U.S. patent application number 11/105820 was filed with the patent office on 2005-08-18 for method of making a custom-fitted tray using a person's teeth as a template.
Invention is credited to Jacobs, Scott.
Application Number | 20050181334 11/105820 |
Document ID | / |
Family ID | 31886918 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050181334 |
Kind Code |
A1 |
Jacobs, Scott |
August 18, 2005 |
Method of making a custom-fitted tray using a person's teeth as a
template
Abstract
A customized dental treatment tray comprising a thermoplastic
material such as ULDPE is formed from a preformed tray or sheet
using a person's own teeth as a template. A preformed dental tray
or sheet comprising a material such as ULDPE is heated to become
plastically deformable and placed over at least a portion of the
person's teeth in order to form an impression of the person's teeth
and yield an intermediate customized dental tray. Upon cooling
sufficiently, the intermediate tray is removed from the persons'
mouth and trimmed as needed to yield a finished customized
treatment tray corresponding to the person's teeth. The performed
tray or sheet preferably comprises ULDPE, which yields a highly
flexible and resilient final tray, although they may also contain
other polymers or blends. The customized dental treatment tray is
useful for teeth bleaching and other dental treatments known in the
art.
Inventors: |
Jacobs, Scott; (Golden,
CO) |
Correspondence
Address: |
WORKMAN NYDEGGER
(F/K/A WORKMAN NYDEGGER & SEELEY)
60 EAST SOUTH TEMPLE
1000 EAGLE GATE TOWER
SALT LAKE CITY
UT
84111
US
|
Family ID: |
31886918 |
Appl. No.: |
11/105820 |
Filed: |
April 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11105820 |
Apr 14, 2005 |
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10224943 |
Aug 20, 2002 |
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10224943 |
Aug 20, 2002 |
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10225000 |
Aug 20, 2002 |
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Current U.S.
Class: |
433/215 |
Current CPC
Class: |
A61C 19/066 20130101;
A61C 19/063 20130101; A61C 9/0006 20130101 |
Class at
Publication: |
433/215 |
International
Class: |
A61C 005/00 |
Claims
What is claimed is:
1. A method of manufacturing a customized flexible and resilient
dental treatment tray corresponding to a person's teeth,
comprising: providing a preformed tray formed from a thermoplastic
material that is flexible and resilient at room temperature and
that becomes plastically deformable at a temperature in a range of
about 110.degree. F. to about 180.degree. F., the preformed tray
including a bottom wall having a substantially U-shaped
configuration, a front side wall extending laterally from an outer
edge of the bottom wall, a rear side wall extending laterally from
an inner edge of the bottom wall, and a hollow interior defined by
the bottom wall, front side wall, and rear side wall that
approximates the size and curvature of a person's dental arch, the
front and rear side walls of the preformed tray having a thickness
less than about 1.5 mm; heating the preformed tray to a temperature
in a range of about 110.degree. F. to about 180.degree. F. so as to
become plastically deformable without causing the preformed tray to
substantially collapse or shrivel; placing the preformed tray over
at least a portion of a person's teeth without any external
mechanical support other than fingers; causing the preformed tray
to at least partially conform to the person's teeth in order to
form a customized dental treatment tray; allowing the customized
dental treatment tray to cool to a temperature at which it is no
longer plastically deformable; removing the customized dental
treatment tray from the person's teeth, the tray being flexible and
resilient; and trimming the customized dental treatment tray to so
as to not significantly overlap the person's gingiva when in
use.
2. A method as defined in claim 1, the preformed tray being heated
by at least one of heated water, a heat gun, or a blow torch.
3. A method as defined in claim 1, the preformed tray being caused
to at least partially conform to the person's teeth by the person
applying suction so as to remove at least of air or water from
between the person's teeth and the preformed sheet or tray.
4. A method as defined in claim 1, the preformed tray being caused
to at least partially conform to the person's teeth by pressing the
preformed tray against the person's teeth by means of at least one
of a finger or the person's tongue.
5. A method as defined in claim 1, the preformed tray comprising
ultra low density polyethylene.
6. A method as defined in claim 5, the preformed tray further
comprising at least one of ethylene vinyl acetate,
polycaprolactone, polypropylene, or another form of
polyethylene.
7. A method as defined in claim 1, the customized dental treatment
tray being trimmed so that an upper periphery of the dental
treatment tray terminates shy of the person's gingival margin when
in use.
8. A method as defined in claim 8, further comprising scalloping
the upper periphery of the dental treatment tray up and around the
person's interdental papilla.
9. A method as defined in claim 1, the preformed tray shrinking and
more closely conforming to the person's teeth upon placing the tray
over the person's teeth and allowing the tray to cool.
10. A method as defined in claim 1, the preformed tray further
including a handle, the method further comprising removing the
handle from the preformed tray and smoothing the customized dental
treatment tray in the area where the handle of the preformed tray
was detached.
11. A method as defined in claim 11, the handle and front sidewall
of the preformed tray having an attachment interface with a length
of about {fraction (1/8)} inch prior to being detached.
12. A method of manufacturing a customized flexible and resilient
dental treatment tray corresponding to a person's teeth,
comprising: providing a preformed sheet or a preformed tray that is
flexible and resilient at room temperature, the sheet or tray being
comprised of ULDPE and having a cross-sectional thickness less than
about 2 mm; heating the preformed sheet or tray to a temperature so
as to become plastically deformable yet able to sufficiently retain
its integrity as a sheet or tray so as to be useful in forming a
dental tray by placing it directly over a person's teeth without
external support other than fingers; placing the preformed sheet or
tray over at least a portion of the person's teeth; causing the
preformed sheet or tray to at least partially conform to the
person's teeth in order to form a customized dental treatment tray;
allowing the customized dental treatment tray to cool to a
temperature at which it is no longer plastically deformable; and
removing the customized dental treatment tray from the person's
teeth, the tray being flexible and resilient.
13. A method as defined in claim 12, further comprising trimming
excess tray material from the customized dental treatment tray.
14. A method as defined in claim 12, the preformed sheet or tray
being placed over the person's teeth without any external
mechanical support other than fingers.
15. A method as defined in claim 12, further including making an
impression of the person's teeth, the method comprising placing the
preformed sheet over the person's teeth by means of the
impression.
16. A method as defined in claim 12, the preformed sheet having a
rectangular or square shape.
17. A method as defined in claim 12, the preformed sheet having a
horse-shoe shape.
18. A method of manufacturing a customized flexible and resilient
dental treatment tray corresponding to a person's teeth,
comprising: providing a preformed sheet having a thickness less
than about 1.8 mm and comprising a flexible thermoplastic material
that becomes plastically deformable at a temperature in a range of
about 110.degree. F. to about 180.degree. F.; heating the preformed
sheet to a temperature in a range of about 110.degree. F. to about
180.degree. F. so as to become plastically deformable yet able to
sufficiently retain its integrity as a sheet so as to be useful in
forming a dental tray having a dental impression formed therein;
placing the preformed sheet over said at least a portion of the
person's teeth without external support other than fingers; causing
the preformed sheet to at least partially conform to the person's
teeth in order to form a customized dental treatment tray; allowing
the customized dental treatment tray to cool to a temperature at
which it is no longer plastically deformable; removing the
customized dental treatment tray from the person's teeth, the tray
being flexible and resilient; and trimming the customized dental
treatment tray to so as to not significantly overlap the person's
gingiva when in use.
19. A method as defined in claim 18, the preformed sheet comprising
ultra low density polyethylene.
20. A method as defined in claim 18, further comprising scalloping
the upper periphery of the dental treatment tray up and around the
person's interdental papilla.
21. A method as defined in claim 18, the preformed sheet having a
rectangular or square shape.
22. A method as defined in claim 18, the preformed sheet having a
horse-shoe shape.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of copending U.S.
application Ser. No. 10/224,943, filed Aug. 20, 2002, and a
division of copending U.S. application Ser. No. 10/225,000, filed
Aug. 20, 2002, the disclosures of which are incorporated in their
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention is in the field of customized dental
trays used to provide a desired dental treatment to a person's
teeth. More particularly, the invention relates to customized
dental trays that are formed using either a person's own teeth as a
template. The tray can be used for dental treatments such as
bleaching, administration of fluoride, or application of other
medicines.
[0004] 2. The Relevant Technology
[0005] Virtually all people desire white or whiter teeth. To
achieve this goal, people either have veneers placed over their
teeth or have their teeth chemically bleached. In the past,
patients who desired to have their teeth bleached had to submit to
conventional in-office bleaching techniques. The process generally
involves: (1) making an alginate impression of the patient's teeth:
(2) making a stone cast or model of the impression; (3) vacuum
forming a dental tray from the model, usually from a sheet of thin
ethyl vinyl acetate (EVA) material, and trimming to exclude
gingival coverage. This method results in a tray that is soft and
flexible, that is very accurately customized to the patient's
teeth, but the method is time consuming and the resulting tray is
expensive.
[0006] Because of the high cost of these very accurate custom
trays, less costly alternatives have been developed, but these
alternatives have substantial disadvantages in terms of accuracy
and comfort of the finished formed tray.
[0007] One alternative is the so-called "boil and bite" tray. A
relatively thick, non-custom preformed tray (similar to a mouth
guard) made of EVA or polyethylene or other material is submerged
in boiling water. Upon removal from the water, the tray is quickly
placed inside the patient's mouth. The patient quickly applies
contact pressure to make an impression of the biting surfaces of
the user's teeth. One problem with "boil and bite" trays is that
they are relatively thick and bulky, which make them intrusive and
uncomfortable to wear. The thickness of large, bulky perform trays
also limits the accuracy with which they can conform to the user's
teeth and/or gums.
[0008] To the extent that preform trays made from EVA and like
materials are made with thinner walls, such trays are extremely
difficult to work with because they tend to shrivel and collapse
outside extremely narrow windows of temperature and heating time.
For example, if left in a hot water bath too long (i.e., for more
than a few seconds) they can quickly become limp and lose their
pre-form shape, making it difficult or impossible to make an
impression of the user's teeth. In view of the foregoing, "boil and
bite" trays that do not have the tendency to collapse and shrivel
when heated generally do not accurately conform to the user's teeth
and are bulky and uncomfortable to wear.
[0009] Another alternative for teeth bleaching involves
non-customized strips of a flexible plastic material coated with a
bleaching agent that can be applied to the teeth. Such strips are
placed against the teeth by the user to cover the teeth. Because
such strips are flimsy and limp at room temperature (i.e., are not
resilient or rigid), they are not useful for creating a customized
dental tray.
[0010] Another alternative is a dual tray assembly as disclosed in
U.S. Pat. No. 5,616,027 to Jacobs et al. The dual tray assembly is
composed of an outer tray that supports or carries an inner tray
made of a thermoplastic material comprising EVA. In use, the tray
assembly is submerged in hot water, where the inner tray becomes
pliable and moldable and the outer tray remains rigid. "Because of
the material and the thinness of the walls of the inner tray, the
inner tray will substantially lose integrity of its shape and form
during the heating process . . . " (Col. 4, ll. 14-16.) Thus,
"[t]he carrier tray is necessary during the heating, handling and
forming process." (Col. 4, ll. 16-17.) The heated assembly is then
placed in the mouth of the patient where the inner tray takes an
impression of the person's teeth. The generally thinner inner tray
results in a final tray that is much thinner and more comfortable
to wear compared to conventional "boil and bite" trays that are
sufficiently thick that they do not need a supporting carrier tray.
Nevertheless, the outer tray can inhibit accurate conformation of
the inner tray to the shape of the patient's teeth.
[0011] Another problem with EVA are concerns about its toxicity.
Whereas trays made using EVA are generally safe to use, the FDA has
guidelines that strictly controls how EVA can be used.
Notwithstanding the foregoing deficiencies, EVA finds wide use in
the manufacture of dental trays, which is strong evidence of the
inadequacy of other possible plastic materials that are suggested
in various existing patents relating to tray technology. EVA is
generally preferred due to its softness and flexibility and the
ease in which it can be heated and formed into a dental tray
compared to other plastic materials suggested in the art.
[0012] In view of the foregoing, there is an ongoing need to
develop new materials for use in manufacturing preformed trays and
sheets that can be easily formed into customized trays that are
thin-walled, flexible, comfortable, and that accurately reflect the
shape of the person's teeth.
SUMMARY OF THE INVENTION
[0013] The present invention is directed to customized dental trays
that in one aspect are formed by using a person's own teeth as a
template. In this case, a preformed tray or sheet is heated to a
point where it is sufficiently softened that it can be plastically
molded so as to conform to the person's teeth. Upon cooling, the
customized tray retains its shape so that it can be used repeatedly
as needed to provide a dental treatment. In another aspect,
preformed trays or sheets comprising ultra low density polyethylene
are formed into customized trays using a stone or plaster model of
the person's teeth.
[0014] The process for making a finished customized tray begins
with a preformed dental tray or flat sheet that may optionally be
available in multiple sizes to allow the selection of a size that
generally conforms to the size of the person's teeth and mouth. The
tray or sheet preferably comprises ultra low density polyethylene
("ULDPE"), either alone or blended with one or more additional
polymers, e.g., ethylene-vinyl acetate copolymer ("EVA"),
F-polycaprolactone ("PCL"), other types of polyethylene ("PE"),
polypropylene ("PE"), or other plastic materials. Plasticizers or
flow additives known in the thermoplastic art can be used as
desired to modify the properties of the thermoplastic material used
to form the preformed dental tray or sheet.
[0015] Preformed trays and sheets made from ULDPE are preferred due
to the unique ability of trays and sheets made therefrom to soften
and yet maintain their physical integrity while in a softened state
compared to previous tray or sheet materials such as EVA. Thus,
ULDPE expands the operational window, both in terms of temperature
and heating time, of manufacturing customized dental trays compared
to previous tray materials. In other words, preformed trays and
sheets made from ULDPE are far less susceptible to over or under
heating compared to trays or sheets made from EVA. Even though
preformed trays and sheets made from ULDPE do not shrink or
otherwise lose their physical integrity when heated as happens
using trays or sheets made from EVA, they do, in fact, shrink over
and around and cling to the person's teeth (or a stone cast of the
person's teeth) when cooling, which greatly simplifies and improves
the ability of such trays or sheets to accurately conform to the
person's teeth (or stone cast). Moreover, ULDPE is non-toxic,
thereby addressing any potential concerns with the toxicity of EVA,
while providing the aforementioned superior physical and/or
mechanical properties. These demonstrate the surprising and
unexpected benefits of using preformed trays or sheets comprising
ULDPE compared to trays materials considered at present to be the
industry standard (i.e., trays comprising EVA).
[0016] The outer configuration of the preformed dental tray is
preferably a horseshoe shape, with a flat planar bottom having an
open U-shaped cross-section to generally fit over the upper and/or
lower teeth. The walls of the preformed tray may be either parallel
or flared, the latter providing a larger top opening than the width
of the tray bottom. The tray advantageously includes a handle,
preferably attached at the front lower portion of the tray.
[0017] The tray or sheet is advantageously designed and formulated
so as to soften when heated to a desired temperature above body
temperature (i.e. 98.6.degree. F.), preferably in a range of about
110.degree. to about 180.degree. F., more preferably in a range of
about 120.degree. to about 170.degree. F., and most preferably in a
range of about 130.degree. to about 160.degree. F. Upon heating to
an appropriate temperature at or above its softening temperature,
the tray or sheet becomes plastically deformable and moldable so
that it can form an impression of the teeth or teeth and gums.
[0018] The tray customization process is done by immersing the
preformed tray or sheet into hot water or by other exposing it to
other suitable heating means known in the art (e.g., heat gun, oven
or torch). A handle can be used to facilitate immersion of the tray
in hot water or heating using other means while reducing the risk
of burning one's fingers. The tray or sheet will typically become
plastically deformable after being submerged within water heated to
a temperature of about 160-212.degree. F. or heated using other
appropriate heating means within a prescribed period of time,
preferably within about 1-30 seconds, more preferably within about
2-15 seconds, and most preferably within about 4-8 seconds.
[0019] When sufficiently softened and plastically deformable, the
tray or sheet is placed over the person's upper and/or lower teeth
and the person closes his or her mouth. A vacuum is advantageously
created inside the tray by the patient sucking in a manner so as to
draw air and/or water out from the space between the tray and tooth
surfaces. Additional forming pressure can be applied by the
person's tongue or by placing the patient's or dental
practitioner's fingers against the outer surfaces of the tray.
Nevertheless, due to the aforementioned benefit of preformed trays
or sheets comprising ULDPE to shrink and cling against and around
the person's teeth when they begin to cool, less mechanical force
is needed to cause the trays or sheets to adequately and accurately
conform to the person's teeth (or a stone model) compared to other
tray materials known in the art.
[0020] As the tray remains in the person's mouth it begins to cool
to body temperature. After the customized tray has been formed and
cooled sufficiently so that it is no longer plastically deformable,
it is removed from the person's mouth. The tray may be further
cooled if desired, such as by placing the tray in cold water or by
letting it air cool to room temperature. The formed tray will have
an impression of the teeth and is therefore a "custom" or
"customized" tray. Upon cooling, the tray may remain flexible and
resilient but it will not be "plastically deformable" so as to
assume a different resting conformation unless reheated and
reshaped. If additional shaping is needed, either immediately or
later, the tray may be heated and customized as before.
[0021] Once the customization process is complete, the detachable
handle can be removed by e.g., cutting or tearing. The customized
tray is preferably trimmed to or shy of the gingival margin of the
frontal and/or lingual surfaces. The tray is preferably scalloped
in around the interdental papilla in order to produce maximum
customization and comfort. Nevertheless, the tray can be trimmed to
cover a portion of the teeth, just the teeth, or to cover a portion
of the gingiva in addition to the teeth, as desired.
[0022] The customized trays formed in this manner are useful for
tooth bleaching or other dental treatments. Bleaching or other
dental compositions can be applied to a person's teeth and/or gums
by placing the composition into the customized tray and placing the
tray over the person's teeth. The tray holds the dental composition
against the person's teeth and/or gums and keeps it from being
diluted by saliva or otherwise being prematurely removed. In a
preferred embodiment, the dental composition may include an
appropriate tackifying agent in order to make it sticky and
viscous. The tray can be used once or many times as desired to
treat the person's teeth and/or gums.
[0023] In some cases, it may be desirable to incorporate reservoirs
within the customized tray. Reservoirs can enhance treatment of the
teeth or other tissue by holding additional treatment material
adjacent to the dental tissue(s) being treated. To form tray
reservoirs, an appropriate blockout material, such as clay, wax, a
light or chemical cure resin, or other suitable coating material
may be placed over one or more of the person's teeth and/or
gingival tissue. The blockout material displaces the perform tray
or sheet material away from the teeth by a distance corresponding
to the thickness of the blockout material, which results in the
creation of reservoirs within the customized tray. After tray
formation, the blockout material is removed from the person's teeth
and/or gingival tissue.
[0024] Whereas preformed trays and sheets are especially useful for
manufacturing customized dental trays using a person's teeth,
rather than a stone cast, as the template, it is certainly within
the scope of the invention to vacuum form preformed trays or sheets
made from ULDPE using a stone cast. An advantage of using preformed
trays or sheets that comprise ULDPE using conventional tray-making
methods that employ a stone cast is that such trays or sheets, by
virtue of their including ULDPE, can be made thinner than preformed
trays or sheets using conventional tray-making materials. In this
way it is possible to manufacture final customized trays that are
even thinner walled and more flexible than conventional trays. This
is a surprising and unexpected result.
[0025] Moreover, ULDPE is more transparent or translucent than
conventional tray materials, which increases the ability to
determine whether the dental composition is sufficiently well
distributed so as to cover the desired tooth and or gingival
surfaces. This is yet another surprising and unexpected result of
employing tray materials that comprise ULDPE.
[0026] These and other features of the present invention will
become more fully apparent from the following description and
appended claims, or may be learned by the practice of the invention
as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] To further clarify the above and other advantages and
features of the present invention, a more particular description of
the invention will be rendered by references to specific
embodiments thereof, which are illustrated in the appended
drawings. It is appreciated that these drawings depict only typical
embodiments of the invention and are therefore not to be considered
limiting of its scope. The invention will be described and
explained with additional specificity and detail through the use of
the accompanying drawings in which:
[0028] FIG. 1 is a perspective view illustrating an embodiment of a
preformed dental tray according to the invention that can be used
to form a customize dental tray;
[0029] FIG. 2 is a perspective view illustrating a preformed sheet
that may be used to form a customized dental tray according to the
invention;
[0030] FIGS. 3A and 3B illustrate alternative methods of applying a
blockout material to a person's teeth (or stone cast) in order to
yield a customized dental tray having reservoirs;
[0031] FIGS. 4A-4C illustrates alternative methods of heating a
preformed tray in order to soften it preparatory to making a
customized dental tray;
[0032] FIG. 5 illustrates the preformed dental tray of FIG. 1 being
placed in a patient's mouth during formation of a custom-fitting
tray using a person's teeth as a template;
[0033] FIGS. 6A and 6B illustrate intermediate customized dental
trays being trimmed in order to remove excess tray forming
material; and
[0034] FIG. 7 illustrates a customized dental tray according to the
invention that has been trimmed and scalloped.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] In one aspect, the invention relates to the manufacture of
customized dental trays using a person's own teeth as the template.
In another aspect, the invention relates to the use of preformed
trays or sheets that comprise ULDPE in making customized dental
trays, either using a person's teeth or a stone cast of the
person's teeth as a template. In another aspect, the invention
relates to customized dental trays that comprises ULDPE. The
inventive dental trays can be used for any desired dental
treatment, such as tooth bleaching, fluoride treatments, and
antimicrobial treatments. Reference is now made to the
drawings.
[0036] FIG. 1 depicts a preformed dental tray 10 that may be used
to manufacture a customized dental tray according to the invention.
The preformed tray 10 comprises a bottom wall 12 having a generally
U-shaped configuration generally conforming to the shape of the
person's dental arch. The bottom wall 12 has a generally flat
planar profile, although it could have other shapes if desired
(e.g., curved). The preformed tray 10 further includes a front side
wall 14 and a rear side wall 16 that, together with the bottom wall
12, form a tray 10 that is open at the top and that terminates at
ends 18. A detachable handle 20 is attached to the tray 10 along an
outer surface of the front side wall 14, preferably near the bottom
center of the side wall 14. The interface between the detachable
handle 20 and the front side wall 14 can be any desired length,
preferably about 2-4 mm long, more preferably about {fraction
(1/8)} inch long (about 3.2 mm).
[0037] The front side wall 14 of the tray 10 is substantially
perpendicular relative to the bottom wall 12. The rear side wall 16
of the tray 10 is substantially perpendicular to the bottom wall 12
at the ends 18 of the horseshoe-shaped tray 10, but gradually opens
up to form an oblique angle near a middle curved portion 22 of the
tray so as to better accommodate the roof of the mouth near the
middle portion 22 of the tray 10. The bottom wall 12 has a width
near the curved middle portion 22 of the tray that is
advantageously less than the width of the bottom wall 12 between
the middle portion 22 and the ends 18 of the tray 10. This allows
for the differences in the radial width of a person's incisors and
canines relative to the bicuspids and molars. It should be
understood, however, that dental trays comprising ULDPE used within
the scope of the invention can have any desired configuration such
that the tray of FIG. 1 is merely a nonlimiting example.
[0038] The tray 10 can be made of any appropriate thermoplastic
material that is able to soften at a predetermined temperature
greater than body temperature so as to become plastically
deformable but that will maintain its shape when cooled to at or
below body temperature. A preferred thermoplastic material is ultra
low density polyethylene (ULDPE), which can be used alone or in
combination with other polymers, such as polypropylene (PP),
ethylene vinyl acetate (EVA), polycaprolactone (PCL), and other
forms of polyethylene (PE). Flow additives and plasticizers may be
added as desired.
[0039] ULDPE is the preferred thermoplastic material because of its
ability to maintain its structural form and integrity even after
being heated sufficiently so as to become plastically deformable.
Though they better maintain their shape and size during the heating
process, preformed trays and sheets provide the unexpected and
surprising benefit of shrinking and clinging against and around the
person's teeth (or stone model of the person's teeth) upon cooling.
This greatly aids in the ability and ease of tray materials
comprising ULDPE to accurately and readily conform to the shape of
the person's teeth (or stone model) compared to all (or virtually
all) other tray materials known in the art. Moreover, customized
trays that comprise ULDPE remain soft, flexible and resilient at
room temperature. They are also more transparent or translucent
than conventional tray materials. ULDPE reduces or eliminates the
toxicity concerns of EVA, while providing superior mechanical
properties. ULDPE helps in the ease of manufacture of the
customized dental tray and it also maximizes patient comfort and
compliance with the desired dental treatment.
[0040] ULDPE refers to a range of polyethylene-based copolymers
defined as having a density of less than 0.914 g/cm.sup.3. By way
of comparison, low density polyethylene (LDPE) is defined as having
a density in a range of 0.915-0.94 g/cm.sup.3 and high density
polyethylene (HDPE) is defined as having a density in a range of
0.94 to 0.97 g/cm.sup.3. Thus, ULDPE can be readily distinguished
from other forms of PE by its density, although its physical
properties also differ significantly in many respects, including
water vapor transmission rate, crystallinity, melting point,
coefficient of linear expansion, elasticity, modulus, yield
strength, tensile strength, hardness, and impact strength. In
general, ULDPE is an ethylene copolymer characterized as having
excellent environmental stress crack resistance, outstanding
flex-life and flex-crack resistance, toughness and good
sealability. It also has a relatively high melt flow index compared
to conventional tray materials, which makes it uniquely suitable
for use in manufacturing thin-walled customized dental trays. It
has been found that, in general, the higher the melt flow index,
the more the preformed trays or sheets made from the material will
tend to maintain their shape after being heated to the material's
softening temperature.
[0041] Examples of suitable ULDPE materials include various
polymers sold under the general trade name Attane.RTM. by Dow
Chemical. In general, Attane.RTM. refers to polyethylene copolymers
made from ethylene and octene. Specific examples include
Attane.RTM. 4201 (density=0.912 g/cm.sup.3), Attane.RTM. 4202
(density=0.913 g/cm.sup.3), Attane.RTM. 4203 (density=0.905
g/cm.sup.3), Attane.RTM. 4301 (density=0.914 g/cm.sup.3), and
Attane.RTM. 4404 (density=0.904 g/cm.sup.3). Another suitable ULDPE
material is Exact.RTM.D 4041 (density=0.878 g/cm.sup.3) made by
Exxon-Mobil Chemical. An example of a suitable EVA material is
Elvax.RTM. 250, available from Dupont. An example of a suitable PCL
material is Capra.RTM. 650 from Solvoy-Interox. Other thermoplastic
materials and blends used in making dental trays are disclosed in
U.S. Pat. No. 5,769,633 to Jacobs et al., U.S. Pat. No. 5,051,476
to Uji et al., and U.S. Pat. No. 6,089,869 to Schwartz. For
purposes of disclosing thermoplastic materials that can be made
into customized dental trays, the foregoing patents are
incorporated herein by reference.
[0042] FIG. 2 depicts a generally flat preformed sheet 24 that may
alternatively be used to form customized dental trays according to
the inventive methods disclosed herein. The preformed sheet 24
preferably comprises ULDPE, either alone or blended with one or
more additional polymers. The preformed sheet 24 is preferably a
square having dimensions of about 5.times.5 inches, although other
shapes and sizes are within the scope of the invention. For
example, the preformed sheet may be cut into a generally
horse-shoe-shaped configuration (not shown) generally corresponding
to the size and curvature of a person's dental arch.
[0043] In a preferred embodiment, the preformed tray 10 or sheet 24
become plastically deformable at a predetermined temperature in a
range of about of about 110.degree. to about 180.degree. F., more
preferably in a range of about 120.degree. to about 170.degree. F.,
and most preferably in a range of about 130.degree. to about
160.degree. F. The preformed tray 10 or sheet 24 preferably becomes
plastically deformable after being immersed in water at temperature
of about 160-212.degree. F. (or by heating using other appropriate
heating means) within about 1-30 seconds, more preferably within
about 2-15 seconds, and most preferably within about 4-8
seconds.
[0044] The preformed tray 10 may advantageously be made available
in a variety of sizes to accommodate varying sizes of teeth and/or
dental arches. This aids tray forming and customization because a
preformed tray that more closely fits the patient's mouth and teeth
size can be selected. The preformed sheet 24 may likewise come in
various sizes although it is more amenable to tray-forming methods
that employ "one size fits all" approach than the preformed tray
10.
[0045] FIGS. 3A and 3B depict the optional use of a blockout
material in order to yield a finished customized tray incorporating
one or more reservoirs therein. Reservoirs may be desirable in
order to provide additional dental: composition adjacent to the
teeth and/or gingival tissue being treated. Once a customized tray
has been formed and then removed from the person's teeth, the
blockout material is removed.
[0046] FIG. 3A depicts the application of a flowable blockout
material 30 (e.g., a curable resin) onto the surfaces 32 of a
person's teeth 34 (or stone cast) using a syringe tip 36 attached
to a syringe (not shown). As shown therein, the flowable blockout
material 30 may be applied to so as to substantially cover the
tooth surfaces 32 just shy of the gingival margin 38, although it
is certainly within the scope to cover the entire tooth surface
and/or at least a portion of the gingiva if desired (or the
portions of the stone cast representative of the person's tooth
surfaces and gingival margin).
[0047] FIG. 3B depicts the application of a wax, clay or putty
blockout material 40 by pressing it against the tooth surfaces (or
stone cast) using a person's finger 42. Alternatively, highly
viscous blockout materials or clays may be applied and/or excess
blockout material may be removed using an application tool (not
shown), such as a spatula.
[0048] The preformed tray 10 preferably has a composition and
thickness so that when it is heated so as to become plastically
deformable, the tray will tend not to collapse but will
substantially retain its shape so that it can be readily molded
into a customized dental tray. The benefit of using ULDPE is that
ULDPE allows for the use of a thinner preformed tray or sheet
compared to conventional tray materials.
[0049] In order to achieve the desired mechanical properties, both
in the preformed tray and in the finished customized tray, the
bottom wall 12 will preferably have a thickness of about 0.4 mm to
about 2 mm, more preferably in a range of about 0.6 mm to about 1.5
mm, and most preferably in a range of about 0.8 mm to about 1.3 mm.
The front side wall 14 and rear side wall 16 preferably have wall
thicknesses in a range of about 0.3 mm to about 1.8 mm, more
preferably in a range of about 0.4 mm to about 1.4 mm, and most
preferably in a range of about 0.7 mm to about 1.2 mm.
[0050] When using a preformed sheet to manufacture the customized
dental trays according to the invention, the preformed sheet will
preferably have a thickness of about 0.4 mm to about 2 mm, more
preferably in a range of about 0.6 mm to about 1.5 mm, and most
preferably in a range of about 0.8 mm to about 1.3 mm.
[0051] Reference is now made to FIGS. 4A-4C, which depict various
methods for heating a preformed tray prior to forming the
customized dental tray. FIG. 4A depicts a preformed tray 10
immersed in a bath 50 of hot or boiling water or other suitable
liquid. The handle 20 allows the tray 10 to be submerged easily by
the user and will advantageously remain outside the bath 50 as
shown in FIG. 4A. This allows the tray 10 to be easily removed from
the bath 50 after being heated to the desired temperature. In the
alternative, the handle 20 may be submerged in the bath 50 along
with the tray 10 and then grasped using a pair of tongues or other
suitable gripping device (not shown) in order to remove the tray 10
from the bath 50.
[0052] FIG. 4B depicts the alternative use of a heat gun 52 to heat
the preformed dental dray 10. FIG. 4C depicts the alternative use
of a torch 54 to heat the preformed dental dray 10. When using
these alternative heat sources, care should be taken to heat the
tray evenly, such as by moving the tray and/or heat source back and
forth to avoid heating a single area to the exclusion of other
areas.
[0053] Referring now to FIG. 5, after the tray 10 (or sheet 24, not
shown) has been heated sufficiently so as to assume a plastically
deformable condition, the tray 10 (or sheet 24, not shown) is
inserted into the mouth of a person 56 (e.g., a patient) over the
upper or lower teeth and the patient 56 closes his or her mouth.
The preformed tray or sheet is plastically deformed (i.e., molded)
so as to conform and correspond to at least a portion of the
person's teeth. The person may assist this process by sucking and
creating a vacuum within the person's mouth. This causes any water
and/or air interposed between the person's teeth and tray material
to be removed so that the tray material can more closely conform to
the shape of the person's teeth. Additional forming pressure can be
applied by the fingers of the person or the fingers of another
assisting in the formation of the customized tray. The person may
also use his or her tongue to press the tray material more closely
against the lingual tooth surfaces. Nevertheless, due to the
aforementioned benefit of preformed trays or sheets comprising
ULDPE to shrink and cling against and around the person's teeth
when they begin to cool, less mechanical force is needed to cause
the trays or sheets to adequately and accurately conform to the
person's teeth (or a stone model) compared to other tray materials
known in the art.
[0054] After the preformed tray 10 (or preformed sheet 24) has been
adapted so as to correspond to the person's teeth and has remained
in the person's mouth for a significant period of time, it will
naturally begin to cool. After the tray 10 (or sheet 24) has been
customized so as to form an impression 58 within the intermediate
customized tray 60 (FIGS. 6A and 6B) and is no longer plastically
deformable, it is taken out of the mouth. It may be further cooled
as desired, such as by placing the intermediate customized tray 60
in cold water or by letting it cool to room temperature. When
cooled sufficiently, the impression 58 within the final customized
tray 70 (FIG. 7) will become permanent. That is, the tray material
can then be deformed to the extent that it is flexible and
resilient but will return to its original customized shape upon
removal of the deformation force. If additional plastic deformation
is needed, either immediately or later, the customized trays 60, 70
may be heated so as to become plastically deformable, plastically
deformed, and then cooled as describe above.
[0055] In the alternative, the intermediate customized tray 60 can
be made by vacuum forming a preformed sheet that comprises UDLPE
using conventional tray forming methods from a stone cast of a
person's teeth. The preformed sheet 24 may be heated before or
during vacuum formation as desired. The advantage of using a
preformed sheet comprising UDLPE is that the final customized tray
made therefrom can be thinner, more flexible, and more transparent
compared to convention vacuum formed dental trays. It is also
within the scope of the invention to form a customized dental tray
from a preformed tray comprising UDLPE using a stone cast in order
to obtain the same advantages.
[0056] In another embodiment, a preformed sheet 24 comprising ULDPE
is placed over the person's teeth with the assistance of an
auxiliary impression of the person's teeth. First, an impression of
the person's teeth (not shown) is made using any suitable
impression material (e.g., alginate or silicone). Second, the
preformed sheet 24 is heated so as to become plastically
deformable. Third, the heated preformed sheet 24 is placed over the
impression of the person's teeth. Fourth, the preformed sheet 24 is
placed over the person's teeth with the assistance of the
impression in order to cause the sheet to conform to the person's
teeth and form a customized tray. The impression assists in causing
the preformed sheet to conform to the person's teeth.
[0057] Once the intermediate customized tray 60 has been formed
using the preformed tray 10, the detachable handle 20 can be
removed, such as by cutting or tearing. The customized trays 60, 70
may be sanded or otherwise smoothed in the area where the
detachable handle 20 was cut or removed so as to remove any points
or edges that might cause discomfort to the patient.
[0058] As shown in FIGS. 6A and 6B, once formed, the intermediate
customized tray 60 formed by whatever means can be trimmed as
desired to yield a finished customized tray of a desired shape,
such as to yield the finished tray 70 depicted in FIG. 7. In one
embodiment, the customized dental tray can be trimmed so as to
terminate at or shy of the gingival margin on both frontal and
lingual surfaces. It may be desirable to scallop or trim the
customized dental tray up and around interdental papilla so that
the finished tray does not overlap them so as to achieve maximum
patient comfort.
[0059] In general, the customized dental tray can be trimmed to
cover a portion of the teeth, just the teeth, or to cover a portion
of the gingival margin in addition to the teeth. In one embodiment,
it may be desirable to trim the customized dental tray so that
enough tray material is left to assure that all of the tooth can be
covered to within about 1/4 mm to about 1/3 mm of the gingival
margin.
[0060] As shown generally in FIG. 7, the finished tray 70 comprises
a front upper periphery 72 that overlaps a desired portion of the
person's frontal tooth surfaces, and optionally at least a portion
of the gingival, when in use. The dental tray also includes a rear
upper periphery 74 that overlaps a desired portion of the person's
lingual tooth surfaces when in use. Together, the front upper
periphery 72 and the rear upper periphery 74 comprise the "upper
periphery" of the customized dental tray. The finished tray 70
further also includes a main body portion 76 having an impression
78 formed therein.
[0061] The customized dental trays made according to the invention
can have any desired thickness. The customized trays wall
preferably have an average wall thickness in a range of about 0.3
mm to about 1.8 mm, more preferably in a range of about 0.4 mm to
about 1.4 mm, and most preferably in a range of about 0.7 mm to
about 1.2 mm.
[0062] The finished customized dental trays according to the
invention are useful for teeth bleaching or other dental
treatments. In use, a desired dental composition is placed within
the main body portion of the tray and the tray is placed over the
person's teeth. The customized tray holds and maintains the dental
composition against the person's teeth. The customized dental trays
according to the invention can be used once or repeatedly as
desired. Transparent trays made using UDLPE or blends thereof are
both visually appealing and more practical in the sense that it can
be readily determined whether the person's teeth are adequately or
evenly covered with the dental composition during treatment.
Comparative Study
[0063] A preformed dental tray similar to the tray depicted in FIG.
1 was made from ULDPE. The tray had a front and rear side wall
thickness of 0.042 inch (1.08 mm) and a bottom wall thickness of
0.5 inch (1.27 mm). A number of such trays were heated in baths of
boiling water having temperatures that ranged between
160-212.degree. F. for a time period ranging from 3 to 20 seconds.
In all cases the trays maintained sufficient physical integrity so
that they could be successfully placed over a person's teeth and
formed into a customized tray. The finished trays were soft,
thin-walled, resilient, comfortable-fitting and virtually
transparent.
[0064] By comparison, preformed trays made from EVA having a
similar wall thickness were not able to maintain their physical
integrity when heated in a similar manner. Instead, such trays
tended to shrink and collapse in a manner that rendered them
virtually useless. The front and rear side walls tended to collapse
together, which made it virtually impossible to place over a
person's teeth. They also shrunk and shriveled in a manner that
substantially altered their initial size prior to being placed over
a person's teeth, thereby further rendering them unsuitable for use
in making a customized dental tray using a person's own teeth as a
template. Studies have shown that preformed trays made from EVA
must be significantly thicker-walled compared to preformed trays
comprising ULDPE in order to perform with minimal adequacy. EVA
trays having a wall thickness less than 1.5 mm have been found to
be inadequate for formation of a customized dental tray using a
person's teeth as a template without the use of an external support
member, such as the outer tray disclosed in U.S. Pat. No. 5,616,027
to Jacobs et al. In general, EVA trays must typically have about
twice the wall thickness as trays made from ULDPE in order to
provide the same structural integrity when heated. This is yet
another surprising and unexpected benefit of using preformed dental
trays that comprise ULDPE.
[0065] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *