Tooth Repositioning System

Abstract

A system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement includes a plurality of incremental positioning appliances, each having an arrangement of cavities shaped to receive and reposition the patient's teeth. The cavity of at least one appliance in the system has a different geometric shape than the geometric shape of at least one other appliance in the system. At least some of the appliances in the system are worn sequentially by the patient to apply a force to at least one tooth to move the patient's teeth from a first arrangement to a subsequent arrangement that is different from the first arrangement. The system has a bending stiffness modulus of about 0.1 GPa. * mm 3 a first multilayer shell having an elastic modulus of about 1.5 GPa or less and a bending stiffness modulus of about 0.1 GPa or less; * mm 3 and a second shell that is super.

Description

[Background technology]

[0001] Orthodontic treatment involves repositioning misaligned teeth and improving bite alignment for improved cosmetic appearance and dental function. Tooth repositioning is accomplished by applying controlled forces to the patient's teeth over an extended treatment period.

[0002] Teeth can also be repositioned by placing dental appliances, such as polymeric incremental positioning appliances, commonly referred to as orthodontic aligners or orthodontic aligner trays, over the patient's teeth. Orthodontic alignment trays include a polymer shell having multiple cavities configured to receive one or more of the patient's teeth. Each cavity in the polymer shell is shaped to hold one or more teeth and the polymer material comprising the shell, and is selected to apply a force to the one or more teeth to resiliently and incrementally reposition selected teeth or groups of teeth on the upper or lower jaw.

[0003] Orthodontic appliances made from relatively rigid polymeric materials with high flexural moduli, such as polyesters and polycarbonates, selected to effectively apply stable and consistent repositioning forces to a patient's teeth, can cause discomfort when the appliances repeatedly contact the patient's oral tissues or tongue over an extended treatment period. These high-modulus polymeric materials can also have poor stress-retention behavior, and over time, repositioning force loss can decrease below desired levels. Rubber-like elastomers have excellent stress-retention behavior, but are often used alone in dental appliances to effectively move teeth into desired alignment over a reasonably short treatment period.

[0004] In some treatment systems, a series of orthodontic aligner trays are provided for the patient to wear sequentially during each stage of orthodontic treatment, gradually repositioning the teeth from a misaligned tooth arrangement to successively more aligned tooth arrangements until the desired, planned tooth alignment is finally achieved. Once the desired alignment is achieved, the aligner tray, or a series of aligner trays, may be used periodically or sequentially in the patient's mouth to maintain the preferred tooth alignment. In addition, orthodontic retainer trays may be used long-term to maintain tooth alignment after initial orthodontic treatment.

[0005] Systematic methods using computer-aided design to develop a series of incrementally positioning polymer aligners used sequentially to progressively reposition teeth have attracted significant interest in dental alignment. In some cases, a system of dental appliances includes at least two different aligner appliances formed from polymer materials with different moduli of elasticity. The polymer materials provide each aligner tray with a different level of stiffness to impart the desired tooth movement force and effectiveness when the appliances are worn by the patient. Summary of the Invention

[0006] In one aspect, the present disclosure relates to a system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement. The system includes a plurality of incremental positioning appliances, each having an arrangement of cavities shaped to receive and reposition the patient's teeth. The cavity of at least one appliance in the system has a geometry different from the geometry of at least one other appliance in the system. At least some of the appliances in the system are worn sequentially by the patient to apply a force to at least one tooth to move the patient's teeth from a first arrangement to a subsequent arrangement different from the first arrangement. The system includes a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell. * mm 3a first multi-layer shell having an elastic modulus of less than about 1.5 GPa and a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell; * mm 3 and a second shell that is superimposed thereon.

[0007] In another aspect, the present disclosure relates to a method of moving one or more of a patient's teeth. The method includes providing a series of dental appliances for sequential placement on at least some of the patient's teeth, at least some of the appliances in the series including tooth-retaining cavities configured to provide a resilient force to reposition at least one of the patient's teeth, and at least one of the appliances in the series has a tooth-retaining cavity with a geometry that differs from the geometry of a tooth-retaining cavity of another appliance in the series. The series of appliances includes a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of the shell. * mm 3 and an elastic modulus of less than about 1.5 GPa, and an elastic modulus of less than about 0.5 GPa and about 0.001 GPa * mm 3 a first multi-layer shell including at least one polymer layer having a flexural stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell; * mm 3 and a second shell that is superimposed thereon.

[0008] In another aspect, the present disclosure relates to an orthodontic treatment kit including a series of dental appliances for sequential placement over at least some of a patient's teeth, at least some of the appliances in the series having tooth-retaining cavities configured to provide a resilient force for repositioning at least one of the patient's teeth, and at least one of the appliances in the series having a tooth-retaining cavity with a geometry that differs from the geometry of a tooth-retaining cavity in another of the appliances in the series. The series of dental appliances includes a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of the shell. * mm 3 a first multi-layer shell having a flexural stiffness modulus of less than about 1.5 GPa and a second shell having a flexural stiffness modulus of less than about 0.1 GPa; * mm 3 and a second shell that is superimposed thereon.

[0009] In another aspect, the present disclosure relates to a method of manufacturing a series of dental appliances, the method comprising: forming a first polymer film having an elastic modulus of less than about 0.5 GPa and an elastic modulus of less than about 0.001 GPa; * mm 3 thermoforming a first polymer film to form a first dental appliance having an array of cavities configured to hold at least one tooth of the patient, the first polymer film including a multilayer polymer film having at least one polymer layer with a bending stiffness modulus less than 10 ...

[0010] In another aspect, the present disclosure relates to a system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement. The system includes a series of polymer shells, at least some of which have an arrangement of cavities configured to receive one or more teeth of the patient's upper or lower arch and apply a resilient positioning force to cause a predetermined incremental movement of the one or more teeth from a first position to a second position. The series of polymer shells includes a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of the shell. * mm 3 a first multi-layer shell having an elastic modulus of less than about 1.5 GPa and a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell; * mm 3 and a second shell that is superimposed thereon.

[0011] In another aspect, the present disclosure relates to a method for designing an orthodontic treatment, the method comprising: determining, at the start of a first phase of treatment, a first bending stiffness appropriate for desired tooth movement in the first phase; and determining a bending stiffness modulus of about 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell. * mm 3 or a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell * mm 3 and determining, prior to the start of a second phase of treatment, a second bending stiffness modulus appropriate for the desired tooth movement in the second phase, and determining a bending stiffness modulus of about 0.1 GPa or greater measured within 2 mm of the incisor trim line on the labial side of the shell. * mm 3 or a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell * mm 3 and fabricating a second polymeric shell device, wherein the second polymeric shell device is either

[0012] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic overhead perspective view of a method of using a dental alignment tray by placing the dental alignment tray over the teeth. [Figure 2] 1 is a schematic diagram of an embodiment of a dental treatment system according to the present disclosure. [Figure 3] 3 is a schematic overhead perspective view of an embodiment of a multi-layer dental appliance suitable for use in an embodiment of the dental treatment system of FIG. 2. [Figure 4] 4 is a schematic cross-sectional view of the embodiment of the multi-layer dental appliance of FIG. 3. [Figure 5] 4 is a schematic cross-sectional view of the embodiment of the multi-layer dental appliance of FIG. 3.

[0014] Like numbers in the drawings refer to like elements. DETAILED DESCRIPTION OF THE INVENTION

[0015] When orthodontic aligners are worn by a patient, they encapsulate the teeth and provide both retentive and actuating forces to move the teeth. Generally, the contours of the dental surfaces (e.g., enamel, gums, and interproximal spaces between the teeth) provide the retentive force, while the elastic bending deformation of the aligner provides the active component for moving the teeth. To provide effective tooth movement, the elastic bending force provided by the aligner should not overcome the retentive force, but should not be so great as to cause undue discomfort to the patient.

[0016] Some treatment systems include multiple multi-layered polymer alignment trays with different retention and actuation forces designed to be worn sequentially by the patient to achieve the final planned tooth alignment. In some cases, the alignment trays are made from more flexible polymer materials to improve patient comfort. To accelerate tooth movement in the early stages of treatment, these flexible materials provide a sustained actuation force. However, this more flexible elastic bending force offers less control for precisely coordinating the patient's tooth movement near the final treatment stage to reach the final planned position. Additional precision adjustment steps may then be required to move the teeth as scheduled to the exact final planned position, which is highly undesirable for both the orthodontist and the patient.

[0017] Flexible aligners may provide a light, continuous force that is more effective at accelerating tooth movement with frontal resorption, as discussed above, while rigid aligners provide a heavier initial force to provide slower tooth movement with undermining resorption. While slower tooth movement performance is undesirable for the early stages of treatment, it is suitable for later stages to reach the final planned or specified position in a more controllable manner and reduce refinement steps.

[0018] The present disclosure relates to a system and orthodontic treatment method that includes multiple orthodontic dental appliances, such as orthodontic aligner trays or retainer trays, configured to move or maintain the position of teeth within a patient's upper or lower jaw. To reduce precision adjustments in the later stages of orthodontic treatment, flexible multi-layer polymer aligners have both physical and mechanical properties selected to efficiently move teeth in the early stages of treatment, while a separate, more rigid aligner material is used in the later stages of treatment to reach the planned final positions while maintaining patient comfort and quality of the patient experience.

[0019] In some embodiments, one of the orthodontic aligner trays in the treatment system includes multiple layers of high and low flexural modulus polymeric materials formed at thicknesses selected to provide a desired average flexural modulus and maintain acceptable levels of force sustainment while improving patient comfort. The combination of thermoplastic polymers in the dental appliance is also selected to provide other beneficial properties, such as good stain resistance, low optical haze, and good release characteristics, after the dental appliance is thermoformed from the multilayer polymer film. The other orthodontic aligner in the treatment system also includes single or multiple layers of polymeric material formed at thicknesses selected to maintain acceptable levels of tooth movement rate while improving patient comfort.

[0020] In various embodiments, at least one of the orthodontic aligner trays in the system includes at least five polymer layers, with a softer polymer inner layer disposed between a harder polymer core layer and two harder polymer outer layers. The hard core layer can improve dimensional stability and strain recovery, while the softer intermediate layers positioned adjacent the outer skin layers can improve patient comfort.

[0021] In some embodiments, the multi-layer dental appliance is transparent or translucent, has crack resistance and force retention, good stain resistance, improved patient comfort, and improved dimensional stability.

[0022] Referring now to FIG. 1 , a shell 102 of an orthodontic appliance 100, also referred to herein as an orthodontic aligner tray, includes an outer surface 106 and an inner surface 108 having a cavity 104 that generally fits over one or more of the patient's teeth 120.

[0023] In some embodiments, the cavity 104 is slightly offset from the patient's initial tooth arrangement, while in other embodiments, the cavity 104 conforms to the patient's teeth to maintain and / or secure the desired tooth arrangement. The shell 102 may be one of a group or series of shells having substantially the same shape or mold, or incrementally different shapes, but formed from different polymeric materials or different layers of polymeric materials selected to provide the desired rigidity or resilience required for moving the patient's teeth. In some embodiments, the shell 102 may be one of a group or series of shells having substantially the same shape or mold, or incrementally different shapes, but formed from the same polymeric material selected to provide the desired rigidity or resilience required for moving the patient's teeth. The patient may alternate between using one of the orthodontic appliances during each treatment phase, depending on the patient's preferred duration of use or the desired treatment period for each treatment phase. The alternating use of appliances can be repeated as many times as necessary to achieve the desired treatment.

[0024] Wires or other means for holding the shell 102 on the teeth 120 may not be provided, although in some embodiments it may be desirable or necessary to provide individual anchors (e.g., so-called attachments) on the teeth with corresponding receivers or openings in the shell 102 so that the shell 102 can apply retentive or otherwise directed orthodontic forces to the teeth that would not be possible in the absence of such anchors.

[0025] Shell 102 may be customized, for example, for daytime and nighttime use, for functional or non-functional use (chewing versus non-chewing), for social occasions (where appearance may be more important) and non-social occasions (where aesthetic appearance may not be an important factor), or based on the patient's desire to accelerate tooth movement (optionally by using more rigid appliances for longer periods of time at each treatment stage rather than less rigid appliances).

[0026] For example, in one aspect, a patient may be provided with clear orthodontic appliances that may be used primarily to maintain tooth position and opaque orthodontic appliances that may be used primarily to move teeth during each treatment phase. Thus, during the day, in social situations, or otherwise in environments where the patient is more acutely conscious of physical appearance, the patient may use the clear appliances. Furthermore, in the evening or at night, in non-social situations, or otherwise in environments where physical appearance is less important, the patient may use opaque appliances that have configurations configured or otherwise designed to provide different amounts of force (e.g., more flexible or more rigid) to accelerate or control tooth movement during each treatment phase. This approach may be repeated, with each pair of appliances being used alternately during each treatment phase.

[0027] The shell 102 of the orthodontic appliance 100 is an arrangement of one or more layers of polymeric material that generally conforms to the patient's teeth and may be transparent, translucent, or opaque. The polymeric material may include at least one semi-crystalline polymer, typically an elastomer, selected to maintain a sufficient and substantially constant stress profile over the desired treatment period and to provide a relatively constant tooth repositioning force over the treatment period to maintain or improve the tooth repositioning efficiency of the shell 102. The shell may include a single layer of semi-crystalline polymer or multiple layers, at least one of which is a semi-crystalline polymer.

[0028] Semicrystalline polymers can be distinguished from purely amorphous polymers in that they are composed of both crystalline and amorphous phases. The presence of crystalline regions can improve mechanical performance at high temperatures, but tends to result in scattering of visible light at the boundaries between the crystalline and amorphous regions. Semicrystalline polymers typically contain a distribution of smaller crystals (e.g., but not exclusively, less than 3 microns) that tend to melt at relatively low melting temperatures, and larger crystals (e.g., but not exclusively, greater than 3 or 4 microns) that tend to melt at relatively high melting temperatures. Semicrystalline polymers may contain one or more crystalline melting temperature ranges (i.e., determinable endothermic peaks) determinable by MDSC™ at a constant heating rate of 4°C per minute. Particularly suitable semicrystalline polymers contain at least one first, distinguishable melting temperature range with a first endothermic peak maximum and a second melting temperature range with a second endothermic peak maximum that appears at a higher temperature than the first maximum. Other semicrystalline polymers may contain three or more melting temperature ranges, each with an associated endothermic peak maximum. For example, certain copolyester elastomers, including copolyester ether elastomers available under the ECDEL brand, have a first discernible melting temperature range (T ) with an upper limit of about 225°C and an endothermic peak (P1) at about 208°C. m1 ), and a second distinguishable melting temperature range (T m2 In some embodiments, the semi-crystalline polymer comprises a first discernible melting point range (T) having a lower limit greater than about 100°C, greater than about 150°C, or greater than about 180°C. m1 Advantageously, the methods of the present disclosure can be used to improve the optical properties of the resulting article by heating the polymer to a temperature near but below the upper end of the first melting temperature range, without necessarily relying on biaxial or uniaxial stretching of the elastomer prior to fabricating the brace. Further details regarding semi-crystalline polymers and methods for controlling the optical properties of braces can be found in U.S. Provisional Patent Application No. 63 / 091144, filed October 13, 2020, and incorporated herein in its entirety.

[0029] Suitable semi-crystalline polymers may include polyesters and copolyesters, which may or may not contain ethylene glycol on the polymer backbone. Other suitable semi-crystalline polymers include polyolefins and polyolefin copolymers. Other suitable semi-crystalline polymers include polyethylene (low and high density), ultra-high molecular weight polyethylene, polyamide, polypropylene, nylon, nylon copolymers, polyacryletherketone, polyimide (AURUM), and ethylene vinyl acetate (EVA). Specific suitable semi-crystalline polymers may further include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetherimide, polyetheretherketone, polyethersulfone, or polytrimethylene terephthalate, polyethylene naphthalate (PEN), polycyclohexyldimethylene terephthalate (PCT), as well as mixtures and combinations thereof. Copolyesters may be synthesized via condensation polymerization, melt polymerization, solid-state polymerization, or a combination thereof.

[0030] Suitable commercially available semi-crystalline polymers include linear low density polyethylenes sold under the BYNEL brand by Dow; polyolefin plastomers sold under the AFFINITY brand by Dow; ethylene-octene copolymers, ethylene butene, and other polyolefin elastomers sold under the ENGAGE brand by Dow; α-olefin copolymers sold under the TAFMER brand by Mitsui Elastomer Singapore PTE LTD; copolymers of ethylene and (meth)ethyl acrylate sold under the ELVALOY brand by Dow; ethylene vinyl acetate copolymer resins sold under the ELVAX brand by Dow; linear low density polyethylenes sold under the ADMER brand by Mitsui & Co., Ltd., thermoplastic polyolefins sold under the HIFLEX and CATALOY brands by LyondellBasell Industries Holdings BV, and polypropylene polymers and copolymers sold under the DEXFLEX and HOSTACOM brands by LyondellBasell.

[0031] The semi-crystalline polymers of the present disclosure may also be formed with a nucleating agent. Nucleating agents induce the formation of crystals in a given polymer composition. In the method of the present disclosure, the use of a nucleating agent tends to suppress the size of the crystallites formed in the polymer. Adding a nucleating agent to a semi-crystalline polymer can accelerate the nucleation rate and effectively reduce the crystal size by adjusting the time scale of crystallization during cooling of the melt after thermoforming, which tends to produce smaller crystals upon cooling. Smaller crystals can be melted and refined at a more tolerant range of melting and / or thermoforming temperatures, improving the ability to routinely produce articles with desired optical properties.

[0032] Suitable nucleating agents can be inorganic, organic compounds, or mixtures thereof. Nucleating agents can be included to enhance the clarity of the device by inducing a greater number of crystals to grow to smaller sizes (otherwise known as clarifiers), and can be added in any amount effective to induce such a crystallization effect, such as an amount of 0 to about 2 weight percent (e.g., about 0.1 to about 0.8 weight percent) of the semi-crystalline elastomeric composition. Suitable nucleating agents may include one or more of inorganic compounds such as talc, silica, kaolin, and the like; organic phosphates such as salts of diesters of phosphoric acid, such as sodium 2,2'-methylenebis(4,6-di-tertbutylphenyl)phosphate, or aluminum-hydroxy-bis[2,2'-methylene-bis(4,6-di-tbutylphenyl)phosphate]; salts of monocarboxylic or polycarboxylic acids, such as sodium benzoate, or aluminum tertbutylbenzoate; nonitol derivatives such as 1,2,3-trideoxy-4,6:5,7-bis-O[(4-propylphenyl)methylene]nonitol; vinylcycloalkane polymers, vinylalkane polymers, and norbornane carboxylates. Preferred nucleating agents in the present invention include sorbitol and its derivatives, such as 1,3:2,4-dibenzylidene sorbitol (DBS), 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS), and 1,3:2,4-bis(3,4-dimethyldibenzylidene) sorbitol (DMDBS). Nucleating agents tend to increase the relative distribution of smaller (e.g., less than 3 microns) crystals within the formed elastomeric device, which can then be melted and refined by thermoforming at a sufficient melt temperature.

[0033] Suitable nucleating agents include, but are not limited to, ADK STAB NA-11, NA-27, NA-902, NA-960, NA-21, and NA-71 from Amfine Chemical Corporation (Hasbrouck Heights, New Jersey), EVERCLEAR 3940 from EVERSPRIN Chemical (Taiwan), OPIMA NA210 and NA 211 from Pluss Polymer Pvt. Ltd. (India), Millad 3905, 3940, 3988, and NX8000 from Milliken Chemical (Spartanburg, South Carolina), and NU-510 from SamA C&I Co., Ltd. (Korea).

[0034] Referring again to FIGS. 1 and 2 , orthodontic treatment systems and methods according to the present disclosure include applying one or more incremental positioning appliances to a patient's teeth, each having substantially the same shape or mold, or incrementally different shapes. The incremental positioning appliances may each be formed from the same polymeric material or a combination of different polymeric materials, as needed for each treatment stage of the orthodontic treatment. The orthodontic appliances may be configured to incrementally reposition individual or multiple teeth 120 in the patient's upper or lower jaw 122. In some embodiments, cavities 104 are configured so that selected teeth are repositioned, while other teeth are designated as base or anchor regions to hold the repositioning appliances in place as the appliances apply a resilient repositioning force against the teeth being repositioned.

[0035] By placing the orthodontic aligner tray 100 over the teeth 120, a controlled force is applied at specific locations, gradually moving the teeth into a new configuration. Repeating this process with successive appliances having different configurations ultimately moves the patient's teeth through a series of intermediate configurations to their final desired configuration, also referred to as the planned final configuration.

[0036] In one aspect, the present disclosure provides a system and method for orthodontic treatment that incrementally repositions a patient's teeth using multiple individual polymer orthodontic alignment or retainer trays worn by the patient in succession. At least some of the alignment trays in the series have at least one of a different shape or flexibility from previous or subsequent appliances in the series. Each orthodontic aligner tray sequentially repositions one or more of the patient's teeth by a relatively small amount. After the alignment trays have repositioned the teeth into the planned tooth arrangement, one or more orthodontic retainer trays can be used to temporarily or permanently maintain the planned tooth alignment.

[0037] In the present application, the flexibility of a polymeric orthodontic aligner or retainer can be defined by its bending stiffness modulus, which is the product of the appliance's average elastic modulus and the cube of the appliance's thickness in selected areas, as shown by the formula in the following example. Individual appliances within the system can be configured so that their flexibility and their tooth-receiving cavities have a shape or geometry that corresponds to the intended intermediate or final tooth arrangement for that appliance. In the orthodontic alignment system of the present disclosure, at least one of (1) the shape of the alignment tray, which depends on the geometry of the tooth-receiving cavities, and (2) the bending stiffness modulus, which depends on the elastic modulus of the polymer material selected for use in forming the tray and the tray's thickness in selected areas, varies throughout the series of alignment trays according to a specified orthodontic treatment plan. Once the planned tooth alignment is achieved according to the orthodontic treatment plan, a retainer tray can be used to maintain the planned tooth alignment.

[0038] In the disclosed system, each successive brace worn by the patient may have a different shape or geometry than the immediately preceding brace. In accordance with the present invention, some or all of the individual braces may also have a bending stiffness modulus that is different from the bending stiffness modulus of the immediately preceding brace. In some cases, the bending stiffness modulus of an individual brace in the system may not change from the previous or subsequent brace, but only the geometry may change. In other cases, the bending stiffness modulus of an individual brace in the series may change only (and the geometry may not change) when compared to the immediately preceding or subsequent brace worn by the patient.

[0039] Referring now to the schematic diagram of FIG. 2, the orthodontic alignment system includes a plurality of individual shell-like polymer orthodontic aligner or retainer trays 2021-2022. n each of which is configured to be worn sequentially by a patient to move at least one tooth from an initial arrangement to a final planned arrangement, and the bending stiffness coefficients differ between at least some of the successive appliances used during the treatment course. n The bending stiffness modulus of a given aligner tray 202 is selected for a particular type of tooth movement, such as translation, tipping, root uprighting, rotation, extrusion, intrusion, or a combination thereof. n Some of the aligner trays may also be configured to maintain alignment of selected teeth, for example, to maintain the final planned position of one or more teeth.

[0040] For example, the overall rigidity of an orthodontic aligner tray is a key factor in providing repositioning forces, so a series of orthodontic aligner trays designed to translate teeth 2021-2022 n may have a greater bending stiffness modulus than trays designed purely for rotating teeth. As another example, in some embodiments, a more flexible aligner tray may be more effective in handling large attachment engagements and rotations in cases of overcrowding, while a stiffer aligner tray may be more effective at providing torque, intrusion, and finishing.

[0041] For another example, light, continuous force is recognized as a more effective method for moving teeth. Thus, in the early stages of treatment, aligner trays with a lower bending stiffness modulus may be used to move teeth more quickly, while toward the end of the treatment plan, stiffer aligner trays (higher bending stiffness modulus) may move teeth more slowly but more precisely to their final positions.

[0042] In some cases, the results of utilizing a series of alignment trays with different levels of stiffness may include one or more of: more predictable treatment outcomes with less precision adjustments at the end of treatment, and overall improved patient comfort.

[0043] In some embodiments, at points in the treatment plan where different types of tooth movement are desired, the aligner trays designed for the new tooth movements may have bending stiffness moduli that are substantially similar to each other but different from the previous appliances. Such a sequence may be repeated at any time, or continued with new trays having different bending stiffness moduli, to produce different prescribed tooth movements.

[0044] Series 2021~202 n Each orthodontic aligner or retainer tray 202 in the series may differ slightly in at least one of shape, tooth geometry, or bending stiffness modulus, representing a stage in the overall treatment plan. In one non-limiting embodiment, several of the aligners or retainer trays in the series may include a substantially uniform bending stiffness modulus selected for a particular type of tooth movement, with varying shapes or tooth geometries. For example, in one stage of treatment, some of the appliances may be configured to translate one or more teeth and may require a relatively high bending stiffness modulus. In a different stage of treatment, an orthodontic aligner or retainer tray may be configured to achieve a different type of tooth movement, such as tipping, and may have a lower bending stiffness modulus than the tray utilized for translation. Thus, a series of aligners 2021-202 ... such as tipping, and may have a lower bending stiffness modulus than the tray utilized for translation. nThe tray 202 may have a different shape or tooth geometry to produce such movement, but the modulus of elasticity may be different from previous or subsequent trays utilized in treatment.

[0045] Series 2021~202 n The first multi-layer polymer aligner tray 240 has an elastic modulus of about 1.5 GPa or less, and an average bending stiffness modulus of about 0.1 GPa measured within 2 mm of the trim line of the labial central incisor. * mm 3 In this application, all listed stiffness modulus values ​​for the formed polymeric aligner tray 240 are measured within 2 mm of the trim line of the portion of the dental appliance configured to fit the central incisors labial to the appliance, in the occlusal direction or any non-lateral direction. In some embodiments, the first alignment tray 240 has an elastic modulus of less than 0.5 GPa and a stiffness modulus of 0.001 GPa. * mm 3 The sample comprises at least one layer obtained from a polymer film having a thickness selected to be less than 1 / 2 . The modulus was tested according to ASTM D790, and the tensile properties according to ASTM D638. The specimens prepared by die cutting were placed in the grips of a universal testing machine. The stress-strain curve was then utilized to determine the modulus and elongation at break.

[0046] A series 2021-202 that can be single layer or multilayer n The second alignment tray 250 had an average bending stiffness modulus of 0.042 GPa measured within 2 mm of the trim line of the labial central incisor. * mm 3 In some embodiments, the second alignment tray 250 has a modulus of elasticity of about 2 GPa and an average bending stiffness modulus of about 0.1 GPa measured within 2 mm of the trim line of the labial central incisors. * mm 3 It is formed to a thickness sufficient to

[0047] Figure 3 shows the series 2021-2022 in Figure 2.n 1 illustrates, but is not intended to be limiting, an example of a multi-layer alignment tray 300 that may be utilized as the first alignment tray 240 in the orthodontic alignment system of . The alignment tray 300 includes a shell 302 having an arrangement of one or more layers of a resilient polymeric material that generally conforms to the patient's teeth and may be transparent, translucent, or opaque. The polymeric material in the one or more layers is selected to provide a bending stiffness modulus in selected regions of the shell 302 to maintain a sufficient and substantially constant stress profile during the desired treatment period and to provide a relatively constant tooth repositioning force over the treatment period to maintain or improve the tooth repositioning efficiency of the shell 302.

[0048] In the embodiment of Figure 3, an arrangement of one or more polymer layers 314, which may also be referred to herein as skin layers, forms the exterior surface 306 of the shell 302. The exterior surface 306 contacts the patient's tongue and cheeks. An arrangement of one or more polymer layers 310, which may also be referred to herein as skin layers, forms the interior surface 308 of the shell 302. The interior surface 308 contacts the patient's teeth. An arrangement of one or more interior polymer layers 312 resides between the polymer layers 310 and 314.

[0049] Figure 4 shows the series 2021-2022 in Figure 2. n4 shows a schematic cross-sectional view of another embodiment of a multi-layer dental appliance 400 that may be utilized as the first alignment tray 240 in the orthodontic alignment system of FIG. 4. The dental appliance 400 of FIG. 4 includes a polymer shell 402 having a multi-layer polymer structure. The polymer shell 402 includes at least three, at least five, or at least seven alternating layers of thermoplastic polymer AB. The polymer shell 402 includes an interior region 475 including a core layer 470 having a first major surface 471 and a second major surface 472. The interior region 475 further includes interior layers 490, 492 disposed on the first major surface 471 and the second major surface 472, respectively, of the core layer 470. The polymer shell further includes exterior regions 485, 487 on opposite sides of the interior region 475. The exterior regions, which may also be referred to herein as skin layers, include first and second exterior surface layers 480, 482 facing outward on the exposed surface of the polymer shell 402.

[0050] The multi-layer polymer shell 402 has an overall flexural modulus necessary to move the patient's teeth as needed in at least one stage of the orthodontic aligner system. In various embodiments, the polymer shell 402 has an overall modulus of greater than about 0.5 GPa, or from about 0.8 GPa to about 1.5 GPa, or from about 1.0 GPa to about 1.3 GPa. In various embodiments, the multi-layer polymer shell 402 has an average flexural stiffness modulus of 0.1 GPa measured within 2 mm of the trim line of the labial central incisor. * mm 3 It should be formed thick enough so that the thickness is less than 1 / 2 mm.

[0051] In some embodiments, the interfacial adhesion between any adjacent layers within polymer shell 402 is greater than about 150 grams / inch (6 grams / mm) or greater than about 500 grams / inch (20 grams / mm).

[0052] In the embodiment of FIG. 4, core layer 470 comprises one or more layers of thermoplastic polymer A having a thermal transition temperature of about 70° C. to about 140° C., or about 80° C. to about 120° C., and a flexural modulus of greater than about 1.3 GPa, or greater than about 1.5 GPa, or greater than about 1.6 GPa, or greater than about 2 GPa. In some embodiments, thermoplastic polymer A has an elongation at break of greater than about 100%. In various embodiments, core layer 470 of thermoplastic polymer A has a flexural stiffness modulus of about 0.02 GPa. * mm 3 It should be thick enough to exceed the

[0053] In various non-limiting embodiments, the thermoplastic polymer A can comprise a polyester or copolyester, which can comprise linear, branched, or cyclic segments on the polymer backbone. Suitable polyesters and copolyesters may or may not contain ethylene glycol on the polymer backbone. Suitable polyesters include, but are not limited to, ethylene glycol-free copolyesters available from Eastman Chemical (Kingsport, TN) under the trade name TRITAN, polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyclohexylene dimethylene terephthalate (PCT), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), polycyclohexylene dimethylene terephthalate glycol (PCTg), polycarbonate (PC), and mixtures and combinations thereof. Suitable PETg resins that do not contain ethylene glycol in the polymer backbone are available from a variety of commercial suppliers, including, for example, Eastman Chemical (Kingsport, Tenn.); SK Chemicals (Irvine, Calif.); DowDuPont (Midland, Mich.); Pacur (Oshkosh, Wis.); and Scheu Dental Tech (Iserlohn, Germany). For example, Eastman Chemical's Eastar GN071 PETg resin and PCTg VM318 resin have been found to be suitable.

[0054] In one embodiment, the first and second outer surface layers 480, 482 may be the same or different and each comprise one or more layers of the thermoplastic polymer A utilized in the core layer 470. However, in various embodiments, the first and second outer surface layers 480, 482 of thermoplastic polymer A have a flexural stiffness modulus of about 0.002 GPa or less. * mm 3 It should have a thickness selected to be less than .

[0055] In another embodiment, the first and second outer surface layers 480, 482 may comprise one or more layers of a thermoplastic polymer C different from thermoplastic polymer A, where the thermoplastic polymer C has a thermal transition temperature of about 70°C to about 140°C, or about 80°C to about 120°C, and a flexural modulus of greater than about 1.3 GPa, or greater than about 1.5 GPa, or greater than about 1.6 GPa, or greater than about 2 GPa. In some embodiments, the thermoplastic polymer C has an elongation at break of greater than about 100%. In various embodiments, the first and second outer surface layers 480, 482 of thermoplastic polymer C have a flexural stiffness modulus of about 0.002 GPa. * mm 3 It should have a thickness selected to be less than .

[0056] For example, in some embodiments, the thermoplastic polymer C may comprise a polyester or copolyester, which may be linear, branched, or cyclic. Suitable polyesters include, but are not limited to, copolyesters available under the trade name Tritan from Eastman Chemical (Kingsport, TN), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyclohexylene dimethylene terephthalate (PCT), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), polycyclohexylene dimethylene terephthalate glycol (PCTg), polycarbonate (PC), and mixtures and combinations thereof. Suitable PETg and PCTg resins are available from various commercial suppliers, such as, for example, Eastman Chemical (Kingsport, TN); SK Chemicals (Irvine, CA); DowDuPont (Midland, MI); Pacur (Oshkosh, WI); and Scheu Dental Tech (Iserlohn, Germany). For example, Eastman Chemical's Eastar GN071 PETg resin and PCTg VM318 resin have been found to be suitable.

[0057] Inner layers 490, 492 may be the same or different and each comprise one or more layers of thermoplastic polymer B, different from thermoplastic polymer A, having a glass transition temperature of less than about 0°C as measured by DSC (differential scanning calorimetry) according to ASTM D3418, a Vicat softening temperature of greater than 65°C or greater than about 100°C as measured according to ASTM D1525, and a flexural modulus of less than about 0.5 GPa, or less than about 0.25 GPa, or less than about 0.2 GPa, or less than about 0.1 GPa (i.e., typically has an insufficient modulus to move teeth without the presence of Layer A and / or Layer C). In some embodiments, thermoplastic polymer B has a melting temperature of greater than about 70°C, or greater than about 100°C, or greater than about 150°C, or greater than about 200°C. In some embodiments, thermoplastic polymer B has an elongation at break of greater than about 300% or greater than about 400%. In some embodiments, the ratio of the elongation at break of polymer B to the elongation at break of either polymer A or C is about 5 or less, or about 3 or less. In various embodiments, the inner layer 490, 492 of thermoplastic polymer B has a flexural stiffness modulus of about 0.001 GPa. * mm 3 It should have a thickness selected to be less than .

[0058] In various embodiments, and not intended to be limiting, the thermoplastic polymer B in the inner layers 490, 492 is independently selected from copolyester ether elastomers, copolymers of ethylene acrylate and methacrylate, ethylene methyl-acrylate, ethylene ethyl-acrylate, ethylene butyl acrylate, maleic anhydride modified polyolefin copolymers, methacrylic acid modified polyolefin copolymers, ethylene vinyl alcohol (EVA) polymers, styrene block copolymers, ethylene propylene copolymers, and thermoplastic polyurethanes (TPUs).

[0059] In some embodiments, the thermoplastic polymer B is selected from copolyester ether elastomers, which may be linear, branched, or cyclic. Suitable examples include materials available from Eastman Chemical under the tradenames Neostar (e.g., FN007) and Ecdel, ethylene and methyl acrylate copolyesters and copolymers available from DowDuPont (Midland, MI) under the tradenames Hytrel, Elvaloy, ethylene vinyl alcohol (EVA) polymers, and the like, and Arnitel from DSM Engineering Materials (Evansville, IN).

[0060] In various embodiments, thermoplastic polyurethane (TPU) polymers suitable for the inner layers 490, 492 of the polymeric shell 202 have a flexural modulus of less than about 0.24 GPa, or less than about 0.12 GPa.

[0061] In one embodiment, the TPU comprises monomer units derived from a polyisocyanate, at least one dimeric aliphatic diol, and an optional hydroxyl-functional chain extender. In some embodiments, the TPU polymer comprises hard microdomains formed by the reaction between the polyisocyanate and the optional chain extender, and soft microdomains formed by the reaction between the polyisocyanate and the dimeric aliphatic diol.

[0062] The dimer aliphatic diols used to form the TPU are derived from dimer fatty acids, which are the dimerization products of mono- or polyunsaturated fatty acids and / or their esters. The related term trimer fatty acid similarly refers to the trimerization products of mono- or polyunsaturated fatty acids and / or their esters.

[0063] Dimer fatty acids are described, for example, in TE Breuer, "Dimer Acids," in J.I. Kroschwitz (ed.), Kirk-Othmer Encyclopedia of Chemical Technology, 4th Ed., Wiley, NY, 1993, Vol. 8, pp. 223-237. Dimer fatty acids are prepared by polymerizing fatty acids under pressure and then removing most of the unreacted fatty acid starting material by distillation. The final product usually contains some small amounts of mono- and tri- fatty acids, but is mostly composed of dimer fatty acids. The resulting product can be prepared using various ratios of different fatty acids as desired.

[0064] The dimer fatty acid used to form the dimer aliphatic diol is derived from the dimerization product of a C10-C30 fatty acid, a C12-C24 fatty acid, a C14-C22 fatty acid, a C16-C20 fatty acid, particularly a C18 fatty acid, and thus the resulting dimer fatty acid contains 20-60, 24-48, 28-44, 32-40, particularly 36 carbon atoms.

[0065] The fatty acid used to form the dimeric aliphatic diol may be selected from linear, branched, or cyclic fatty acids, which may be saturated or unsaturated. The fatty acid may be selected from fatty acids having either a cis / trans configuration and may have one or more unsaturated double bonds. In some embodiments, the fatty acid used is a linear monounsaturated fatty acid. The fatty acid may be hydrogenated or non-hydrogenated, and in some cases, hydrogenated dimeric fatty acid residues may have better oxidative or thermal stability, which may be desirable in polyurethanes.

[0066] In some embodiments, suitable dimer fatty acids may be the dimerization products of fatty acids, including, but not limited to, oleic acid, linoleic acid, linolenic acid, palmitoleic acid, or elaidic acid. Particularly suitable dimer fatty acids are those derived from oleic acid. Dimer fatty acids may also be the dimerization products of unsaturated fatty acid mixtures obtained from the hydrolysis of natural fats and oils, such as sunflower oil, soybean oil, olive oil, rapeseed oil, cottonseed oil, or tall oil.

[0067] In various embodiments, the molecular weight (weight average) of the dimeric fatty acid used to make the TPU polymers described herein is 450-690, or 500-640, or 530-610, or 550-590.

[0068] In addition to dimeric fatty acids, dimerization typically results in the presence of various amounts of residues of trimeric, oligomeric, and monomeric fatty acids, or their esters. In various embodiments, the dimeric fatty acids used to produce dimeric fatty diols should have relatively small amounts of these additional dimerization products, and the dimeric fatty acids should have a dimeric fatty acid (or dimer) content of more than 80% by weight, or more than 85% by weight, or more than 90% by weight, or more than 95% by weight, or up to 99% by weight, based on the total weight of the polymerized and mono-fatty acids present.

[0069] Any of the above dimer fatty acids may be converted to a dimer fatty diol, and the resulting dimer fatty diol may have the properties of the dimer fatty acid described herein, except that the acid groups in the dimer fatty acid are replaced with hydroxyl groups in the dimer fatty diol. The dimer fatty diol may be hydrogenated or non-hydrogenated.

[0070] In some non-limiting embodiments, the dimeric aliphatic diol is derived from a fatty acid having a C18 alkyl chain. In one embodiment, the dimeric aliphatic diol is a C36 diol available from Croda, Inc., New Castle, Del., under the trade name Pripol 2033. A depiction of the structure of Pripol 2033 is shown below: [ka]

[0071] The polyisocyanate reactant used to make the TPU polymer comprises at least one isocyanate having a functionality of at least 2, which in various embodiments may be an aliphatic isocyanate such as hexamethylene 1,6-diisocyanate or isophorone diisocyanate (IPDI), or an aromatic isocyanate.

[0072] In some embodiments, the polyisocyanate is an aromatic isocyanate, suitable examples include, but are not limited to, toluene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, polymethylene polyphenyl diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3,3-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, modified compounds thereof such as uretonimine modified compounds thereof, and mixtures and combinations thereof.

[0073] In one embodiment, the isocyanate component comprises 4,4'-diphenylmethane diisocyanate (MDI) or a mixture of MDI and uretonimine-modified 4,4'-diphenylmethane diisocyanate (modified MDI).

[0074] The optional hydroxyl-functional chain extender has two or more active hydrogen groups and in some embodiments includes polyols such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butylene glycol, 1,5-pentylene glycol, methylpentanediol, isosorbide (and other iso-hexides), 1,6-hexylene glycol, neopentyl glycol, trimethylolpropane, hydroquinone ether alkoxylates, resorcinol ether alkoxylates, glycerol, pentaerythritol, diglycerol, and dextrose; dimeric aliphatic diols; aliphatic polyamines such as ethylenediamine, hexamethylenediamine, and isophoronediamine; aromatic polyamines such as methylene-bis(2-chloroaniline), methylenebis(dipropylaniline), diethyl-toluenediamine, trimethylene glycol di-p-aminobenzoate; alkanolamines such as diethanolamine, triethanolamine, diisopropanolamine, and mixtures and combinations thereof.

[0075] In various embodiments, the hydroxyl-functional chain extender is a polyol, particularly a diol having an aliphatic straight or branched carbon chain having 1 to 10, or 3 to 7, carbon atoms. Suitable diols include, but are not limited to, ethylene glycol, propylene glycol, diethylene glycol, propylene glycol, 1,4-butylene glycol, 1,5-pentylene glycol, 1,6 hexylene glycol (1,6-hexanediol), methylpentanediol, isosorbide (and other iso-hexides), and mixtures and combinations thereof.

[0076] In some embodiments, the TPU can be most conveniently prepared by a reactive extrusion process in which a polymeric reactive extrusion composition containing a polyisocyanate, at least one dimeric aliphatic diol, an optional hydroxyl-functional chain extender, and any other optional ingredients such as a crosslinker, catalyst, etc., is charged into an extruder and extruded through a suitable die to form layers in a multilayer polymer film. In some embodiments, the multilayer film can be subsequently thermoformed into a dental appliance having a tooth-retaining cavity. In another embodiment, the reactive extrusion composition containing the TPU can be injected into a mold.

[0077] 4, polymer shell 402 further includes additional optional performance-enhancing layers that may be included to improve the properties of shell 402. In various non-limiting embodiments, the performance-enhancing layer may be, for example, a barrier layer that is resistant to stains and moisture absorption, an abrasion-resistant layer, a cosmetic layer that may optionally include a colorant or may include a polymeric material selected to adjust the optical haze or visible light transmission of polymer shell 402, a tie layer that improves the fit or adhesion between layers AB or BC, an elastic layer that provides a softer mouthfeel for the patient, a thermoforming-assist layer to enhance thermoforming, a layer to enhance mold release during thermoforming, etc.

[0078] Although the performance-enhancing layer may comprise a wide variety of polymers selected to provide specific performance benefits, the polymer in the performance-enhancing layer is generally selected from materials that are softer and more elastic than polymer ABC. In various non-limiting embodiments, the performance-enhancing layer comprises a thermoplastic polyurethane (TPU) and an olefin.

[0079] In some non-limiting examples, the olefin in the performance-enhancing layer is selected from polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), cyclic olefins (COP), copolyolefins having a portion selected from ethylene, propylene, butene, pentene, hexene, octene, C2 to C20 hydrocarbon monomers having polymerizable double bonds, and mixtures and combinations thereof, olefin hybrids selected from olefin / acid anhydride, olefin / acid, olefin / styrene, olefin / acrylate, and mixtures and combinations thereof.

[0080] For example, in the embodiment of FIG. 4 , the polymeric shell 402 includes an optional moisture barrier layer 440 on each exterior surface, which prevents moisture intrusion into the underlying polymer layers and allows the shell 402 to maintain a substantially constant stress profile during treatment. The polymeric shell 402 further includes an optional bonding or thermoforming auxiliary layer 450, which may be the same or different between the individual layers AB or BC. In some embodiments, the bonding / thermoforming auxiliary layer 450 can improve compatibility between the polymers within layers AB or BC when the polymeric shell 402 is formed from a multilayer polymer film, or reduce delamination between layers AB or BC, improving the durability and crack resistance of the polymeric shell 402 over extended treatment periods. The polymeric shell 402 of FIG. 4 further includes an optional elastic layer 460, which may be the same or different, and may be included to improve the flexibility or mouthfeel of the shell 402. In the embodiment of FIG. 4 , the elastic layer 460 is located proximal to the major surfaces 420, 422 of the shell 402.

[0081] Figure 5 shows the series 2021-2022 in Figure 2. n 1 is a schematic cross-sectional view of another embodiment of a dental appliance 500 that may be utilized as the first alignment tray 240 in the orthodontic alignment system of FIG. 1. The dental appliance 500 is made of a multi-layer polymer structure (AB). nwhere n=2 to about 500, or about 5 to about 200, or about 10 to about 100. Layer AB includes core layers 570, 590 of thermoplastic polymers A and B described above with respect to Figure 4 and configured to a thickness appropriate to provide the respective flexural thickness moduli outlined above. In some embodiments, outer layer 580 of polymer shell 502 can include one or more layers of either thermoplastic polymer A or C described above.

[0082] Referring again to Figure 3, in some embodiments, the polymer shell 302 is formed from a substantially transparent polymer material. In this application, the term substantially transparent refers to a material that transmits light in the wavelength region of the electromagnetic spectrum to which the human eye is sensitive (about 400 nm to about 750 nm), but blocks light in other regions. In some embodiments, the reflective edge of the polymer material selected for the shell 302 should be above about 750 nm, just outside the sensitivity range of the human eye.

[0083] In some embodiments, any or all layers of the polymer shell 302 can optionally include dyes or pigments to provide a desired color, which can be, for example, decorative or selected to improve the appearance of the patient's teeth.

[0084] Referring again to FIG. 2, a series of 2021-2022, which may be single layer or multi-layer, n The second alignment tray 250 has an average bending stiffness modulus of 0.042 GPa. * mm 3 The second alignment tray 250 may be selected from any polymeric material having a sufficient modulus and thickness to exceed the labial incisor trim line. In some non-limiting embodiments, the second alignment tray 250 has a modulus of elasticity of about 2 GPa and an average bending stiffness modulus of about 0.1 GPa within 2 mm of the labial incisor trim line. * mm 3 It is formed to a thickness sufficient to

[0085] In some exemplary embodiments, which are not intended to be limiting, a series of 2021-202 n The second alignment tray 250 may comprise a polyester or copolyester, which may contain linear, branched, or cyclic segments on the polymer backbone. Suitable polyesters and copolyesters may or may not contain ethylene glycol on the polymer backbone. Suitable polyesters include, but are not limited to, ethylene glycol-free copolyesters available under the tradename Tritan from Eastman Chemical (Kingsport, TN), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyclohexylene dimethylene terephthalate (PCT), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), polycyclohexylene dimethylene terephthalate glycol (PCTg), polycarbonate (PC), and mixtures and combinations thereof. Suitable PETg resins that do not contain ethylene glycol in the polymer backbone are available from a variety of commercial suppliers, including, for example, Eastman Chemical (Kingsport, Tenn.); SK Chemicals (Irvine, Calif.); DowDuPont (Midland, Mich.); Pacur (Oshkosh, Wis.); and Scheu Dental Tech (Iserlohn, Germany). For example, Eastman Chemical's Eastar GN071 PETg resin and PCTg VM318 resin have been found to be suitable.

[0086] Series 2021~202 iThe first and second orthodontic appliances 240, 250 can be fabricated using a variety of techniques. In one embodiment, the preferred configuration of tooth-retaining cavities is formed into a substantially flat sheet of single layer or multilayer polymer film comprising layers of polymeric material arranged as described above. In some embodiments, the polymer film may be formed into a dispersion and cast into a film, or applied onto a mold having tooth-receiving cavities. In some embodiments, the polymer film may be prepared by extruding the polymer layer material through an appropriate die to form a film. In some embodiments, a reactive extrusion process may be used in which one or more polymeric reaction products are charged into an extruder to form one or more layers during the extrusion procedure.

[0087] In some embodiments, the polymer film may be subsequently thermoformed into a dental appliance having a tooth-retaining cavity, injected into a mold containing the tooth-retaining cavity, or manufactured using a three-dimensional (3D) printing process. The tooth-retaining cavity may be formed by any suitable technique, including thermoforming, laser processing, chemical or physical etching, and combinations thereof, but thermoforming has been found to provide good results and superior efficiency. In some embodiments, the polymer film may be heated before forming the tooth-retaining cavity, or its surface may optionally be chemically treated, for example, by etching, or mechanically embossed by contacting the surface with a tool, before or after forming the cavity.

[0088] The general process for thermoforming appliances using the semi-crystalline polymer-containing films of the present disclosure may share similarities with general thermoforming techniques. One, some, or all steps of the method may be performed in a temperature and pressure controlled chamber. First, a physical dental model of the patient's teeth in a target or current arrangement is provided. A sheet of material including at least one layer comprised of a semi-crystalline polymer is provided and placed on the dental model. The model and sheet of material are placed under a first pressure, and the semi-crystalline polymer is melted to a first identifiable melting temperature range (T m1 In a particularly preferred method, the model and sheet of material are placed under a first pressure and heated to a first temperature that is close to, but preferably below, the upper limit of a first identifiable melting temperature range (T m1 The material is heated to a first temperature that is close to, but preferably below, the endothermic peak maximum (P1) of the model. The combination of heat and pressure / negative pressure causes the material to become flexible. The model and sheet are maintained at the first temperature and pressure until the sheet conforms to the shape and orientation of the dental model and some of the crystalline structure of the polymer melts. The temperature is then lowered (preferably isobarically) to create a shell appliance in a configuration having a geometry corresponding to the dentition of the first model. In some embodiments, a polymer film comprising one or more semi-crystalline polymers undergoes a temperature gradient during the forming process. g The film is heated to a temperature above 120° C., about 130° C., or above 140° C., for example. Typically, the first temperature is above a first identifiable melting temperature range (T m1 ) (e.g., about 200°C to about 220°C), although various temperatures and times may be used. m1By heating at a temperature near but below the upper limit of the T , a sufficient number of seed crystals or nucleation sites remain in the semi-crystalline polymer to allow for the formation of heterogeneous crystals upon cooling. The formation of heterogeneous crystals allows the crystalline phase of the cooled semi-crystalline polymer to retain desired mechanical performance while reducing the haze of the article. In other embodiments, the forming temperature is below the first identifiable melting temperature (T ) of at least one of the one or more semi-crystalline polymers present in the film. m1 ), and in some embodiments at least 7°C, at least 8°C, at least 9°C, at least 10°C, at least 11°C, or at least 12°C. The possibility of melting but allowing for heterogeneous nucleation upon cooling is enhanced by the addition of a nucleating agent to one or more of the semi-crystalline polymer layers, as described above.

[0089] By heating to a temperature near the first melting peak but above the glass transition temperature of the film, typically at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90% of the crystallinity present in one or more semi-crystalline elastomers is converted to a first discernible melting temperature (T m1) and / or the upper limit of the endothermic peak maximum (P1). The degree of melting can be determined by the melt fraction ratio for each example. However, by keeping the molding temperature below the upper limit, if not the endothermic peak maximum, at least some of the crystalline structure or nucleation sites can remain in the film before cooling. In some embodiments, the applied pressure is greater than 10 kPa, e.g., greater than 50 kPa, 75 kPa, 100 kPa, 125 kPa, or greater than 150 kPa. In some embodiments, the pressure is maintained for more than 30 seconds, e.g., 45 seconds, 60 seconds, 2.5 minutes, 5.0 minutes, 10 minutes, 20 minutes, 30 minutes, more than 60 minutes, more than 90 minutes, or even more than 120 minutes, before releasing the pressure and returning to atmospheric pressure. Pressure can be applied by direct force on the polymer film material and / or negative pressure. A first plurality of crystalline structures is formed in any semi-crystalline polymeric material as the temperature is reduced from the first molding temperature to a subsequent temperature (e.g., room temperature). The formed crystalline structures help to hold the appliance in a storage geometry prior to irradiation or other suitable methods of creating crosslinks in the polymeric material, and are preferably small enough so as not to contribute to a cloudy appearance. In some or all embodiments, the temperature is reduced gradually. In other embodiments, the appliance may be quenched by rapidly reducing the temperature. In either case, it is preferred that the selected parameters be consistent for each appliance in the present invention. For example, the temperature reduction rate can range from about 0.5°C to about 10°C per minute, but is typically maintained at the same rate within this range for each temperature reduction step in the process. The multilayer polymeric film, the formed dental appliance, or both, may optionally be crosslinked with radiation selected from electron beam, gamma radiation, UV, and mixtures and combinations thereof.

[0090] When used to crosslink materials, irradiation can be at room temperature or at elevated temperatures, typically below the first molding temperature. Irradiation can be carried out in air, vacuum, or an oxygen-free environment containing an inert gas such as nitrogen or a noble gas. Irradiation can be carried out by electron beam, gamma radiation, or X-ray irradiation. In some embodiments, ionizing radiation (e.g., electron beam, X-ray radiation, or gamma radiation) is used to crosslink non-segmented polymeric materials. In certain embodiments, gamma radiation is used to crosslink substantially uncrosslinked polymeric materials. In some embodiments, irradiation (by any radiation source) is carried out until the sample receives a dose of at least 0.25 Mrad (2.5 kGy), e.g., at least 1.0 Mrad (10 kGy), at least 2.5 Mrad (25 kGy), at least 5.0 Mrad (50 kGy), or at least 10.0 Mrad (100 kGy). In some embodiments, irradiation is carried out until the sample receives a dose of 1.0 Mrad to 6.0 Mrad, e.g., 1.5 Mrad to 4.0 Mrad. In other embodiments, the appliance is treated to create chemical crosslinks using methods known in the art. For example, peroxide may be added to a polymer, and the polymer may be maintained at an elevated temperature after forming the first storage geometry to react the peroxide. Additionally, silanes may be grafted to a polymer backbone, such as polyethylene, which may crosslink upon exposure to a moist, hot environment. The thickness of the multilayer polymer film is selected to provide a clinically appropriate thickness of material for the resulting appliance. The material thickness should typically be selected so that the appliance is stiff enough to apply sufficient force to the teeth, yet remains thin enough to be comfortably worn. In various embodiments, the multilayer polymer film used to form the dental appliance has a thickness of less than about 1 mm, or less than about 0.8 mm, or less than about 0.5 mm. The resulting wall thickness of the brace can be between 0.05 mm and 2 mm, or between 0.1 mm and 1 mm.

[0091] In various embodiments, dental appliances, particularly those comprising one or more semi-crystalline polymers, are substantially optically transparent. Expected light transmittance can be determined according to ISO 13468-1:2019 or ASTM D1003-13 using CIE illuminant C, and expected haze can be determined according to ISO 14782-1:1999 or ASTM D1003-13 using CIE illuminant C. Because the geometry of the appliance (e.g., size and surface features) does not directly contribute to the test, the term "expected" is used herein to indirectly describe the transmittance and haze of the formed appliance. Instead, a representative polymer film is subjected to the same temperature and processing conditions typically used to fabricate the appliance, but without lowering the film onto a mold, ensuring the film remains sufficiently flat for subsequent testing.

[0092] Some embodiments have an expected light transmission of at least about 50%. Some embodiments have an expected light transmission of at least about 75%. Some embodiments have an expected haze of 15% or less, or 10% or less. Some embodiments have an expected haze of 5% or less. Some embodiments have an expected haze of 2.5% or less. Certain preferred embodiments of the present invention have a dental appliance with an expected haze of less than 10% and an expected light transmission of greater than 80%.

[0093] The polymer film, the formed dental appliance, or both may optionally be crosslinked with radiation selected from electron beam, gamma radiation, UV, and mixtures and combinations thereof.

[0094] In various embodiments, the polymeric films used to form the dental appliances have a thickness of less than about 1 mm, or less than about 0.8 mm, or less than about 0.65 mm.

[0095] In some embodiments, the polymer film may be manufactured in a roll-to-roll manufacturing process and may optionally be wound into a roll until further processing operations are required to form one or more dental appliances.

[0096] In some examples, a dental treatment system according to the present disclosure is provided to a dental practitioner in the form of a kit including a set of orthodontic aligner trays and patient instructions for use, as shown in Figure 2. Non-limiting additional items suitable for the kit include one or more of the following: a carry case, a removal tool to help the patient remove the aligners from the teeth, a fastening tool to help press the aligners onto the teeth, a toothbrush, aligner tray cleaning tablets, powder / crystals, or gel / foam / liquid, abrasive paper or object to address discomfort from sharp edges or corners of dental appliances, whitening gel or pen, dental floss, dental picks, wax, etc.

[0097] The devices of the present disclosure are further described in the following non-limiting examples. [Example]

[0098] These examples are for illustrative purposes only and are not intended to unduly limit the scope of the appended claims. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques; this is not intended to limit the application of the doctrine of equivalents to the scope of the claims.

[0099] All parts, percentages, ratios, etc. in the examples and elsewhere in this specification are by weight unless otherwise noted. Solvents and other reagents used were available from Sigma-Aldrich Chemical Company (Milwaukee, WI) unless otherwise noted.

[0100] material PETg: Copolyester manufactured by Eastman Chemicals (Kingsport, TN), Grade: Eastar GN071 PCTg: Copolyester manufactured by Eastman Chemicals, Grade: VM318 Tritan: Eastman Chemicals copolyester, grade MX710 Elvaloy: Copolymer of ethylene and methyl acrylate: manufactured by DowDuPont (Midland, Mich.), Grade: Elvaloy 1609 Pellethane: Thermoplastic polyurethane from Lubrizol (Wickliffe, OH): Grade 65D Texin: Thermoplastic polyurethane, grade RxT50D, manufactured by Covestro (Pittsburgh, PA). Admer: Thermoplastic elastomer (TPE), grade SE810, manufactured by Mitsui Chemicals America, Rye Brook, NY Zeonor: Thermoplastic cycloolefin polymer (COP), grade 1060R, manufactured by Zeon Chemicals (Louisville, KY). Ecdel: Copolyester elastomer available from Eastman Chemicals, Grade: 9967

[0101] Properties of selected polyesters of layers ABC Some properties of the polymeric materials used in the following examples are shown in Table 1 below.

[0102] [Table 1]

[0103] The solubility parameters in Table 1 were estimated according to the group contribution method outlined in Chapter 3 of Sperling, LH, Introduction to Physical Polymer Science, John Wiley & Sons, Inc.: Hoboken, New Jersey, 2006.

[0104] Comparative Example 1 Several currently available manufacturers of orthodontic alignment trays disclose that the desired range of elastic modulus to provide effective tooth-moving forces is from about 0.1 GPa to about 1.5 GPa. Using various elastic modulus values ​​within this range, the bending stiffness modulus of a 0.75 mm monolayer film was calculated and is shown in Table 2 below. In Table 2, Et 3 is the bending stiffness modulus of the aligner film before thermoforming, and Etw 3 is the bending stiffness coefficient of the aligner tray, where t w is the wall thickness of the aligner tray within 2 mm of the labial incisor trim line. The most likely thickness reduction near the trim line is calculated using the bending stiffness coefficient (Etw 3 ) were allocated in the range of 40% to 60%.

[0105] Table 2 below shows the calculated bending stiffness modulus of thermoformed trays with 40%, 50%, and 60% wall thickness reduction from 0.75 mm aligner film and polymers with different moduli of elasticity of 0.1 GPa, 0.5 GPa, 0.8 GPa, and 1.5 GPa.

[0106] [Table 2]

[0107] Table 2, in relevant part, shows that: (1) when the wall thickness is reduced by 60%, if the aligner modulus is 0.1 GPa, the elastic modulus is 0.0027 GPa; * mm 3 is the minimum bending stiffness modulus required for the aligner tray to move teeth, while the elastic modulus of 0.5 GPa is 0.0135 GPa* mm 3 and (2) the most likely desired bending stiffness modulus of the aligner tray is 0.042 GPa with a 50% wall thickness reduction from moduli of 0.8 GPa and 1.5 GPa. * mm 3 to 0.079 GPa * mm 3 Wall thickness is assigned within 2 mm of the incisor trim line on the labial side of the appliance.

[0108] Comparative Examples 2 and 3 The bending stiffness moduli of commercially available orthodontic aligner tray materials, aligner trays, and orthodontic treatment systems available under the tradenames SMARTTRACK (designated CE2 in Table 3) from Align Technology, Inc. (San Jose, CA) and ZENDURA FLX (CE3) from Bay Materials (Fremont, CA) were calculated with a 50% wall thickness reduction, and the results are shown in Tables 3-4. The bending stiffness moduli highlighted in columns 5 and 6 of Tables 3 and 4 are calculated from the tensile modulus approximated by the rule of mixtures of the thickness and modulus of each of the individual layers, while the bending stiffness moduli in columns 7 and 8 of Tables 3 and 4 are from the flexural modulus calculated from the multilayer beam model. The calculated BSF of the SmartTrack material was 0.042 GPa, as determined from Tables 2-5 above. * mm 3 to 0.079 GPa * mm 3 falls within the most likely desired range.

[0109] [Table 3]

[0110] [Table 4]

[0111] CE2 and CE3 were developed to replace previous, harder (stiffer) single-layer aligners, reportedly to reduce the modulus of elasticity (stiffness at a given thickness) and limit the reduction in elastic positioning force applied to the teeth when the aligners are worn by the patient. These more elastic aligners are less stiff, have better force retention, and have improved strain recovery than their predecessor single-layer materials, resulting in reportedly increased efficacy and significantly reduced pain with shorter treatment times.

[0112] When worn by a patient, aligners must encapsulate the teeth and provide both retention and actuation to move them. Generally, desired undercuts on the teeth provide retention, while actuation components move the teeth through elastic bending deformation of the aligner. The elastic bending force of the aligner cannot be large enough to overcome the retentive force. The aligner trays in Tables 3 and 4 above are designed to accelerate tooth movement with reduced stiffness for improved patient comfort. Their actuation forces are more sustained, while, due to their reduced stiffness, they can sometimes be very close to the retentive force. Thus, the combined effect may result in effective (faster) movement in the early stages of treatment, but less control to coordinate precise movement and reach the planned position near the end. Precision adjustments are then required to move the teeth to the exact position as planned, which is highly undesirable for orthodontists and patients.

[0113] Example 1 The monolayer PETg film in the following examples is the substrate used in orthodontic aligner trays available from 3M (St. Paul, MN). The PETg film was made by an extrusion cast film process and had a thickness of 0.75 mm before thermoforming.

[0114] PETg aligner trays were thermoformed onto the 3D printed arches. The properties and bending stiffness modulus of the monolayer film are shown in Table 8 below.

[0115] [Table 5]

[0116] Example 2 A pilot-scale coextrusion line equipped with a feedblock and film die was used to extrude a 5-layer ABCBA (Tritan MX710 / Ecdel 9967 / Tritan MX710 / ECDEL 9967 / Tritan MX710) film. The overall thickness of the film sheet was controlled at approximately 25 mil (0.625 mm).

[0117] The five-layer film was then thermoformed onto the 3D-printed arch. The thermoforming temperature was varied to change the thickness of the aligner tray.

[0118] The properties and calculated bending stiffness moduli of the five-layer material are shown below in Tables 6 and 7. The bending stiffness moduli of the five-layer film and aligner highlighted in Table 6 are calculated from the tensile moduli approximated by the rule of mixtures of the thicknesses and moduli of each of the individual layers, while the bending stiffness moduli highlighted in Table 7 are determined from the bending moduli calculated from the multilayer beam model.

[0119] [Table 6]

[0120] [Table 7]

[0121] The single-layer PETg aligner (Example 1) showed a higher bending stiffness modulus (0.105 GPa) within 2 mm of the labial incisor trim line. * mm 3) and elastic modulus (2 GPa), and are therefore expected to provide better retention while moving teeth toward the end of treatment, minimizing the need for precision adjustments. Five-layer aligners, on the other hand, have better force retention and a lower elastic modulus (<1.5 GPa), and are therefore expected to provide effective tooth movement in the early stages of treatment.

[0122] The five-layer film (Example 2) has a bending stiffness coefficient of 0.02 GPa. * mm 3 Ultra-thin core layer with a bending stiffness coefficient of 0.0001GPa * mm 3 Furthermore, the preferred thermoforming process window is 0.036 GPa. * mm 3 to 0.079 GPa * mm 3 It was suggested that a reduction in wall thickness of more than 35% within 2 mm of the labial incisor trim line would provide effective elastic bending forces with a bending stiffness modulus in the desired range of .

[0123] The proposed system and treatment plan can treat patients in the early stages of treatment using five-layer aligners, while single-layer PETg aligners can be used in later stages. Alternatively, the treatment plan can use single-layer PETg aligners in the early stages, followed by trays with higher bending stiffness moduli (e.g., trays of Example 2) in later stages. The treatment plan can include any number of alternating trays with different bending stiffness moduli in any given pattern (e.g., ABBA, AABB, ABAB, ABAA, etc.). The combined treatment system can improve the overall patient experience with more predictable treatment outcomes by minimizing the need for precision adjustments.

[0124] Various embodiments of the present invention have been described. These and other embodiments are within the scope of the following claims. In addition to the above-described embodiments, the following aspects will be noted. (Appendix 1) 1. A system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement, the system comprising a plurality of incremental positioning appliances, each appliance including an arrangement of cavities shaped to receive and reposition the patient's teeth, the cavity of at least one appliance in the system having a geometric shape that is different from the geometric shape of at least one other appliance in the system, at least some of the appliances in the system being worn sequentially by the patient to apply a force to at least one tooth to move the patient's teeth from a first arrangement to a subsequent arrangement that is different from the first arrangement, the system comprising: a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said shell; * mm 3 a first multilayer shell having a modulus of elasticity of about 1.5 GPa or less; a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of said shell; * mm 3 A system comprising: a second shell that is superimposed; (Appendix 2) the second shell has a resistance of about 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell; * mm 3 and an elastic modulus of about 2 GPa. (Appendix 3) 3. The system of claim 2, wherein the second shell comprises polycyclohexylene dimethylene terephthalate glycol (PCTg), polyethylene terephthalate glycol (PETG), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), and mixtures and combinations thereof. (Appendix 4) the first multilayer shell having an elastic modulus of less than about 0.5 GPa and a hardness of less than about 0.001 GPa * mm 3 10. The system of claim 1, comprising at least one polymer layer having a bending stiffness modulus less than (Appendix 5) Multilayer film, a core layer having a first major surface and a second major surface, the core layer having an elastic modulus of 1.55 GPa and a flexural rigidity coefficient of 0.02 GPa; * mm 3 The super core layer, Each has an elastic modulus of 0.2 GPa and a bending stiffness coefficient of 0.001 GPa. * mm 3 a first inner layer on the first major surface of the core layer and a second inner layer on the second major surface of the core layer, the first inner layer being less than Each has an elastic modulus of 1.55 GPa and a bending stiffness coefficient of 0.002 GPa. * mm 3 a first outer layer on the first inner layer and a second outer layer on the second inner layer, the first outer layer being less than 1 / 2 mm. (Appendix 6) 6. The system of claim 5, wherein the multilayer film has five layers, and the first outer layer, the second outer layer, and the core layer comprise the same thermoplastic polymer. (Appendix 7) 6. The system of claim 5, wherein the thermoplastic polymers in the first and second outer layers and the core layer comprise polyesters or copolyesters, which may be the same or different. (Appendix 8) 8. The system of claim 7, wherein the polyesters are independently selected from polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyclohexylene dimethylene terephthalate (PCT), polycyclohexylene dimethylene terephthalate glycol (PCTg), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), 2,2,4,4-tetramethyl-1,3-cyclobutanediol-modified polycyclohexylene dimethylene terephthalate, and mixtures and combinations thereof. (Appendix 9) 9. The system of claim 8, wherein the polyester is selected from PCTg, PETg, PCTA, 2,2,4,4-tetramethyl-1,3-cyclobutanediol-modified polycyclohexylene dimethylene terephthalate, and mixtures and combinations thereof. (Appendix 10) 6. The system of claim 5, wherein the first and second inner layers comprise a thermoplastic polymer independently selected from a copolyester ether elastomer, a copolymer of ethylene and (meth)acrylate, ethylene methyl-acrylate, ethylene ethyl-acrylate, ethylene butyl acrylate, a maleic anhydride-modified polyolefin copolymer, a methacrylic acid-modified polyolefin copolymer, an ethylene vinyl alcohol (EVA) polymer, a styrene block copolymer, an ethylene propylene copolymer, and a thermoplastic polyurethane (TPU). (Appendix 11) 11. The system of claim 10, wherein the thermoplastic polymer in the first and second inner layers comprises a copolyester ether elastomer, which may be the same or different. (Appendix 12) 11. The system of claim 10, wherein the thermoplastic polymer in the first and second inner layers comprises ethylene methyl acrylate, which may be the same or different. (Appendix 13) 11. The system of claim 10, wherein the thermoplastic polymer in the first and second inner layers comprises a thermoplastic polyurethane, which may be the same or different. (Appendix 14) 1. A method of moving one or more of a patient's teeth, comprising: providing a series of dental appliances for sequential placement on at least some of the patient's teeth, at least some of the dental appliances in the series including tooth-retaining cavities configured to apply a resilient force to reposition at least one tooth of the patient, at least one of the dental appliances in the series having a tooth-retaining cavity with a geometry that is different from the geometry of the tooth-retaining cavity of another of the dental appliances in the series; The set of dental appliances comprises: a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said shell; * mm 3 and an elastic modulus of less than about 1.5 GPa, and an elastic modulus of less than about 0.5 GPa and about 0.001 GPa * mm 3 a first multilayer shell including at least one polymer layer having a bending stiffness modulus less than a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of said shell; * mm 3 and a second shell, the second shell being superimposed. (Appendix 15) the second shell has a resistance of about 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of the shell; * mm 3 and an elastic modulus of about 2 GPa. (Appendix 16) Multilayer film, a core layer having a first major surface and a second major surface, the core layer having an elastic modulus of 1.55 GPa and a flexural rigidity coefficient of 0.02 GPa; * mm 3 The super core layer, Each has an elastic modulus of 0.2 GPa and a bending stiffness coefficient of 0.001 GPa. * mm 3 a first inner layer on the first major surface of the core layer and a second inner layer on the second major surface of the core layer, the first inner layer being less than Each has an elastic modulus of 1.55 GPa and a bending stiffness coefficient of 0.002 GPa. * mm 3 15. The method of claim 14, comprising a first outer layer on the first inner layer and a second outer layer on the second inner layer, wherein the thickness of the first outer layer is less than 1 / 2 mm. (Appendix 17) 1. A system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement, the system comprising a series of polymeric shells, at least some of the polymeric shells comprising an array of cavities configured to receive one or more teeth of an upper or lower arch of the patient and to apply a resilient positioning force to cause predetermined incremental movement of the one or more teeth from a first position to a second position, the series of polymeric shells comprising: a first multi-layer shell having a bending stiffness modulus of about 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said shell; * mm 3 a first multilayer shell having a modulus of elasticity of about 1.5 GPa or less; a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of the incisor trim line on the labial side of said shell; * mm3 A system comprising: a second shell that is superimposed; (Appendix 18) the first multi-layer shell has a resistance of about 0.2 GPa measured within 2 mm of the incisor trim line on the labial side of the shell; * mm 3 18. The system of claim 17, having a bending stiffness coefficient of less than (Appendix 19) the second shell has a resistance of 0.05 GPa measured within 2 mm of the incisor trim line on the labial side of the shell * mm 3 19. The system of claim 17 or 18, having a bending stiffness coefficient of greater than

Claims

1. 1. A system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement, the system comprising a plurality of incremental positioning appliances, each including an arrangement of cavities shaped to receive and reposition the patient's teeth, the cavity of at least one appliance in the system having a geometric shape that is different from the geometric shape of at least one other appliance in the system, at least some of the appliances in the system being worn sequentially by the patient to apply a force to at least one tooth to move the patient's teeth from a first arrangement to a subsequent arrangement that is different from the first arrangement, the plurality of incremental positioning appliances comprising: a first multi-layer shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said first multi-layer shell; ＊ mm ３ a first multilayer shell having a modulus of elasticity of 1.5 GPa or less; a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said second shell; ＊ mm ３ a second shell that is greater than The first multi-layer shell comprises: a core layer having a first major surface and a second major surface, the core layer having an elastic modulus of 1.55 GPa and a flexural rigidity coefficient of 0.02 GPa; ＊ mm ３ The super core layer, Each has an elastic modulus of 0.2 GPa and a bending stiffness coefficient of 0.001 GPa. ＊ mm ３ a first inner layer on the first major surface of the core layer and a second inner layer on the second major surface of the core layer, Each has an elastic modulus of 1.55 GPa and a bending stiffness coefficient of 0.002 GPa. ＊ mm ３ a first outer layer on the first inner layer and a second outer layer on the second inner layer, the first outer layer being less than 1 / 2 mm.

2. 10. The system of claim 1, wherein the second shell comprises polycyclohexylene dimethylene terephthalate glycol (PCTg), polyethylene terephthalate glycol (PETG), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), and mixtures and combinations thereof.

3. 3. The system of claim 1 or 2, wherein the thermoplastic polymers in the first and second outer layers and the core layer comprise polyesters or copolyesters, which may be the same or different.

4. 4. The system of claim 3, wherein the polyesters are independently selected from polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETg), polycyclohexylene dimethylene terephthalate (PCT), polycyclohexylene dimethylene terephthalate glycol (PCTg), poly(1,4 cyclohexylene dimethylene) terephthalate (PCTA), 2,2,4,4-tetramethyl-1,3-cyclobutanediol-modified polycyclohexylene dimethylene terephthalate, and mixtures and combinations thereof.

5. 3. The system of claim 1 or 2, wherein the first and second inner layers comprise a thermoplastic polymer independently selected from a copolyester ether elastomer, a copolymer of ethylene and (meth)acrylate, ethylene methyl-acrylate, ethylene ethyl-acrylate, ethylene butyl acrylate, a maleic anhydride modified polyolefin copolymer, a methacrylic acid modified polyolefin copolymer, an ethylene vinyl alcohol (EVA) polymer, a styrene block copolymer, an ethylene propylene copolymer, and a thermoplastic polyurethane (TPU).

6. 1. A system for repositioning a patient's teeth from an initial tooth arrangement to a final tooth arrangement, the system comprising a series of polymeric shells, at least some of the polymeric shells comprising an array of cavities configured to receive one or more teeth of the patient's upper arch or lower arch and to apply a resilient positioning force to cause predetermined incremental movement of the one or more teeth from a first position to a second position, the series of polymeric shells comprising: a first multi-layer shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said first multi-layer shell; ＊ mm ３ a first multilayer shell having a modulus of elasticity of 1.5 GPa or less; a second shell having a bending stiffness modulus of 0.1 GPa measured within 2 mm of an incisor trim line on the labial side of said second shell; ＊ mm ３ a second shell that is greater than The first multi-layer shell comprises: a core layer having a first major surface and a second major surface, the core layer having an elastic modulus of 1.55 GPa and a flexural rigidity coefficient of 0.02 GPa; ＊ mm ３ The super core layer, Each has an elastic modulus of 0.2 GPa and a bending stiffness coefficient of 0.001 GPa. ＊ mm ３ a first inner layer on the first major surface of the core layer and a second inner layer on the second major surface of the core layer, Each has an elastic modulus of 1.55 GPa and a bending stiffness coefficient of 0.002 GPa. ＊ mm ３ a first outer layer on the first inner layer and a second outer layer on the second inner layer, the first outer layer being less than 1 / 2 mm.

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