Elastic orthodontic appliances, systems, and methods of use

Abstract

Orthodontic appliances are comprised of shells shaped to receive the teeth. The shells are constructed from one or more polymeric materials, stacked, and can be attached to one another in various ways, including being attached only around the edges of each shell. An orthodontic appliance can be one of a series of similar devices for the gradual orthodontic correction of teeth.

Description

[Technical field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 62 / 797,797, filed January 28, 2019, which is incorporated herein by reference.

[0002] FIELD OF THE PRESENT APPLICATION The subject matter of the present disclosure relates generally to the field of orthodontic appliances. More particularly, the present disclosure relates to user removable orthodontic appliances. [Background technology]

[0003] The goal of orthodontics is to move a patient's teeth to positions that optimize function and / or aesthetics. Traditionally, appliances such as orthodontic braces are applied to the patient's teeth by a treating practitioner, with a set of braces exerting a continuous force on the teeth and gradually urging the teeth toward the intended position. Over time, and with a series of clinical visits and adjustments to the appliances by the practitioner to accommodate changing conditions, the appliances move the teeth toward their final destination.

[0004] Recently, alternatives to traditional orthodontic treatment using traditional fixed orthodontic appliances (e.g., braces) have become available. For example, a system including a series of molded plastic aligners has become commercially available from Align Technology, Inc. of San Jose, Calif., under the trade name Invisalign™ System. The Invisalign™ System is described in numerous patents and patent applications assigned to Align Technology, Inc., including U.S. Patent No. 6,450,807 and U.S. Patent No. 5,975,893.

[0005] The Invisalign™ system typically involves designing and fabricating multiple aligners for the patient to wear before administering them to the patient and using them to reposition the teeth (e.g., at the beginning of treatment). Often, developing and planning the patient's treatment involves the use of computer-assisted three-dimensional design tools. The design of the aligners relies on computer modeling of the patient's teeth in a series of planned sequential tooth positions, and the individual aligners are designed to be worn over the teeth so that each aligner applies a force to the teeth and elastically repositions the teeth to each of the planned tooth positions.

[0006] Naturally, such aligners are less noticeable than traditional braces because they are typically made from a transparent material, however, many people believe that the aligners are easily noticeable due to the glossy sheen of the transparent material. The aligners, like traditional braces, must be worn nearly all the time (20-22 hours per day), with breaks allowed for eating and cleaning the teeth. Only minor breaks are permitted, and the aligners do not have sufficient malleability to account for tooth deviations from alignment, based on the physical and material properties of the aligners. Increasing the operating tolerance to account for higher deviations requires increasing the working elasticity of the aligners, i.e., the aligners can stretch to fit the teeth without causing permanent deformation, but highly elastic aligners would not provide enough force to move the teeth as typically required for orthodontic treatment. Problems such as these can ultimately contribute to failure and the need to restart treatment because of failure to wear the aligners according to prescribed requirements. Summary of the Invention

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention relate to orthodontic appliances, systems, and methods of use as summarized in the following paragraphs. Some embodiments relate to orthodontic appliances that maximize working elasticity.

[0008] Some embodiments relate to orthodontic appliances that can have shells shaped to receive teeth. The shells can be stacked and are not substantially affixed to one another.

[0009] Some embodiments relate to orthodontic appliances that can have shells shaped to receive teeth. The shells can be stacked and affixed to one another in various ways.

[0010] Some embodiments relate to orthodontic appliances and can have multiple shells that are substantially unattached to maximize working resiliency and are shaped to receive teeth that are mechanically engaged to provide stiffness to apply force to reposition the teeth.

[0011] Some embodiments relate to orthodontic appliances that can have a stack of mechanically engaged shells. The stack of mechanically engaged shells can have a hardness substantially equivalent to a single shell of the same thickness as the stack. The stack of mechanically engaged shells can have the ability to be at least partially mechanically disengaged to increase working resiliency.

[0012] Some embodiments relate to an orthodontic appliance that can have a first shell with several cavities shaped to receive teeth. The orthodontic appliance can include a second shell than can be shaped to receive the first shell. The second shell can be stacked on top of the first shell. Between the surfaces of the first shell is that the second shell can be mechanically interlocked with each other but are not substantially affixed to each other.

[0013] In some embodiments, the second shell and the first shell can be affixed to one another at discrete attachment locations on the first shell and the second shell.

[0014] In some embodiments, the first shell can have a bottom first surface for direct engagement with a tooth and a top first surface opposite the bottom first surface. The second shell can have a bottom second surface for mechanically engaging the top first surface of the first shell and a top second surface opposite the bottom second surface. The top first surface and bottom second surface are not significantly attached to one another.

[0015] In some embodiments, the fixed, discrete attachment locations comprise less than 1-80% of the combined surface area of ​​the upper first surface and the lower second surface.

[0016] In some embodiments, the first shell has a first edge between an upper first surface and a lower first surface, and the second shell has a second edge between an upper second surface and a lower second surface, and the discrete attachment locations are located about the first edge and the second edge.

[0017] In some embodiments, the shells can be made of the same material.

[0018] In some embodiments, a relatively highly elastic shell can be provided between the shells.

[0019] In some embodiments, the shells can include a first shell, which can have a cavity shaped to receive a tooth, and at least one additional shell, which can be shaped to receive the first shell, where the at least one additional shell can be stacked over the first shell.

[0020] In some embodiments, the first shell and the at least one additional shell can be attached to one another at spaced attachment locations of the first shell and the at least one additional shell.

[0021] In some embodiments, the first shell can have a bottom first surface for direct engagement with a tooth and a top first surface opposite the bottom first surface. At least one additional shell can have a bottom second surface for mechanically engaging the top first surface of the first shell and a top second surface opposite the bottom second surface. The top first surface and bottom second surface can be arranged such that they are not significantly (to a large extent) attached to one another.

[0022] In some embodiments, the first shell can have a first edge between an upper first surface and a lower first surface, and the at least one additional shell can have a second edge between an upper second surface and a lower second surface. Discrete attachment locations can be located about the first edge and the second edge.

[0023] In some embodiments, the first shell can have a bottom first surface for direct engagement with a tooth, a top first surface opposite the bottom first surface, and a first edge defined therebetween. At least one additional shell can have a bottom second surface for mechanically engaging the top first surface of the first shell, a top second surface opposite the bottom second surface, and a second edge defined therebetween. Some or all of the first edge and second edge can be positioned such that they do not contact one another.

[0024] In some embodiments, the at least one additional shell can be a second shell, which can include a third shell.

[0025] In some embodiments, the shells may consist of only a first shell, a second shell, and a third shell.

[0026] In some embodiments, the second edge can be affixed to the upper first surface or the lower first surface.

[0027] In some embodiments, the first edge can be affixed to the lower second surface or the upper second surface.

[0028] In some embodiments, the first edge and the second edge can be spaced apart by 0.2 to 2.0 mm.

[0029] In some embodiments, the at least one additional shell can be a second shell, which can include a third shell that can include a bottom second surface for mechanically engaging a top second surface of the second shell, a top third surface opposite the bottom third surface, and a third edge defined therebetween, and some or all of the first edge, second edge, and third edge can be positioned such that they do not contact one another.

[0030] In some embodiments, the first edge, the second edge, and the third edge can be spaced apart by 0.2 to 3.0 mm.

[0031] In some embodiments, all of the shells can be constructed from the same type of material.

[0032] In some embodiments, variously affixed can mean having attachment locations that can be less than 1-80% of the total area of ​​the shell.

[0033] In some embodiments, variously affixed can mean having attachment locations that can be less than 1-60% of the total surface area of ​​the shell.

[0034] In some embodiments, variously affixed can mean having attachment locations that can be less than 1-40% of the total surface area of ​​the shell.

[0035] In some embodiments, variously affixed can mean having attachment locations that can be less than 1-20% of the total surface area of ​​the shell.

[0036] Some embodiments relate to a system for repositioning teeth from an initial tooth arrangement to a final tooth arrangement. The system can include a plurality of orthodontic appliances configured to receive and reposition the teeth. The plurality of orthodontic appliances can include at least one aspect of the orthodontic appliance described herein.

[0037] Some embodiments relate to a method for repositioning teeth from an initial tooth arrangement to a final tooth arrangement, which may include progressive use of the system.

[0038] In some embodiments, at least one orthodontic appliance of the system can be used less than 12 hours per day. [Brief description of the drawings]

[0039] For a better understanding of at least certain embodiments, reference is made to the following detailed description, which should be read in conjunction with the accompanying drawings.

[0040] [Figure 1] FIG. 1 is a perspective view of a jaw and an orthodontic appliance, according to some embodiments. [Diagram 2] FIG. 2 is an exploded view of an orthodontic appliance, according to some embodiments. [Figure 3A] FIG. 3A is a connection schematic for an orthodontic appliance, according to some embodiments. [Figure 3B] FIG. 3B is a detailed diagram of a connection schematic for an orthodontic appliance, according to some embodiments. [Figure 4] FIG. 4 is a perspective view of a process for molding an orthodontic appliance, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The drawings depict various embodiments of the present invention for illustrative purposes only, where the drawings use like reference numerals to identify like elements. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated in the drawings may be used without departing from the principles of the present invention described herein.

[0042] Embodiments are disclosed that relate to orthodontic appliances constructed from multiple shells with the goal of maximizing working resilience, defined as the ability of the appliance to elastically deform to accommodate initial tooth positions. This flexibility allows the appliance to obtain a greater range of initial tooth placement (i.e., flexion) positions that differ from the appliance's target tooth placement (i.e., rest) positions. Potential advantages include greater rest periods (e.g., 8-12 hours) between required wear periods and greater discretion regarding patient non-compliance with required wear times and therefore increased efficacy.

[0043] Before the present invention is described in more detail, it is to be understood that the invention is not limited to the particular embodiments described, as such may, of course, vary. Moreover, the scope of the present invention will be limited only by the appended claims, and the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting of the terminology used herein.

[0044] When a range of values ​​is provided, it is understood that each intermediate value, to the tenth of the unit of the lower limit, between the upper and lower limits of that range and any other stated range, or each intermediate value within that stated range, is encompassed within the scope of the invention, unless the context clearly dictates otherwise. The upper and lower limits of these smaller ranges may be independently included in the smaller ranges, and are also encompassed within the scope of the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also encompassed within the invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any materials and methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, representative exemplary methods and materials are described herein.

[0046] Please note that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Additionally, please note that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as a predicate for the use of exclusive terminology such as "solely," "only," and the like, in connection with the use of "negative" limitations or recitations of claim elements.

[0047] As will be apparent to one of ordinary skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has distinct components and features which may be readily separated from or combined with the features of several other embodiments without departing from the scope or spirit of the invention. Any recited method can be carried out in the order of events recited or in any other order which is logically possible.

[0048] FIG. 1 relates to a tooth repositioning device designed to apply a repositioning force to the teeth and provides a suitable starting point for the detailed description of various embodiments of the present invention. An orthodontic appliance 10 can be worn by a patient to effect gradual repositioning of individual teeth in a jaw 12. The orthodontic appliance 10 can include a shell having a cavity for receiving the teeth and resiliently repositioning the teeth. In some embodiments, the polymeric appliance can be formed from a sheet of suitable layers of polymeric material. The appliance can be worn over all or less than all of the teeth in the upper and lower jaws.

[0049] In some embodiments, only the specific teeth that are accepted by the appliance will be repositioned by the appliance, while other teeth can provide bases or anchor areas to hold the appliance in place as the specific teeth apply forces against the tooth or teeth targeted for repositioning. In some cases, many, most, or even all of the teeth will be repositioned (repositioned) at some point during treatment. The teeth that are moved can also serve as bases or anchors to hold the appliance when the patient wears it. Generally, no wires or other means are provided to hold the appliance over the teeth. However, in some cases, it may be desirable or necessary to provide corresponding receptacles or apertures in the appliance to individual anchors on the teeth so that the appliance can apply selected forces to the teeth. Basic methods for specifying an orthodontic treatment plan using a series of progressive appliances, as well as instructions for molding the orthodontic appliances, are described in the following U.S. patents: U.S. Pat. No. 6,450,807; and U.S. Pat. No. 5,975,893. Those patents are incorporated herein by reference only to the extent that they do not conflict with the more recent teachings disclosed herein.

[0050] An appliance can be designed and / or provided as part of a set of appliances. In such an embodiment, each appliance may be configured such that the tooth-receiving cavity has a geometry corresponding to the intermediate or final tooth arrangement intended for that appliance. The patient's teeth can be steadily repositioned from an initial arrangement of the teeth to a target arrangement of the teeth by attaching a series of incremental positioning appliances onto the patient's teeth. The target arrangement can be a planned final arrangement selected for the patient's teeth at the end of all planned orthodontic treatment. Alternatively, the target arrangement can be one of many intermediate arrangements for the patient's teeth during the course of orthodontic treatment. As such, it is understood that the target arrangement can be any resulting planned arrangement for the patient's teeth following one or more incremental repositioning steps. Similarly, the initial arrangement can be any initial arrangement for the patient's teeth followed by one or more incremental repositioning steps.

[0051] Orthodontic appliances can be all produced in the same phase, or in sets or batches, for example, at the beginning of a phase of treatment, and the patient wears each appliance until the pressure of each appliance can no longer be felt on the teeth or the maximum amount of expressed tooth movement for that given phase has occurred. A number of different appliances (e.g., a set) can even be designed and manufactured before the patient wears any of the appliances. After wearing an appliance for an appropriate period of time, the patient replaces (changes) the current appliance with the next appliance in the series until no appliances remain. Orthodontic appliances are generally not affixed to the teeth, and the patient can wear and change appliances (e.g., patient removable appliances) at any time during treatment.

[0052] The final orthodontic appliance or some appliances in the series may have one or more geometries selected to overcorrect the tooth position, i.e., have geometries that would move individual teeth beyond the tooth position selected as "final" (if fully achieved). Such overcorrection may be desirable to offset potential relapse after the repositioning procedure is terminated, i.e., to allow individual teeth to move back to their pre-corrected positions. Overcorrection may also be beneficial to accelerate the rate of correction, i.e., by having appliances with geometries positioned beyond the desired intermediate or final positions, individual teeth will be shifted into position at a greater rate. In such cases, use of the appliance may be terminated before the teeth reach the positions prescribed by the appliance.

[0053] 2 shows an exploded view of one example of an orthodontic appliance 10. The orthodontic appliance 10 can include a first shell 14 having a tooth-engaging surface and an opposing top surface. The orthodontic appliance 10 can also include a second shell 16 having a lower shell-engaging surface and an opposing top surface exposed to the mouth. Optionally, one or more additional shells 18 can be positioned between the first shell 14 and the second shell 16. In some embodiments, the more shells used, the greater the working resilience of the orthodontic appliance 10, assuming the same material is used for each shell.

[0054] While the orthotic device 10 is shown in an exploded view for better understanding, it is intended that the shells of the orthotic device 10 are mechanically engaged with each other in a stack. "Mechanically engaged" is defined herein as a substantially non-attached or variably affixed engagement between one or more shells to approximate the strength of a single shell device of approximately the same thickness as the stacked shells. The mechanical engagement can be achieved by stacking the shells with the engagement surface of the lower shell of the second shell largely conforming to the upper surface of the first shell. In some embodiments, the shells can be loosely stacked, i.e., without the shells of the inverted stack disintegrating or creating a compression or interference fit between the shells before being substantially affixed or variably affixed. The shells are substantially non-affixed (or variably affixed) because a significant amount of the surface area between the shells is not bonded or otherwise rendered inseparable through some process, and the remaining surfaces are affixed. In some embodiments, the substantially non-attached or variously-attached shells have less than 1-2%, 1-5%, 1-10%, 1-20%, 1-40%, 1-60%, or 1-80% of the joint contact surface of the affixed shells. The non-fixed area can be limited according to the needs of the device, thus in some embodiments, most of the surface area of ​​the device is affixed while the remaining part is not affixed, because only the latter requires high working elasticity.

[0055] In some embodiments, the lack of substantial fixation between the shells provides greater working resilience to the orthodontic appliance 10 because the tooth-engaging shells are thinner and therefore more flexible, allowing the outer shells to flex in multiple directions away from the tooth-engaging shells. In some embodiments, this may result in partial mechanical dissociation between some of the engaging surfaces of the shells, however, this dissociation is not sufficient to significantly impair the flexural modulus of the appliance necessary to align the teeth to their target positions.

[0056] FIG. 3A shows a schematic diagram for attaching the shells of the orthodontic appliance 10 to different locations. Each enclosed "X" represents a potential fixation point between the shells. Alternatively, as shown by the dashed lines, the edges of each shell can act as a continuous or discontinuous fixation area. In general, the more fixation provided, the weaker working elasticity the appliance 10 will have. Fixation points can be identified based on which teeth are moving, which teeth are acting as anchors, and the amount of working elasticity required. Alternatively, the shells can be uniformly and weakly bonded with a highly elastic material with low adhesive strength that allows for a large amount of stretch and / or shear. Such embodiments can be substantially non-bonded or variably bonded because the working flexibility of such appliances is maintained due to the weak adhesive properties.

[0057] In some embodiments, the shells of the orthodontic device 10 may not be identical, such as one shell having a larger or smaller surface area than another. Accordingly, in some embodiments, edges are defined by the upper and lower surfaces of each shell, and the edges of such shells may be separated by a gap (e.g., 0.20-3.0 mm), as illustrated by FIG. 3B, which shows an example having three shells 14, 16, 18 and three edges 14a, 16a, 18a. In some embodiments, referring to the arrangement shown in FIG. 2, the bottom shell 14 may have the largest surface area, such that edge 14a is in the bottom position shown, and shells 18 and 16 each have a smaller surface area, such that edge 16a is in the top position. In such embodiments, the shells 14, 16, 18 are stacked such that the step formed by edges 14a, 16a, 18a faces outward, away from the teeth. 2, the top shell 16 can have the greatest surface area, such that edge 16a is in the bottom position shown, and shells 18 and 14, respectively, have the smaller surface area such that edge 14a is in the top position. In such an embodiment, shells 14, 16, 18 are stacked such that the step formed by edges 14a, 16a, 18a faces inward, i.e., toward the teeth.

[0058] Providing such a gap or gaps can be used to adjust the bending elasticity of the orthodontic device 10 and also results in less tongue irritation to the patient that may occur due to the thickness of the material to which the edges are bonded at the same location. To mitigate irritation, the gaps can be located in the area facing inward toward the mouth, resulting in a stepped edge (e.g., edges 14a, 16a, 18a) facing the tongue, or the tooth-engaging shell can have a smaller surface area than the shells stacked on it, resulting in an internal, tooth-facing step and a single shell edge (e.g., edge 16a) that can contact the tongue. In some embodiments, the shell that engages the bottom tooth can have a larger or smaller total surface area than the second shell stacked on it, resulting in at least a portion of the edge of the second shell being separated from the edge of the tooth-engaging shell. In some embodiments, only a portion of the edges that face toward the mouth have such gaps, while in other embodiments, a uniform or non-uniform gap can exist between the entirety of the edges. In some embodiments, the orthodontic appliance 10 can include multiple shells, each having a different surface area.

[0059] The shells can have thicknesses ranging from 0.001 to 0.015 inches thick and can be constructed from polyester, copolyester, polycarbonate, thermoplastic polyurethane, polypropylene, polyethylene, polypropylene and polyethylene copolymers, acrylic, cyclic block copolymers, polyetheretherketone, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyetherimide, polyethersulfone, polytrimethylene terephthalate, or combinations thereof. In some embodiments, the shells are coated with a lubricious material or provided with a surface treatment to reduce friction between the shells. In some embodiments, the interior portion of the shell is treated with a hydrophobic coating to prevent the ingress of liquids into the shell. In some embodiments, a relatively flexible shell can be used in combination with a harder shell. The flexible shell can be constructed from hydrogels, styrenic block copolymers (SBC), silicone rubbers, elastomeric alloys, thermoplastic elastomers (TPEs), thermoplastic vulcanizates (TPVs) elastomers, polyurethane elastomers, block copolymer elastomers, polyolefin blend elastomers, thermoplastic copolyester elastomers, thermoplastic polyamide elastomers, or combinations thereof. Flexible shells may also offer the benefit of a gasket to prevent ingress of liquid between the shells.

[0060] FIG. 4 shows an example of a basic process 30 for forming an orthodontic appliance. As shown, material 32 can be formed into an orthodontic appliance 36. Material 32 can be one layer to form a single shell, or multiple unapplied layers to form multiple shells at once. In this example process, tooth positioning device 36 can be made using a physical tooth model, or mold 34. Tooth positioning device 36 can be made by heating thermoformable material 32 and then vacuum or pressure forming the material over the teeth of physical tooth model 34. Tooth positioning device 36 is a direct representation of the physical tooth model. In some embodiments, material 32 is shaped to the required dimensions (e.g., 120 mm and / or 125 mm diameter circles) for preparation on a commercially available forming device (e.g., Erkoform™, Erkoform-3dmotion™, Biostar™, Ministar S™, Drufomat Scan™, Drufosmart™, Essix™ SelectVac™). Guidelines for the operation of such molding devices can be found in: Scheu Dental Technology, Biostar Operating Manual, DE / GB / FR / IT / ES / 1.000 / 06 / 19 G REF PM 0113.01; Scheu Dental Technology, Application booklet for the pressure moulding technique, GB 2.000 / 07 / 19 G REF 0111.02; Erkodent, Thermoforming, S15-3106-48; Erkodent, Erkoform 3D, 61-8002-2; Erkodent, Erkoform-3D+ Instructions, BA-Erkoform-3d+-anl-EN-04-04-2019, which are incorporated herein by reference.

[0061] Once formed, the shells can be affixed to each other depending on the desired working elasticity required for the patient. Methods of fastening include chemical bonding, localized melting, fixtures, and / or localized physical deformation to fasten the shells together, such as with pins. Before or after fastening occurs, excess material from the sheet can be cut (trimmed) to form a final tooth positioning device that can be used in the patient's orthodontic treatment. The edges of the shells can be sealed with a flexible material such as silicone to prevent the ingress of liquids.

[0062] One or a series of physical tooth models such as the above models can be used in the production of elastic repositioning appliances for orthodontic treatment. Similar to the above process, each appliance can be produced by thermoforming a multi-layer polymeric material over a mold of the desired tooth arrangement to form a dental appliance. The tooth positioning device of the desired arrangement of teeth is generally adapted to the patient's teeth, but slightly out of alignment with the initial tooth form. When the elastic positioner is placed over the teeth, a controlled force is applied at specific locations to gradually move the teeth to the desired form. This process is repeated with successive appliances with new forms, eventually moving the teeth through a series of intermediate forms to the final desired form.

[0063] Throughout the above description, and for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the described technology. However, it will be apparent to one of ordinary skill in the art that these technologies may be practiced without some of these specific details. Although various embodiments incorporating these teachings have been shown and described in detail, one of ordinary skill in the art can readily devise many other various embodiments or mechanisms to incorporate these technologies. Also, embodiments may include various operations, fewer or more operations, or operations in a certain order as described above. Thus, the scope and spirit of the present invention should be judged in terms of the claims that follow, as well as their legal equivalents.

Claims

1. 1. An orthodontic appliance comprising: a shell shaped to receive teeth in the upper or lower jaw; the shells include a first shell and at least one additional shell; The additional shell comprises a second shell; The shell further comprises a third shell, the first shell has a first cavity shaped to receive the tooth; the second shell has a second cavity shaped to receive the first shell; the third shell has a third cavity shaped to receive the second shell; the first shell, the second shell and the third shell are stacked successively and variously attached to one another to form a stack; It can be attached in various ways, the first shell, the second shell, and the third shell having surface areas not attached between adjacent shells; the remaining areas between the adjacent shells are glued together; the first shell defines the first cavity and has a bottom first surface shaped to directly engage the tooth, a top first surface opposite the bottom first surface, and a first edge defined by an edge of the bottom first surface and an edge of the top first surface; the second shell defines a second cavity and has a bottom second surface having a shape adjacent the top first surface of the first shell, a top second surface opposite the bottom second surface, and a second edge defined by an edge of the bottom second surface and an edge of the top second surface; the third shell defines a third cavity and has a bottom third surface having a shape adjacent the top second surface of the second shell, a top third surface opposite the bottom third surface, and a third edge defined by an edge of the bottom third surface and an edge of the top third surface; The first shell, the second shell, and the third shell are each an elastic body. Dental orthodontic appliance.

2. all or some of the first edge, the second edge, and the third edge do not contact one another; 10. The orthodontic appliance of claim 1.

3. The second edge is attached to the upper first surface.

3. The orthodontic appliance of claim 2.

4. The first edge is attached to the bottom second surface.

3. The orthodontic appliance of claim 2.

5. The distance between the first edge and the second edge is in the range of 0.2 to 3.0 mm.

3. The orthodontic appliance of claim 2.

6. The distance between the first edge, the second edge, and the third edge is in the range of 0.2 to 3.0 mm.

3. The orthodontic appliance of claim 2.

7. all of the first shell, the second shell, and the third shell are constructed from polyester, copolyester, polycarbonate, thermoplastic polyurethane, polypropylene, polyethylene, polypropylene and polyethylene copolymers, acrylic, cyclic block copolymers, polyetheretherketone, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyetherimide, polyethersulfone, polytrimethylene terephthalate, or combinations thereof; 10. The orthodontic appliance of claim 1.

8. The shell consists of only the first shell, the second shell, and the third shell.

10. The orthodontic appliance of claim 1.

9. the first shell having a relative elasticity greater or less than that of the second shell; 10. The orthodontic appliance of claim 1.

10. The upper first surface of the first shell has an area greater than or less than the bottom second surface of the second shell such that the first edge of the first shell is below or above the second edge of the second shell.

10. The orthodontic appliance of claim 1.

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