Dual shell dental device and material construction

Abstract

To provide a dental appliance and a polymer sheet composition capable of dissipating impact forces, being thin, and not interfering with the natural occlusion of human teeth.SOLUTION: The polymeric sheet composition is useful for making dental devices having an outer layer composed of a "hard"material having a modulus of about 1, 000 MPA to 2, 500 MPA and an inner core composed of an elastomeric material or a "soft" material having a modulus of about 50 MPA to 500 MPA, exhibiting improved flexibility and strength, and stain and tear resistance better than currently available materials and dental devices.SELECTED DRAWING: FIG. 1A

Description

Detailed Description of the Invention

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0001] This patent application claims priority to U.S. Provisional Patent Application No. 16 / 719,256, entitled "DUAL SHELL DENTAL APPLIANCE AND MATERIAL CONSTRUCTIONS," filed December 18, 2019, the entire contents of which are incorporated herein by reference.

[0002] [Technical field]

[0002] Disclosed is a composition in the form of a polymer sheet useful, for example, in dental appliances, which is composed of layers that impart flexibility, strength, and stain resistance to devices made from the sheet.

[0003] [background]

[0003] Improved orthodontic and dental devices are needed that can facilitate orthodontic tooth movement, stabilize tooth position, or protect teeth from potentially damaging external forces. Existing materials and products are constructed from single-, two-, or three-layer materials with limited functionality and can suffer from performance shortcomings. Aligners are plastic shells that fit over the teeth and are designed to apply translational or rotational forces to the teeth. The ability of aligners to precisely move teeth is limited by the aligner's effective modulus, resilience, and ability to resist creep and stress relaxation. Additionally, aligners should generally exhibit stain and environmental stress crack resistance.

[0004]

[0004] Devices for protecting teeth, such as sports mouth guards and dental splints, have conflicting requirements: on the one hand, the devices should be able to dissipate impact forces, and on the other hand, they should be thin and not interfere with the natural occlusion of human teeth or hinder speech.

[0005] [overview]

[0005] In one embodiment, there is provided a composition comprising at least two outer layers A and C and an intermediate layer B. The A and C layers each comprise a thermoplastic polymer having a modulus of elasticity of about 1,000 MPa to 2,500 MPa and a glass transition temperature and / or melting point of about 80°C to 180°C, and the intermediate B layer is at least comprised of an elastomer having one or more of a modulus of elasticity of about 50 MPa to about 500 MPa and a glass transition temperature and / or melting point of about 90°C to about 220°C.

[0006] In one embodiment, the A and C layers are comprised of one or more of a copolyester, a polycarbonate, a polyester-polycarbonate blend, a polyurethane, a polyamide, or a polyolefin.

[0007]

[0007] In another embodiment, the intermediate B layer is composed of one or more of polyurethane elastomers, polyolefin elastomers, polyester elastomers, styrene-based elastomers, polyamide elastomers, cyclic olefin elastomers, acrylic elastomers, aromatic or aliphatic polyethers, and polyester polyurethanes.

[0008] In yet another embodiment, the material of the intermediate B layer has a compression set after 22 hours at 25°C of less than 35%, less than 30%, less than 25%, less than 20%, or less than 10%.

[0009] In yet another embodiment, the A and C layers have a displacement of 1 cm when displaced 0.05 mm to 0.1 mm relative to each other. 2 Less than 100N (Newtons) per 1cm 2 Less than 50N per 1cm 2 Less than 25N per 1cm 2 It has a lateral restoring force of less than 10N per

[0010] In another embodiment, the delamination strength between layers A and C and layer B is greater than 50 N per 2.5 cm.

[0011]

[0011] In one embodiment, the combined thickness of the A, B, and C layers is from about 250 microns to about 2,000 microns, and the combined thickness of the A and C layers is from 25 microns to 750 microns, 50 microns to 1,000 microns, 100 microns to 700 microns, 150 microns to 650 microns, 100 microns to 200 microns, 200 microns to 600 microns, 100 microns, 125 microns, 150 microns, 175 microns, 200 microns, 225 microns, 250 microns, 275 microns, or 300 microns.

[0012]

[0012] In yet another embodiment, one or more of the A and C layers comprises a microcrystalline polyamide composed of 50-100 mol % C6-C14 aliphatic diacid moieties and about 50-100 mol % 4,4'-methylene-bis(cyclohexylamine) (CAS [1761-71-3]), having a glass transition of about 100°C to 180°C, a heat of fusion of less than 20 J / g, and a light transmittance of greater than 80%.

[0013]

[0013] In another embodiment, one or more of the A and C layers comprises a copolyester consisting of (a) a dicarboxylic acid component comprising 70 mol % to 100 mol % of terephthalic acid residues and (b) a diol component, the diol component comprising: i) 0 to 95 mol % of ethylene glycol; ii) 5 mol % to 50 mol % of 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; iii) 50 mol % to 95 mol % of 1,4-cyclohexanedimethanol residues; and iiii) 0 to 1% of a polyol having three or more hydroxyl groups, wherein the sum of the mol % of the diol residues i), ii), iii), and iiii) amounts to 100 mol %, and the copolyester exhibits a glass transition temperature, Tg, of 80°C to 150°C.

[0014]

[0014] In another embodiment, the intermediate B layer comprises an aromatic polyether polyurethane having a Shore hardness of about A90 to D55, about A85 to D60, or about A80 to D65, and a compression set of less than 35%, and the interlayer peel strength between the A and C layers and the B layer is greater than 50 N per 2.5 cm.

[0015]

[0015] In one embodiment, one or more of the A and C layers comprise a polyurethane composed of (a) a diisocyanate comprising 80 mol% to 100 mol% of methylene diphenyl diisocyanate residues, and / or hydrogenated methylene diphenyl diisocyanate, and (b) a diol component, the diol component comprising i) 0 to 100 mol% hexamethylene diol, and ii) 0 to 50 mol% 1,4-cyclohexanedimethanol, the sum of i) and ii) being greater than 90 mol%, and the polyurethane having a glass transition temperature Tg of about 85°C to about 150°C.

[0016] In another aspect, a dental appliance conforming to one or more teeth made from a composition or polymer sheet as described herein.

[0017]

[0017] In one embodiment of the dental device, the combined thickness of the A, B, and C layers is from about 250 microns to about 2,000 microns, and the combined thickness of the A and C layers is from 25 microns to 750 microns, 50 microns to 1000 microns, 100 microns to 700 microns, 150 microns to 650 microns, 100 microns to 200 microns, or 200 microns to about 600 microns.

[0018] In another aspect, a reversibly deformable dental device constructed from a composition or polymeric sheet material as described herein, wherein the elastomeric intermediate layer and outer layer are reversibly movable relative to one another and have a resilience of 1 cm when displaced 0.05 mm to 0.1 mm relative to one another. 2 Less than 100N per 1cm 2 Less than 50N per 1cm 2 Less than 25N per 1cm 2A dental appliance is provided having a lateral restoring force of less than 10 N per tooth.

[0019] In one embodiment, the elastomeric intermediate layer comprises a polyurethane having a hardness of about A80 to D75, A85 to D65, A90 to D55, for example, A95, A90, A85, A80, A75, D50, D55, D60, D65, or D70.

[0020]

[0020] In another aspect, there is provided a composition, polymer sheet, or dental device having environmental stress resistance and comprising at least two outer layers and an elastomeric inner layer, wherein one or more of the outer layers is a polyester or copolyester having a modulus of elasticity of about 1,000 MPa to 2,500 MPa, and the inner layer comprises an elastomer having a modulus of elasticity of about 50 MPa to about 500 MPa, and wherein the interlayer peel strength between at least one outer layer and the elastomer is greater than about 50 N / inch.

[0021]

[0021] In another aspect, there is provided a reversibly deformable dental device, wherein the thickness of the outer A layer is about 175 microns to about 250 microns, about 100 microns to about 200 microns, e.g., 100 microns, 125 microns, 150 microns, 175 microns, 200 microns, 225 microns or 250 microns, the thickness of the outer C layer is about 175 microns to about 250 microns, 100 microns to 200 microns, e.g., 100 microns, 125 microns, 150 microns, 175 microns, 200 microns, 225 microns or 250 microns, the thickness of the middle B layer is 300 to 500 microns, and the total thickness of the A, B, and C layers is 850 to 1,000 microns, or 600 microns to 800 microns. [Brief explanation of the drawings]

[0022] [Figure 1A]1A is a schematic diagram of a three-layer sheet cross section with a simple ABC structure. Layers A and C may be the same or different materials, and each layer may be composed of one or more materials, or a blend or alloy. Layer B may be a single material, a blend of materials, or an alloy. [Figure 1B] 1B is a schematic diagram of a cross-sectional view of a multilayer sheet. Each layer A, B, and C may be composed of a single layer or multiple layers, and each layer may be composed of one or more materials or blends of materials. As illustrated in FIG. 1B, layer A may be composed of more than one layer, such as layers a and a', layer B may be composed of more than one layer, such as layers b and b', and layer C may be composed of more than one layer, such as layers c and c'. [Figure 2A] 2A and 2B are schematic diagrams of an exemplary test specimen for determining the displacement (FIG. 2A) and lateral restoring force (translation; FIG. 2B) of a simple three-layer sheet composed of two rigid outer layers and an inner elastomeric layer, where A, B, and C are the individual layers of the sheet. In this example, layers A and C are reversibly translated relative to one another, with layer B providing the restoring force. In one more detailed example, layers A, B, and C may each be approximately 250 microns thick, and layers A, B, and C may be composed of one or more materials and may each individually include one or more layers. [Figure 2B] 2A and 2B are schematic diagrams of an exemplary test specimen for determining the displacement (FIG. 2A) and lateral restoring force (translation; FIG. 2B) of a simple three-layer sheet composed of two rigid outer layers and an inner elastomeric layer, where A, B, and C are the individual layers of the sheet. In this example, layers A and C are reversibly translated relative to one another, with layer B providing the restoring force. In one more detailed example, layers A, B, and C may each be approximately 250 microns thick, and layers A, B, and C may be composed of one or more materials and may each individually include one or more layers. [Figure 3A]Figure 3A is a graphical depiction of the displacement / force curves of elastomers with different degrees of hardness. The graph shows the restoring force (N) resulting from the translation of layer A relative to layer C, with an intermediate layer B comprising a TPU elastomer of different hardness, and demonstrates that the hardness of the elastomer affects the displacement and restoring force. A harder thermoplastic urethane (TPU) generates a larger restoring force, but may limit the amount of movement. [Figure 3B] 3B is a graphical representation of the recovery force (N) as a function of time (0-48 hours) for a given displacement between layers A and C, with an intermediate layer B comprising a TPU elastomer of different hardness in the B layer. TPU75A has a low compression set and exhibits the smallest initial force, but the force decays only slightly over time. TPU75D has a high compression set and exhibits a much higher initial recovery force, but the force decays rapidly over time. [Figure 4] FIG. 4 is a graphical depiction of the retention force at 5% stress of different structures exposed to 37° C. and water for 48 hours.

[0023]

[0028] It should be understood that the structures and properties illustrated in Figures 1-4 are detailed examples and are not intended to limit the scope of structures and tests that may be used. Other materials, structures, and sequences of steps may be implemented in accordance with alternative embodiments. For example, alternative embodiments may contain additional layers, including adhesion layers, pigments, optical additives, or reinforcing agents, and may be constructed by any means known in the art, such as flat extrusion, coextrusion blown film, calendaring, lamination, and adhesive bonding. Structures (or polymer sheets) and devices may be fabricated by 3D printing or dip coating in some embodiments. Those skilled in the art will recognize and appreciate the many variations, modifications, and alternatives of the structures.

[0024]

[0029] Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the appended claims.

[0025]

[0030] Other variations are within the spirit of the present disclosure. Accordingly, while the disclosed embodiments are susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and described herein. It should be understood, however, that there is no intention to limit the disclosure to the particular 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 present disclosure, as defined by the appended claims.

[0026] [Detailed explanation]

[0031] Current orthodontic aligners have a very limited elastic range (typically 4%-7%) and exhibit rapid decay of resilience when deformed. As a result, frequent replacement of the appliance may be necessary, which increases manufacturing costs, teeth may not move as desired, and patients may experience discomfort from excessively high initial forces. Attempts to improve the elastic range by providing a thin outer layer of elastomer (typically polyurethane, as described in U.S. Pat. No. 9,655,693, for example) result in a tooth-contacting surface that deforms easily, which may reduce the accuracy of tooth movement and increase the tendency for unsightly staining from common foods, beverages, or tobacco. U.S. Pat. No. 6,524,101 describes dental appliances with regions having different elastic moduli and appliances with added reinforcing elements. Non-staining polyurethanes used to fabricate dental appliances, such as Zendura® A available from BayMaterials, LLC (Fremont, CA), have excellent properties, but are hygroscopic, require rigorous drying before thermoforming, can be uncomfortable initially, are difficult to clean, and may not be ideal for some applications.

[0027]

[0032] Many other polyurethanes similarly must be dried before thermoforming, adding time and cost to the manufacturing process. Aromatic polyesters or copolyesters may be used to form aligners, but they exhibit poor chemical resistance and low impact and tear strength. Aligners constructed from stiff materials, such as polyesters or rigid polyurethanes, have a high modulus of elasticity, e.g., greater than about 1,000 or 1,500 MPa, and if deformed, can exert excessive force on the teeth, causing discomfort and potential damage to the roots. Highly elastomeric polymers, such as thermoplastic polyurethane elastomers (TPUs), styrene-based elastomers (e.g., SBS, SEBS, SIS, etc.), have a low modulus of elasticity (typically less than 100 MPa or less than 200 MPa) that may be insufficient to move teeth and are easily stained. This limits their usefulness for producing aligners.

[0028]

[0033] The present disclosure is based on the discovery that many of the defects in prior art materials, and dental appliances constructed from prior art materials, can be reduced or eliminated using a sheet or device having an outer layer constructed from a material having a modulus of elasticity of greater than about 1,000 MPa up to 2,500 MPa and an inner elastomeric layer or core constructed from one or more elastomeric materials having a modulus of elasticity of about 50 MPa to 500 MPa, which sheet or device may be non-staining, cost less than rigid urethanes, exhibit improved elastic properties, and have surprisingly greater environmental stress crack resistance.

[0029]

[0034] The polymer sheet or device may be composed of more than two rigid layers, for example, a third rigid layer may be disposed between two or more elastomeric layers. The multi-layer construction provides a dual-shell dental appliance that can be adapted to move teeth, hold teeth in their existing position, or protect teeth from impact. As disclosed herein, the outer shell material that contacts the teeth can be substantially rigid to precisely engage with the teeth, providing precise force while maintaining the ability to exert a more constant force over longer distances.

[0030]

[0035] By selecting appropriate elastic moduli and thicknesses of the outer and inner materials, two or more substantially rigid shells can be reversibly displaced relative to one another to a greater extent than rigid materials of comparable thickness and shape, providing a dental appliance that can apply desired forces to teeth and move them over a greater range without generating excessive forces or exhibiting excessive stress relaxation when deformed. While not limiting the present disclosure to a particular structure, the sheet or dental appliance may be referred to herein as a "dual-shell" sheet or appliance. A "dual-shell" sheet or appliance may include two or more shells or layers. The shells or layers may have the same or different thicknesses. A series of dental appliances constructed with this "dual-shell" structure may be used to move teeth in stages, and the two or more appliances may be constructed from the same or different materials. The dental appliance may be constructed by thermoforming the dual-shell material onto one or more dental models, by sequentially thermoforming rigid and elastomeric precursor sheets, or by sequentially dip-coating the models with polymer solutions or polymer-forming monomers or oligomers, which may optionally be cured or otherwise post-treated. The inventors have discovered that this unique structure can significantly reduce the amount of stress cracking that a shell or material exhibits, thereby expanding the range of materials that can be used for the sheet or device.

[0031] [Definition]

[0036] The use of the terms "a," "an," and "the" and similar referents in the context of describing the disclosed embodiments (particularly in the context of the claims below) should be interpreted to encompass both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" should be interpreted as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The term "connected" should be interpreted as contained within, connected to, or joined together, either partially or wholly, even if there is something intervening. The phrase "based on" should be understood to be open-ended and in no way limiting, and is intended to be interpreted as "based at least in part on," or otherwise read, as appropriate. The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within that range, unless otherwise indicated herein, and each separate value is incorporated into this 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. Any and all examples, or the use of exemplary language (e.g., "such as") provided herein, are intended merely to facilitate a better understanding of embodiments of the disclosure and do not limit 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.

[0032]

[0037] The term "dental appliance" is used herein to refer to any device that is placed in or on a subject's teeth. Dental appliances include, but are not limited to, orthodontic, prosthetic, retaining, snoring / airway, cosmetic, therapeutic, protective (e.g., mouthguards), and habit correction devices.

[0033]

[0038] The term "ASTM D638" is used herein in reference to testing for tensile strength of plastics.

[0034]

[0039] The term "ASTM D1364" is used herein in reference to the test for delamination strength.

[0035]

[0040] The term "compression set" is used herein to refer to the permanent deformation of a material when a force is applied and removed. Unless otherwise specified, compression set is measured according to ASTM D305-B for a specified time and temperature, e.g., 23°C for 22 hours.

[0036]

[0041] The term "flexural modulus" is used herein in reference to the stiffness of a material and / or its resistance to deformation in bending. The higher the flexural modulus of a material, the more resistant it is to bending. For an isotropic material, the modulus of elasticity measured in all directions is the same.

[0037]

[0042] The term "hardness" is used herein in reference to the Shore hardness scale and is measured in accordance with ASTM D2240 unless otherwise specified. Durometer measures the indentation of a metal foot or pin into the surface of a material. There are various durometer scales, but Shore A and Shore D are commonly used. Materials with higher durometer values ​​are harder compared to materials with lower durometer values. Shore hardness and modulus of elasticity are generally correlated and can be converted by approximation when only one value is known using methods described in the art.

[0038]

[0043] The terms "elastic modulus," "Young's modulus," and "elastic modulus" are used herein in reference to the stiffness of a material and / or its resistance to elongation. The higher the modulus of a material, the stiffer it is. The flexural modulus and elastic modulus of a material may be the same or different. For isotropic materials such as A, B, and C, the flexural modulus and elastic modulus (sometimes called modulus of elasticity) are substantially the same, and either one can be measured depending on the situation. For polymers, mechanical properties, including modulus of elasticity and other properties, can be measured as regulated by ASTM D638. Flexural modulus can be measured by the test described in ASTM D790, and uses units of force per area. Unless otherwise specified, "elastic modulus" refers to the elastic modulus.

[0039]

[0044] The term "polymer sheet" is used interchangeably herein with the term "plastic sheet."

[0040]

[0045] The term "lateral restoring force" with respect to the A and C layers of a polymer sheet is used in reference to the force that may be exerted by one layer being translated relative to another layer that is fixed in place. If the A and C layers are moved independently of each other, the A and C layers will later return to their original positions unless restrained.

[0041]

[0046] "Translational force" refers to the amount of force required to displace layers A and C a given distance from their neutral position, with a given displacement of 1 cm 2 It is measured as Newtons per square meter (N / cm²). 2 ) is calculated as the area where layers A and C overlap. Measurements can be made by preparing a test specimen with a known overlap and displacing layers A and C relative to each other a predetermined distance using a mechanical force testing machine, for example an Instron Materials Tester, applying a force of 0.04 MPa / min. The forces measured at various displacements are recorded. The lateral translational force and the lateral restoring force will be the same for elastic materials.

[0042]

[0047] Figure 2A shows a test for determining the displacement force. Figure 2B shows a test for determining the recovery force. The diagrams in Figures 2A and 2B show a simple three-layer sheet consisting of two rigid outer layers and an inner elastomeric layer, where layers A and C are reversibly translated relative to each other and layer B provides the recovery force. Figure 3A shows the force (N) that stretches layer A and causes it to translate relative to layer C, which has an intermediate elastomeric B layer (the hardness of the elastomer affects the displacement and recovery force). Example 2 and Table 4 show the lateral / translational recovery forces for various B layers.

[0043]

[0048] The term "shear force," as used herein, means a translational force applied to two surfaces connected by an elastic material.

[0044]

[0049] The term "shell" is used herein in reference to a polymeric shell that fits over and is removably positionable on a tooth.

[0045]

[0050] The term "stain resistant" is used herein in reference to materials that are designed to resist being stained.

[0046]

[0051] The term "thermoplastic polymer" is used herein to refer to a polymer that becomes flexible or moldable above a certain temperature and solidifies upon cooling, provided that heat and pressure do not chemically degrade the polymer.

[0047]

[0052] The term "tooth(s)" includes natural teeth, including natural teeth modified with a filling or crown, implant teeth, artificial teeth that are part of a bridge or other appliance fixed to one or more natural or implant teeth, and artificial teeth that are part of a removable appliance.

[0048]

[0053] In the following description, various embodiments are described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified so as not to obscure the described embodiments.

[0049] [Embodiment]

[0054] In some embodiments (referred to herein as Embodiment #1), the thermoformable polymer sheet is comprised of at least two outer layers A and C, and a middle layer B, wherein the A and C layers have a compressive strength greater than about 1,000 MPa, e.g., 1,000 MPa to 1,500 MPa; 1,100 MPa to 1,600 MPa; 1,200 MPa to 1,700 MPa; 1,300 MPa to 1,800 MPa; 1,400 MPa to 1,900 MPa; 1,500 MPa to 2,000 MPa; 1,100 MPa; 1,200 MPa; 1,300 MPa; 1,400 MPa a; a modulus of elasticity of 1,500 MPa; 1,600 MPa; 1,700 MPa; 1,800 MPa, 1,900 MPa; 2,000 MPa; or up to 2,500 MPa; and a glass transition temperature (Tg) and / or melting point of about 80°C to 180°C; 90°C to 170°C; 100°C to 160°C; 110°C to 150°C; 120°C to 150°C; 130°C to 170°C; 140°C to 180°C; 80°C; 90°C; 100°C; 110°C; 120°C; 130°C; 140°C; 150°C; 160°C; 170°C; or 180°C.

[0050]

[0055] In such an embodiment, the intermediate B layer may be from about 50 MPa to about 500 MPa; 60 MPa to 470 MPa; 70 MPa to 440 MPa; 80 MPa to 400 MPa; 100 MPa to 350 MPa; 150 MPa to 300 MPa; 200 MPa to 400 MPa; 60 MPa, 70 MPa; 80 MPa, 90 MPa; 100 MPa; 110 MPa; 120 MPa; 130 MPa; 140 MPa; 150 MPa, 160 MPa a; 170 MPa; 180 MPa; 190 MPa; 200 MPa, 250 MPa, 300 MPa, 350 MPa, 400 MPa, 450 MPa, or up to 500 MPa, and one or more of (a) a glass transition temperature, or (b) a melting point, of about 90° C. to about 220° C.; 100° C. to about 200° C.; 120° C. to about 180° C.; 140° C. to 220° C.; or 160° C. to about 220° C. In some embodiments, the intermediate B layer is an elastomeric layer or shell, which may comprise one or more materials and one or more layers.

[0051]

[0056] In embodiment #1, layers A and C may comprise polyester or copolyester, polyurethane, polyamide, polyolefin, (meth)acrylic polymer, polycarbonate, vinyl polymer such as polyvinyl chloride, or fluoropolymer.

[0052]

[0057] In embodiment #1, Layer B may comprise 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 fluoroelastomer.

[0053]

[0058] In embodiment #1, the B layer material has a compression set at 25°C for 22 hours of less than about 35%, less than 30%, less than 25%, less than 20%, less than 10%, i.e., less than 35%, less than 34%, less than 33%, less than 32%, less than 31%, less than 30%, less than 29%, less than 28%, less than 27%, less than 26%, less than 25%, less than 24%, less than 23%, less than 22%, less than 21%, less than 20%, less than 19%, less than 18%, less than 17%, less than 16%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, or less than 10%. Contrary to the findings of U.S. Patent No. 9,655,693, where an elastomer is used as the outer layer, applicants have discovered that a lower compression set is more effective, rather than a higher compression set.

[0054]

[0059] In one particular aspect of Embodiment #1, the sheet has an overall thickness of about 250 microns to about 2,000 microns.

[0055]

[0060] In certain aspects of Embodiment #1, the combined thickness of the A and C layers is from about 25 microns to about 1,000 microns, 50 microns to 750 microns, 100 to 750 microns, 250 microns to 750 microns, or 250 microns to about 600 microns.

[0056]

[0061] In certain aspects of Embodiment #1, the thermoformable sheet has a flexural modulus of about 100 MPa to about 2,000 MPa, about 250 MPa to about 2,000 MPa, about 500 MPa to 1,500 MPa, about 750 MPa to about 2,000 MPa, or about 750 microns to about 1,500 MPa.

[0057]

[0062] In certain aspects of Embodiment #1, the A and C layers have a Tg between about 80°C and 150°C, and the B layer has a Tg or melting point between about 180°C and 220°C and a heat of fusion of about 5 Joules / g to about 20 Joules / g, or 5 Joules / g to 15 Joules / g.

[0058]

[0063] In certain aspects of Embodiment #1, the peel strength of Layer A is greater than about 50 N / inch, greater than about 60 N / inch, or greater than about 70 N / inch.

[0059]

[0064] In certain aspects of embodiment #1, the A and C layers each have a thickness of 25 microns to about 1000 microns, 50 microns to 750 microns, 100 to 750 microns, 125 to 300 microns, 250 microns to 750 microns, or 250 microns to about 600 microns, and may have a total thickness of about 250 microns to about 600 microns, 200 microns to 300 microns, or 150 microns to 250 microns, and have a Tg between 95°C and 150°C, a stiffness of 1000 MPa to 2,500 MPa, and and a thickness of about 200 microns to about 1,000 microns or 200 to 500 microns, for example, 200 microns, 225 microns, 250 microns, 300 microns, 350 microns, 375 microns, 400 microns, 425 microns, 450 microns, 475 microns, 500 microns, 550 microns, 600 microns, 650 microns, 700 microns, 750 microns, 800 microns, 850 microns, 900 microns, 950 microns, or 1,000 microns. The elastomer B layer has a hardness of about D35 to about D65, for example, D35, D40, D45, D50, D55, D60, or D65, and a hardness of less than about 35%, less than 30%, less than 25%, less than 20%, or less than 10%, i.e., less than 35%, less than 34%, less than 33%, less than 32%, less than 31%, less than 30%, less than 29%, less than 28%, less than 27%, less than 26%, less than 25%, less than 24%, less than 23%, less than 22%, less than 21%, less than 20%, less than 19%, less than 18%, less than 17%, less than 16%, less than 15%, or less than 14%. , has a compression set at 25°C for 22 hours of less than 13%, less than 12%, less than 11%, or less than 10%, is made of polyether or polyester polyurethane, Layer A has an interlayer peel strength of greater than about 50 N / inch, greater than about 60 N / inch, or greater than about 70 N / inch, and the polymer sheet has a flexural modulus of about 750 MPa to about 1,500 MPa; about 100 MPa to about 2,000 MPa; about 250 MPa to about 2,000 MPa; about 500 MPa to 1,500 MPa; or about 750 MPa to about 2,000 MPa.

[0060]

[0065] In some aspects of Embodiment #1, thin layers of additional polymers (adhesion layers) may be present to improve adhesion of polymer layers that do not naturally adhere to each other; for example, a layer of maleic anhydride grafted polypropylene may be used to increase adhesion between a polypropylene A layer and a polyester or polyamide B layer.

[0061]

[0066] In some embodiments (referred to herein as Embodiment #2), the A and C layers of the sheet or device are 1 cm 2 Less than 100N per 1cm 2 Less than 50N per 1cm 2 Less than 25N per 1cm 2 They can reversibly move relative to each other (eg, translationally) by about 0.05 mm to about 0.1 mm with a force of less than 10 N per one.

[0062]

[0067] In some aspects of Embodiment #2, the A and C layers of the sheet or device have a total thickness of about 500 microns to 1,000 microns and are 1 cm 2 Less than 100N per 1cm 2 Less than 50N per 1cm 2 Less than 25N per 1cm 2 They can reversibly move relative to each other by a distance of 0.05 mm to 0.1 mm with a force of less than 10 N each.

[0063]

[0068] In some aspects of Embodiment #2, the B Layer material has a compression set at 25°C for 22 hours of less than about 35%, less than 30%, less than 25%, less than 20%, less than 10%, i.e., less than 35%, less than 34%, less than 33%, less than 32%, less than 31%, less than 30%, less than 29%, less than 28%, less than 27%, less than 26%, less than 25%, less than 24%, less than 23%, less than 22%, less than 21%, less than 20%, less than 19%, less than 18%, less than 17%, less than 16%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, or less than 10%.

[0064]

[0069] In some embodiments (referred to herein as Embodiment #3), one or more of the A and C layers comprises a microcrystalline polyamide composed of 50-100, 50-90, 50-80, 50-70, 60-90, 60-80, or 70-90 mole % C6-C14 aliphatic diacid moieties and about 50-100, 50-90, 50-80, 50-70, 60-90, 60-80, or 70-90 mole % 4,4'-methylene-bis(cyclohexylamine) (CAS [1761-71-3]), and has a glass transition temperature between about 100°C and 180°C, and a heat of fusion of less than 20 J / g, e.g., 5 Joules / g to about 20 Joules / g, or 5 Joules / g to 15 Joules / g. See, for example, German Patent Application Publication No. 4310970 (Embodiment 3). In some aspects of Embodiment #3, the combined thickness of the A and C layers is less than about 500 microns, less than about 400 microns, or less than about 300 microns.

[0065]

[0070] In some embodiments (referred to herein as embodiment #4), a dental appliance conforming to one or more teeth includes at least two outer layers A and C and an intermediate layer B, wherein the A and C layers have a resistance greater than about 1,000 MPa, e.g., 1,000 MPa to 1,500 MPa; 1,100 MPa to 1,600 MPa; 1,200 MPa to 1,700 MPa; 1,300 MPa to 1,800 MPa; 1,400 MPa to 1,900 MPa; 1,500 MPa to 2,000 MPa; 1,100 MPa; 1,200 MPa; 1,300 MPa; 1,400 MPa; 1,500 MPa; 1,600 MPa; 1,700 MPa; 1,800 MPa; 1,900 MPa; 1,500 MPa to 2,000 MPa; 1,100 MPa; 1,200 MPa; 1,300 MPa; 1,400 MPa; 1,500 MPa; 1,600 MPa; , 700 MPa; 1,800 MPa, 1,900 MPa; 2,000 MPa; up to 2,500 MPa, and in certain embodiments greater than 1,500 MPa, and a glass transition temperature and / or melting point of about 80°C to 180°C; 90°C to 170°C; 100°C to 160°C; 110°C to 150°C; 120°C to 150°C; 130°C to 170°C; 140°C to 180°C; 80°C; 90°C; 100°C; 110°C; 120°C; 130°C; 140°C; 150°C; 160°C; 170°C; or 180°C, and in certain embodiments 80 to 150°C or 95 to 150°C. In such an embodiment, the intermediate B layer is at least comprised of an elastomer having one or more of a modulus of elasticity of about 50 MPa to 500 MPa; 70 MPa to 450 MPa; 80 MPa to 400 MPa; 100 MPa to 350 MPa; 150 MPa to 300 MPa; 200 MPa to 400 MPa; 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, up to 250 MPa, and a glass transition temperature or melting point of about 90°C to about 220°C.

[0066]

[0071] In some aspects of Embodiment #4, the A and C layers have a combined thickness of about 25 microns to about 600 microns, e.g., 100 microns, 125 microns, 150 microns, 175 microns, 200 microns, 225 microns, 250 microns, 300 microns, 350 microns, 400 microns, 450 microns, 500 microns, 550 microns, or 600 microns, and a Tg of 80°C to 180°C; 90°C to 170°C; 100°C to 160°C; 110°C to 150°C; 120°C to 150°C; 130°C to 170°C; 140°C to 180°C; 80°C; 90°C; 100°C; 110°C; 120°C; 130°C; 140°C; 150°C; 160°C; 170°C; or 1 and 80°C, e.g., 80-150°C or 95-150°C, and composed of a rigid copolyester or polyurethane having a modulus of elasticity of greater than 1,000 MPa, e.g., 1,000 MPA to 1,500 MPA; 1,100 MPA to 1,600 MPA; 1,200 MPA to 1,700 MPA; 1,300 MPA to 1,800 MPA; 1,400 MPA to 1,900 MPA; 1,500 MPA to 2,000 MPA; 1,100 MPA; 1,200 MPA; 1,300 MPA; 1,400 MPA; 1,500 MPA; 1,600 MPA; 1,700 MPA; 1,800 MPA, 1,900 MPA; 2,000 MPA; or up to 2,500 MPA.

[0067]

[0072] In some aspects of Embodiment #4, the elastomeric B layer has a thickness of about 200 microns to about 1,000 microns, e.g., 100 microns, 125 microns, 150 microns, 175 microns, 200 microns, 225 microns, 250 microns, 300 microns, 350 microns, 375 microns, 400 microns, 425 microns, 450 microns, 475 microns, 500 microns, 550 microns, 600 microns, 650 microns, 700 microns, 750 microns, 800 microns, 850 microns, 900 microns, 950 microns, or 1,000 microns, and a hardness of about D35 to about D65, e.g., D35, D40, D45, D50, D55, D60, or D65, and a hardness of less than about 35%, less than 34%, less than 33%, less than 32%, less than 31%. a polyether or polyester polyether having a compression set at 25°C for 22 hours of less than 30%, less than 29%, less than 28%, less than 27%, less than 26%, less than 25%, less than 24%, less than 23%, less than 22%, less than 21%, less than 20%, less than 19%, less than 18%, less than 17%, less than 16%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, or less than 10%; It is made of urethane, and layer A has an interlayer peel strength of greater than about 50 N / inch, greater than about 55 N / inch, greater than about 60 N, or greater than about 70 N, and the polymer sheet has a flexural modulus of about 100 MPa to about 2,000 MPa, about 250 MPa to about 2,000 MPa, about 500 MPa to 1,500 MPa, or about 750 MPa to about 2,000 MPa, for example, about 750 microns to about 1,500 MPa.

[0068]

[0073] In some aspects of embodiment #4, the A and C layers are 2 Less than 100N per 1cm 2 Less than 50N per 1cm 2 Less than 25N per 1cm 2 With a force of less than 10N, it has a lateral restoring force of 0.05mm to 0.1mm.

[0069]

[0074] In some embodiments (referred to herein as Embodiment #5), the dental appliance is formed by thermoforming a multi-layer sheet over a dental model, the thermoforming being carried out at a temperature at least above the glass transition temperature and / or melting point of the outer layer and at least below the higher glass transition temperature and / or melting point of the inner layer elastomeric material.

[0070]

[0075] In one embodiment of Embodiment #5, the dental device is made by thermoforming a multilayer sheet having at least A and C layers having a Tg of about 80°C-180°C; 90°C-170°C; 100°C-160°C; 110°C-150°C; 120°C-150°C; 130°C-170°C; 140°C-180°C; 80°C; 90°C; 100°C; 110°C; 120°C; 130°C; 140°C; 150°C; 160°C; 170°C; or 180°C, wherein the B layer has a glass transition temperature and / or melting point of about 90°C-220°C, e.g., 180°C-220°C, and a heat of fusion of about 5 J / g to about 20 J / g, e.g., about 5 J / g to about 20 Joules / g, or 5 Joules / g to 15 Joules / g.

[0071]

[0076] In one aspect of embodiment #5, the A and C layers comprise a copolyester or polyurethane having a Tg of about 90°C to about 120°C, the B layer is composed of a polyurethane having a modulus of about 50 MPa to 500 MPa and a glass transition temperature and / or melting point of about 170°C to about 220°C, and thermoforming is carried out at a temperature between about 150°C and 200°C.

[0072]

[0077] It should be understood that elements of more than one embodiment may be combined.

[0073]

[0078] In some embodiments, a thermoformable polymer sheet is comprised of at least two outer layers, A and C, and an intermediate layer, B, wherein one or more of the A and C layers comprises a microcrystalline polyamide comprised of 50-100 mole % C6-C14 aliphatic diacid moieties and about 50-100 mole % 4,4'-methylene-bis(cyclohexylamine) (CAS [1761-71-3]), and has a glass transition of about 100°C to 180°C, a heat of fusion of less than 20 J / g, and a light transmittance of greater than 80%.

[0074]

[0079] In some embodiments, a thermoformable polymer sheet is comprised of at least two outer layers, A and C, and an intermediate layer, B, wherein one or more of the A and C layers comprises a copolyester comprised of a dicarboxylic acid component comprising 70 mol % to 100 mol % of terephthalic acid residues and a diol component, the diol component comprising: (i) 0 to 95 mol % ethylene glycol; (ii) 5 mol % to 50 mol % of 2,2,4,4-tetramethyl-1,3-cyclobutanediol residues; (ii) 50 mol % to 95 mol % of 1,4-cyclohexanedimethanol residues; and (iii) 0 to 1 % of a polyol having three or more hydroxyl groups, wherein the sum of the mol % of the diol residues (i), (ii), and (iii) amounts to 100 mol %, and the copolyester exhibits a glass transition temperature, Tg, of 80°C to 150°C. In some aspects of this embodiment, the thermoformable polymer sheet includes an intermediate B layer comprising an aromatic polyether polyurethane having a Shore hardness of about A90 to D55 and a compression set of less than 35%, and the interlayer peel strength between the A and C layers and the B layer is greater than 50 N per 2.5 cm.

[0075]

[0080] In some embodiments, the dental appliance conforming to one or more teeth is made from the microcrystalline polyamide or copolyester described above.

[0076]

[0081] In one embodiment, a polymer sheet construction is provided that is comprised of at least two rigid or hard outer layers A and C, at least two soft inner layers B and B', and at least one rigid or hard inner layer D. The A, C, and D layers may be the same or different. The B and B' layers may be the same or different.

[0077]

[0082] In some embodiments, stiff or rigid layers A, C, and D individually comprise a thermoplastic polymer having a modulus of elasticity between about 1,000 MPa and 2,500 MPa.

[0078]

[0083] In some embodiments, stiff or rigid layers A, C, and D individually comprise a thermoplastic polymer having a glass transition temperature and / or melting point between about 80°C and 180°C.

[0079]

[0084] In some embodiments, the stiff or rigid layers A, C, and D comprise one or more of polyesters, copolyesters, polycarbonates, polyester-polycarbonate blends, polyurethanes, polyamides, polyolefins, microcrystalline polyamides, copolyesters comprising terephthalic acid and / or isophthalic acid, cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, copolyesters comprising terephthalic acid and / or isophthalic acid, ethylene glycol, and diethylene glycol, aromatic polyurethanes based on MDI and hexanediol, aromatic polyurethanes with aliphatic diols, polypropylene or copolymers of propylene, ethylene, and C4-C8 α-olefins, cycloaliphatic polyamides, (meth)acrylic polymers, vinyl polymers such as polyvinyl chloride, and fluoropolymers.

[0080]

[0085] In some embodiments, inner layers B and B' individually comprise one or more of polyurethane elastomers, aromatic polyether polyurethanes, polyolefin elastomers, polyester elastomers, styrenic elastomers, anhydride-functionalized styrenic elastomers, polyamide elastomers, polyether polyamides (polypropylene oxide-based or polytetramethylene oxide-based), cyclic olefin elastomers, acrylic elastomers, aromatic or aliphatic polyethers, polyester polyurethanes, siloxane elastomers, polyether elastomers, olefin copolymers, acrylic elastomers, and fluoroelastomers.

[0081]

[0086] In some embodiments, inner layers B and B' comprise a polymeric material having a hardness of about A60 to D85, about A70 to D75, about A80 to D65, or about D40 to D70.

[0082]

[0087] In some embodiments, inner layers B and B' comprise a polymeric material having a glass transition temperature and / or melting point between about 90°C and 220°C.

[0083]

[0088] In some embodiments, inner layers B and B' comprise a polymeric material having a modulus of elasticity between about 50 MPa and 500 MPa.

[0084]

[0089] In some embodiments, the sheet has an overall thickness of about 250 microns to about 2,000 microns, about 300 microns to about 1,900 microns, about 400 microns to about 1,750 microns, or about 500 microns to about 1500 microns.

[0085]

[0090] In some embodiments, stiff or rigid layers A, C, and D have a combined thickness of about 100 microns to about 750 microns, about 150 microns to about 600 microns, or about 200 microns to about 500 microns.

[0086]

[0091] In some embodiments, the stiff or rigid layers A and C have a combined thickness of about 50 microns to about 250 microns, about 40 microns to about 150 microns, or about 25 microns to about 50 microns.

[0087]

[0092] In some embodiments, soft layers B and B' have a combined thickness of about 200 microns to about 1,000 microns, about 250 microns to about 900 microns, or about 150 microns to about 750 microns.

[0088]

[0093] In some embodiments, a dental appliance conforming to one or more teeth is made from a polymer sheet composition including at least layers A, B, B', C, and D as described herein. In some embodiments, the order of these layers may be different.

[0089]

[0094] In some embodiments, the dental appliance has a total thickness of about 250 microns to 2,000 microns and a flexural modulus of about 500 MPa to 1,500 MPa.

[0090]

[0095] In some embodiments, the dental appliance is configured to position the teeth sequentially.

[0091]

[0096] In some embodiments, the dental appliance exhibits improved tear resistance compared to the A, C, or D layers alone.

[0092]

[0097] In some embodiments, the dental appliance exhibits improved resistance to environmental stresses compared to the A, C, or D layers alone.

[0093]

[0098] When one hard outer layer is thinner than another, thermoforming the thin hard layer to the model can improve contact and fit to the model, increasing comfort, fit, and mechanical force coupling.

[0094]

[0099] In some embodiments, a tooth-contacting hard layer within the appliance has a thickness that is less than another hard layer.

[0095]

[0100] In some embodiments, the thickness of the hard tooth-contacting layer can be less than about 250 microns, or even as low as about 50 microns.

[0096]

[0101] In one embodiment, the polymer sheet composition is composed of three or more layers, and one outermost hard layer (A1) has a different thickness from another outermost hard layer (A). In some embodiments, one outermost hard layer (A1) is thinner than another outermost hard layer (A).

[0097]

[0102] In some embodiments, the outermost hard layer (A1) has a thickness of about 25 to about 250 microns, about 25 to about 150 microns, or about 25 to about 100 microns.

[0098]

[0103] In some embodiments, the ratio of the thickness of the outermost hard layer (A1) to the thickness of the second outermost hard layer (A) is less than about 0.9, less than 0.85, less than 0.8, less than 0.75, less than 0.7, less than 0.6, less than 0.5, less than 0.35, less than 0.25, or less than 0.15, for example, from about 0.9 to about 0.2, from about 0.8 to about 0.3, or from about 0.5 to about 0.15.

[0099]

[0104] In some embodiments, the thickness of the polymer sheet composition including the outermost hard layer (A), the inner soft layer (B), and the outermost hard layer (A1) is about 500 microns to about 2,000 microns, or about 625 microns to about 1,000 microns. In some aspects of this embodiment, the ratio of the thickness of the outermost hard layer (A1) to the thickness of the second outermost hard layer (A) is about 0.9 to about 0.2, about 0.8 to about 0.3, or about 0.75 to about 0.25.

[0100]

[0105] [Table 1]

[0101]

[0106] In some embodiments, the flexural modulus of the polymer sheet composition including the outermost hard layer (A), the inner soft layer (B), and the outermost hard layer (A1) is about 100 MPa to about 2,000 MPa, about 250 MPa to about 2,000 MPa, about 500 MPa to 1,500 MPa, about 750 MPa to about 2,000 MPa, or about 750 microns to about 1,500 MPa.

[0102]

[0107] In some embodiments, the flexural modulus of the outermost hard layer (A) and the outermost hard layer (A1) is about 1,000 MPa to 2,500 MPa, about 1,000 MPa to about 1,500 MPa, about 1,100 MPa to about 1,600 MPa; about 1,200 MPa to about 1,700 MPa; about 1,300 MPa to about 1,800 MPa; or about 1,400 MPa. about 1,900 MPA, about 1,500 MPA to about 2,000 MPA, about 1,100 MPA, about 1,200 MPA, about 1,300 MPA, about 1,400 MPA, about 1,500 MPA, about 1,600 MPA, about 1,700 MPA, about 1,800 MPA, about 1,900 MPA, about 2,000 MPA, or up to 2,500 MPA. The flexural modulus of the outermost hard layer (A) and the flexural modulus of the outermost hard layer (A1) may be the same or different.

[0103]

[0108] In some embodiments, the Shore hardness of the inner soft layer B is about A60 to about D85, about A65 to about D80, about A70 to about D75, about A85 to about D70, about A90 to about D65; or about D35 to about D65.

[0104]

[0109] In some embodiments, the glass transition temperature or melting point of the outermost hard layer (A) and the outermost hard layer (A1) is about 80°C to 180°C; 90°C to 170°C; 100°C to 160°C; 110°C to 150°C; 120°C to 150°C; 130°C to 170°C; 140°C to 180°C; 80°C; 90°C; 100°C; 110°C; 120°C; 130°C; 140°C; 150°C; 160°C; 170°C; or 180°C; 95°C to 150°C.

[0105]

[0110] In some embodiments, the glass transition temperature or melting point of the inner soft layer B is from about 90°C to about 220°C; 100°C to about 200°C; 120°C to about 180°C; 140°C to 220°C; or 160°C to about 220°C.

[0106]

[0111] In some embodiments, the compression set of the inner soft layer B after 22 hours at 25°C is less than about 35%, less than 30%, less than 25%, less than 20%, or less than 10%, i.e., less than 35%, less than 34%, less than 33%, less than 32%, less than 31%, less than 30%, less than 29%, less than 28%, less than 27%, less than 26%, less than 25%, less than 24%, less than 23%, less than 22%, less than 21%, less than 20%, less than 19%, less than 18%, less than 17%, less than 16%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, or less than 10%.

[0107]

[0112] In some embodiments, the outermost hard layer (A) and the outermost hard layer (A1) are made of one or more of copolyester, polycarbonate, polyester-polycarbonate blend, polyurethane, polyamide, or polyolefin. In some embodiments, the outermost hard layer (A) and the outermost hard layer (A1) are made of the same material. In some embodiments, the outermost hard layer (A) and the outermost hard layer (A1) are made of different materials.

[0108]

[0113] In some embodiments, the intermediate B layer is comprised of one or more of polyurethane elastomers, polyolefin elastomers, polyester elastomers, styrenic elastomers, polyamide elastomers, cyclic olefin elastomers, acrylic elastomers, aromatic or aliphatic polyethers, and polyester polyurethanes.

[0109] (How to build)

[0114] Multi-layer sheets may be made by several means, including but not limited to hot or cold lamination, adhesive lamination, melt lamination, coextrusion, multi-layer extrusion, or other known methods. The sheet may be completely made before being formed into an orthodontic appliance, or the appliance may be produced using a series of individual thermoforming steps that create the multiple layers.

[0110]

[0115] Thermoforming of the sheets to produce test specimens or dental appliances may be performed using procedures commonly used in the industry, such as a "Biostar" pressure former available from Great Lakes Orthodontics. Alternatively, thermoforming may be performed using a roll-fed thermoformer, vacuum former, or other known thermoforming techniques. Thermoforming may be performed using different conditions, configurations, or patterns to vary the stretch ratio and thickness of the molded article. Multilayer devices may be fabricated by one or more 3D printing processes, or by sequential dip coating, spray coating, powder coating, or similar processes known to produce films, sheets, and 3D structures.

[0111]

[0116] The temperature of the sheet during thermoforming can be measured using an infrared thermometer or a surface thermocouple.

[0112] (usefulness)

[0117] The sheets and materials described herein have utility as thermoformable materials with excellent dimensional stability, impact cushioning, and resilience. The sheets can be converted into several types of oral appliances, for example, for tooth movement, for use as sports mouthguards with improved impact resistance, and for use as orthodontic retainers. Compared to currently available materials and appliances, the improved properties of the materials and appliances described herein include, but are not limited to, greater flexibility, resulting in improved end-user comfort, improved tooth movement results, greater stain and stress crack resistance, and superior appearance, all of which promote more consistent wear by the subject.

[0113] (Test Method)

[0118] Tensile properties were measured using an Instron Universal Materials Tester, following ASTM D638 procedures unless otherwise noted. Color and clarity were measured using a BYK Gardner Spin colorimeter.

[0114]

[0119] Impact resistance was measured using a Gardner impact tester. Tear strength was measured using a materials testing machine at a speed of 250 mm per minute.

[0115]

[0120] The stress relaxation of the samples in water at 37° C. was measured by the method described in US Pat. No. 8,716,425.

[0116]

[0121] Stain resistance was measured by exposing the test specimens to a staining medium such as mustard or coffee at 37°C for 24 hours and measuring the color on a white tile before and after exposure.

[0117]

[0122] The translational recovery force was measured by constructing a three-layer structure (or polymer sheet) as shown in Figures 1 and 2. The sample was displaced from 0 to 0.5 mm, and the force was measured in N / cm 2 reported in.

[0118]

[0123] Peel strength is measured at a rate of 50 mm / min and may be reported as Newtons (N) per inch or per 2.54 cm (N). Details can be found in test method ASTM D3164.

[0119]

[0124] Thermal testing to determine glass transition temperature, melting point and freezing point was measured using a differential scanning calorimeter at heating and cooling rates of 10° C. per minute unless otherwise indicated.

[0120]

[0125] Environmental stress crack resistance can be determined by clamping a sheet sample around a cylindrical mandrel, subjecting the outer surface to a specific strain, e.g., 3% or 5%, and exposing the sample to a defined environment, e.g., a saliva-mimicking solution, mouthwash, or other solution of interest, for a defined period of time. The response can be measured semi-quantitatively by visual observation of the type and number of cracks, or quantitatively by subsequent measurement of mechanical properties such as tear strength.

[0121] Materials and Methods

[0126] Materials of Construction. Numerous commercially available materials can be utilized in producing the sheets and devices described herein. Table 1 provides a list of exemplary materials for use in the A or C components. Table 2 provides a list of exemplary materials for use in the B component. Similar or related materials can be obtained from other manufacturers or produced by known methods. [Table 2] [Table 3]

[0122]

[0127] Further suitable materials for the A, B, or C layers can include compatible or incompatible blends, such as blends of two or more copolyesters, blends of polypropylene, polyethylene, and ethylene propylene elastomers, fluoropolymers such as polyvinylidene fluoride or copolymers thereof, styrene acrylonitrile resin, acrylonitrile styrene butadiene resin (ABS), polyurethanes containing polycarbonate soft blocks, siloxane soft blocks, silicone elastomers such as Geniomer™, siloxane urea copolymers, and cyclic olefin copolymers and elastomers. [Example]

[0123]

[0128] The present disclosure is further illustrated by the following examples, which are provided for illustrative purposes only and should not be construed in any way as limiting the scope or content of the present disclosure.

[0124] [Example 1]

[0129] A series of single-layer and multi-layer sheets with a nominal total thickness of 0.76 mm were prepared as shown in Table 3. Test samples 1-4 were prepared by compression molding and heat laminating individual films or by extrusion lamination. Prior art material examples P1, P2, and P3 were prepared by compression molding and optionally heat laminating films.

[0125]

[0130] Press lamination was performed at 200-220° C., extrusion lamination was performed using a polyurethane melt temperature of 210-240° C., and coextrusion was performed using a polyester melt temperature of 240-260° C. and a polyurethane melt temperature of 210-240° C. The time, temperature, and pressure conditions were varied to maximize structural (polymer sheet) quality, thickness, and adhesion.

[0126]

[0131] Mechanical properties, optical properties, stress relaxation, and shape recovery were measured to compare the suitability of the resulting structures (polymer sheets). [Table 4]

[0127]

[0132] Prior art material P1 is a commercially available thermoformable aligner material supplied by Bay Materials, LLC, Fremont, Calif. Prior art material P2 is a polyester manufactured by Eastman Chemical having a glass transition temperature of approximately 90°C and sold under the trade name Eastar 6763. Prior art material P3 is described in U.S. Pat. No. 9,655,693. Test samples 1-4 are multilayer laminates (as described herein) that demonstrate improved stress relaxation properties, increased tear strength, and excellent stain resistance.

[0128]

[0133] Compared to prior art materials, Test Samples 1-4 exhibited several unexpected properties. Comparing Test Samples 1-4 and prior art materials P1 and P2, Test Samples 1-4 exhibit substantially lower initial force in stress relaxation tests (believed to translate into better user comfort), but surprisingly, maintain force over a longer period of time. This contradicts the teachings of U.S. Pat. No. 9,655,693, which teaches that an elastomeric outer layer is necessary to protect the inner rigid layer. The ability of the multilayer sheet to maintain adequate force levels over time under harsh conditions is readily apparent in Figure 4. Samples A and B in Figure 4 are single-layer sheets, while Samples 1 and 2 are multilayer sheets as described in Table 3.

[0129]

[0134] Tear strength is an important property of dental appliances. Materials with low tear strength are less durable and may crack at locations of concentrated stress. Comparing the tear strength of prior art materials P1, P2, and P3 with test samples 1-4 shows that such multilayer structures (or polymer sheets) including an elastomer B layer have significantly higher tear strength than comparable single layer structures or prior art multilayer structures.

[0130]

[0135] To further investigate the effect of construction on tear strength, another laminate (#5) was made with 0.25 mm A and C layers composed of Eastar 6763, a copolyester available from Eastman Chemical with a Tg of 86°C, and a 0.2 mm B layer of a Shore 50D urethane elastomer, for a total thickness of 0.7 mm. The tear strength of this sample was compared with that of prior art materials P1, P2, and P3. Sample #5, despite having a similar ratio of polyurethane and polyester, exhibited a tear strength of 120 N, more than 200% of the value for prior art material P3.

[0131] [Example 2 (Measurement of translational force)]

[0136] A three-layer sheet was prepared as described in Example 1 for Test Material 2. A 2.54 cm x 1 cm piece of the sheet was glued between two 2.54 cm wide pieces of rigid polyester, creating a 0.5 cm overlap ("Multi-Layer Sample A2"). A control test sample was prepared using the same size and thickness of Polyester A (prior art) between two pieces of rigid polyester. The displacement / force response was measured at a rate of 0.04 MPa / min, and the results are reported in Table 4. The multi-layer structure allows the two outer layers (or two shells) of the device to accommodate greater elastic movement at moderate forces than prior art structures. [Table 5]

[0132]

[0137] Orthodontic devices were made using the materials and methods described herein and compared to devices of the same shape and thickness made from Zendura A and Essix Plus. The disclosed devices were substantially more resilient and more comfortable to wear. Because the inner and outer shells can deform independently of each other, the devices can accommodate larger offsets between the actual teeth and the appliances without causing unnecessary discomfort to the patient, and can exert a nearly constant force over time to precisely move teeth.

[0133] [Example 3]

[0138] A 0.25 mm thick clear polypropylene film, designated BFI257, supplied by Blue Ridge Films (Petersburg, Virginia), was laminated to both sides of a 0.25 mm thick film made from Kraton GF (maleic acid-modified SEBS, available from Kraton Polymers) in a hot press at 180°F, cooled, and cut into 125 mm circles. The modulus of elasticity of polypropylene is reported at 1,100 MPa. SEBS elastomer has a reported hardness of 71A and a modulus of elasticity of 25 MPa. The multilayer film exhibited low staining and could be thermoformed onto dental models to produce retainers with excellent elastic recovery properties.

[0134] [Example 4]

[0139] Because dental appliances are known to be easily damaged by alcohol and / or surfactants, the durability of sheet materials in the presence of mouthwash was investigated. Test sheets with a thickness of 0.75 mm were prepared, measuring 2.54 cm wide and 12 cm long. Prior art materials P1, P2, and P3, as well as multilayer sheet (test material) #2, were wound around a mandrel of sufficient diameter to induce a 5% strain. The samples were immersed in the mouthwash and maintained at 37°C. This environment is known to promote environmental stress cracking, inducing strain that causes the material to assume a hoop shape instead of flat. After 24 hours, the samples were rinsed with deionized water, and the amount of recovery was measured immediately at ambient temperature and again after 24 and 48 hours. The samples were then viewed under a microscope to determine the amount of stress cracking on the side that had been under tension. Samples that returned completely flat were scored as having 100% recovery. Stress cracking was rated from 1 to 5, with 5 being no visible cracking and 1 being severe cracking. The shape recovery of the samples is shown in Table 5. The multilayer sheet (#2) recovered more rapidly and completely than the prior art materials P1, P2, and P3. [Table 6]

[0135] [Example 5]

[0140] Three laminates were prepared as in Example 1, Sample 2, and designated Samples #6, #7, and #8. Sample #6 was extrusion laminated using untreated polyester film at a roll temperature of 40°C, Sample #7 was extrusion laminated using corona-treated polyester film at a roll temperature of 60°C, and Sample #8 was extrusion laminated using corona-treated film at a roll temperature of 80°C. Corona treatment is commonly used to activate the film surface and increase its polarity. A control sample of Polyester A was designated Sample #9. The mechanical properties and environmental stress crack resistance of the three samples are shown in Table 6. [Table 7]

[0136]

[0141] The dramatic improvement in environmental resistance observed for Samples #7 and #8 compared to Samples #6 and #9 is unexpected and unexpected. In each case, the materials exposed to the environment are chemically identical and under equal amounts of stress. While not wishing to be bound by theory, Applicants hypothesize that some concentrated strain-induced stress present in the outer polyester layer may be transferred to the elastomeric material, with force transfer being more efficient in materials with higher interlayer bond strength. However, Applicants are not aware of any precedent for this result.

[0137]

[0142] It is well known that thermoplastic amorphous copolyesters (PETG and PCTG) have poor environmental stress crack resistance and tend to degrade rapidly when used as dental appliances. U.S. Pat. No. 9,655,691 teaches that coating both sides of such copolyesters with thermoplastic polyurethane elastomers having hardnesses of about 60A to about 85D surprisingly increased the durability of dental aligners made from such materials (described as "a hard polymer layer disposed between two soft polymer layers"). Presumably, the outer material provides a physical and / or chemical protective layer. Disadvantages of such materials include poor stain resistance for polyurethane elastomers and other elastomers, and poor tear resistance for the disclosed multilayer structures.

[0138]

[0143] The present inventors have unexpectedly discovered that the stress crack resistance of amorphous polyester films, sheets, or thermoformed parts made therefrom can be dramatically improved by adhering an elastomeric material, such as polyurethane, between two layers of polyester. The resulting structure, having a soft polymer layer disposed between two hard polymer layers, has excellent chemical resistance, high transparency, and excellent stain resistance. Furthermore, the tear resistance of the multilayer structure exceeds that of either polyester or elastomer alone. The inventors have also discovered that the improved properties require high adhesive strength between the layers, and that materials with poorly adhering layers exhibit poor crack resistance and tear strength.

[0139]

[0144] It is known in the art that rigid polyurethane sheets have very good stress crack resistance by themselves. Unexpectedly, Applicants observed that a three-layer ABA structure having a rigid polyurethane A (exterior) layer and an elastomeric B (interior) layer with excellent adhesion had poorer environmental stress crack resistance than rigid polyurethane alone, with the opposite effect observed with the polyester exterior layer.

[0140] [Example 6]

[0145] Tests were conducted to investigate the effect of heat treatment and thermoforming conditions on the performance of devices made from the sheets. Three sheets (2A, 2B, and 2C) of Test Material 2 (three-layer, polyester, polyurethane, polyester) were dried at 60°C under vacuum for 12 hours. The samples were placed in moisture-proof bags and subjected to the heat treatment and thermoforming conditions shown in Table 7. Sample 2A was maintained at 22°C, while samples 2B and 2C were annealed at 100°C for 24 hours. The samples were then thermoformed to produce plaques using different thermoforming temperatures. Samples 2A and 2B were thermoformed at temperatures below the upper limit of the polyurethane's melting range, while 2C was thermoformed at a temperature above the polyurethane's melting range. [Table 8]

[0141]

[0146] Test specimens were cut from the thermoformed samples, analyzed by DSC, and subjected to stress relaxation tests in water at 37°C. DSC showed that the melting point and heat of fusion of the samples increased by annealing at 100°C, and that thermoforming reduced the heat of fusion and melting range. However, samples thermoformed below the upper limit of the polyurethane's melting range retained higher crystallinity and performed better in stress relaxation tests. The conditions for Sample 2B in Table 7 were used to fabricate dental appliances.

[0142] [Example 7]

[0147] Further constructions can be made by selecting appropriate layer materials with modulus and elasticity differences as shown in Table 8. [Table 9]

[0143] [Example 8]

[0148] A 2-mm-thick sheet was fabricated by laminating two outer films of 0.250-mm-thick polypropylene homopolymer (Blue Ridge Films BFI3270, 1,200 MPa modulus) and an inner layer of 1.50-mm-thick ethylene propylene microcrystalline elastomer (Noito PN2070, Mitsui Chemicals, 150 MPa modulus). The sheet was cut into 125-mm-diameter disks and thermoformed and shaped over a cast of an individual's maxillary teeth to create a highly impact-resistant sports mouthguard. Surprisingly, the mouthguard provided better impact protection and was more comfortable than a standard device fabricated from a 4-mm-thick ethylene vinyl acetate copolymer sold by Dreve under the trademark Drufosoft.

[0144] [Example 9]

[0149] The aligners were fabricated by thermoforming a three-layer sheet onto a dental model. The two outer layers were composed of a rigid polyurethane with a Tg of approximately 120°C, and the inner B layer was composed of an aromatic ether polyurethane with a Shore A of 85, having a hard block melting point of 160-195°C and a heat of fusion of 8 J / gram. The devices were annealed at 100°C, below the Tg of the outer layers, for 24 hours. No deformation was observed. Testing demonstrated that the devices were more elastic and had lower load creep than before annealing at 100°C. The improvement is believed to be due to an improved microstructure of the polyurethane elastomer.

[0145]

[0150] In a second study, multilayer and single-layer devices were compared, with Zendura A material used as the A / C or A / B / C material, respectively, in each case. The devices were annealed at 90°C for 24 hours. It was observed that the single-layer device deformed extensively, while the multilayer device maintained its shape. It is hypothesized that in the multilayer device, the elastomer maintains a stabilizing force on the stiffer material during annealing, preventing undesired dimensional changes.

Claims

1. 1. A polymer sheet construction comprising at least two outer layers A and C and an elastomeric inner layer B, wherein one or both of said outer layers A and C individually comprise a thermoplastic polymer having a flexural modulus of about 1,000 MPa to 2,500 MPa, and said inner layer B is composed of an elastomeric material having a hardness of about A60 to D85.

2. 10. The polymer sheet construction of claim 1, wherein the A, B, and C layers of the polymer sheet construction have a combined thickness of 250 microns to 2,000 microns and a flexural modulus of 500 MPa to 1,500 MPa.

3. 3. The polymer sheet construction of claim 2, wherein the outer layers A and C comprise one or more of polyesters, copolyesters, polycarbonates, polyester-polycarbonate blends, polyurethanes, polyamides, polyolefins, microcrystalline polyamides, copolyesters of terephthalic acid, cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, copolyesters of terephthalic acid, ethylene glycol, and diethylene glycol, aromatic polyurethanes based on MDI and hexanediol, aromatic polyurethanes with aliphatic diols, copolymers of propylene, ethylene, and C4 to C8 α-olefins, cycloaliphatic polyamides, (meth)acrylic polymers, vinyl polymers such as polyvinyl chloride, and fluoropolymers.

4. 3. The polymer sheet construction of claim 2, wherein the inner layer B comprises one or more of polyurethane elastomers, aromatic polyether polyurethanes, polyolefin elastomers, polyester elastomers, styrenic elastomers, polyamide elastomers, polyether polyamides (polypropylene oxide based or polytetramethylene oxide based), cyclic olefin elastomers, acrylic elastomers, aromatic or aliphatic polyethers, polyester polyurethanes, siloxane elastomers, polyether elastomers, polyolefin elastomers, olefin copolymers, and fluoroelastomers.

5. 4. The polymer sheet construction of claim 3, wherein one or more of the outer layers A and C comprises a microcrystalline polyamide having a heat of fusion less than 20 J / g and a light transmission greater than 80%.

6. 5. The polymer sheet construction of claim 4, wherein said inner layer B comprises an anhydride-functionalized styrenic elastomer having a hardness of about A60 to D50.

7. one or more of the A and C layers (a) a dicarboxylic acid component, and (b) Diol component 3. The polymer sheet composition of claim 2, comprising a copolyester having:

8. one or more of the A and C layers (a) a diisocyanate, and (b) a diol component containing one or more of hexanediol and cyclohexanedimethanol; 3. The polymer sheet composition of claim 2, comprising a polyurethane consisting of: wherein the polyurethane has a glass transition temperature, Tg, of from about 85°C to about 150°C.

9. 3. The polymer sheet construction of claim 2, wherein said inner layer B comprises an aromatic polyether polyurethane having a compression set of less than 35%.

10. 3. The polymer sheet construction of claim 2, wherein the inner layer B comprises an aromatic polyether polyurethane, and the interlayer peel strength between the A and C layers and the B layer exceeds 50 N per 2.5 cm.

11. 1. A polymer sheet construction comprising at least two rigid or hard outer layers A and C, at least two soft inner layers B and B', and at least one rigid or hard inner layer D, wherein the rigid or hard layers A, C, and D individually comprise a thermoplastic polymer having a modulus of elasticity of about 1,000 MPa to 2,500 MPa, and the soft inner layers B and B' individually comprise an elastomeric material having a hardness of about A60 to D85.

12. 12. The polymer sheet construction of claim 11, wherein the polymer sheet construction has a total thickness of 250 microns to 2,000 microns and a flexural modulus of 500 MPa to 1,500 MPa.

13. 13. The polymer sheet construction of claim 12, wherein the stiff or rigid layers A, C, and D individually comprise one or more of polyesters, copolyesters, polycarbonates, polyester-polycarbonate blends, polyurethanes, polyamides, polyolefins, microcrystalline polyamides, copolyesters of terephthalic acid and / or isophthalic acid, cyclohexanedimethanol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, copolyesters of terephthalic acid and / or isophthalic acid, ethylene glycol, and diethylene glycol, aromatic polyurethanes based on MDI and hexanediol, aromatic polyurethanes with aliphatic diols, copolymers of propylene, ethylene, and C4 to C8 α-olefins, alicyclic polyamides, (meth)acrylic polymers, vinyl polymers such as polyvinyl chloride, and fluoropolymers.

14. 13. The polymer sheet construction of claim 12, wherein the soft inner layers B and B' individually comprise one or more of polyurethane elastomers, aromatic polyether polyurethanes, polyolefin elastomers, polyester elastomers, styrenic elastomers, anhydride-functionalized styrenic elastomers, polyamide elastomers, polyether polyamides (polypropylene oxide-based or polytetramethylene oxide-based), cyclic olefin elastomers, acrylic elastomers, aromatic or aliphatic polyethers, polyester polyurethanes, siloxane elastomers, polyether elastomers, polyolefin elastomers, olefin copolymers, acrylic elastomers, and fluoroelastomers.

15. 15. The polymer sheet construction of claim 14, wherein one or more of the soft inner layers B and B' comprises an anhydride-functionalized styrenic elastomer having a hardness of about A60 to D50.

16. 15. The polymer sheet construction of claim 14, wherein said stiff or rigid layers A, C, and D have a combined thickness of from about 100 microns to about 750 microns.

17. 15. The polymer sheet construction of claim 14, wherein said flexible layers B and B' have a combined thickness of from about 150 microns to about 1,000 microns.

18. A dental appliance conforming to one or more teeth comprising the polymer sheet composition of claim 12.

19. A polymer sheet construction comprising three or more layers A, A1, and B, wherein the outermost layers A and A1 have different thicknesses and each comprise a thermoplastic polymer having a flexural modulus of about 1,000 MPa to 2,500 MPa, and the inner layer B is composed of an elastomeric material having a hardness of about A60 to D85.

20. 20. The polymer sheet construction of claim 19, wherein the A, A1, and B layers of the polymer sheet construction have a combined thickness of about 500 microns to 2,000 microns.

21. 21. The polymer sheet construction of claim 20, wherein the outermost layer A1 has a thickness of about 25 to about 250 microns.

22. 21. The polymer sheet construction of claim 20, wherein the ratio of the thickness of the outermost layer A1 to the thickness of the outermost layer A is from about 0.9 to about 0.

2.

23. 21. The polymer sheet construction of claim 20, wherein the outermost layer A and the outermost layer A1 are composed of one or more of polyester, copolyester, polycarbonate, polyester-polycarbonate blend, polyurethane, polyamide, and polyolefin.

24. 21. The dental device of claim 20, wherein the outer layers A and A1 comprise the same material.

25. 21. The dental device of claim 20, wherein the outer layers A and A2 comprise different materials.

26. 21. The polymer sheet composition of claim 20, wherein the intermediate layer B is composed of one or more of polyurethane elastomers, polyolefin elastomers, polyester elastomers, styrene-based elastomers, polyamide elastomers, cyclic olefin elastomers, acrylic elastomers, aromatic or aliphatic polyethers, and polyester polyurethanes.

27. 21. A dental appliance conforming to one or more teeth comprising the polymer sheet composition of claim 20.

28. 30. The dental appliance of claim 27, wherein the dental appliance exhibits improved tear resistance compared to the A, C, or D layer alone.

29. 30. The dental appliance of claim 27, wherein the dental appliance exhibits improved environmental stress resistance compared to the A, C, or D layer alone.

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