Multi-layer dental appliance with customized transition temperatures and thicknesses

Abstract

Improved dental appliances and polymeric sheet compositions are disclosed. The polymeric sheet compositions are useful for making dental appliances having outer layers comprised of a material having an increased glass transition temperature (Tg) greater than 110°C. In multi-layer appliances, the outer layers may have an increased Tg in combination with a greater thickness than an inner elastomeric layer.

Description

Leydig Docket No.515189 (001010PC) MULTI-LAYER DENTAL APPLIANCE WITH CUSTOMIZED TRANSITION TEMPERATURES AND THICKNESSES CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is claims the benefit of priority to US Provisional Patent Application No.63 / 549,687, filed on February 5, 2024, titled “MULTI-LAYER DENTAL APPLIANCE WITH CUSTOMIZED TRANSITION TEMPERATURES AND THICKNESSES,” which is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0002] Compositions in the form of polymeric sheets are disclosed. The polymeric sheets are useful, for example, in a dental appliance, and are constructed of layers that impart flexibility and strength and stain resistance to devices made from the sheets. BACKGROUND

[0003] There is a need for improved orthodontic and dental appliances capable of facilitating orthodontic tooth movements, stabilizing tooth positions or protecting teeth from potentially damaging outside forces. Existing materials and products are constructed from single layer materials, bi-layer materials or tri-layer materials which have limited functionality and may suffer from performance deficiencies. Aligners are plastic shells which fit over teeth and are designed to apply translational or rotational forces to teeth. Their ability to accurately move teeth is limited by their effective modulus of elasticity, elasticity, hardness, and ability to resist creep and stress relaxation. Additionally, they generally should be resistant to staining and environmental stress cracking.

[0004] Appliances for protection of teeth, for example, sports mouth guards, and dental splints have contradictory requirements. On the one hand, they should be capable of dissipating impactLeydig Docket No.515189 (001010PC) forces and on the other hand should be thin and not interfere with the natural occlusion of a person’s teeth or impede speaking. BRIEF SUMMARY

[0005] In one aspect, the present disclosure relates to a polymeric sheet composition, including an elastomeric inner layer disposed between two outer layers. The two outer layers are polyesters or copolyesters with a glass transition temperature between about 110°C to about 130°C. The elastomeric inner layer is a polyester or copolyester with an inherent viscosity of about 1.0 to 1.3 dL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C. Polyester or copolyester resins with higher inherent viscosity general provide for better coextrusion capabilities and more robust sheet constructions, such as better impact resistance. It has been found that such a polymeric sheet composition provides an optimal combination of strength, flexibility, and durability, ensuring effective performance in orthodontic and dental applications by maintaining consistent force application, resisting deformation over time, and withstanding environmental stresses and staining. In some embodiments, the polymeric sheet composition has a stiffness D value from about 0.4 to about 0.5. In some embodiments, the thickness of each of the outer layers is greater than the thickness of the elastomeric inner layer. In some embodiments, the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:14. Such multi-layer constructions significantly enhance performance compared to traditional materials. The specified thickness ratios optimize key properties like modulus, elasticity, and hardness, important for effective tooth movement and lasting durability. The harder outer layers resist staining and environmental stress cracking, maintaining both function and aesthetics.

[0006] In some embodiments, the two outer layer materials are different, with each outer layer polyester or copolyester material having a glass transition temperature between about 110°C to about 130°C. The Tg of each differing outer layer may be the same or similar or different.

[0007] In some embodiments, the polymeric sheet composition is a three-layer composition with an asymmetric thickness ratio of the three layers, e.g., 12:8:10, 13:6:11, 14:4:12, or 15:2:13, etc. which advantageously provides enhanced directional / controlled bending behavior.Leydig Docket No.515189 (001010PC)

[0008] In some embodiments, at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C, resulting in a blend material having a Tg of between about 110°C to about 130°C or greater. In some embodiments, the blend of the two materials reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events. This leads to enhanced longevity and consistent performance of an appliance including the sheet composition, as it maintains its shape and force application capabilities over extended periods of use.

[0009] In some embodiments, a combined thickness of all layers is from about 250 microns to about 2,000 microns; this provides a balance between flexibility and durability, ensuring an appliance is both comfortable for the wearer and robust enough to apply the necessary forces for effective orthodontic treatment. In some embodiments, the two outer layers have a stiffness value D from about 0.45 to about 0.50. In some embodiments, the polymeric sheet composition also includes two intermediate layers, wherein each intermediate layer is disposed between the elastomeric inner layer and one of the two outer layers, which helps minimize / prevent cracking at the interface between the outermost layer and the inner layer.

[0010] . In some embodiments, the two intermediate layers each have glass transition temperatures lower than a glass transition temperature of their adjacent outer layer, which advantageously results in improved fatigue properties and durability or sustainability. In some embodiments, the two intermediate layers each have thicknesses less than a thickness of their adjacent outer layer and advantageously act as an interface modifier.

[0011] In some embodiments, a dental appliance, such as dental retainer, conformal to one or more teeth is made from the multi-layer sheet compositions described herein.

[0012] In another aspect, the present disclosure relates to a dental aligner for repositioning one or more teeth of a patient formed from a polymeric sheet composition including an elastomeric inner layer disposed between two outer layers. The two outer layers are polyesters or copolyesters with a glass transition temperature between about 110°C to about 130°C, and the elastomeric inner layer is a polyester or copolyester with an inherent viscosity of about 1.0 to 1.3 dL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C. In some embodiments, the polymeric sheet composition has a stiffness D value fromLeydig Docket No.515189 (001010PC) about 0.4 to about 0.5. In some embodiments, the thickness of each of the two outer layers is greater than the thickness of the elastomeric inner layer. In some embodiments, the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:14. In some embodiments, at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C. In some embodiments, the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events. In some embodiments, a combined thickness of all layers is from about 250 microns to about 2,000 microns. In some embodiments, the two outer layers have a stiffness value D from about 0.45 to about 0.50. In some embodiments, the dental aligner also includes two intermediate layers disposed between the elastomeric inner layer and one of the two outer layers. In some embodiments, the two intermediate layers each have glass transition temperatures lower than a glass transition temperature of their adjacent outer layer. In some embodiments, the two intermediate layers each have thicknesses less than a thickness of their adjacent outer layer.

[0013] In another aspect, the present disclosure relates to a method of forming a dental aligner for repositioning one or more teeth of a patient including: coextruding a polymeric sheet composition, and thermoforming the polymeric sheet composition over a model of a patient’s dentition to form the dental aligner. The coextruded layers of the polymeric sheet composition includes an elastomeric inner layer disposed between two outer layers. The two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, and the elastomeric inner layer is a polyester or copolyester having inherent viscosity of about 1.0 to 1.3 dL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C. In some embodiments, a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer. In some embodiments, the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:14. In some embodiments, at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C. In some embodiments, the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.Leydig Docket No.515189 (001010PC)

[0014] In another aspect, the present disclosure relates to a method of forming a dental aligner for repositioning one or more teeth of a patient including coextruding a polymeric sheet composition having five layers. The five layers include a first outer layer; a second outer layer; a first intermediate layer adjacent to the first outer layer; a second intermediate layer adjacent to the second outer layer; and an inner layer between the first intermediate layer and the second intermediate layer. The first and second outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C. The inner layer is an elastomeric layer including a polyester or copolyester having an inherent viscosity of about 1.0 to 1.3 dL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C. The first and second intermediate layers each have glass transition temperatures lower than a glass transition temperature of their adjacent outer layer.

[0015] Reference to the remaining portions of the specification, including the drawings and claims, will realize other features and advantages of the present invention. Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The detailed description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items.

[0017] FIG. 1 is a schematic depiction of a cross sectional view of a three-layer sheet having thicker outer layers than the inner layer, according to an embodiment of the present disclosure.

[0018] FIG. 2 is another schematic depiction of a cross sectional view of a three-layer sheet having thicker outer layers than the inner layer, according to an embodiment of the present disclosure.Leydig Docket No.515189 (001010PC)

[0019] FIG.3 is a schematic depiction of a cross sectional view of a five-layer sheet having rigid outer layers that are thicker than the inner layer, and an intermediate layer, according to an embodiment of the present disclosure.

[0020] FIG.4 is a graph depicting stress relaxation data for three-layer materials with different outer layer glass transition temperatures (Tg), according to an embodiment of the present disclosure.

[0021] FIG. 5 is a graph depicting force retention over time for three-layer materials with different outer layer glass transition temperatures, according to an embodiment of the present disclosure.

[0022] FIG. 6 is a graph depicting a correlation between stiffness and initial force, according to an embodiment of the present disclosure.

[0023] FIGS. 7-9 show plots of tensile stress vs tensile strain in several three-layer materials, according to an embodiment of the present disclosure.

[0024] FIG. 10 is a graph depicting tensile hysteresis (%) vs cycle count for three materials, according to an embodiment of the present disclosure.

[0025] It should be appreciated that the constructions and properties illustrated in FIGS.1-10 are specific examples and not intended to limit the scope of constructions and testing that may be used. Other materials, constructions and sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments may contain additional layers including tie layers, pigments, optical additives or reinforcing agents and may be constructed in any manner known in the art such as flat sheet extrusion, multi-layer sheet coextrusion, coextrusion blown film, calendaring, laminating and adhesive bonding. The structures (or polymer sheets) and devices may in some embodiments be made by 3D printing or dip coating. One of ordinary skill in the art would recognize and appreciate many variations, modifications, and alternatives of the constructions.

[0026] The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the disclosure as set forth in the claims.

[0027] Other variations are within the spirit of the present disclosure. Thus, while the disclosed embodiments are susceptible to various modifications and alternative constructions, certainLeydig Docket No.515189 (001010PC) illustrated embodiments thereof are shown in the drawings and are described herein. It should be understood, however, that there is no intention to limit the disclosure to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the disclosure, as defined in the appended claims. DETAILED DESCRIPTION

[0028] The present disclosure relates to dental appliances which can include, for example, transparent dental aligners. In the course of an orthodontic treatment plan, dental aligners are often worn for a period of time (e.g., seven to fourteen days) before being replaced with a new set. Examples of multilayer materials and dental appliance manufacturing techniques can be found in U.S. Patent No. 11,541,643; US Patent 11,325,358; US Patent 10,987,907; US Patent 10,870,263; US Patent 10,549,511; and International Application Serial No. PCT / US2018 / 035384, each of which is incorporated herein by reference in its entirety.

[0029] During each term or stage in a treatment plan, often lasting between seven to fourteen days, the appliances are continuously deforming and losing force, at least slightly. This force, however, is needed to push teeth to pre-determined positions. Generally, one of the approaches to achieve better force retention in dental appliances, including multi-layer systems, is to adopt higher modulus materials. Such higher modulus materials translate to stiffer appliances with additional pain to the patient. The stiffness of a material generally translates to added pain for the patient during the initial hours or days of wearing a new aligner. However, a less stiff material does not necessarily result in less effective aligner, since the effectiveness of an aligner relates more to force retention over time rather than stiffness.

[0030] According to one embodiment of the present disclosure, a multilayer aligner material can include a flexible middle layer with one or more rigid outer layers (hard-soft-hard arrangement), where the more rigid outer layers have a higher glass transition temperature (Tg) than previously used outer layer materials. Furthermore, in some embodiments the rigid outer layers can have a greater thickness than the softer middle layer.

[0031] As an example, the Bay Materials product marketed as Zendura FLX™ is constructed of equal thickness (mils) layers (10:10:10 ratio), and uses outer layer materials that have a Tg ofLeydig Docket No.515189 (001010PC) about 110°C. According to one embodiment of the present disclosure, a three-layer material is constructed with, for example, a thickness ratio of 11:8:11 for the three layers, and outer layers having a Tg greater than 110°C (e.g., Tg ^ 120°C). This combination of a thicker outer rigid layers with the outer layers having a higher Tg surprisingly results in significantly higher force retention values over time.

[0032] Moreover, in some embodiments the multilayer materials can be produced via multi-layer co-extrusion processing, eliminating entrapped bubbles and defects observed in extrusion- laminated products. Multi-layer coextrusion also eliminates a processing step, and therefore reduces processing costs and provides a more efficient and streamlined manufacturing process. Furthermore, in some embodiments the multilayer material can be fabricated of all copolyester materials, in all layers, enabling full recyclability in future products.

[0033] According to some embodiments, it has been discovered that a multilayer polymer material having outer layers made from polymers having a higher glass transition temperature can produce orthodontic appliances, such as dental aligners, endowed with greater force retention during wear. One such example polymer includes, for example, Tritan MP200™ copolyester, which has a Tg of about 120°C. In other embodiments, material constructions including polymer materials having a Tg > 110°C can provide the increased force retention properties described herein. In some embodiments, suitable polymer materials for the outer layers of a multilayer polymer construction can include polymers, or polymer blends, having a Tg between about 110°C to 200°C, 115°C to 200°C, 115°C to 190°C, 115°C to 180°C, 115°C to 170°C, 115°C to 160°C, 115°C to 150°C, 115°C to 140°C, 115°C to 130°C, 120°C to 200°C, 120°C to 190°C, 120°C to 180°C, 120°C to 170°C, 120°C to 160°C, 120°C to 150°C, 120°C to 140°C, 120°C to 130°C, and 120°C to 125°C.

[0034] Polymer materials having a glass transition temperature higher than 110°C, when used as the outer layers of a multilayer dental appliance, can provide increased force retention when worn by a patient because, in part, they have a Tg that is higher than the internal temperature of a patient’s mouth when compared to materials that have a lower Tg. This benefit in force retention can be observed, surprisingly, even if the higher Tg material has a lower stiffness. Thus, an additional benefit of the present disclosure can include a dental appliance with higher force retention properties and lower stiffness (which translates to lower initial pain for the patient).Leydig Docket No.515189 (001010PC)

[0035] In one specific example embodiment, an orthodontic appliance was produced using a three-layer polymeric sheet that included Tritan MP200 copolyester with a Tg of about 120°C as the outer layers, with a copolyester elastomer (for example Ecdel 9967™) as the inner layer. The three-layer polymeric sheet had a total thickness of about 750 microns, in this example embodiment. The resulting orthodontic appliance had greater force retention during wear than other appliances.

[0036] In another example embodiment, orthodontic appliances were produced using three-layer polymeric sheets that included Tritan MP200 copolyester with a Tg of about 120°C as the outer layers, with a copolyester elastomer (for example Ecdel 9967) as the inner layer. The three-layer polymeric sheets had a total thickness of about 750 microns, in this example embodiment, where the layer thickness ratios included 11:8:11, 12:6:12, and 13:4:13 (i.e., the outer layers were thicker than the inner layers by the respective ratio indicated). It was discovered that using outer layer materials with a combination of higher Tg and increased thickness (relative to the inner layer) resulted in orthodontic appliances with greater force retention during wear.

[0037] In some embodiments, the selection of outer layer and inner layer materials and constructions where the composite stiffness (which integrates the various layers modulus and thickness) unitless value falls within a moderate stiffness range (e.g., between about 0.4 to about 0.6) translated to an efficient orthodontic appliance without additional discomfort or pain to the patient during application and removal. In comparison, aligners based on other common materials such as PETG, PCTG, as well as rigid thermoplastic polyurethanes have stiffness values in the range of about 0.6 to about 0.8, resulting in increased pain and discomfort to the patient.

[0038] FIG. 1 is a schematic depiction of a cross sectional view of a three-layer sheet having thicker outer layers 101 than the inner layer 103, according to an embodiment of the present disclosure. In some embodiments, the outer layers 101 can include the same or different materials, and each layer may be comprised of one or more materials, or blends or alloys. Likewise, the inner layer 103 may be a single material or a blend of materials or alloys, in some embodiments. In some embodiments, each of the layers 101, 103 may be comprised of a single layer or multiple layers.

[0039] In the example embodiment shown in FIG.1, the outer layers 101 are thicker than the inner layer 103, and may have a thickness ratio that is in the range of about 10:10:10 to aboutLeydig Docket No.515189 (001010PC) 4:1:4. For example, the embodiment shown corresponds to a thickness ratio of 11:8:11. The outer layers 101 may comprise a polymeric material (such as a copolyester) that has a Tg higher than 110°C, and the inner layer 103 may comprise an elastomeric material (also can be a copolyester e.g., Ecdel 9967). It has been discovered that using an outer layer material with a combination of a Tg higher than 110°C along with an increased thickness compared to the inner layer resulted in orthodontic appliances with greater force retention during wear.

[0040] FIG. 2 is a schematic depiction of a cross sectional view of a three-layer sheet having thicker outer layers 201 than the inner layer 203, according to an embodiment of the present disclosure. In some embodiments, the outer layers 201 can include the same or different materials, and each layer may be comprised of one or more materials, or blends or alloys. Likewise, the inner layer 203 may be a single material or a blend of materials or alloys, in some embodiments. In some embodiments, each of the layers 201, 203 may be comprised of a single layer or multiple layers.

[0041] In the example embodiment shown in FIG.2, the outer layers 201 are thicker than the inner layer 203, and may correspond to a thickness ratio of 12:6:12 (2:1:2). The outer layers 201 may comprise a polymeric material (such as a copolyester) that has a Tg higher than 110°C, and the inner layer 203 may comprise an elastomeric material (also can be a copolyester e.g., Ecdel 9967). It has been discovered that using an outer layer material with a combination of a Tg higher than 110°C along with an increased thickness compared to the inner layer resulted in orthodontic appliances with greater force retention during wear.

[0042] FIG.3 is a schematic depiction of a cross sectional view of a five-layer sheet having rigid outer layers 301 that are thicker than the inner layer 303, and intermediate layers 304, according to an embodiment of the present disclosure. In this example embodiment, a five-layer polymeric sheet is disclosed which includes outer layers 301 and intermediate layers 304 made of materials having different glass transition temperatures, which result in improved fatigue properties and high force retention. In one example embodiment, the outer layers 301 include a more rigid copolyester material having a glass transition temperature greater than 110°C, the inner layer 303 includes an elastomeric (can be a copolyester) material, and the intermediate layers 304 include a rigid copolyester material that has a glass transition temperature that is lower than that of the outer layers 301 (e.g., a Tg between about 80°C to about 110°C). As shown in FIG.3, the different layers can include different thickness ratios. For example, the five layers can have aLeydig Docket No.515189 (001010PC) thickness ratio of, for example 9:2:8:2:9, in some embodiments, with a total thickness of about 750 microns. In this example, the thickness ratio between the outermost layer and intermediate layer may be for example 10:1, 9:2, 8:3, 7:4, or 6:5, where the middle layer is constant at 8 in this example. The use of a thinner intermediate layer with a slightly lower Tg, compared to the thicker outermost layers, can provide an interface layer between the rigid and high-Tg outer layer and the elastomeric inner layer. In some embodiments, the 5-layer material constructions may have asymmetric thickness ratios.

[0043] According to some embodiments, a five-layer polymeric material according to the design shown in FIG. 3 can be manufactured using all copolyester materials. In such an example embodiment, the outer layers 301 can me made of the Tritan MP200 material (Tg of about 120°C), the intermediate layers 304 can be made of the Tritan MP100™ material (Tg of about 110°C), and the inner layer 303 can be made of Ecdel 9967 (a copolyester elastomer). Each of the five layers can have different thickness ratios, as mentioned above. In some embodiments, the thickness of the outermost rigid layers 301 can be greater than or equal to half of the combined thickness of the layers 301 + 304. The use of an intermediate layer 304 that is thinner than the outer layer 301 provides an interface modifier between the outer layers 301 and the elastomeric inner layer 303. Table 1 Polymer Polymer Polymer Polymer Polymer Polymer 1 2 1 2 Tg1-Tg2 1 2 E2-E1% Break Break 301 304 Tg1 °C Tg2 °C Tg °C E% E% EB MP100 PETG 110 80 30 125 250 125 MP100 PCTG 110 85 25 125 200 75 MP200 MP100 120 110 10 95 125 30 MP200 DA001 120 87 33 95 150 55 MP200 PCTG 120 85 35 95 200 105 MP200 PETG 120 80 40 95 250 155 PC MP100 150 110 40 120 125 5 PC PETG 150 80 70 120 250 130 PESU MP100 180 110 70 80 125 45 PESU PETG 180 80 100 80 250 170Leydig Docket No.515189 (001010PC)

[0044] Examples of materials that can be used for the outer layers 301 (Polymer 1) and the intermediate layers 304 (Polymer 2) are shown above in Table 1. Preferably, the outermost layer Tg1 is from about 180°C to about 110°C, and the intermediate layer Tg2 is from about 110°C to about 80°C, wherein the difference (Tg1 – Tg2) is from about 10°C to about 100°C. Also, in some embodiments, the intermediate layer 304 has greater (%) Elongation to break than outermost layer 301, where the Elongation to Break difference (EB2% - EB1%) is from about 5% about 170%.

[0045] In some embodiments, the Polymer 2 material may have a lower elongation to yield than Polymer 1. With a higher elongation to break value, Polymer 2 will still act as a beneficial intermediate layer. The benefit of an intermediate outer layer can be achieved both in a layered (up to 5-layers or more, depending on the coextrusion capability), or in a blend.

[0046] DA001 in Table 2 represents an example of a useful Tritan™-grade polymer material.

[0047] FIG.4 is a graph depicting stress relaxation data for three-layer materials with different outer layer material glass transition temperatures (Tg), according to an embodiment of the present disclosure. FIG. 4 illustrates the 48 hour stress relaxation behavior for three-layer laminates having an inner elastomeric layer of Ecdel 9967 (copolyester elastomer), with increasing Tg outer layers: 110°C, 120°C, 150°C, and 190°C. The four materials tested in FIG. 4 are each constructed with substantially equal thickness for all three layers (i.e., 10:10:10 thickness ratio). As can be in FIG. 4, the laminates having outer layers with increased Tg provide greater force retention over time.

[0049] Table 2 below shows outcome properties for a series of three-layer laminates using outer layers with increasing Tg values, and an inner layer of Ecdel 9967 copolyester. The thicknesses of layer is 10 mils, providing laminates with a thickness ratio (10:10:10) and a total thickness of about 750 microns. The five materials used for the outer layers include MedstarTM, Tritan MP100TM, Tritan MP200TM, Polycarbonate (PC), and Polyethersulfone (PESU). Table 2 Material 1 Material 2 Material 3 Material 4 Material 5Outer Layer 1 Medstar MP100 MP200 PC PESU Inner Layer Ecdel 9967 Ecdel 9967 Ecdel 9967 Ecdel 9967 Ecdel 9967 Outer Layer 2 MP100 MP200 PC PESULeydig Docket No.515189 (001010PC) Construction (Layers thickness, mils) 10:10:10 10:10:10 10:10:10 10:10:10 10:10:10 Outer Layers, Nominal Tg °C 85 110 120 150 190 Tensile Yield E% 4.71 5.49 5.86 5.28 5.31 Tensile Break E% 160 99.8 77.5 64.4 22.3 Tensile Stress @ Yield, psi 4391 4464 4638 6045 7791 Tensile Strength, psi 5242 5378 5003 6270 7733 Tensile Elastic Modulus, psi 132,837 124628 127,487 172,977 205,325 Tensile Max. Load, lbf 40.6 42.4 40 49.2 61.4 Flexural Modulus, psi 217,255 200,892 196,833 263,166 328,951 Flexural Strength, psi 8,063 7,904 7,882 10,626 14,052 Flexural Strain at Yield, % 5.18 6.01 5.42 6.1 6.1 Trouser Tear, Ave N / mm 187 186 110 61 17 SR at 5 3 DI-H2O, As Pressed, 0Initial Force, g 3363 3021 2968 4291 5421 1hr gf 1072 1559 1651 3223 4217 24hr gf 436 1089 1251 2842 3762 48hr gf 353 1015 1182 2589 3670 Force Retention Ratio, 24hr / 1hr 0.41 0.70 0.76 0.88 0.89 SR at D 2 54 3 DI-H2O, -TF'd-Soaked, 0 9-0 0Initial Force, g 2138 2185 3118 1hr gf 1392 1476 2365 24hr gf 1043 1174 2061 48hr gf 1103 1899 Force Retention Ratio, 24hr / 1hr 0.75 0.80 0.87

[0050] The outer layer materials described in Table 2 range in Tg from 85°C to 190°C, with a 10:10:10 construction. As the outer layer Tg increases from 110°C to 190°C, the tear property decreases from 186 N / mm to 110N / mm to 61N / mm and to 17 N / mm. The tear target for a three- layer sheet is greater than 60 N / mm, and preferably greater than 100 N / mm.

[0051] The initial stress relaxation (SR) force (g) normally correlates with stiffness or modulus of the material and its resistance to flexural bending. However, force retention over time is more important than initial stiffness. As shown in Table 1, the Medstar material has a Tg of about 85°C, and is a stiffer and higher modulus material than its copolyester counterparts (Tritan MP100 and MP200), but exhibits decreased force retention over time. The retained force ratio (24hr / 1hr) increases from 41% to 70%, 76%, 88%, and 89% trending clearly with Tg of the outer layer materials.

[0052] Table 3 shows data comparing a number of 750 micron laminates with different constructions. Materials 3 and 6-8 are all 30 mil three-layer laminates with Tritan MP200 (Tg = 120°C) as the outer layers and Ecdel 9967 copolyester elastomer as the inner layer. Material 3Leydig Docket No.515189 (001010PC) has a 10:10:10 thickness ratio; Material 6 has an 11:8:11 thickness ratio; Material 7 has a 12:6:12 thickness ratio, and Material 8 has a 13:4:13 thickness ratio. Material 9 is a single layer of Tritan MP200 with a thickness of about 750 microns (about 30 mils). TABLE 3 Hot-Pressed Materials Material 3 Material Material Material 8 Material 9 Outer Layer 1 MP200 MP200 MP200 MP200 Inner Layer Ecdel 9967 Ecdel 9967 Ecdel 9967 Ecdel 9967 MP200 Outer Layer 2 MP200 MP200 MP200 MP200 ostr tio 101010 11811 12 12 13413 30O ter Layers o i al Tg 120 120 120 120 120Tensile Yield E% 5.9 5.9 6.1 5.9 6.1 Tensile Break E% 78 79 96 86 86 Tensile Stress @ Yield, psi 4638 5030 5359 5633 6624 Tensile Strength, psi 5003 5494 6334 6399 6600 Tensile Elastic Modulus, psi 127487 157435 155100 172485 209015 Flexural Modulus, psi 196,833 216,967 224,476 233,557 205,263 Flexural Strength, psi 7,882 8074 8,604 8,587 8,856 Trouser Tear, Ave N / mm 110 195 93 106 19.5 SR at 5 3 DI-H2O, As Pressed 0Initial Force, g 2968 3041 3130 3123 3708 1hr gf 1651 1776 1793 1780 2514 24hr gf 1251 1321 1294 1312 2005 48hr gf 1182 1250 1234 1246 1915 Force Retention Ratio, 24hr / 1hr 0.76 0.74 0.72 0.74 0.80 SR at D 2 54 3 DI-H2O, TF'd-Soaked, 0 9-0 0Initial Force, g 2185 2823 1957 2517 2816 1hr gf 1476 1980 1374 1736 1990 24hr gf 1174 1573 1093 1373 1600 48hr gf 1103 1472 1030 1296 1520 Force Retention Ratio, 24hr / 1hr 0.80 0.79 0.80 0.79 0.80

[0053] As shown in Table 3, surprisingly the tear property increases from 110 to 230 N / mm between 10:10:10 (Material 3) and 11:8:11 (Material 6) constructions. While the next sets, Material 7 and Material 8, registered lower tear values of 93 and 106 N / mm, these are still acceptable tear numbers compared to 19.5 N / mm for the single layer of Material 9 (single layer of 30 mil MP200).Leydig Docket No.515189 (001010PC)

[0054] In stress relaxation tests for the pressed samples, the 11:8:11 construction (Material 6) demonstrates higher 24hr and 48hr retained forces compared to the 10:10:10 construction, Material 3 (1321g vs 1251g, and 1250g vs 1182g). The next sets, 12:6:12 and 13:4:13, show slightly greater forces relative to the 10:10:10 construction. The 11:8:11 construction also shows favorable 24hr and 48hr force retention in thermoformed-soaked samples, tested at a constant Deflection of 2.54mm. Table 3 also shows improved force retention for all constructions using an outer layer with a higher Tg.

[0055] Table 4 shows data relating to a one-week force retention (g) after stress relaxation test at equal flexural deflection of 2.54mm, in 37°C de-ionized water. TABLE 4 Material 10 Material 11 Material 12 Material Outer Layer 1 MP100 MP100 MP200Inner Layer RPU PUE PUE Ecdel 9967 Outer Layer 2 MP100 MP100 MP200Construction 30 10:10:10 10:15:10 11:8:11 Outer Layers, Tg °C 95 110 110 120 days mins. Force, g Force, g Force, g Force, g 0 0 3206 2302 3308 2823 0.0417 60 1910 1500 1996 1980 1 1440 1054 1164 1511 1573 2 2880 874 1084 1411 1472 3 4320 779 1032 1348 1405 4 5760 717 1009 1302 1355 5 7200 684 976 1272 1322 6 8640 641 950 1235 1289 7 10080 608 937 1200 1269

[0056] Table 4 test specimens include thermoformed sheets of four materials (Materials 10, 11, 12, and 6), where Material 10 is a 30 mil thick (before thermoforming) monolayer construction of rigid Polyurethane), Material 11 is a 30 mil 3-layer (10:10:10 construction) material, withLeydig Docket No.515189 (001010PC) Polyurethane Elastomer (50D) inner layer sandwiched between Tritan MP100 outer layers; Material 12 is a 35 mil 3-layer (10:15:10) material, with Polyurethane Elastomer (50D) inner layer sandwiched between Tritan MP100 outer layers. Material 6 is a 30 mil 3-layer (11:8:11) material, with Ecdel 9967 inner layer and Tritan MP200 outer layers. Each sheet was thermoformed in a Biostar™ VII equipment, at a maximum temperature of 428F, over a rectangular Polycarbonate Block. The top flat surface of the formed part was cut out and used for testing. Formed test parts were pre-conditioned by soaking for 48 hours in 37°C de-ionized water.

[0057] After soaking for 48hrs prior to testing for stress relaxation (at constant deflection of 2.54mm), Material 6 with a 11:8:11 construction demonstrated the more favorable 7-day force retention. Material 12 registers the highest initial force, among the group, due to its greater total thickness (35 mils compared to 30 mils). After the first 24 hours and through 7 days on test, Material 12 force drops below Material 6. Material 6 exhibits substantially greater force retention over Material 11. Material 10 shows the lowest 7 day force retention . These results are summarized in Table 4 and illustrated in FIG.5.

[0058] FIG. 5 is a graph depicting force retention over time for three-layer materials with different outer layer glass transition temperatures, according to an embodiment of the present disclosure. What is also apparent from FIG.5 is that Material 6 has the greatest force retention over seven days, while also having a lower initial force compared to Materials 10 and 12. This decreased initial force translates to decreased initial pain for the patient, while still providing better force retention over time.

[0059] Stiffness D of a shell which consists of three layers (two face layers and one core layer) may be calculated according to the Linear Sandwich Theory equation shown below as equation (1). Equation (1) integrates modulus, thickness, and location of the layers (inner or outer). For a sandwich beam with identical face sheets and unit width, the value D is calculated according to equation (1), where Ef= modulus of outer layer, Ec= modulus of core, f = face layer thickness, and 2h = core thickness.

[0060] Equation (1):Leydig Docket No. 515189 (001010PC)

[0061] Table 5 below shows stiffness values D calculated for different three-layer constructionsand single layer products, according to equation (1). Initial load (g) values are taken from stress relaxation tests run on Instron machine equipped with a 37°C water bath. Tests were performed in 30 mil (about 750 micron) coupons. TABLE 5 Material Sti ess D Load I (g)PUE-MP100-PUE 0.3325 1956Material 11 0.4608 3006Material 2 0.4612 3252Tritan MP100 0.4772 3465Material 3 (101010) 0.4786 3272Material 6 (11811) 0.4866 3041Material 7 (12612) 0.4916 3130Material 8 (13413) 0.4941 3123Material 9: Tritan MP200 0.4952 3708PCTG (Medstar) 0.5875 3884PETG (Eastar 6763) 0.6303 3956Material 10 (RPU) 0.6831 4244PC (Lexan 3412) 0.7429 4803Material 12 0.7025 3409

[0062] In Table 5, calculated stiffness is sorted in increasing value, with corresponding initialforce (Load, g) for various 30 mil (about 750 micron) single layer products, as well as three-layer sheets. All copolyester three-layer products (also about 750 microns in total thickness) based on MP100 or MP200 as outer layers, including Material 2 and Material 5, show stiffness values in aLeydig Docket No.515189 (001010PC) tight range of about 0.46 to about 0.50, and corresponding moderate initial force values of between about 3,000 to about 3,300 gf (excluding single-layer MP100 and MP200).

[0063] The first row of Table 5 shows a three-layer product with a 3:25:3 construction based on outer layers comprising a polyurethane elastomer (hardness of about 65D), and an MP100 inner layer (about 25 mils, or 635 microns), referenced in Table 5 as PUE-MP100-PUE. This first construction, which corresponds to a soft-hard-soft construction, resulted in the lowest stiffness of about 0.3325. Varying the construction to 1:28:1 in these soft-hard-soft materials increases the stiffness to about 0.39.

[0064] With further reference to Table 5, PCTG and PETG copolyester types show high stiffness values (0.5875 and 0.6303, respectively) due to their inherently high modulus properties which are greater than MP100 and MP200. Accordingly, these materials generate large initial forces, which normally translates to greater pain to patients when wearing aligners made from these materials. Material 12 stiffness (10:15:10 construction) corresponds to a high value of about 0.7025 due to its higher total thickness of 35 mils (about 889 microns); however, it produces a relatively lower initial force compared to other stiff products.

[0065] FIG.6 is a graph depicting a correlation between stiffness (D) of single and three-layer sheets and initial force (g), according to an embodiment of the present disclosure. The initial force (g) was calculated during a stress relaxation test at 5% strain in 37°C water. As shown in FIG. 6, the materials with the highest initial load (g) correspond to the materials with the highest stiffness. Thus, a decrease in initial load, which can result in a decreased stiffness, may be desirable for a patient to reduce initial pain upon wearing an aligner.

[0066] FIG. 6 illustrates the general dependence of initial product forces on stiffness. This plot also illustrates the uniquely moderate stiffness-load window (highlighted) where Material 2 and Material 5 products operate. Material 5 constituents and construction are designed with minor increases in stiffness (compared to 10:10:10) while producing significantly enhanced force retention characteristics.

[0067] Table 6 shows mechanical properties, tensile hysteresis, and stress relaxation properties for Material 6 and Material 13. Material 6 includes a three-layer material with a 11:8:11 construction having MP200 as the outer layers and Ecdel 9967 as the elastomeric inner layer.

[0068] Material 13 corresponds to a three-layer material with a 11:8:11 construction, where the outer layer includes a blend of MP200 and MP100, and the inner layer is Ecdel 9967. In thisLeydig Docket No.515189 (001010PC) particular embodiment, the outer layer included a 75%-25% blend of MP200 and MP100. In some embodiments, the outer layer material(s) can be blended before extrusion.

[0069] In some embodiments, the outer layer materials can be blended at different blend ratios of MP200 : MP100 (99 : 1 to 1 : 99) , such as 95%:5%, 90%:10%, 85%:15%, 80%:20%, 75%:25%, 70%:30%, 65%:35%, 60%:40%, 55%:45%, 50%:50%, preferably the material with the higher Tg has a greater percentage of the blend, targeting higher force retention properties. As would be apparent to one skilled in the art, blending may include mixing two resin materials (e.g., not yet melted) together, at the same or different rates to produce the blended material, followed by extrusion of the blended resins.

[0070] In some embodiments, at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C, resulting in a desired blend material having a desired Tg, e.g., >110°C. Examples are described herein of a blend of Tritan MP200 (75%) and MP100 (25%), however, it will be clear to one skilled in the art that other polyester or copolyester materials may be blended, at the various exemplary blend ratios above, to achieve desired Tg properties in a blend material. For example, different Tritan grade materials may be blended together with other Tritan grade materials, or other materials. Similarly, other non-Tritan grade polyesters or copolyesters may be blended together. Examples of other materials may include SkygreenTM(a copolyester developed by SK Chemicals) or Ecozen T120 and Ecozen T110 copolyester materials produced by SK Chemical. Other examples of useful polyester materials or copolyester materials will be apparent to one skilled in the art..

[0071] The improvement in tensile fatigue properties of Material 13 over Material 6 is noteworthy, and is obtained without any significant loss in stress relaxation performance. TABLE 6 Material # Material Material 13 Outer Layer 1 Tritan MP200 MP200 / MP100(75 / 25) Inner Layer (Clearer Ecdel) Ecdel 9967 Ecdel 9967 Outer Layer 2 Tritan MP200 MP200 / MP100(75 / 25) Construction 11811 11811Leydig Docket No.515189 (001010PC) Outer Layers Nominal Tg °C 120 114 Tensile Strength, psi 5,494 4,869 Tensile Elastic Modulus, psi 157,435 137,086 Flexural Modulus, psi 216,967 197,725 Flexural Strength, psi 8,074 8,604 Tensile Hysteresis Survived Cycles 1,210 10,000 Cycles to 50% Tensile Hysteresis 1,200 10,000 Stress Relaxation at 5%ם, 37C de-ionized water thickness, mm 0.77 0.77 Initial Force, g 3041 3031 1hr 1776 1795 24hr 1321 1315 48hr 1250 1230 Force Retention Ratio, 24hr / 1hr 0.74 0.73 TENSILE HYSTERESIS

[0072] Additional experiments were conducted to explore alternative methods and constructions to attain higher force retention and improved tensile fatigue (tensile hysteresis) properties. As a means of measuring the tensile fatigue properties in three-layer sheets, tensile hysteresis tests are run for 10,000 cycles, at a 0-3% strain, at a rate of 2in / min, as described herein.

[0073] Accordingly, tensile fatigue properties were determined and compared in three different materials: Material 3, Material 6 and Material 13 and illustrated in Figures 7-9.

[0074] FIG. 7 shows a plot of tensile stress (psi) versus tensile strain in Material 3, cycled at room temperature between 0 and 3% strain, for 10,000 cycles at 2 in. / min. Material 3 corresponds to a three-layer material with a 10:10:10 construction, using MP200 as the outer layers and Ecdel 9967 as the inner layer.

[0075] FIG. 8 shows a plot of tensile stress(psi) versus tensile strain in Material 6, cycled at room temperature between 0 and 3% strain, for 10,000 cycles at 2 in. / min. Material 6 corresponds to a three-layer material with a 11:8:11 construction, including MP200 as the outer layers and Ecdel 9967 as the inner layer.Leydig Docket No.515189 (001010PC)

[0076] FIG. 9 shows a plot of tensile stress(psi) versus tensile strain in Material 13, cycled at room temperature between 0 and 3% strain, for 10,000 cycles at 2 in. / min. Material 13 corresponds to a three-layer material with a 11:8:11 constructions, where the outer layer includes a blend of MP200 and MP100, and the inner layer is Ecdel 9967. In this particular embodiment, the outer layer included a 75% / 25% blend of MP200 and MP100. In other embodiments, different percentages of these materials can be blended together to achieve outer layer materials with customized Tg values (along with customized stiffness and modulus values as well).

[0077] The test method described above was used to evaluate the tensile hysteresis (%) in Material 3 (see Table 3), as illustrated in Figure 7. This material survived 10,000 cycles, and showed 54% tensile hysteresis (TH%) at the end of the test.

[0078] In a similar test, Material 6 survived only 1210 cycles to reach 100% TH, and failure by sample break. This TH behavior of Material 6 is illustrated in Figure 8. This TH performance difference between the 10:10:10 and 11:8:11 constructions in the MP200-Ecdel-MP200 systems suggests some loss in elasticity as the Ecdel elastomer inner layer is reduced from 10 mils thickness to 8 mils and / or increase in thickness of the MP200 outer layers.

[0079] It was surprisingly discovered that the TH behavior in the 11:8:11 three-layer system can be restored, to surviving 10,000 cycles, by using a blend of different Tg °C materials (Tg1 and Tg2) in the outer layers (keeping Ecdel 9967 inner layer unchanged), where Tg1 > Tg2 and Tg1 constitutes ^50% of the blend composition.

[0080] For example, a (75% / 25%) blend of Tritan MP200 (Tg 120C) and Tritan MP100 (Tg 110C) is used as outer layers, and Ecdel 9967 as the inner layer in Material 13, Table 6. The TH result for Material 13 is illustrated in Figure 9, which clearly exhibits substantial improvement in tensile fatigue properties.

[0081] FIG. 10 is a graph depicting tensile hysteresis (%) vs cycle count for three materials, according to an embodiment of the present disclosure. The three materials compared in FIG.10 include Material 3, Material 6, and Material 13. Tests were run at room temperature for 10,000 cycles between 0-3% strain, at 2 inches per minute.

[0082] As discussed above, Material 3 corresponds to a three-layer material with a 10:10:10 construction, including MP200 as the outer layers and Ecdel 9967 as the inner layer. Material 6 corresponds to a three-layer material with a 11:8:11 construction, including MP200 as the outer layers and Ecdel 9967 as the inner layer. Material 13 corresponds to a three-layer material with aLeydig Docket No.515189 (001010PC) 11:8:11 constructions, where the outer layer includes a 75% / 25% blend of MP200 and MP100, and the inner layer is Ecdel 9967.

[0083] The techniques and materials disclosed herein provide increased force retention and reduced stress relaxation over time. These benefits can be linked to a number of properties of the new materials disclosed, including increased Tg of the outer layers, and thicker outer layers compared to the elastomeric inner layer (e.g., thickness ratios of 11:8:11, 12:6:12, 13:4:13, etc.).

[0084] A particular benefit in force retention is found when the Tg of the outer layers of a multi- layer material is increased. In addition to this, the thicker outer layers also increase performance. In some embodiments, a combination of increased Tg and increased thickness of the outer layers can provide increased performance. In some embodiments, the use of a thin intermediate layer between the thicker outer layers and the inner layer, or the use of a blended outer layer, can also increase performance.

[0085] High modulus materials are stiff, and therefore typically more painful to a patient. Accordingly, PETG materials are often stiff and painful. The Tg of PETG is 80, but its modulus is higher than copolyester materials such as MP100 and MP200. However, MP200 has a high enough Tg to be stronger than PETG. This is because the internal temperature of the mouth of 37°C is close enough to the Tg of PETG at 80°C that it can weaken. The modulus is less effected by the mouth temperature when the Tg is higher. DEFINITIONS

[0086] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the disclosed embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. The phrase “based on” should be understood to be open-ended, and not limiting in any way, and is intended to be interpreted or otherwise read as “based at least in part on,” where appropriate. Recitation of ranges of values herein are merely intended to serve as a shorthand method ofLeydig Docket No.515189 (001010PC) referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

[0087] The term "dental appliance" is used herein with reference to any device placed in or on the teeth of a subject. Dental appliances include but are not limited to orthodontic, prosthetic, retaining, snoring / airway, cosmetic, therapeutic, protective (e.g., mouth guards) and habit- modification devices.

[0088] The term "flexural modulus" is used herein with reference to the rigidity of a material and / or resistance of the material to deformation in bending. The higher the flexural modulus of the material, the more resistant to bending it is. For an isotropic material the elastic modulus measured in any direction are the same.

[0089] The term "hardness” is used herein with reference to a Shore hardness scale, and unless otherwise stated is measured according to ASTM D2240. A durometer measures the penetration of a metal foot or pin into the surface of a material. There are different durometer scales, but Shore A and Shore D are commonly used. Materials with higher durometer values will be harder compared to materials with a lower durometer value. Shore hardness and modulus are generally correlated and can be converted by approximation if only one value is known by methods described in the art.

[0090] The expressions "modulus," “Young’s modulus” and “elastic modulus” are used herein with reference to the rigidity of a material and / or resistance of the material to stretching. The higher the modulus of the material, the more rigid. The flexural modulus and elastic modulus of a material may be the same or different. For polymers, the mechanical properties including elastic modulus and other properties may be measured as proscribed by ASTM D 638. Flexural modulus may be measured by the test listed in ASTM D790, and uses units of force per area. Unless designated otherwise, “modulus” refers to elastic modulus.Leydig Docket No.515189 (001010PC)

[0091] The term "lateral restoring force” with respect to outer layers of a polymeric sheet is used with reference to the force which may be exerted by one layer which has been translated relative to another layer which is fixed in position. If the outer layers are caused to move independently of each other they will subsequently return to their original positions if not restrained.

[0092] “Translational force” refers to the amount of force required to displace outer layers from their neutral position a given distance and is measured as Newtons per cm2 (N / cm2) at a given displacement where the area (cm2) is calculated as the overlap area of the outer layers. The measurement can be made by preparing a test sample of known overlap and displacing the outer layers relative to each other a given distance, for example, by applying a force of 0.04 MPa / min using a mechanical force tester such as an Instron Materials Tester. The force measured at different displacements is recorded. The lateral translational force and the lateral restoring force will be the same for an elastic material.

[0093] The term “shearing force,” as used herein means the translational force applied to two surfaces which are connected by an elastic material.

[0094] The term "shell" is used herein with reference to polymeric shells which fits over the teeth and are removably placeable over the teeth.

[0095] The term "stain resistant" is used herein with reference to a material designed to be resistant to being stained.

[0096] The term "thermoplastic polymer” is used herein with reference to a polymer is a polymer that becomes pliable or moldable above a specific temperature and solidifies upon cooling, provided that the heat and pressure do not chemically decompose the polymer.

[0097] The terms "tooth" and "teeth" include natural teeth, including natural teeth which have been modified by fillings or by crowns, implanted teeth, artificial teeth that are part of a bridge or other fitting secured to one or more natural or implanted teeth, and artificial teeth that are part of a removable fitting.

[0098] In the following description, various embodiments are described. For purposes of explanation, specific configurations and details are described in order to provide a thorough understanding of the embodiments. However, it will also be apparent to those skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.Leydig Docket No.515189 (001010PC) EMBODIMENTS

[0099] In some embodiments, the outer layers may comprise a polyester or copolyester, a polyurethane, a polyamide, a polyolefin, a (meth) acrylic polymer, a polycarbonate, a polyether sulfone, a vinyl polymer such a polyvinyl chloride, or a fluoropolymer.

[0100] In some embodiments, the inner layer may comprise a copolyester elastomer, a polyurethane elastomer, a polyester elastomer, a styrenic elastomer, a polyamide elastomer, a siloxane elastomer, a polyether elastomer a polyolefin elastomer, an olefin copolymer, an acrylic elastomer or a fluroelastomer.

[0101] In some embodiments, the inner layer material has a 22 hours at 25 °C compression set of less than about than 35%, 30%, 25%, 20% 10%, less than 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11% or 10%. In contradiction to the findings of US 9,655,693 B2 where an elastomer is used as an outer layer, the inventors have found that a lower compression set rather than higher compression set is more effective.

[0102] In some embodiments, the sheet has an overall thickness of from about 250 microns to about 2,000 microns, from about 300 microns to about 1900 microns, from about 400 microns to about 1750 microns or from about 500 microns to about 1500 microns.

[0103] In some embodiments, the combined thickness of the outer layers is from about 25 microns to about 1000 microns, 50 microns to 750 microns, 100 to 750 microns, 250 microns to 750 microns, or 250 microns to about 600 microns.

[0104] In some embodiments, the outer layers have a Tg of between about 110oC and 180oC, and the inner layer has a Tg or melting point of between about -30oC and 206oC, and a heat of fusion of from about 5 Joules / g to about 20 Joules / g, or 5 Joules / g to 15 Joules / g.

[0105] It should be understood that elements of two or more embodiments may be combined.

[0106] In some embodiments, the thermoformable polymeric sheet is comprised of at least two outer layer, and a middle layer, wherein one or more of the outer layers comprises a co- polyester, or a blend of two different copolyesters, comprised of a dicarboxylic acid component comprising 70 mole % to 100 mole % of terephthalic acid residues, and a diol component comprising, (i) 0 to 95% ethylene glycol, (ii) 5 mole % to 50 mole % of 2,2,4,4-tetramethyl-1,3- cyclobutanediol residues, and (ii) 50 mole % to 95 mole % 1,4-cyclohexanedimethanol residues,Leydig Docket No.515189 (001010PC) and (iii) 0 to 1% of a polyol having three or more hydroxyl groups, wherein the sum of the mole % of diol residues (i) and (ii) and (iii) amounts to 100 mole % and the copolyester exhibits a glass transition temperature Tg from 80 °C to 150 °C. In some aspects of this embodiment, the thermoformable polymeric sheet includes a middle layer which comprises an aromatic polyether polyurethane having a Shore hardness of from about A90 to D55 and a compression set of less than 35%, wherein the interlayer peel strength between the outer layers and the inner layer is greater than 50 N per 2.5 cm.

[0107] In some embodiments, a dental appliance conformal to one or more teeth is made from the microcrystalline polyamide or the co-polyester described above. MATERIALS CONSTRUCTION METHODS

[0108] Multilayer sheets may be prepared by a number of means including without limitation, hot or cold lamination, adhesive lamination, melt lamination, coextrusion or multilayer extrusion, or other known methods.

[0109] In some embodiments, the dental appliance can be made from multilayer sheets, prepared by coextrusion as described and illustrated by the following five coextrusion examples. Examples 1-4.

[0110] 3-layer ABA material (Material 6, Table 6 : MP200-Ecdel 9967-MP200), in thickness (mil) ratios 11:8:11, was extruded in a Pilot scale coextrusion line equipped with a feedblock and sheet die. MP200 resin comprising the outer layers was fed in extruder A. Ecdel 9967 comprising the inner layer was fed in extruder B. The extrusion temperatures (°C) for the outer layers (MP200) and inner layer (Ecdel 9967), of examples 1-5, are summarized in Table 7. The three-layer extruded sheet, of examples 1-4, was quenched on a three rolls stack (Top roll, middle roll and lower roll), at four different temperatures. Example 1, three rolls quench temperature was 20C / 20C / 16C; example 2 quench temperature 37C / 37C / 30C; example 3 quench temperature 50C / 50C / 40C; example 4 quench temperature 60C / 60C / 50C. The total sheet thickness, in examples 1-4, was controlled at 30 mils (0.76mm).Leydig Docket No.515189 (001010PC) TABLE 7 Example 1 Example 1 Example 2 Example 2 Example 3 Example 3 Example 4 Example 4 Example 5 Example 5 Extruder AExtruder B Extruder A Extruder B Extruder A Extruder B Extruder A Extruder B Extruder A Extruder B (outer (inner (outer (inner (outer (inner (outer (inner (Blend outer (inner layers) layer) layers) layer) layers) layer) layers) layer) layers) layer) Zone 1 270 230 270 230 270 230 270 230 270 230 Zone 2 275 235 276 235 276 235 277 236 276 235 Zone 3 280 235 281 236 280 235 281 235 281 236 Zone 4 280 240 281 240 281 239 281 240 281 240 Zone 5 280 240 280 240 280 240 280 240 280 240 Die 275 - 274 - 275 - 276 - 274 - Top roll 20C - 37C - 50C - 60C - 37C - Middle roll 20C - 37C - 50C - 60C - 37C - Bottom roll 16C - 30C - 40C - 50C - 30C - Example 5.

[0111] A 3-layer ABA material using a resins blend MP200 / MP100 (75 / 25 wt%), also described as Material 13 in Table 6, for outer layers A and Ecdel 9967 inner layer, in thickness (mils) ratio 11:8:11, was extruded in a Pilot scale coextrusion line equipped with a feedblock and sheet die. The MP200 / MP100 (75 / 25) resins blend, comprising the outer layers was fed in extruder A. Ecdel 9967 comprising the inner layer was fed in extruder B. The extrusion temperatures for MP200 / MP100 (blend outer layers) and Ecdel 9967 (inner layer) is summarized in Table 7. The three-layer extruded sheet was quenched on a three rolls stack at 37°C / 37°C / 30°C. The total sheet thickness was controlled at 30 mils (0.76mm).

[0112] Properties of coextruded Materials of examples 1-5 are summarized in Table 8. As summarized in Table 8, all 3-layer coextruded materials, composed of MP200 outer layers and Ecdel 9967, in thickness targets 279μm and 203μm for outer and inner layers, demonstrate excellent layers thickness. As anticipated, increasing the chill rolls temperature (quenching temperature) resulted in some increase in sheet haze and smaller change in dB color (yellow). Surprisingly, the materials of examples 1-5 exhibit similar flexural modulus (MPa) values, suggesting that this bulk property is unaffected by the variation in chill rolls temperature (20°C – 60°C). At the end of a 24hr tube wrap test in 37C DI-water, all archedLeydig Docket No.515189 (001010PC) materials of examples 1-5 were intact, and exhibited good elastic recovery (>70%). The 20C-chilled sample, example 1, exhibited the highest recovery of 84%. However, it also showed more crazing than the higher temperatures (37°C-60°C chill rolls temperature) counter parts. All samples of examples 1-5 also demonstrate similar force retention properties at the end of 48 hour stress relaxation testing at 5%strain.

[0113] Perhaps the primary noticeable difference between material of example 5 (blend outer layers) compared to examples 2 (similar quench temperature 37°C) is the lower glass transition temperature (116.2°C cf 118.8°C). TABLE 8 Example 1 Example 2 Example 3 Example 4 Example 5 Initial outer layer 1 thickness (Digital), μm 285 287 291 288 287 Initial inner layer thickness (Digital), μm 203 203 190 195 211 Initial outer layer 2 thickness (Digital), μm 279 274 289 284 285 Initial total layers thickness (Digital), μm 767 764 770 766 783 DSC Heat1 Tg C 118 118.8 117.5 118.6 116.2 Sheet Haze,% 3.2 5.5 10.8 12.9 8.1 Sheet Transparency, % 91.8 91.3 90.6 90.1 90.8 Sheet Clarity, % 99.6 99.5 99.6 99.5 99.7 LAB Color , dB 1.51 1.53 2.24 2.54 2.17 Modulus, MPa 1581 1559 1559 1570 1569 Elastic Recovery, % 84 75 77 79 71 Crazing Resistance Fair-Poor Good Good Good Good Force Retention( SR at 5%ם / 37C DI-H2O) Initial Force, gf 3410 3332 3486 3419 3393 1hr, gf 1584 1503 1675 1642 1585 24hr, gf 1105 1124 1168 1150 1144 48hr, gf 1034 1066 1105 1070 1067 24hr / 1hr 0.70 0.75 0.70 0.70 0.72

[0114] Table 9 summarizes four properties in thermoformed coextruded materials of Examples 1-5: three properties tested in thermoformed flat sheet, and one in thermoformed aligner. All five examples thermoformed easily over tooth models, producing very good clear aligners, easily removable from the model.

[0115] Thermoformed sheets showed thickness is in the range 0.68mm – 0.69mm and haze between 2.4% and 13.4%. Stress relaxation properties of thermoformed-soakedLeydig Docket No.515189 (001010PC) specimens are all characterized with nice low initial force 2559gf – 2949gf, and excellent force retention at the end of 24 hours or 48 hours.

[0116] Properties of Thermoformed Coextruded Materials of Examples 1-5 are summarized in Table 9. TABLE 9 Example 1 Example 2 Example 3 Example 4 Example 5 Thermoformed sheet thickness, mm 0.68 0.69 0.68 0.68 0.69 Thermoformed sheet Haze,% 2.4 5.4 11.2 13.4 8.8 Thermoformed sheet Transparency,% 91.5 91.7 90.7 89.6 91.0 Thermoformed sheet Clarity,% 99.4 99.5 99.5 99.5 99.6 Thermoformed Aligner Very Good Very Good Very Good Very Good Very Good Force Retention ( SR at D=2.54 / 37C DI-H2O) Thermoformed parts soaked 48 hrs in 37C DI-water prior to testing. Thickness, mm 0.69 0.71 0.70 0.70 0.70 Initial Force, gf 2559 2942 2813 2949 2816 1hr, gf 1464 1725 1596 1672 1594 24hr, gf 1106 1334 1200 1272 1212 48hr, gf 1020 1220 1115 1195 1106 24hr / 1hr 0.76 0.77 0.75 0.76 0.76

[0117] Sheets may be fully prepared before forming into an orthodontic appliance, or an appliance may be produced using a sequence of individual thermoforming steps to create multiple layers.

[0118] Thermoforming of sheets to produce test samples or dental appliances may be performed using a “Biostar” pressure former available from Great Lakes Orthodontics using procedures commonly used in the industry. Alternatively, thermoforming may be performed using a roll fed thermoformer, a vacuum former or other known thermoforming techniques. Thermoforming may be conducted using different conditions, forms or models to vary draw ratio and part thickness. Multilayer appliances may be fabricated through one or more 3D printing processes or by sequential dip coating, spray coating, powder coating or similar processes known for producing films, sheets and 3D structures.Leydig Docket No.515189 (001010PC) MATERIALS

[0119] Example Materials useful for outer layers include: Tritan MP200: A copolyester made from three monomers: dimethyl terephthalate (DMT), cyclohexanedimethanol (CHDM), and 2,2,4,4-Tetramethyl-1,3- cyclobutanediol (TMCD), from Eastman Chemicals, Kingsport, Tennesy. Tritan MP100: A copolyester made from three monomers: dimethyl terephthalate (DMT), cyclohexanedimethanol (CHDM), and 2,2,4,4-Tetramethyl-1,3- cyclobutanediol (TMCD), from Eastman Chemicals, Kingsport, Tennesy Eastar 6763 (PETG): CHDM-modified PET copolyester, from Eastman Chemicals; Medstar (PCTG): Glycol-modified PCT copolyester, from Eastman Chemicals. Lexan 3412 (PC): Polycarbonate, from Sabic (formerly GE Plastics). Udel 1708HC (PESU): Polyethersulfone, high clarity grade, from Solvay.

[0120] Example Materials useful for the inner layer include Ecdel 9967: Copolyester Elastomer, from Eastman Chemicals. Ecdel 9966: Copolyester Elastomer, from Eastman Chemicals. Ecdel 9965: Copolyester Elastomer, from Eastman Chemicals. Texin RxT50D (PUE 50D): Polyurethane Elastomer, hardness 50D, from Covestro.

[0121] Properties of example polymers used for outer layers are shown in Table 10.Leydig Docket No.515189 (001010PC) TABLE 10 Tritan MP100 Tritan MP200 Medstar Eastar 6763 Lexan 104 Udel 1708HC Copolyester Copolyester PCTG PETG PC PESU Specific gravity, g / cc 1.19 1.19 1.23 1.27 1.20 1.19 Inherent Viscosity, dL / g (Eastman). 0.69-0.75 0.61-0.67 0.71 0.73-0.77 Melt Index , g / 10'min. / 260°C / 2.16kg 7.1 5.4 28.5 10.5 7.0 DSC Heat 2, Glass transition Temperature, Tg C° 110 120 87 80 149 190 Hardness Shore D 79.5 79.8 76.4 109R* 80.6 Tensile Elongation at Break, % 120 90 230 250 73 65 Tensile Elastic Modulus, MPa1462 1500 1700 1900 1808 1713Flexural Modulus, MPa 1500 1510 1700 1830 1850 2358 * Rockwell Hardness, 109

[0122] Properties of example copolyester elastomers used for the inner layer are shown in Table 11. TABLE 11 DL 99 D L 99 D L 99 5Specific gravity, g / cc 1.13 1.13 1.13 Inherent Viscosity , dL / g (Eastman) 1.20-1.26 1.13-1.19 1.02-1.08 Melt Index , g / 10'min. / 230°C / 2.16kg 12.3 21.5 43.4 DSC Heat 2, Melting Temperature, Tm C° 206 204 209 DSC Heat 2, Melting Temperature, Tm C° (Eastman) 200 202 207 Hardness Shore D 52.6 51.2 55.0 Tensile Elongation at Break, % 444 382 367 Tensile Elastic Modulus, MPa176 168 182Preparation of Three-layer laminates, Materials 1-12.

[0123] 30 mil thick three-layer laminates were prepared in two processing steps: First, different thickness thin sheets, for use as outer or inner layer, were produced by hot- pressing pre-dried resin, in a 6”x6” metal frame, of matching thickness, surrounded by twoLeydig Docket No.515189 (001010PC) Teflon release films, and two metal plates, in a heated Carver Press. All resins were pre-dried five hours in a vacuum oven at the following specified drying temperatures. Resin weight(g) and pressing conditions, for making different thickness sheets, are summarized in Tables 12 and 13. TABLE 12 Oter layer sheets Material 1 Material 2, 11, 12 Material 3 Material 4 Material 5Medstar MP100 MP200 PC PESU Drying temperature 66C 88C 88C 120C 140C Sheet thickness, mils 10 10 10 10 10 Resin weight, g 7.62 7.37 7.37 7.43 7.37 Press Temperature, F 520 520 520 540 600 Maximum Pressure, tons 8 8 8 10 10 Total pressing time 6 6 6 6 6 Transfer to Cold Press 2:Clamping Temp in Cold, F 120 120 120 150 150 Clamping Pressure, tons 8 8 8 10 10 Table 13 Ier layer sheets Material 1-5 Material 11 Material 12Ecdel 9967 RxT50D RxT50D Drying temperature 66C 90C 90C Sheet thickness, mils 10 10 15 Resin weight, g 7.00 7.12 10.78 Press Temperature, F 464 430 430 Maximum Pressure, tons 8 8 8 Total pressing time 6 6 6 Transfer to Cold Press 2: Clamping Temp in Cold, F 80 80 80 Clamping Pressure, tons 8 8 8

[0124] In a second step, 30 mil Three-layer laminates, of Materials 1-12, were prepared by hot pressing a 10 mil sheet of inner layer material sandwiched between two 10 mil outer layer materials, in a 30 mil metal frame, surrounded by two Teflon release films, and two metal plates,Leydig Docket No.515189 (001010PC) in a heated Carver Press, at a specified temperature, pressure and time, as described in the following Tables 14 and 15. TABLE 14 Material 1 Material 2 Material 3 Material 4 Material 5 Outer layer 1 Medstar MP100 MP200 PC PESU Inner layer Ecdel 9967 Ecdel 9967 Ecdel 9967 Ecdel 9967 Ecdel 9967 outer layer 2 Medstar MP100 MP200 PC PESU Construction 101010 101010 101010 101010 101010 Lamination in Hot Press 1:Lamination Temperature, F 464 464 464 500 520 3 mins, at Pressure 1 0-2 tons 0-2 tons 0-2 tons 0-2 tons 0-2 tons 1 mins, at Pressure 2 5 tons 5 tons 5 tons 5 tons 5 tons Transfer to Cold Press 2:Clamp in Cold Press at 120F 120F 120F 150F 150F Clamping Pressure 5 tons 5 tons 5 tons 5 tons 5 tons Clamping time 3 mins. 3 mins. 3 mins. 3 mins. 3 mins. TABLE 15 Material 6 Material 7 Material 8 Material 9 Material 10 Material 11 Material 12 Material 13 Outer layer 1 MP200 MP200 MP200 MP100 MP100 MP200 / MP100Inner layer Ecdel 9967 Ecdel 9967 Ecdel 9967 MP200 RPU PUE 50D PUE 50D Ecdel 9967 outer layer 2 MP200 MP200 MP200 MP100 MP100 MP200 / MP100Construction 11811 12612 13413 30 30 101010 101510 11811 Lamination in Hot Press 1:Lamination Temperature, F 464 464 464 520 430 430 430 464 3 mins, at Pressure 1 0-2 tons 0-2 tons 0-2 tons 0-2 tons 0-2 tons 0-2 tons 0-2 tons 0-2 tons 1 mins, at Pressure 2 5 tons 5 tons 5 tons 5 tons 5 tons 5 tons 2 mins, at Pressure 3 6 tons 6 tons 2 mins, at Pressure 4 10 tons 10 tons Transfer to Cold Press 2:Clamp in Cold Press at 120F 120F 120F 150F 150F 120F 120F 120F Clamping Pressure 5 tons 5 tons 5 tons 5 tons 5 tons 5 tons 5 tons 5 tons Clamping time 3 mins. 3 mins. 3 mins. 3 mins. 3 mins. 3 mins. 3 mins. 3 mins.Leydig Docket No.515189 (001010PC)

[0125] Material 9 is a 30 mil single layer sheet of Tritan MP200, prepared by hot pressing 22g of dried MP200 resin, in a 6”X6”X0.030” frame, at 520F and maximum pressure of 10 tons.

[0126] Material 10 is a 30 mil single layer sheet of Rigid Polyurethane, prepared by hot pressing 22g of dried Isoplast 2530 resin (from Lubrizol), in a 6”X6”X0.030” frame, at 430F and maximum pressure of 10 tons.

[0127] Materials 11 and 12 are three-layer sheets produced by lamination in a hot press, at 430F and maximum pressure of 5 tons, as summarized in Table 15.

[0128] Material 13 uses a (75 / 25 wt%) Blend of Tritan MP200 / MP100, as outer layers, sandwiching an inner layer of Ecdel 9967, in thickness ratios 11:8:11.

[0129] Material 13 is produced in three step as follows: First, the Copolyesters blend (MP200 / MP100) is prepared by blending 37.5g of dried Tritan MP200 resin and 12.5g Tritan MP100 resin, and mixing the blend in a 60cc Brabender mixer at 260C, at rollers speed of 60 rpm for five minutes. 7.72g of the mixed blend is hot- pressed in a 6”X6” frame, to produce a 11 mil thick sheet for use as an outer layer. A second 11 mil sheet of the mixed blend is pressed in a similar manner, for use as a second outer layer.

[0130] In a second step, 5.6g of Ecdel 9967 resin is pressed in a 6X6X0.008 inch frame, at 464F, as described in Table 3, to produce a 8 mil sheet for use as inner layer.

[0131] In a third step, two 11 mil sheets of the MP200 / MP100(75 / 25) blend are assembled above and below the 8 mils sheet of Ecdel 9967, in a 6”X6”X0.030” frame, and the stack press-laminated at a temperature of 464F, at a maximum pressure of 5tons for one minute, to produce the three- layer laminate, Material 13, Table 15. THERMOFORMING

[0132] All 30 mil Laminate Materials # 1-13 (except #10: single layer MP200, and #11: single layer RPU) were punched into 125mm round parts and thermoformed in a Biostar VII pressure former (available from Great Lakes Orthodontics). Thermoforming was performed over a square block measuring 63.5mm X 63.5mm X 10mm height, and the flat formed top surface used for testing. Thermoforming of the different material types was done at the temperatures, heating time pressure and cooling time, summarized in Table 16.Leydig Docket No.515189 (001010PC) Table 16 Te erat re heati g ti e Press re ooli gTy e se si seMaterial #1 Medstar-Ecdel 220 25 64 60 Material #2,3; 6-8; 13 MP-Ecdel 220 45 64 60 Material #11-12 MP-PUE 220 45 64 60 Material #9 MP200 220 45 64 60 Material #10 RPU 220 50 64 60 Material 4 PC-Ecdel 230 70 64 60

[0133] Thermoforming over tooth or other models, to make orthodontic aligners, retainers, or other appliances, was performed using these conditions as well. TESTING SUMMARY

[0134] Tensile and Elongation.

[0135] The tensile properties were tested according to ASTM D638-14 test method. Test specimens, were die cut using type IV punch die. Testing was done in an Instron machine, equipped with Blue Hill Universal software. Specimens were clamped between the grip jaws, and pulled at a cross-head speed of two inches per minute, until the sample broke. The tensile modulus (MPa) was determined from the slope in the linear part of the stress-strain curve. Tensile elongation at yield ( %), elongation at break (%), Yield Stress (MPa) and tensile strength (MPa) properties were all determined from the stress-strain curve.

[0136] Flexural Modulus.

[0137] Three-point Flexural Bending properties were tested according to ASTM D790- 17 test method.0.76mm thick rectangular test specimens, measuring 25.4mmX50.8mm, were die cut, and tested on a flexural fixture with a span of 16mm. Flexural test was performed at a strain rate of 6.04mm / minute, to a total of 10 percent strain. Flexural modulus (MPa) was determined from the slope of the stress-strain curve in the linear part of the curve. The maximum Flexural stress (MPa) was recorded as the Flexural strength (MPa).Leydig Docket No.515189 (001010PC)

[0138] Trouser Tear.

[0139] Trouser Tear properties were tested according to ASTM D1938-02 test method. 1in X 3in test specimens were die cut, with a 2in. slit in the middle. Trouser tear test was performed in an Instron machine, at a pull rate of 250mm / minute, for a total of 50mm. The maximum tear force (N) was measured, and tear strength (N / mm) determined.

[0140] Hardness

[0141] Hardness of materials was tested according to ASTM D2240 test method, using shore D Hardness Tester. 6.35mm thick compression molded parts, measuring 76mm X 76mm, were used as test specimens. Test specimens were conditioned at ambient room temperature for 24 hours before testing. Tests were run manually, at room temperature, and the initial maximum registered hardness was recorded as shore D hardness value.

[0142] Haze, Transparency and Clarity.

[0143] Haze %, Transparency % and Clarity % properties were tested according to ASTM D1003-13 test method.0.76mm test specimens, measuring 50.8 X 50.8mm, were tested in a Byk haze-gardi equipment, at room temperature.

[0144] Layers Thickness.

[0145] Individual Layers thickness (μm), in Multi-layer parts, was measured with a Leica DMS300 Digital microscope system equipped with Application Suite X software (LAS X). Outer layers 1, 2 (upper and lower) and inner layer thickness (μm) was measured at a magnification of about 280X.

[0146] DSC Thermal properties.

[0147] Differential Scanning Calorimeter (DSC) Thermal properties including glass transition temperature, Tg °C, melting temperature, Tm°C, and enthalpies of fusion (J / g) and crystallization (J / g), were measured according to ASTM D3418 test method. DSC tests were run in TA instrument model Q2000, for three cycles: heat / cool / heat, at a heating rate of 10°C per minute and a cooling rate of 10°C per minute. Tg °C value was taken from the second heat.Leydig Docket No.515189 (001010PC)

[0148] Color LAB

[0149] LAB color properties were tested according to ASTM D2244 test method. Byk- Gardner Color meter: Spectro-guide sphere gloss instrument was used to measure color differences dL, dA, dB between materials. A gloss white tile was used as standard reference. 0.76mm transparent test specimens, measuring 25.4mm X 50.8mm, with a smooth surface, were tested on the gloss white tile, and the color measured in reflection. In the CIE LAB system, L is the lightness of the object; A is green-red and B is the blue-yellow chromaticity components.

[0150] Elastic Recovery

[0151] This is an in-house test aka “Tube Wrap test” developed to measure the elastic recovery properties of a material after being wrapped around a piece of PVC pipe, and immersed in 37C de-ionized (DI) water for 24 hours. In this test, a 0.76mm rectangular strip specimen, measuring 1.0in X 4.0in, is wrapped half the way around a PVC pipe, with outer diameter 48.5mm, and clamped at both ends with C-Clamps. The clamped specimen is immersed in 37C DI water for 24 hours. At the end of immersion time, the sample is removed to room temperature, and allowed to recover for 24 hours. Elastic recovery is determined as the percent recovered distance between the bowed ends of the strip, where 100% recovery is the distance between the ends of the flat strip. Recovered strips are also examined for tiny crazes.

[0152] Tensile Hysteresis

[0153] Tensile fatigue properties in three-layer sheets were tested on an Instron machine according to the ASTM D638-17 test method, by measurement of tensile hysteresis (losses) after numerous cyclic deformations. For test specimens, 4.5 in tensile bars, type IV, were punched using a Pioneer Die-tecs Punch. Tensile hysteresis tests were run for 10,000 cycles, at 0-3% strain, at a rate of 2in / min, as described below. In the pre-cycle category, 10,000 cycles were selected. Parts were cycled between a minimum 0% and a maximum 3% strain ڙ, at a speed of 2inches per minute. Data was collected at the rate of 10 readings per second. Collected data includes time (msec), minimum and maximum tensile strain (%), and tensile stress (psi); force (lbs) is optional. Cycled stress (psi) data is plotted continuously between 0 and 3% strain for 10,000 cycles or until the part fails (breaks).Leydig Docket No.515189 (001010PC)

[0154] Tensile Hysteresis (%) is calculated using the following equation:

[0155] TH (%) = 100*((ıi*ڙi) - (ın*ڙn)) / (ıi*ڙi)

[0156] Where, ıi = initial (1st cycle) maximum stress (psi); ڙi = initial maximum strain (3.00 / 100); ın = maximum stress at cycle (n), psi; ڙn = maximum strain at cycle (n), i.e. (3.00 - lost strain / 100).

[0157] Stress Relaxation

[0158] Stress Relaxation tests were performed in an Instron Machine, equipped with a controlled temperature water bath, a 3-Point Flexural Bending fixture, with supports span of 16mm and a loading nose of 2mm radius.0.76mm test specimens, measuring 25.4mm X 50.8mm were tested after exposure to ambient room temperature for 24 hours. Stress relaxation tests were performed at 5% strain, in 37C de-ionized water for 48 hours. With the test specimen placed on the fixture supports, immersed in 37C de-ionized water, the specimen is loaded at the rate of 36.3kg per minute, to reach 5% strain in about 5 seconds. The test specimen is held under constant 5% strain for 48 hours, or longer time. The maximum force (g) at 5%strain is recorded as initial force (g). The force decay is monitored, and recorded every 2 seconds for 48 hours, or end of test. The 48 hour stress relaxation results at 5%strain, in 37C de-ionized water, are compared for different materials. Initial force (g), 60 minute force(g), 24 hours and 48 hours force are tabulated. Force retention, taken as the force ratio (24hr gf) / (1hr gf) is determined and compared.

[0159] Stress Relaxation Tests in Thermoformed shapes.

[0160] The top flat surface of Thermoformed square shape, described earlier, was cut out and rectangular test specimens, 25.4mm X 50.8mm, punched. Typical thickness of test specimens was 0.68mm-0.70mm. Thermoformed test specimens were soaked 48 hours in de- ionized water prior to testing for stress relaxation properties. Stress relaxation testing of thermoformed-soaked specimens was performed in a similar test setup to the unmodified 0.76mm specimens. However, for thermoformed-soaked parts, loading was applied at a reduced rate of 31.8kg per minute, and testing carried out at a constant Deflection of 2.54mm for 48 hours.Leydig Docket No.515189 (001010PC)

[0161] The sheets and materials described herein have utility as thermoformable materials having superior dimensional stability, impact cushioning, and restorative forces. The sheets may be converted into a number of types of oral appliances, for example for moving teeth, for use as a sports mouth guard with improved impact resistance and for use as an orthodontic retainer. Improved properties of the materials and appliances described herein relative to currently available materials and appliances include but are not limited to greater flexibility resulting in improved end user comfort, improved tooth movement results, greater stain and stress cracking resistance and excellent cosmetics all of which promote more consistent wear by the subjects.

[0162] Clauses: Clause 1: A polymeric sheet composition, comprising: an elastomeric inner layer disposed between two outer layers, wherein the two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, and wherein the elastomeric inner layer is comprised of a polyester or copolyester having inherent viscosity of about 1.0 to 1.3 DL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C.

[0163] Clause 2: The polymeric sheet composition of clause 1, wherein the polymeric sheet composition has a stiffness D value from about 0.4 to about 0.5.

[0164] Clause 3: The polymeric sheet composition according to any of the preceding clauses, wherein a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer.

[0165] Clause 4: The polymeric sheet composition according to any of the preceding clauses, wherein the polymeric sheet composition is a three-layer composition and a thickness ratio of the three layers is 11:8:11, 12:6:12, 13:4:13, or 14:2:14.

[0166] Clause 5: The polymeric sheet composition according to any of the preceding clauses, wherein at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C.Leydig Docket No.515189 (001010PC)

[0167] Clause 6: The polymeric sheet composition according to any of the preceding clauses, wherein the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.

[0168] Clause 7: The polymeric sheet composition according to any of the preceding clauses, comprising a combined thickness of all layers from about 250 microns to about 2,000 microns.

[0169] Clause 8: The polymeric sheet composition according to any of the preceding clauses, wherein the two outer layers have a stiffness value D from about 0.45 to about 0.5.

[0170] Clause 9: The polymeric sheet composition according to any of the preceding clauses, further comprising two intermediate layers, wherein each intermediate layer is disposed between the elastomeric inner layer and one of the two outer layers.

[0171] Clause 10: The polymeric sheet composition according to any of the preceding clauses, wherein the two intermediate layers each have glass transition temperatures lower than a glass transition temperature of their adjacent outer layer.

[0172] Clause 11: The polymeric sheet composition according to any of the preceding clauses, wherein the two intermediate layers each have thicknesses less than a thickness of their adjacent outer layer.

[0173] Clause 12: A dental aligner for repositioning one or more teeth of a patient formed from a polymeric sheet composition comprising: an elastomeric inner layer disposed between two outer layers, wherein the two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, and wherein the elastomeric inner layer is comprised of a polyester or copolyester having inherent viscosity of 1.0 to 1.3 DL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C.

[0174] Clause 13: The dental aligner of clause 12, wherein the polymeric sheet composition has a stiffness D value from about 0.4 to about 0.5.

[0175] Clause 14: The dental aligner according to any of clauses 12 to 13, wherein a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer.Leydig Docket No.515189 (001010PC)

[0176] Clause 15: The dental aligner according to any of clauses 12 to 14, wherein the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:14.

[0177] Clause 16: The dental aligner according to any of clauses 12 to 15, wherein at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C.

[0178] Clause 17: The dental aligner according to any of clauses 12 to 16, wherein the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.

[0179] Clause 18: The dental aligner according to any of clauses 12 to 17, comprising a combined thickness of all layers from about 250 microns to about 2,000 microns.

[0180] Clause 19: The dental aligner according to any of clauses 12 to 18, wherein the two outer layers have a stiffness value D from about 0.45 to about 0.5.

[0181] Clause 20: The dental aligner according to any of clauses 12 to 19, further comprising two intermediate layers, wherein each intermediate layer is disposed between the elastomeric inner layer and one of the two outer layers.

[0182] Clause 21: The dental aligner according to any of clauses 12 to 20, wherein the two intermediate layers each have glass transition temperatures lower than a glass transition temperature of their adjacent outer layer.

[0183] Clause 22: The dental aligner according to any of clauses 12 to 21, wherein the two intermediate layers each have thicknesses less than a thickness of their adjacent outer layer.

[0184] Clause 23: A method of forming a dental aligner for repositioning one or more teeth of a patient comprising: coextruding a polymeric sheet composition comprising: an elastomeric inner layer disposed between two outer layers, wherein the two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, andLeydig Docket No.515189 (001010PC) wherein the elastomeric inner layer is comprised of a polyester or copolyester having inherent viscosity of about 1.0 to 1.3 DL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C; and thermoforming the polymeric sheet composition over a model of a patient’s dentition to form the dental aligner.

[0185] Clause 24: The method of claim 23, wherein a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer.

[0186] Clause 25: The method according to any of clauses 23 to 24, wherein the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:14.

[0187] Clause 26: The method according to any of clauses 23 to 25, wherein at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C.

[0188] Clause 27: The method according to any of clauses 23 to 26, wherein the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.

[0189] Clause 28: A method of forming a dental aligner for repositioning one or more teeth of a patient comprising: coextruding a polymeric sheet composition having five layers, the five layers including: a first outer layer; a second outer layer; a first intermediate layer adjacent to the first outer layer; a second intermediate layer adjacent to the second outer layer; and an inner layer between the first intermediate layer and the second intermediate layer, wherein the first and second outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, the inner layer is an elastomeric layer comprised of a polyester or copolyester having an inherent viscosity of about 1.0 to 1.3 DL / g as determined in 60 / 40 (wt / wt) phenol / tetrachloroethane at a concentration of 0.5 g / 100ml at 25°C,Leydig Docket No.515189 (001010PC) and the first and second intermediate layers each have glass transition temperatures lower than a glass transition temperature of their adjacent outer layer.

[0190] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0191] The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the disclosed subject matter (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or example language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosed subject matter and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0192] Certain embodiments are described herein. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the embodiments to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, anyLeydig Docket No.515189 (001010PC) combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

Leydig Docket No.515189 (001010PC) CLAIMS WHAT IS CLAIMED IS:

1. A polymeric sheet composition, comprising: an elastomeric inner layer disposed between two outer layers, wherein the two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, and wherein the elastomeric inner layer is comprised of a polyester or copolyester having inherent viscosity of about 1.0 to 1.3DL / g.

2. The polymeric sheet composition of claim 1, wherein the polymeric sheet composition has a stiffness D value from about 0.4 to about 0.

5.

3. The polymeric sheet composition of claim 1, wherein a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer.

4. The polymeric sheet composition of claim 3, wherein the polymeric sheet composition is a three-layer composition and a thickness ratio of the three layers is 11:8:11, 12:6:12, 13:4:13, or 14:2:

14.

5. The polymeric sheet composition of claim 1, wherein at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C.

6. The polymeric sheet composition of claim 5, wherein the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.

7. The polymeric sheet composition of claim 1, comprising a combined thickness of all layers from about 250 microns to about 2,000 microns.Leydig Docket No.515189 (001010PC) 8. The polymeric sheet composition of claim 1, wherein the two outer layers have a stiffness value D from about 0.45 to about 0.

50.

9. The polymeric sheet composition of claim 1, further comprising two intermediate layers, wherein each intermediate layer is disposed between the elastomeric inner layer and one of the two outer layers.

10. The polymeric sheet composition of claim 9, wherein the two intermediate layers each have glass transition temperatures lower than a glass transition temperature of an adjacent outer layer.

11. The polymeric sheet composition of claim 9, wherein the two intermediate layers each have thicknesses less than a thickness of an adjacent outer layer.

12. A dental aligner for repositioning one or more teeth of a patient formed from a polymeric sheet composition comprising: an elastomeric inner layer disposed between two outer layers, wherein the two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, and wherein the elastomeric inner layer is comprised of a polyester or copolyester having inherent viscosity of about 1.0 to 1.3DL / g.

13. The dental aligner of claim 12, wherein the polymeric sheet composition has a stiffness D value from about 0.4 to about 0.

5.

14. The dental aligner of claim 12, wherein a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer.

15. The dental aligner of claim 14, wherein the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:14.Leydig Docket No.515189 (001010PC) 16. The dental aligner of claim 12, wherein at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C.

17. The dental aligner of claim 16, wherein the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.

18. The dental aligner of claim 12, comprising a combined thickness of all layers from about 250 microns to about 2,000 microns.

19. The dental aligner of claim 12, wherein the two outer layers have a stiffness value D from about 0.45 to about 0.

50.

20. The dental aligner of claim 12, further comprising two intermediate layers, wherein each intermediate layer is disposed between the elastomeric inner layer and one of the two outer layers.

21. The dental aligner of claim 20, wherein the two intermediate layers each have glass transition temperatures lower than a glass transition temperature of an adjacent outer layer.

22. The dental aligner of claim 20, wherein the two intermediate layers each have thicknesses less than a thickness of an adjacent outer layer.

23. A method of forming a dental aligner for repositioning one or more teeth of a patient comprising: coextruding a polymeric sheet composition comprising: an elastomeric inner layer disposed between two outer layers, wherein the two outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, andLeydig Docket No.515189 (001010PC) wherein the elastomeric inner layer is comprised of a polyester or copolyester having inherent viscosity of about 1.0 to 1.3DL / g; and thermoforming the polymeric sheet composition over a model of a patient’s dentition to form the dental aligner.

24. The method of claim 23, wherein a thickness of each of the two outer layers is greater than a thickness of the elastomeric inner layer.

25. The method of claim 24, wherein the polymeric sheet composition is a three-layer composition with a thickness ratio of the three layers of 11:8:11, 12:6:12, 13:4:13, or 14:2:

14.

26. The method of claim 23, wherein at least one of the two outer layers is a blend of two materials having glass transition temperatures (Tg) between about 80°C to about 190°C.

27. The method of claim 26, wherein the blend reduces a tensile hysteresis loss (tensile fatigue) property of the polymeric sheet composition and improves resistance to cyclic deformation during repeated extension-release events.

28. A method of forming a dental aligner for repositioning one or more teeth of a patient comprising: coextruding a polymeric sheet composition having five layers, the five layers including: a first outer layer; a second outer layer; a first intermediate layer adjacent to the first outer layer; a second intermediate layer adjacent to the second outer layer; and an inner layer between the first intermediate layer and the second intermediate layer, wherein the first and second outer layers are polyesters or copolyesters having a glass transition temperature between about 110°C to about 130°C, the inner layer is an elastomeric layer comprised of a polyester or copolyester having an inherent viscosity of about 1.0 to 1.3 DL / g, and the first and second intermediate layers each have glassLeydig Docket No.515189 (001010PC) transition temperatures lower than a glass transition temperature of an adjacent outer layer.