Note: Descriptions are shown in the official language in which they were submitted.
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TOOTH POSITIONING APPLIANCE WITH
CURVED INTERCONNECTING ELEMENTS
BACKGROUND OF THE INVENTION
Field of the Invention. The present invention relates generally to the field
of orthodontics. More specifically, the present invention discloses a tooth
positioning appliance with curved interconnecting elements.
Statement of the Problem. A wide variety of orthodontic aligners have
been used for many years in repositioning teeth during orthodontic treatment.
It
should be noted that the terms "aligner", "positioner" and "tooth positioning
appliance" are largely synonymous as used in the orthodontic field.
This type of orthodontic treatment typically involves separate tooth
positioning appliances for the upper and lower teeth. The tooth positioning
appliances fit over the teeth, covering nearly all of the facial and lingual
surfaces,
and also most of the occlusal, or biting surfaces of the teeth. The early
positioners described in the prior art were made from a set of plaster models
derived from three-dimensional negative dental impressions of the patient's
teeth. The plaster dental models were modified by cutting the teeth apart
using a
small jeweler's saw or rotary cutting discs and repositioning the plaster
teeth in a
better, straighter, desired arrangement, and holding the teeth in the new
arrangement by using dental wax. The reset teeth molds provide the basis for
manufacturing the positioners. The resilience of the material from which the
positioner is made provides the energy to move the teeth from their original
position toward the new straightened position. From the earliest disclosure of
the
tooth positioner, many of the proposed designs in the prior art have shown
moving the teeth in a series of incremental steps. Making a series of
appliances
is difficult if the tooth arrangement for each step must be made by hand using
plaster and wax.
Starting in the early 1990's, digital technologies have begun to provide
orthodontists with fundamentally new tools for delivering orthodontic
treatment by
fabricating tooth models in small but accurate incremental steps. Commercially-
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available CAD/CAM software can produce the desired tooth models, from which
a progressive series of appliances can be manufactured. These tools include 3D
imaging of the patient's dentition, and CAD/CAM (computer-aided design and
manufacturing) systems for creating virtual models in orthodontic treatment to
then produce customized orthodontic appliances.
An example of the successful orthodontic application of these digital
technologies is seen in the commercial service known as the Invisalign
program
by Align Technology, Inc. of San Jose, California. The Invisalign program is
largely based on U.S. Patent No. 5,975,893 (Chishti et al.) and many related
patents, including U.S. Patent No. 6,398,548 (Muhammad et al.). Invisalign
tooth
positioners are a progressive series of thin, transparent, U-shaped plastic
appliances formed over computer-generated forming patterns grown from a
virtual model of the patient's dental anatomy. The process for forming
aligners
uses a combination of vacuum, pressure and heat. This forming process is
informally referred to within the orthodontic laboratory community as the
"suck
down" process.
In order to produce a series of Invisalign-type tooth aligners, a technician
first scans a patient's upper and lower model set to obtain CAD-manipulatable
virtual models of a patient's dental anatomy. A model set normally consists of
one upper and one lower plaster model of the teeth, palate and gums. Once the
virtual model of the original malocclusion has been obtained, a technician
will
then undertake steps involving extensive manipulation of the virtual
malocclusion. This involves extensive repositioning of the teeth according to
a
comprehensive and sequential procedure, ultimately arriving at a finished or
ideal
occlusion for that patient. The finished occlusion in the virtual model is
consistent
with the complete repositioning of the patient's upper and lower occlusion
that
would result at the end of successful conventional orthodontic treatment.
After the steps described above are accomplished, the technician
possesses two versions of the patient's teeth available within the virtual CAD
environment. One version represents the original malocclusion and the other
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represents the ideal occlusion. In other words, the technician has the
beginning
and the end states.
The next step in the Invisalign process involves the creation of an
incremental, progressive series of physical forming models. Each of these
forming models represents a snapshot of the patient's future occlusion at
specific
incremental steps along the patient's proposed treatment sequence between the
beginning and the end conditions as described above. To accomplish this, the
technician creates a virtual "first transition model" that sees a slight
repositioning
of all or most of the teeth. This first transition model sees some or all of
the teeth
being subtly moved from their original pre-treatment positions to a virtual
first
transition position that is in the direction of their intended finished
positions.
Similarly, a second virtual transition model is created that sees the virtual
teeth
being moved again slightly further in the desired directions. The objective of
the
Invisalign technician is to create a series of progressive models, each biased
slightly further than the previous one, and each moving the teeth slightly
closer to
their finished target positions. A final forming model will take the teeth
from the
series of transition positions and move them into their final, desired
positions.
Once such a series of virtual intermediate forming models has been
created and a final forming model has been created by the Invisalign
technician,
the digital code representing each of the models in the series is directed to
operate a computer numerically-controlled (CNC) machine known as a rapid
prototyping machine. Within a rapid prototyping machine, the series of
physical
forming models are grown using any of number of conventional processes, such
as stereo lithography or 3D printing. The growing step results in the
production of
hard, physical duplicates of each of the series of virtual intermediate models
and
the final model.
The next step of the Invisalign process sees each of the series of physical
models being in turn mounted in a suck-down machine where a combination of
pressure, heat and vacuum is used to form the actual series of progressive
aligners from plastic sheet material of a constant thickness. Once the series
of
progressive aligners are formed and trimmed, they are sequentially labeled,
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packaged and shipped to the attending orthodontist. The orthodontist then
schedules an appointment for the patient, at which time the aligners and
instructions for their use are given to the patient. The patient is instructed
to wear
the first set of aligners for a period of time, typically two weeks. After
that, the first
set is discarded and the patient transitions to the next set of the series and
so on.
The aligners serve to urge the patient's teeth to move according to the
positional biases created virtually by the lnvisalign technician. The teeth
are
progressively biased and urged to move in desired directions toward their
predetermined finished positions by the resilience of the polymeric material
of the
aligner. In response to the gentle but continuous forces delivered by the
aligners,
certain physiological processes involving the creation and resorbtion of the
bone
supporting the roots of the teeth are initiated. The net result is the slow,
progressive orthodontic movement of the roots of the teeth through the
underlying bone toward desirable positions and orientations.
Physiologic processes occur when forces are applied to teeth, resulting in
bone resorption and new bone apposition. Studies have shown that the most
rapid tooth movement occurs when light gentle continuous forces are applied to
teeth. Conventional aligner appliances tend to apply heavier forces when the
appliance is first placed on the teeth, and the forces decay away fairly
rapidly
after the appliance has been in place for a day or so. The reason for making
many stages of aligners corresponding to very small incremental movements is
to keep the forces lighter, and to re-establish the force when it decays by
going
on to the next aligner stage. Although in principle the use of many stages of
aligners should allow the delivery of lighter more continuous forces, in
practice
there are still problems with providing adequate tooth engagement and with
keeping force delivery within the desired physiological range.
Many conventional removable aligners are limited by their design and the
mechanical properties of the clear thermoplastic materials that are currently
utilized. The clear polymeric materials make the aligner nearly invisible, and
that
is a great advantage over fixed stainless steel hardware and metal braces. On
the other hand, conventional polymeric materials used in forming aligners have
a
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very limited ability to flex. This is particularly a problem when aligning
teeth that
are not fairly well lined up in the beginning of treatment.
Even when very small movements during each stage are attempted, the
appliance may fail to properly engage teeth that need to be moved because the
appliance is not adequately flexible and is not designed to allow movement
within
the plane of the material. If a particular aligner fails to properly engage a
tooth,
then that tooth will not move to the proper place to engage the next
successive
aligner in the series. The only present solutions available when aligners fail
to
properly engage a tooth are: (1) reduce the amount of movement attempted for
that particular stage; or (2) place a larger bonded attachment on the tooth.
Both
of these solutions require reworking the computerized treatment plan. If the
plan
is not revised, with each successive stage of the appliance, the fit of the
aligners
deteriorates, and after just a few stages, it becomes obvious that the teeth
are
not moving according to the original computerized treatment plan, forcing a
revision of the treatment plan.
Solution to the Problem. The present invention seeks to overcome the
limitations of the lack of flexibility of the appliance material by providing
a tooth-
clasping element for each tooth that is connected by curved interconnecting
elements to the tooth-clasping elements of nearby teeth. The curved
interconnecting elements are flexible enough to allow each tooth-clasping
element to remain firmly engaged in place. The flexible properties of the
interconnecting elements are controlled by the choice of materials, by the
cross-
section of the interconnecting elements, and by the shape of the
interconnecting
elements. The shape chosen in most of the embodiments of the interconnecting
element in the present invention is a small radius loop configuration, where
the
radius of the loop is preferably about half of the width of the tooth.
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SUMMARY OF THE INVENTION
This invention provides a removable, thin-shell tooth positioning appliance
having a plurality of tooth-clasping elements for removably engaging
attachments
bonded onto selected teeth, with flexible curved interconnecting elements
connecting the tooth-clasping elements on nearby teeth.
These and other advantages, features, and objects of the present
invention will be more readily understood in view of the following detailed
description and the drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be more readily understood in conjunction with
the accompanying drawings, in which:
FIG. 1 is a perspective view of a lower dental arch 10 with the present
appliance positioned above it. The U-shaped wire interconnecting elements 17
are shown on both buccal and lingual sides of the teeth 11. Dotted lines
indicate
the path the appliance would follow to be seated in place on the teeth 11.
FIG. 2 is a front elevational view of an interconnecting element 17 having
flattened ends 18.
FIG. 3 is a side view of a portion of the appliance fitted on some of the
teeth in the upper right quadrant.
FIG. 4 shows views from five different directions of a single tooth (upper
right first premolar) with bonded attachments 12A and 12B, a tooth-clasping
element 15, and U-shaped wire-loop interconnecting elements 17 in place.
FIG. 5 shows a 3-dimensional view of a rectangular bonded attachment
12A with the X, Y, and Z axes indicated.
FIGS. 6 ¨ 9 provide views of three types of simple tooth movement in the
transverse plane. FIG. 6 illustrates an initial view of unmoved tooth, with CR
and
CC points located. FIG. 7 shows lingual root tipping movement with crown
center
remaining stationary. FIG. 8 shows a buccal crown tipping movement with center
of resistance remaining stationary. FIG. 9 indicates horizontal transverse
translational (bodily) movement without tipping.
FIG. 10 is a side view of an appliance fitted on some of the teeth in the
upper right quadrant. The appliance is similar to that shown in FIG. 3, but a
tooth
has been extracted and other teeth are being moved to close the extraction
space. The tooth-clasping element of the teeth adjacent to the extraction
space
on either side has been modified to include a straight arm extension of the
buccal
flange. The arm extends over the gum line and includes a hook, or button, or
other attachment means for installing an elastic band to apply additional
force to
close the space. Because the elastic band is attached near the center of
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resistance of the tooth near the center of the root of the tooth, the tipping
moment
is reduced, thereby making it easier to avoid tipping the tooth while the
space is
closing.
FIG. 11 shows a perspective view of a lower arch dental model with
another embodiment of the appliance positioned above it. The appliance is made
of a single piece of material, but localized regions of the appliance function
as
tooth-clasping elements and as flexible curved interconnecting elements.
Dotted
lines indicate the path the appliance would follow to be seated in place on
the
model.
FIG. 12 shows a side view of a portion of the appliance in FIG. 11 fitted on
some of the teeth in the upper right quadrant.
FIG. 13 presents an enlarged view of FIG. 12 with added support ridges
43 to the interconnecting elements and added support ridges 44 around the
bonded attachments.
FIGS. 14 -21 show cross-sectional views of interconnecting elements with
a variety of shapes for the added support ridges 43, 44.
FIG. 22 shows another embodiment of the appliance fitted on teeth in the
upper right quadrant, similar to the view shown in FIG. 12. In this embodiment
the large curved loops of the interconnecting elements 41 are folded over so
they
are in an inverted position. In this position they still function in much the
same
way, but they are less likely to interfere with buccal frenum attachments. The
mechanics of the inverted loop tend to keep the root positions closer together
as
the loop is stretched open. It should be noted that the entire appliance,
including
the interconnecting elements 41, can still be fabricated as a single piece.
FIG. 23 is a modification of the embodiment shown in FIG. 12 in which
different materials are used to fabricate the tooth-clasping elements 15 and
the
curved interconnecting elements 42.
FIG. 24 shows a side view of another embodiment of the appliance fitted
on some of the teeth in the upper right quadrant. This embodiment is also a
single piece appliance like that shown in FIGS. 11 and 12. The difference is
the
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flange portion 16 of the appliance covering some of the gum tissue on the
facial
side (shown) and lingual side (not shown) and the interdental portion 52 of
the
flange function as the flexible interconnecting elements.
FIG. 25 shows a perspective view of a lower arch dental model with
another embodiment of the appliance positioned above it. The small curved
flexible polymer interconnecting elements are shown between the tooth-clasping
elements. Dotted lines indicate the path the appliance would follow to be
seated
in place on the model.
FIG. 26 shows a side view of the appliance fitted on some of the teeth in
the upper right quadrant.
FIG. 27 shows views from five different directions of a single tooth (upper
right first premolar) with bonded attachments 12A and 12B, a tooth-clasping
element 15, and small, curved flexible interconnecting elements 30 in place.
FIG. 28 is a cross-sectional view of a dental model 10 of the lower teeth
with the plane passing transversely through the centers of the second premolar
teeth 11. The tooth-clasping elements on the lower second premolar teeth are
shown in place, seated on the teeth of the dental model. The external surfaces
13A and 13B of the teeth in the model, on both the buccal and lingual sides of
the teeth, between the gum line and the bonded attachment have been moved
inward (toward the center of the tooth) a small distance, as indicated by the
dotted lines.
FIG. 29 is a detail cross-sectional view of the dental model with the tooth-
clasping elements corresponding to FIG. 28.
FIG. 30 is a perspective view of a lower dental arch 10 with another
embodiment of an appliance having longer interconnecting elements 17A and
17B on both the buccal and lingual aspects of the appliance segments.
FIG. 31 is a front view of another embodiment of the appliance with longer
interconnecting elements 17 on the buccal aspect of the appliance segments.
FIG. 32 is a bottom view corresponding to FIG. 31.
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FIG. 33 is a front view of yet another embodiment of an appliance having
longer interconnecting elements 17 between the tooth-clasping elements 15 on
individual teeth.
FIG. 34 is a side view corresponding to FIG. 33.
FIG. 35 is a right side view of another embodiment of an appliance on the
upper right teeth with an interconnecting element 17 connected from the
posterior appliance segment near the first molar tooth to the anterior
appliance
segment directly above the central incisors.
FIG. 36 is a right side view of another embodiment of an appliance on the
upper right teeth with an interconnecting element 17 made of wire connecting
the
posterior appliance segment with the anterior appliance segment.
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DETAILED DESCRIPTION OF THE INVENTION
Turning to FIG. 1, the present tooth positioning appliance includes the
following major elements: (1) bonded attachments 12A, 12B bonded to the
lingual or buccal surfaces of selected teeth 11; (2) tooth-clasping elements
15
removably engaging the bonded attachments 12A, 12B; and (3) curved
interconnecting elements 17 extending between adjacent tooth-clasping
elements 15. In particular, the tooth-clasping elements 15 include recesses
designed to fit over projecting elements or buttons called "bonded
attachments"
12A, 12B that are bonded directly to the teeth. The bonded attachments 12A,
12B are not typically removable by the patient during the course of active
orthodontic treatment.
It is desirable to have the tooth-clasping elements 15 on the front teeth
made of a clear polymeric material. Currently, several different plastic
materials
including urethanes and polycarbonates can be thermoformed over tooth models
to produce the desired tooth alignment appliances. The material can be any
suitable material. It should also be noted that the tooth-clasping element 15
can
be a separately manufactured part or a functional region of a single-piece
appliance.
The bonded attachments 12A, 12B are typically bonded to the buccal or
lingual surfaces of selected teeth 11, as shown in FIG. 1. For example, the
bonded attachments can have a substantially rectangular shape with parallel
sides, as shown in FIG. 5, although it is to be understood that there are many
possible shapes for bonded attachments that would be suitable. The bonded
attachments 12A, 12B are utilized for two purposes: (1) the bonded attachments
12A, 12B increase the retention of the tooth-clasping elements 15 to the teeth
11,
(or in other words, the appliance is less likely to become dislodged from the
desired location on the teeth); and (2) the bonded attachments 12A, 12B have a
shape that allows the tooth-clasping elements 15 to transmit desired forces to
the
teeth in three-dimensions, thereby providing control over root movement. In
the
rectangular bonded attachment 12A shown in FIG. 5, the parallel outer edges of
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the attachment 12A provide surfaces for positive engagement to allow forces to
be applied to the teeth to accomplish root movement under control. Inner
surfaces of an attached projection such as can be provided by grooves or
special
shapes can also provide this control. Grooves or special outside shaping can
help guide the tooth-clasping element into position. The bonded attachments
can
be pre-made of any suitable material including dental composite, clear or
tooth-
colored ceramic materials, or any suitable clear plastic material. The
attachments
12A can be bonded to the teeth using conventional bonding techniques and
adhesives that are well-known in the art including the steps of mildly acid-
etching
the enamel prior to bracket placement. A technique well known in the art
called
indirect bonding can be utilized, with a pre-formed guide made of flexible
material
holding the attachments in the desired position while the adhesive is curing
to
ensure accurate attachment placement on the teeth. The bonded attachments
can alternatively be fabricated out of dental composite using pre-made hand-
held
molds for one tooth at a time placement, commercially available for this
purpose.
A third alternative is to utilize a mold made using 3D CAD/CAM technology,
where the shape and the size of the bonded attachments are planned in the
computer and a model of the entire dental arch with attachments in place is
printed using a 3-D printer. From this model, a mold is made from which to
fabricate and place dental composite attachments in precisely the right
location
directly on the teeth.
Preferably, the tooth-clasping elements 15 include a hole of precise
dimensions (e.g., a rectangular hole) through which the bonded attachment 12A,
12B projects to removably engage the tooth-clasping element 15. Alternatively,
a
recess on the inside of the tooth-clasping element 15 of exactly the same
shape
and size as the bonded attachment 12A, 12B should work equally as well,
particularly if the tooth-clasping element 15 is printed, because of the
ability of
the printing process to produce a more precise fit than can be obtained by
thermoforming.
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The tooth-clasping elements 15 are be attached to flexible curved
interconnecting elements 17 of many types, as illustrated in the drawings. In
some embodiments of the present invention, the appliances are made of one
piece of material, and the tooth-clasping element and the flexible
interconnecting
elements are all part of a monolithic whole unit. Functionally, different
regions of
the single-piece positioner serve as the tooth-clasping element 15 and the
flexible interconnecting elements 17.
It is anticipated that the improved tooth positioners of the present invention
will be produced by planning and designing the appliances using computerized 3-
D CAD/CAM software. Many off-the-shelf software programs are currently
available that are capable of this function. Over the long-term, it will be
beneficial
to write new software that integrates easily with the skill levels of
orthodontist
end-users, to simplify their use of the product. Open-source software that can
be
modified is currently available to perform this function. The standard surface
mapping computer algorithms define the surface as a series of triangles. The
actual physical production of the appliances can be accomplished by vacuum-
forming thermoplastic materials over models produced digitally and combining
the thermoformed portion of the appliance with the other necessary elements.
This step is followed by using computer automated trimming technologies such
as CNC milling or laser cutting. In particular, the clear tooth-clasping
elements
could be produced by vacuum thermoforming. In the single-piece embodiments
of the present invention, the tooth-clasping elements and the flexible
interconnecting elements could all be vacuum thermoformed together.
Alternatively, positioners can be made without first producing 3D models
via 3D printing. A big advantage of direct 3D printing is that more complex
shapes could be more easily printed, and almost no trimming of excess material
would be necessary, saving time and avoiding wasted material. Some new 3D
printers can print more than one material at the same time. The flexible
interconnecting elements could be printed along with the tooth-clasping
portion,
and they could be made of differing materials. The materials can be blended or
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intertwined which will avoid the need for a separate attachment step in
manufacturing. Another option involves direct CNC milling of the appliances or
portions of the appliances from a block of plastic material. It is anticipated
that
the present appliances will be made in a series. Each appliance will move
teeth a
small distance, and then successive stages will continue the movement in small
steps toward the desired goal. Each stage of the appliance can be fabricated
in
such a way as to fit over the teeth where they ideally should be for the next
step
or stage. The appliance will have to be deformed to fit over the teeth in
their
present position. The tooth-clasping elements 15 should fully engage each
tooth.
If the patient wears the appliance for a sufficient number of hours each day,
after
the appliance has been worn for a few weeks, the resiliency of the appliance
will
carry the teeth toward the desired position for the end of that particular
stage.
Then the next stage of the appliance will be placed on the teeth and will
carry the
teeth another prescribed distance, and so on until the desired final position
is
reached. It is likely to be necessary to take new impressions or new digital
scans
every few stages to keep the appliances fitting accurately as the process of
straightening the teeth progresses.
Many of the accompanying drawings show tooth-clasping elements fitted
over individual teeth. If adjacent teeth are aligned, and it is anticipated
that this
will routinely occur during later stages of treatment, it is not necessary to
generate a separate tooth clasp for each individual tooth in each stage.
Groups
of adjacent teeth may have tooth-clasping portions combined if these teeth are
well aligned with each other. It may also be desirable in certain stages of
treatment to combine teeth together in groups to be used as anchorage units,
to
provide better control over the movements of other groups of teeth. In these
cases, the present appliance can be divided into multiple thin-shell segments.
Each thin-shell segment can be designed to engage a group of adjacent teeth
(i.e., one or more adjacent teeth). However, only select teeth in each group
are
equipped with bonded attachments 12A, 12B to engage corresponding tooth-
clasping elements in the thin-shelled segment. This concept is somewhat
similar
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to that used in orthodontic treatment with fixed braces, especially when
extraction
spaces are being closed and is well-described in the prior art. It is also
possible
to combine features of several of the embodiments described in this disclosure
into one appliance to accomplish certain types of movements more efficiently.
To summarize, the embodiment of the present invention shown in FIGS. 1
¨ 4 includes clear tooth-clasping elements 15 fitted over teeth 11 to which
bonded attachments 12A, 12B have been placed on both the buccal and lingual
sides. The tooth-clasping elements 15 are connected together using flexible U-
shaped interconnecting elements 17 made of wire loops attached to the flange
(or extension) 16 of the tooth-clasping element 15 that covers part of the gum
tissue adjacent to the teeth on both the buccal and lingual sides. FIG. 2 is a
front
elevational view of a wire interconnecting element 17 having flattened ends
18.
The wire can be made preferably of nickel-titanium shape-memory wire, heat
treated to the desired shape and of the appropriate dimensions, although other
suitable materials can be utilized. The clear tooth-clasping elements 15 will
be
nearly invisible on the teeth 11, and the wire interconnecting elements 17
will go
over the gum tissue in a less visible zone. This embodiment may have the
greatest flexibility, and it is therefore anticipated this will be used to
correct tooth
rotations and crowding in situations where other embodiments cannot be used.
This embodiment may be somewhat more difficult to manufacture because of the
multiple parts and materials. The curved interconnecting elements 17 can also
be
mounted in an inverted position. Although the loops will be in a more visible
location, inverted loops may be preferred for posterior teeth.
In particular, the bonded attachments 12A, 12B are preferably placed on
the buccal and lingual aspects of all teeth, upper and lower, although there
may
be some instances where not all teeth have all the attachments. In the
illustrations, rectangular bonded attachments are shown. The tooth-clasping
elements 15 are preferably made of a clear plastic material or other suitable
material cover most of the facial, occlusal, and lingual surfaces. The tooth-
clasping elements adapt tightly to and conform to the outer contours of the
teeth
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and the bonded attachments. There can optionally be an open window through
which the bonded attachment 12A, 12B projects, or the bonded attachment can
be covered completely by the appliance. Either way, the tooth-clasping element
15 adapts tightly to the bonded attachment 12A, 12B and the portion of the
crown
of the tooth covered by the tooth-clasping element so as to allow forces
transmitted to the tooth-clasping element 15 to be directly transmitted to the
tooth. The forces can be in any direction needed to correct the malocclusion.
The
curved interconnecting elements 17 are preferably made of wire with flattened
ends to prevent the wire from being pulled out of the material covering it
that
forms the bond of the wire with the tooth-clasping element 15.
This embodiment of the present invention includes a removable
orthodontic appliance that will be worn by an orthodontic patient after the
bonded
attachments 12A, 12B have been placed on the teeth by the orthodontist,
preferably using a method that allows great precision such as the
aforementioned indirect bonding method or a computer-generated mold. The
appliance will be made in multiple stages, each one moving the teeth in small
increments toward a final desired goal envisioned by the orthodontist and
planned in the computer using commercially-available CAD/CAM software
designed for this purpose. This embodiment is most likely to be used in the
early
stages of treatment when the teeth are in their most crowded or irregular
state.
The flexibility of Ni-Ti wires is greater than the flexibility of any of the
other
materials utilized on the interconnecting elements in other embodiments
disclosed herein. Therefore, this should allow complete engagement of the
tooth-
clasping elements in more complex orthodontic cases than have previously been
treatable with removable positioner appliances.
The present appliance may be formed from a model of the patient's dental
anatomy made of conventional plaster or a dental stone model, made by pouring
the plaster or dental stone when it is uncured (wet) into an impression made
of
alginate, polyvinyl siloxane, silicone, polysulfide rubber or other suitable
dental
impression material. After the plaster or stone has cured (dried), the excess
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material is trimmed using a conventional rotating wheel model trimmer so the
base is flat and the edges of the base are smooth. Alternatively, the dental
model
can be obtained by using conventional digital scanning techniques of the teeth
directly in the mouth using a commercially-available digital intra-oral
scanner, or
the plaster or stone model can be scanned using a commercially available
digital
model scanner, or the impression itself can be scanned using a digital scanner
or
a computerized tomography scanner (CT). From the digital data obtained by the
scan, a three-dimensional model can be produced using a commercially
available stereo lithographic printer, or a commercially-available rapid
prototyping
printer, or a model can be produced using a commercially-available CNC milling
machine operating on any suitable material, most likely a plastic block.
The three-dimensional images of the teeth (anatomic portion) are attached
to the base of the dental model. The images of the teeth (virtual teeth) are
the
same size and shape and in the same relative location to each other as the
real
teeth in the mouth of the dental patient. In other words, the model of the
teeth is
an accurate representation of the real teeth in the mouth of the patient.
The bonded attachments 12A, 12B serve the purpose of providing an
altered shape attached to, but different from the surface of the tooth. The
bonded
attachments are vital for retention of the removable appliance in the correct
location on each tooth. The bonded attachments also allow the tooth-clasping
element to transmit forces to the tooth so as to provide complete control over
the
position of the tooth in three dimensions. The bonded attachments protrude
from
the surfaces of the teeth, and in this particular illustration, the
attachments have
straight sides to properly orient the tooth-clasping elements in a desired
position.
As a general rule, the bonded attachments will be placed on the teeth prior to
beginning any tooth movement.
The tooth-clasping elements 15 are formed utilizing an accurate model of
the teeth 11. As shown in FIG. 1, there are separate tooth-clasping elements
15
to fit over each tooth in the arch, with shapes corresponding to the shape of
each
tooth. It can be seen that there are spaces between each tooth-clasping
element
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(even if the teeth themselves are touching). The inner surface of the tooth-
clasping element should be almost exactly the same shape and dimensions as
the outer surface of the tooth to which it will be applied. Because the
material
from which the tooth-clasping element 15 is made has some thickness, the outer
surface of the tooth-clasping element 15 will have greater dimensions but a
similar shape corresponding to the inner surface of the tooth-clasping
element.
The outer surface is essentially a slightly enlarged or inflated version of
the inner
surface. The tooth-clasping element 15 typically has components that touch the
tooth 11 on the buccal (outer), occlusal (top of bottom teeth, and bottom of
top
teeth) and lingual (inner) surfaces.
The tooth-clasping element 15 may also include a clear flange (or
extension) 16 as an integral part of the tooth-clasping element 15. The flange
16
generally extends over the gum tissue of the patient on the facial and lingual
sides of each tooth by a distance of approximately 2 to 3 mm, although the
flange
does not have to project that far. The flange 16 does not typically contact
the
gum tissue. There is clearance of at least 0.5 to 1 mm.
The flange 16 can serve as the attachment area for the flexible curved
interconnecting elements 17. It is also possible to attach the flexible
interconnecting element 17 directly to the main body of the tooth-clasping
element 15, for example in the area between the bonded attachment 12A, 12B
and the gum line without utilizing the flange. This may be particularly
desirable on
posterior teeth where the need to hide the loop behind the lips would not be
as
much of a cosmetic concern. The advantage this would provide is to reduce the
risk of interference between the loops and the buccal frenum attachments.
There
would be a smaller vertical dimension to the appliance with the same sized
loops.
In this particular embodiment, each interconnecting element 17 is a U-
shaped wire, preferably made of heat-treated Ni-Ti shape memory wire. The U-
shaped interconnecting element 17 extends outward slightly to avoid contact
with
the gum tissue, and maintains an open space 19 between adjacent tooth-
clasping elements and allows range of movement. The exact dimensions of the
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U-shaped loop, and the thickness and heat-treatment of the wire to achieve the
desired shape-memory properties can be varied to produce the desired
physiologic forces applied to the tooth-clasping elements, and therefore the
desired forces applied to the teeth. Alternatively, the flexible
interconnecting
element could be made of any suitable material. In this particular embodiment,
the attachment means of the interconnecting element 17 to the tooth-clasping
portion is not shown, primarily because it is transparent, and therefore would
not
be readily visible.
It should be noted that the interconnecting elements 17 have flattened
ends 18 in the embodiment shown in FIGS. 1 and 2. If the flexible
interconnecting element 17 is made of wire, the end of the wire is bent
approximately 90 degrees and is placed in a hydraulic press to flatten the end
18,
possibly with some small serrations pressed into the metal wire. The bent ends
prevent the wire from being pulled out of the clear plastic that encases them.
There are several conventional methods by which the interconnecting element
could be attached to the flange of the tooth-clasping element. (1) Clear cold-
cure
acrylic could be applied over the wire in much the same way that wire elements
are attached to the plastic of retainers commonly used in orthodontics today.
(2)
The same plastic material from which the tooth-clasping element is made could
be applied in a molten state using a glue-gun nozzle and could cover the wire
with a thin layer. This technique could be automated, and the nozzle could be
robotically controlled on an assembly line. (3) A small plastic panel of
approximately the same size as the flange of the tooth-clasping element could
be
placed over the flexible interconnecting element ends, and while being held in
place, a focused ultrasonic welder waveguide horn could be placed adjacent to
the two pieces of plastic to fuse the flange and the small panel together.
Alternatively, rather than flattening the ends of the wire segments, other
means could be employed to prevent the wire from pulling out of the plastic,
such
as a zigzag in the wire, or bending the wire into an L-shape, or doubling it
back
on itself to form a T-shape, or forming the wire into a small circle, etc.
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It should be noted that larger segments of wire could be used than the
short segments shown in FIGS. 1 and 2. A longer segment of wire, containing
multiple loops could be used to connect multiple tooth-clasping elements
together. The wire could be attached using various means, including: (1)
direct
cementation using a composite or plastic cement, covering the wire; or (2) the
tooth clasping elements could be printed or formed in such a way as to have a
groove or recess to receive the wire, and the wire could even snap into place
if
the groove is designed so that the opening to receive the wire is slightly
smaller
than the wire and the portion of the groove where the wire is intended to
reside.
The groove can be square or rectangular in cross-section to receive a wire
which
is square or rectangular in cross-section. The wire could even be one piece
with
multiple loops in it.
FIG. 3 shows a right side view of some of the upper teeth with a portion of
the same type of removable appliance shown in FIG. 1 installed on these teeth.
Reference number 11A designates the root of the upper right cuspid tooth. The
mesial surface 11B of the crown of the upper right cuspid tooth can be seen
just
sticking out beyond the mesial edge of the tooth-clasping element. FIG. 4
shows
views from five different directions of a single tooth (upper right first
premolar)
with bonded attachments 12A and 12B, a tooth-clasping element 15, and U-
shaped wire-loop interconnecting elements 17 in place.
Note the size of the bonded attachments 12A varies with the size of the
teeth. The bonded attachments in this view protrude through holes in the clear
tooth-clasping elements. The holes are of the same size and shape as the
bonded attachments. As discussed earlier, it is not necessary to use
rectangular
bonded attachments, nor is it necessary to use holes in the tooth-clasping
elements to allow protrusion of the bonded attachments through the tooth-
clasping elements. A simple recess in the inner surface of the tooth-clasping
element precisely corresponding to the size and shape of the chosen bonded
attachment geometry will still provide the necessary clasp function that is
vital to
the proper functioning of this appliance. Note there are spaces 19 between
each
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of the tooth-clasping elements 15 even though the teeth themselves may be in
contact. The space prevents the tooth-clasping elements from interfering with
each other. Figure 4 provides an upper right first premolar tooth viewed from
five
different angles showing a single tooth-clasping element 15 with
interconnecting
elements 17 attached as they would be positioned to reach toward adjacent
teeth.
FIG. 5 shows a perspective view of a bonded attachment 12A, with the
three axes of tooth movement intersecting within the center of the crown of
the
tooth (not shown) on which the bonded attachment is fixedly mounted. The x-
axis
in this case is a horizontal axis in the anterior-posterior direction. The y-
axis is a
vertical axis. The z-axis is a horizontal axis in the transverse direction.
The
bonded attachment can be positioned away from the center of the crown of the
tooth. When forces act on the bonded attachment, depending on the direction of
the force, the force produces a moment, which may cause a more complex
movement of the tooth than is at first anticipated.
FIGS. 6 - 9 illustrate three different transverse movements, along the z-
axis, as shown in Figure 5 (i.e., not in the X-Y planes of the bonded
attachments.) An upper right first premolar tooth is shown in all the
drawings,
viewed on the distal side. All of these movements require the resetting of
teeth
from the original position to a new desired position, either in a digital 3-
dimensional file representing the positions of teeth, or using a dental model,
whether resetting teeth manually, or when generating 3-D models from
computerized digital files. FIG. 6 provides a reference view. FIG. 7 shows
lingual
transverse movement of the root with the center of the crown (CC) staying in
the
original position. The movement is a root tipping movement that is relatively
difficult to accomplish, even when using fixed braces. For this movement, it
would be desirable to use a trans-palatal bar to provide additional support to
assure the desired movement. The movement is accomplished primarily by
vertically moving the buccal and lingual sides of the teeth with the bonded
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attachments, although it can be seen that there are small transverse movements
of the tooth surface taking place along with the bonded attachments.
FIG. 8 shows buccal transverse movement of the crown with the center of
the root (or center of resistance, CR, to movement of the tooth) staying in
the
original position. This tipping movement of the crowns of the teeth is
relatively
easy to accomplish, because the roots of the teeth naturally tend to remain in
place. The movement is accomplished by a combination of movements of the
buccal and lingual surfaces of the teeth along with the bonded attachments. In
this drawing, it can be seen that there is approximately the same amount of
vertical and transverse movement of the bonded attachments taking place,
although the transverse tipping movements of the crown tend to naturally occur
when opposing vertical forces are applied to the crowns of teeth, because of
the
resistance of the bone surrounding the roots.
FIG. 9 shows buccal or lingual transverse movement of the entire tooth,
with the center of resistance (CR) and the center of the crown (CC) moving
exactly the same distance and in the same direction. There is no tipping of
the
tooth taking place. This type of movement requires bonded attachments, with
very good engagement of the tooth-clasping element with the flat top and
bottom
surfaces of the bonded attachments to prevent the tooth from tipping.
FIG. 10 shows an embodiment of the present invention that includes a
localized extension of the flange 16 of the tooth-clasping element 15 on
selected
teeth to produce what is essentially an arm 70 for the attachment of
stretchable
elastic members 71 (e.g., rubber elastic bands, made of any suitable
material).
For instance, if a tooth has been extracted as part of the orthodontic
treatment
plan, the closure of the space while keeping the tooth roots parallel on
either side
of the extraction space (avoiding tipping the crowns of the teeth into the
extraction site) has typically been a severe problem when using removable
orthodontic appliances in the past. This is also a problem with fixed braces
on
teeth. One of the solutions routinely used with fixed braces is to place a
rigid arm
with a retentive hook on the brackets (an element commonly used with fixed
CA 02932100 2016-06-03
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braces) on either side of the extraction space to allow the use of elastic
bands to
help close the space. The center of resistance for each tooth is located
approximately in the center of the root of the tooth. Placing the attachment
point
for the elastic band very close to the center of resistance of the tooth
reduces the
tipping moment as the force from the elastic is applied. The roots tend to
stay
more parallel when this method is used to close the space. In the same way,
the
flange 16 of the tooth-clasping element 15 can be extended to a point close to
the center of resistance of the tooth, and an elastic band 71 can be utilized
in the
same way. If there are arms on both the buccal and lingual side of the teeth,
the
forces would be parallel, and the rotational moment present with a band 71
only
on the buccal side would be cancelled. As a practical matter, it would be
uncomfortable for the dental patient with a long appliance arm covering the
gum
tissue on the lingual side of the teeth to wear such a rubber band, although
perhaps not impossible under certain circumstances. It depends on the
curvature
of the palatal tissue. Another possible use might be where root movement is
desired, such as to upright a tipped tooth, but where there is no interdental
space. To avoid tipping teeth that we do not want to tip, a group of teeth
could
serve as the anchor.
FIGS. 11 and 12 show an embodiment formed from a single piece of clear
vacuum-formed or printed material. Functionally, the flexible plastic
interconnecting elements 40 may not have the flexibility of wire
interconnecting
elements, but they will be far easier to manufacture if the appliance is
printed,
and the loops will be less visible. It is anticipated that the flexibility of
the clear
plastic curved interconnecting elements will be sufficient to make the
appliance
workable without resorting to the complex manufacturing and assembly process
required to utilize wire loops as in the first embodiment. If the appliance is
thermoformed and then cut, the instruction set for computerized mill cutting
or
laser cutting will be complex.
This embodiment utilizes the same bonded attachments 12A, 12B as the
other embodiments. The removable positioning appliance is in two pieces, upper
CA 02932100 2016-06-03
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and lower. Each arch appliance is fabricated as a single piece appliance with
regions that function as tooth-clasping elements 15 and curved, flexible
interconnecting elements 40. The regions of the appliance that engage the
teeth
and function as tooth-clasping elements are almost identical in size shape and
form to those of the previous embodiments. The regions 40 of the appliance
that
serve the function of the flexible interconnecting elements are curved, and
are
approximately the same overall size as the U-shaped wire connecting elements
of the first embodiment. Functionally it is almost identical to the first
embodiment,
except the plastic loop is not as flexible or as strong as a wire loop. This
embodiment can be made as a thermoformed appliance over a series of tooth
models, much like currently-marketed aligners, but trimming away the excess
material may be more difficult. It can be accomplished using a CNC milling
cutter,
or a laser cutter, but will require more complex programming than is needed
for
currently used aligners, where only the edge along the gum line needs to be
trimmed. Alternatively, the entire apparatus can be 3-D printed and it is
likely that
is the way the industry will turn once non-toxic printable plastics become
available.
The curved interconnecting elements can be a relatively flat, U-shaped
ribbon made of plastic or metal, for example. However, FIGS. 13 - 21
illustrate
that the physical properties of the curved interconnecting elements can be
modified by the placement of reinforcing ribs or ridges 43, 44 to change the
cross-section of the interconnecting elements 40. The ribs 43 strengthen the U-
shaped loops and can change the torsional and flex properties of the loops.
The
ribs 44 can extend beyond the loops onto the bodies of the tooth-clasping
elements 15 to increase the strength of the tooth-clasping elements,
especially in
the central areas of the clasps 15 where they engage the bonded attachments
12A, 12B. It is relatively easy to manufacture these strengthening ribs 43, 44
if
the appliances are printed using a 3-D printer. In addition, the
interconnecting
elements are not necessarily flat, but rather could have any desired cross-
CA 02932100 2016-06-03
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sectional shape (e.g., circular, oval, tubular, a multi-strand cable, or a
composite
structure).
FIG. 13 is an enlargement of a portion of the appliance shown in Figure
12. The outer edge of the flexible interconnecting elements include
reinforcing
ridges 43 that will be printed into the material forming the interconnecting
elements. Note that the ridges 43 extend onto the flange section of the tooth-
clasping elements and also onto the main tooth-contacting portion of the tooth-
clasping elements. On one tooth, in this case the upper right canine tooth,
the
reinforcing ridge extends to and becomes continuous with a reinforcing ridge
44
that surrounds entirely the bonded attachment on the buccal surface of that
tooth. The purpose of the reinforcing ridges is to add strength and to control
the
flex properties of both the tooth-clasping elements and the flexible
interconnecting elements. It is to be understood that this disclosure does not
limit
the reinforcing ridges 43, 44 to this particular location or configuration.
The
reinforcing ridges can be located anywhere they are needed to add strength and
to control the flex properties of the tooth-clasping elements and the flexible
interconnecting elements.
FIGS. 14 - 21 illustrate several possible configurations for reinforcing
ridges that can be placed where they are needed on the flexible
interconnecting
elements or on tooth-clasping elements. These reinforcing ridges can be any
suitable cross-sectional shape. FIG. 14 shows two rectangular projections to
form a C-shape. FIG. 15 shows a single rectangular projection to form a T-
shape.
FIG. 16 shows double rectangular projections. FIG. 17 shows two rectangular
projections to form an I-shape. FIG. 18 shows two tapered projections to form
a
C-shape. FIG. 19 shows a single tapered projection to form a T-shape. FIG. 20
shows double tapered projections. FIG. 21 shows double tapered projections on
each side to form an I-shape.
The embodiment in FIG. 22 utilizes interconnecting elements 41 in an
inverted U-shape. The inverted loop geometry may be better for keeping
favorable forces applied to the teeth to minimize tooth tipping during space
CA 02932100 2016-06-03
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closure. Conversely, the tooth-clasping elements may be more difficult to
place
on the teeth if the loops are stretched open when the loops are inverted. In
this
embodiment, if produced by using vacuum-formed thin-shell plastic, the
appliance can be fully fabricated with the loops in the normal configuration.
After
completion, the loops can be heated and flexed downward to assume their
reverse configuration. This embodiment should become easily mass-producible
using computer 3-D printing technology, and the inverted configuration should
not require a separate step for loop flexion. The first embodiment shown in
FIGS.
1 ¨ 4 using wire interconnecting elements can also be manufactured with the
wire loops in an inverted position, because a wire loop embodiment may be
better suited for closing interdental spaces.
Returning to FIG. 22, this type of appliance can also be made from a
thermoformed sheet by reheating the loops of the interconnecting elements 41
and flexing them downward into the inverted position. An electric heat gun
with a
blower, or an ultrasonic welder could be used to heat and re-form the
thermoplastic material. If the appliance is printed, it can simply be printed
in the
inverted position. The appliance does not extend as deeply into the buccal
vestibule, and therefore would not be as likely to cause irritation of the
tissue of
the cheek or gum tissue. It also conveys a mechanical advantage. If a loop is
stretched open, such as when there is a space between teeth you are trying to
close, there is not as much pressure placed to move the root apices closer
together. If the loop is inverted, and the loop is stretched open, it tends to
move
the roots closer together. This same inverted loop geometry could be
considered
in the first embodiment, although you would not want to bend the wires
downward. They should be mounted in the inverted position in the beginning.
The embodiment in FIG. 23 involves a modification of the materials
utilized in forming positioner appliances and could be applied to any or all
of the
embodiments of the present invention disclosed herein. If a 3-D printer is
utilized
to manufacture a tooth-positioning appliance, we can take advantage of the
current capabilities of some of the newer printers currently available.
Multiple
CA 02932100 2016-06-03
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print nozzles can print more than one material with each pass of the printer
over
a given location. With this capability, we can print an appliance made
entirely of
one material, or we can print an appliance with blended or mixed materials, or
we
can print an appliance with some portions made of one material, and some
portions made of another material. This capability will allow certain regions
of the
appliance to have greater or lesser flexibility, depending on the elastic
modulus
of the materials chosen for that particular region of the appliance. In the
embodiment disclosed in FIG. 23, the tooth-clasping elements 15 are made of
one material, while the curved interconnecting elements 42 are made of another
material. The appliance will be printed as one monolithic whole, and the
components will not need to be assembled or attached in a fabrication
sequence.
The printer will print one portion of the appliance and will go right on to
print the
other portion in a continuous motion as it is laying down the appliance layer
by
layer. The junction of the two materials can be a simple butt-joint junction
where
one material ends and another begins, or the junction can be a more complex
intertwined zone with two materials interconnecting in such a way as to make
the
junction stronger, and more resistant to pulling apart. The two materials can
have
differing properties, such as elastic modulus, color, translucency, clarity,
and
strength such as yield strength, tensile strength, breaking strength, etc. The
junction of the two materials may be stronger if the printer is programmed to
mix
or intertwine the materials in a brief junction zone.
The flexibility of the interconnecting elements can be varied depending on
the type of malocclusion problem to be solved. In the early stages of
treatment a
very flexible interconnecting element material can be chosen to make it easier
to
engage a severely rotated tooth or a significantly tipped tooth. In later
stages of
treatment, the loops can be stiffer for better control over final tooth
position just
as the wire sizes are currently varied with the stage of treatment when fixed
braces are used. The materials can also be chosen so that flexible materials
are
used for some interconnecting elements and stiffer interconnecting elements
are
used for other interconnecting elements.
CA 02932100 2016-06-03
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In the embodiment shown in FIG. 12, the U-shaped interconnecting
element 40 is made of the same clear material that forms the tooth-clasping
elements 15. In other words, the appliance in FIG. 12 is a one-piece
monolithic
structure. In contrast, the appliance shown in FIG. 23 is preferably
fabricated in
one piece by using a 3-D printer that is capable of printing more than one
material at a time. The tooth-clasping element 15 is preferably made of a
clear
material, and the interconnecting element 42 is preferably made of a different
material, perhaps with a differing elastic modulus to control the flex
properties of
the curved loop. Because of the way the printer prints using multiple print
nozzles, it is possible to gradually blend the materials into one another at
the
junction where the two materials join. It is unnecessary to attach the two
portions.
The embodiment shown in FIG. 24 is formed of a single piece of material
that is clear as it covers the anterior teeth. It can be manufactured by
thermoforming a sheet of plastic material over a model of teeth, or it can be
printed using a 3-D printer. There are no separately manufactured
interconnecting elements as in the first embodiment. In its simplest
embodiment,
a single-piece tooth positioning appliance can be vacuum-formed over a plastic
model. Flanges 16 of the appliance extend over the gum tissue. A difference in
this embodiment is the flange 16 of the appliance also covers the interdental
area
including the interdental papillae, not just the gum tissue over the roots of
the
teeth as in the other embodiments of the present invention. Cuts are made
between each tooth through the plastic shell material, but they do not
entirely
separate the shell into individual tooth-clasping elements. The cut-away area
51
between the teeth ends near the gum line in a small radius arch forming a U-
shaped interconnecting element 52. The region of the appliance consisting of
the
flange portion of the appliance, including the flange area between the teeth
covering the interdental papillae area adjacent to the interdental cuts 51
serves
the same function as the interconnecting loop-shaped element 17 between two
adjacent tooth-clasping elements in the earlier embodiments. Without the
flange
extension of the appliance over the gum tissue there would not be sufficient
CA 02932100 2016-06-03
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material to provide the needed flexibility for the interdental portion of this
appliance to serve the function of the flexible interconnecting elements as
shown
in the third embodiment. If this appliance is printed using a 3-D printer, the
same
basic shape and size of the appliance as in the thermoformed version would be
produced. Rather than making cuts in the material to produce the interdental
voids, the printer would simply not print the areas where the thermoformed
appliance is cut away.
Alternatively, the embodiment depicted in FIG. 24 can be fabricated by
removing some of the appliance material to make the appliance more flexible.
There are two ways this material can be considered to be "removed." First, if
the
appliance is made by thermoforming a sheet of material over a model, then a
portion of that material can be removed by cutting it away using a CNC milling
machine or a CNC laser cutter. Second, if the appliance is fabricated by a 3-D
printer, then selected portions of the coverage of the plastic over the teeth
will not
be printed, leaving spaces where the coverage is chosen to be absent. The
embodiment shown in FIG. 24 is much like the embodiment in FIGS. 11 and 12,
in that both embodiments can be made of a single piece of material covering
each dental arch. The flange material on the facial and lingual sides of the
teeth
covering the gum tissue area, and the additional flange material covering the
interdental area, serves as the flexible interconnecting element. This
additional
flange material covering the interdental gum tissue area (specifically
covering the
interdental papillae) is shown only in FIG. 24 but it is to be understood that
it
could be present in any of the embodiments described herein if there is not a
need for a separate tooth-clasping element for each tooth.
In some stages of treatment using an appliance system, one may use the
embodiment from FIGS. 1 - 4 between two adjacent teeth, the embodiment from
FIGS. 11 - 12 between the next two teeth, and possibly the embodiment from
FIG. 24 between the next two teeth. In later stages of treatment, as the teeth
become better aligned, there will be groups of teeth combined together into
units
where there are no interconnecting elements. This combining of the teeth into
CA 02932100 2016-06-03
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groups is shown in a separate related disclosure of a space closing appliance.
In
FIG. 24 there are no added curved loops to serve as the flexible
interconnecting
elements as in FIGS. 11 and 12. The flange material serves as a smaller loop
or
interconnecting element in FIG. 24. This embodiment is simpler and smaller
than
FIGS. 11 and 12, and could still be more effective for small movements than a
conventional tooth positioning appliance as is now manufactured by several
companies.
FIGS. 25 ¨ 27 show an embodiment having clear tooth-clasping elements
with interconnecting elements 30 that are U-shaped in horizontal planes
10 extending outward from the tooth-clasping elements. In other words, each
tooth-
clasping element 15 is connected to the adjacent tooth-clasping element using
short flexible U-shaped interconnecting elements 30 curving outward in
horizontal planes, attached between the crown portion of the tooth-clasping
elements and also between the flange section over the gum line. It should be
15 noted that the curvature of the interconnecting elements 30 could be in
more
than one plane. The materials of the tooth-clasping elements 15 and the
materials of the interconnecting elements 30 are preferably of differing
materials,
with the interconnecting elements 30 being more flexible. This embodiment
could
be easily printed, using a multiple nozzle 3D printer. The interconnecting
elements 30 would be oriented in a flat horizontal plane with the outer
portion of
the curve directed away from the teeth (i.e., toward the cheek on the buccal
side
attachment and toward the tongue on the lingual side). Preferably, there are
four
interconnecting elements between each adjacent pair of tooth-clasping
elements,
one above the other on both the buccal and lingual sides of the teeth.
However,
any number of interconnecting elements could be used. It is anticipated that
this
embodiment would work well to correct minor rotations and crowding.
This embodiment may also offer the advantage of being less visible than
the embodiments in FIGS. 1 ¨4 and 11 - 12. For example, the interconnecting
elements 30 can be made of any suitable flexible material including but not
limited to: clear vinyl, clear silicone, and clear urethane, or some other
material
CA 02932100 2016-06-03
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that is not clear. In the posterior teeth, they do not have to be clear
because they
will be seldom seen. If this positioner is fabricated by a 3-D digital
printer, the
flexible interconnecting elements can be printed simultaneously with the clear
tooth-clasping portion.
FIGS. 28 and 29 show an embodiment of a tooth-clasping element 15 that
is pre-loaded to more effectively engage a tooth. This modification could be
applied to any or all of the previous embodiment disclosed herein. The digital
data set corresponding to the shape of the dental model for any particular
stage
could be modified to move the labial and/or lingual surfaces 13A, 13B of the
tooth, found between the level of the bonded attachment and the gum line,
inward toward the center of the tooth by a small distance. Then, whether the
appliance is printed, or if it is thermoformed over a digitally printed tooth
model,
the appliance will have a tighter fit along the gum line. Currently,
thermoformed
positioners have a tendency to become stretched after they have been worn for
a
few days. The material relaxes. The appliances become loose after they have
been worn. The modification of the digital representation of the tooth surface
prior to formation of the appliance will result in a tooth-clasping element
that is
pre-loaded when it fits over the full-sized natural tooth, resulting in a
tighter fit of
the appliance.
In particular, the area of the CAD model located between the bonded
attachments and the gum line is modified in the digital file representing the
3-D
surface contours of the model. The surfaces 13A and 13B representing the
portions of the patient's tooth on both the buccal and lingual sides of the
tooth
from the gingival edge of the bonded attachment to the gum line are moved
inward toward the center of the tooth by a distance representing about 1 ¨ 25%
of the thickness of the tooth. When a digital model is made of the tooth upon
which to fabricate a thermoformed appliance, or when a 3-D printed appliance
is
fabricated which does not require the use of a 3D model under it for support
for
printing purposes, the corresponding modified surface contours 15A, 15B in the
tooth-clasping element based with the aforementioned areas 13A, 13B of the
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model that were moved inward, will cause the fabricated appliance to have a
pre-
load so in these areas, resulting in a tighter fit in these areas. The gum
line
flange areas will not be affected by the change in the surface contours, but
when
the appliance is placed on the teeth, the real contour of the tooth will force
the
tooth-clasping element outward, and the gingival flange area will be forced
outward slightly away from the gum tissue, providing a little more clearance
to
avoid having the flange region of the appliance impinge on the gum tissue.
FIG. 30 illustrates another embodiment of the present invention having
longer interconnecting elements 17A and 17B on both the buccal and lingual
aspects. The interconnecting elements 17A, 17B extend between the appliance
segments 60 ¨ 62 and skip over one or more teeth. FIGS. 31 and 32 show
another embodiment of the appliance with longer interconnecting elements 17 on
only the buccal aspect of the appliance segments.
These embodiments can be used, for example, in cases where we are
trying to intrude incisors. Here, the interconnecting elements 17A, 17B extend
from the canine over to the central incisor, skipping the lateral incisor. All
four
incisors are held together as a unit by a single appliance segment 61, and the
remaining teeth on either side of the incisors are held together by two
appliance
segments 60 and 62. These embodiments are primarily intended to overcome
the problem during intrusion where most of the intrusive force is placed on
the
lateral incisor, and the intrusion force is dissipated somewhat by the time it
is
transferred to the larger central incisor, which is a larger tooth and
requires more
force to intrude it.
FIGS. 33 and 34 show yet another embodiment of the present invention
having longer interconnecting elements 17 between the tooth-clasping elements
15 on individual teeth. These interconnecting elements 17 have a more
elongated, irregular shape that allow a greater range of relative motion
between
the tooth-clasping elements 15 and their respective teeth. In addition, the
physical properties of interconnecting elements 17 can be individually
designed
based on their dimensions, shapes and material properties.
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FIG. 35 shows the posterior teeth all connected into one tooth clasping
element, extending from the second molar to the cuspid. A flexible clear
plastic
interconnecting element 17, (there is one on each side with only the right
side
shown in this figure) in this case made of the same continuous piece of
plastic
that forms the rest of the appliance, extends forward and drops down directly
above the central incisor to engage a four-unit anterior tooth clasping
element
that envelopes the incisors, in much the same manner as was shown in FIGS. 33
and 34. The appliance is activated so that vertical force is directed straight
up at
the central incisors.
FIG. 36 shows a similar appliance to figure 35, but in this case the active
interconnecting element 17 is made of wire connected to the posterior tooth
clasping element. The means of attachment is not shown, but could include all
of
the methods discussed earlier for attaching wires. The wire has a helical coil
near
to where it attaches to the posterior tooth clasping element, and
the anterior end of the wire extends forward to the four-unit tooth clasping
element surrounding the incisor teeth. It is anticipated that the wire will be
attached to the four-unit anterior tooth clasping element in the flange area
covering the gum tissue above the crowns of the teeth where it will be less
visible
under the upper lip. Preferably, the wire will be attached and will extend all
the
way across above the four incisor teeth to the left side of the mouth where it
will
be a mirror image of the wire on the right side and will be the active arm on
the
left side, also containing a helical coil before it is attached to the
posterior tooth
clasping element on the left side. The left and right side posterior tooth
clasping
elements will likely be attached together across the palate by any suitable
rigid
means including clear plastic. The left and right posterior segments can also
be
attached to each other across the palate using a plastic or metal trans-
palatal
arch or bar.
The above disclosure sets forth a number of embodiments of the present
invention described in detail with respect to the accompanying drawings. Those
skilled in this art will appreciate that various changes, modifications, other
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structural arrangements, and other embodiments could be practiced under the
teachings of the present invention without departing from the scope of this
invention as set forth in the following claims.
