indicated in FIG. 2 the bur may be inserted into the chuck to any
desired depth of penetration.
The turbine-bearing assembly 28 may be mounted within a preferably
hard rubber or neoprene enclosure 37 electrically to insulate the
assembly from the casing 18 and otherwise to secure the turbine
tightly within the casing 18. The hard rubber enclosure is
preferably provided with a longitudinal slot 38 for the purpose of
engaging a pair of guide pins 39 and 39a which may extend laterally
inwardly from the turbine casing 18. The pins 39 and 39a serve both
to orient the turbine 28 within the casing and to anchor the hard
rubber enclosure so as to prevent the cartridge from rotating along
with the turbine blades and rotor shaft during the drilling
operation.
Electrical conductor means, preferably a coil 41 (FIG. 3) having a
predetermined number of windings may be mounted within the casing
18. This coil may be mounted on an armature or coil form 42. The
mumber of windings may vary. By way of example,however, where 0.005
inch diameter wire is used, it has been found that 21 turns is
suitable, although these requirements may be varied depending upon
whether more or less voltage is desired.
It is important to not that the present invention is not to be
limited by either the configuration or the number of conductive
elements operative within the head 13. Conductor configurations,
other than a coil, such as a grid or similar arrangement, may also
be suitable. In the preferred embodiment however, one coil has been
found suitable, although other coils, for example two or more
connected in series or in parallel, may be utilized respectively to
increase voltage or dependability, as desired, without departing
from the scope of the invention. One lead 43 of the coil,
arbitrarily referred to as the "common" lead, is electrically
connected to the casing 18, while the other lead 44, or "hot" lead,
is preferably electrically connected to the drilling bur 14 through
contact means to be described in detail below.
Magnet means, consisting of a permanent magnet rotor 45 of
preferably ceramic material, may be mounted for rotation on the
turbine rotor shaft 32 proximal to the coil 41, but separated
therefrom by an air gap 46 (FIG. 4). The rotor 45 is preferably
annular, having permanently magnetized areas of alternating
polarity spaced around its circumference. During operation of the
dental turbine, rotation of the rotor shaft 32 and the rotor 45
will cause each of the magnetized areas of the rotor to move
successively past the coil windings 41. In accordance with known
principles, an electric potential will be induced in the coil as
the magnetic flux lines cross the windings. By way of example,
suitable analgesic results are obtained when this induced voltage
is approximately 0.6 volts, yielding an AC current of substantially
2 to 10 microamps. The air gap 46 may be adjustable to aid in
determining suitable voltage levels, as desired.
It is to be understood that numerous changes in the details of
construction and the combination and arrangement of the generator
parts may be resorted to without departing from the scope of the
invention. For example, the specific location of the magnet and
coil windings need not be the same as specifically described
herein. Suitable voltages have been generated when the windings are
mounted for rotation on the turbine drive shaft and are encircled,
or partially encircled, by a fixed permanent magnet. In addition,
other conductive means may be used in place of the coil 41 to cut
the lines of magnetic flux. The present embodiment is preferable
because it is mechanically more efficient to rotate at high speeds
a body of uniform density, such as the permanent magnet rotor 45,
and it has been found that more dependable voltages may be
generated in this manner, and by the use of the coil 41.
The rotor 45 is preferably mounted coaxially with the shaft 32 so
that its axis of rotation is substantially perpendicular to the
longitudinal axis of the coil. It is also preferable that the coil
form 42 and the rotor 45 are substantially laterally aligned. Under
such conditions, the coil windings 41 are aligned to intersect
magnetic flux lines of maximum density originating with the rotor
45.
Electrical contact between the drilling bur 14 and the coil 41 may
be accomplished in several ways, such as by using conventional
brushes. Contact may also be made through the bearing races of the
turbine assembly. Such an arrangement, however, has been found to
be somewhat inefficient. Furthermore, fluid turbine drills may
rotate at approximately 300,000 to 400,000 revolutions per minute.
For such high rotational speeds it has been discovered that
suitable electrical connection is afforded by means of continuous
contact between a pair of juxtaposed contact buttons 47 and 48. The
contact button 47 is preferably formed of hardened silicon carbide,
but may be composed of other materials such as stainless steel, and
is connected to the innermost end of the rotor shaft 32. The
contact surface 49 of button 47 is preferably machine flat;
however, a substantially convex contact surface has also been found
suitable.
The contact button 48 is connected to one side of a support member
or circuit board 51 which is slidably arranged within the reduced
diameter portion 23 of the bore 22 in cap 19. The button 48 is also
electrically conductive and is preferably composed of a material
such as silver graphite. The contact surface 49 of button 47 abuts
against the button 48 during operation of the handpiece. It should
be noted that a spindle contact (not shown) has also been found to
provide an effective connection, and may be employed where desired,
in place of either of the contact buttons 47 and 48.
The extremely high rotational speeds achieved by the turbine will
cause constant erosion of the silver graphite button 48. To insure
that there is continuous contact between the buttons 47 and 48, a
spring 52 is positioned on the other side of the circuit board 51,
between the board 51 and the insert 26, so that the former is
continuously biased toward the button 47. The spring 52 is
preferably a conical coil spring so that it collapses to the width
of one of its coils. When the contact button 48 is new, the spring
52 is compressed between the circuit board 51 and the insert 26,
thereby storing energy. As the button 48 begins to erode from
rotational friction, the spring 52 gradually releases its stored
energy, the effect of which urges the circuit board 51 and the
eroding contact 48 longitudinally along the bore 22. When the
button 48 has worn away completely, further movement of the circuit
board is prevented by a stop 50 preferably protruding laterally
from the side walls of the bore 22. The insert 26 may then be
unscrewed from the cap 19 and the circuit board 51 simply replaced
by a new circuit board and contact button. Alternatively, the cap
19, having the coil 41 and circuit board 51 connected thereto, may
simply be replaced as a modular unit.
At least one contact shoe 53 may be mounted on the inner side wall
of the casing 18. A lining or bushing 54 is provided to insulate
the shoe 53 from electrical contact with the casing. A resilient
contact arm 56 is fixed to the board 51 and is electrically
connected to the contact button 48. The arm 56 is biased against
the shoe 53 to complete the circuit between the coil windings 41
and the drilling bur 14, as will be described below. As the board
51 moves under impetus from the spring 52, the arm 56 slides along
the contact surface of the shoe to maintain the electrical
connection between the coil 41 and the button 48. This sliding
contact between the arm 56 and the shoe 53 is inherently
self-cleaning, and therefore minimizes the possibility of
operational failure due to dirty and inefficient electrical
connections.
In the event that a source of electricity such as an alternating
current source (not shown) external to the medical handpiece 10, is
desirable, the component unit consisting essentially of the circuit
board 51 and the contact button 48 may be employed to connect the
external source to the pain-producing tool. The lead from the
source may be connected to the contact button 48 in any manner
known to those skilled in the art. Current from the source will
therefore flow into the button 47 and from there through any
appropriately insulated conductor to the pain-producing tool. It
should be noted that a direct current source such as a battery cell
may also be employed either externally of or within the handpiece,
as desired, to provide the desensitizing current for application to
the tooth or other affected area of the patient. Where a dental
handpiece such as that indicated by reference numeral 10 is
employed, current may flow from the button 47 into the turbine
rotor 32, the collet member 34 and drilling bur 14. When an
appropriate return connection from patient to the external source
is provided to complete the electrical circuit, contact between the
bur and the patient will allow current to flow from the bur and
through the affected tooth to desensitize the same and return to
the source. It should be noted that the lead from the external
source may also be connected in any suitable manner to the contact
shoe 53. In this event the resilient contact arm 56 may be utilized
as described above.
In the operation of the preferred form of dental handpiece 10 the
desensitizing current will flow along the following circuit: from
the coil 41 through the "hot" lead 44 to the contact shoe 53; into
the contact arm 56; to the button 48; to the button 47; to the
rotor shaft 32, and hence into the drilling bur 14. When the tooth
16 has been properly connected to the circuit common 17, the
current will flow into the tooth upon contact with the drill bur,
thereby to desensitize the dentinal nerves.
The connection between the tooth and the "common" to complete the
electrical circuit may be accomplished in several ways. For
example, a wire lead extending from the handpiece housing to the
patient may be provided. A metal clip (not shown) may be used to
connect the lead to the patient's lip. In the absence of a wire
lead, the operator, or dentist, may complete the circuit by
touching the patient while holding the dental handpiece. Patient
and handpiece may be otherwise connected to a common ground. It
should be noted that other techniques known to those skilled in the
art may be utilized without departing from the scope of the
invention.
Since, in the preferred embodiment, electrical connection between
the coil 41 and the button 48 is easily broken simply by
withdrawing the board 51 and its contact arm 56 and button 48 from
the housing 18, such component unit may be easily replaced by the
operator when the button 48 has become ineffective. Such an
arrangement serves to minimize time loss and the usual expenses of
maintaining operational dental equipment.
The contact shoe 53 is preferably provided with a vertical guide
slot 57 to be engaged by the contact arm 56. The slot 57 serves to
prevent the circuit board 51 from beginning to rotate under impetus
from rotational forces transmitted through the button 48 during
operation of the turbine.
Stability may be enhanced by providing a second contact shoe 58
symmetrically arranged within the casing 18 with respect to the
shoe 53. A second resilient contact arm 59, similar to the contact
arm 56, may be provided on the circuit board 51 for engagement with
the shoe 58. Although one contact shoe and contact arm have been
found suitable for present purposes, others may be utilized in the
present device without departing from the scope of the
invention.
It should be noted that the continuous contact between the buttons
47 and 48 generates substantial frictional forces during operation
of the turbine. The retarding effect of such friction on the speed
of rotation of the turbine rotor 32 is relatively insignificant
when the turbine is being activated. Upon deactivation of the
turbine however, such frictional forces act as a brake rapidly to
decelerate the rotational speed of the rotor 32 until it stops
rotating. This arrangement serves to minimize the chances of an
injury occurring to the patient's tooth or mouth when the handpiece
is being removed from the affected area.
FIGS. 4 and 5 illustrate an embodiment of the present invention in
which miscellaneous pain-producing medical tools, and particularly
dental tools such as picks, probes, excavators and other similar
tools may be used interchangeably in connection with the handpiece
110. The arrangement of magnetoelectric components is essentially
the same as has been described above in connection with FIGS. 1
through 3. In this embodiment, however, the turbine-bearing
assembly 128 is used only for rotating the permanent magnet rotor
145. Accordingly, the coil 141 may be electrically connected
through the casing 118 to a known type of non-rotating metal chuck
160 which is adapted to accept a plurality of different medical
tools. Contact between the coil 141 and the chuck 160 may be made
in any convenient manner; however, it has been found preferable to
connect one lead 144, arbitrarily designated the "return" lead, to
the cap 119, which in the preferred embodiment serves as a circuit
common. A lead 143, arbitrarily designated as the "hot" lead, may
be soldered to a metal ring 161 which is insulated from the cap 119
by a nylon or teflon bushing 162.
In the preferred arrangement, current generated in the coil by
movement of the magnet rotor 145 will flow from the coil 141
through the "hot" lead 143 to the ring 161. Any convenient
electrical connection between the ring 161 and the patient, as
described above, may be utilized to construct the appropriate
electrical circuit. Upon contact between the tool 114 and the
patient the circuit is complete, and current will flow through the
drilling bur and into the tooth to the circuit common thereby
desensitizing the affected dentinal nerve.
It should be noted that it is within the scope of the present
invention to utilize the same dental handpiece 10 with either
drilling burs or other pain-producing dental and medical tools. For
example, if the coil 41 and shoe 53 of the embodiment of FIG. 2
were fixed to the cap 19, then the handpiece of FIG. 4 could be
converted to the drilling mode simply by replacing the
turbine-bearing assembly 128 with the bearing assembly 28 having a
rotatable chuck, and by replacing the cap 119 with the cap 19. Such
interchangeability may be easily and inexpensively accomplished in
accordance with the present invention.
In the event that the pain-producing medical tool, or drilling bur,
is formed of non-electrically conductive material, it is within the
scope of this invention to supply current from the coil 41 to the
affected area of the patient through electrical conduits other than
the tool itself. Accessory probes, formed of electrically
conductive material, may be utilized, or other means such as
electrically conductive straps or clips may be provided, as
desired, to contact the affected area.
Referring now to FIGS. 6,7 and 8, there is illustrated a wrench
implement generally indicated by reference numeral 70, and intended
particularly for use in manipulating the rotatable chuck 60 to aid
in replacement of dental medical tools in the handpiece 10. The
wrench 70 preferably consists of a shank or handle portion 71
having a plunger member 72 mounted at one end for longitudinal
movement relative to the handle. The plunger may be connected to
the handle in any suitable way; however, it has been found
convenient to support the plunger within the bore of a hollow
enlarged portion 73, so that the plunger is free to slide back and
forth, as desired, when the implement is being used. A coil spring
74 serves to bias the plunger outward to the position illustred by
the broken lines in FIG. 6.
A pair of laterally extending members 76 and 77 may be provided at
the other end of the shank 71 for gripping the handpiece 10.
Preferably, these members consist of integral wall members
separated by a fixed predetermined distance substantially equal to
the longitudinal dimension of the head 13 of the handpiece. It
should be noted, however, that the invention is not to be limited
by such wall members, and that other types of gripping means may be
provided without departing from the scope of the invention. The
wall members 76 and 77 need not be immobile. Adjustable members
capable of gripping several different types and sizes of dental
handpieces may also be utilized.
A radial slot 78 may be provided in the wall member 77 (FIG. 7).
The slot 78 is adapted to fit securely over the hexagonal extension
35 of the rotor shaft 32, when the head of the handpiece 10 is
positioned between the gripping members 76 and 77, as illustrated
in FIG. 6. The purpose of the slot 78 is to hold the rotor shaft
against rotation during manipulation of the chuck.
The interior end 79 of the plunger 72 is provided with a central
bore 81 having a reduced diameter portion 82 and a recessed portion
83 (FIG. 8) of larger diameter. The configuration of the recessed
portion 83 is such as to correspond to the shape of the collet
extension 36 so that the latter may be engaged for movement
independent of the rotor shaft 32.
In operation, the plunger 72 is pressed inward against the bias of
the spring 74 until the recessed portion 83 engages the collet
extension 36. The drilling bur 14 extends harmlessly into the
remainder of the bore 81. The bur 14 is released by appropriately
rotating the plunger 72 which in turn rotates the collet 34. As the
collet rotates, it moves axially relative to the rotor shaft 32 by
virtue of the motion translating characteristics of threaded
portion 40. When the collet moves axially outward, it relaxes its
grip on the drilling bur according to known principles of chuck
design. The bur may then be removed and another inserted. The
replacement bur may be secured in the chuck simply by reversing the
direction of rotation of the collet. A knurled portion 84 is
provided on the plunger to facilitate manual turning of the plunger
and collet.
* * * * *