Methods for making dental aligners from multilayer sheets

1. A method of making a multilayer dental aligner for positioning a patient's teeth from a first arrangement toward a second arrangement, the method comprising:

providing a multilayer sheet comprising:

a first layer;

a second layer; and

a third layer;

wherein the first layer consists of a co-polyester, the co-polyester having an elongation at break of greater than 70%;

wherein the second layer consists of a thermoplastic polyurethane elastomer, the thermoplastic polyurethane elastomer having an elongation at break of greater than 200% and a hardness of about 60 A to about 85 D; and

wherein the first layer has a hardness greater than the hardness of the second layer;

providing a mold;

thermoforming the multilayer sheet over the mold to form a plurality of tooth-receiving cavities configured to receive and reposition the patient's teeth from the first arrangement toward the second arrangement; and

trimming excess material from the thermoformed multilayer sheet to form the multilayer dental aligner.

2. The method of claim 1 , wherein the co-polyester has a tensile strength at yield of between about 4000 psi and 6500 psi, and wherein the thermoplastic polyurethane elastomer has an ultimate tensile strength of greater than about 5000 psi.

3. The method of claim 1 , wherein the thermoplastic polyurethane elastomer has a flexural modulus greater than 35,000 psi.

4. The method of claim 1 , wherein the co-polyester has a flexural modulus greater than 150,000 psi.

5. The method of claim 1 , wherein the co-polyester and the thermoplastic polyurethane elastomer both have a light transmission between 400 nm and 800 nm of greater than about 75%.

6. The method of claim 1 , wherein the thermoplastic polyurethane elastomer has a compression set at about 70° C. of greater than 40% after 24 hours.

7. The method of claim 1 , wherein the first layer is coextruded with or laminated to the third layer.

8. The method of claim 1 , wherein the co-polyester has a stress relaxation at 24 hours in a wet environment of between 90-100% humidity of greater than 10%.

9. The method of claim 1 , wherein the third layer comprises a same or different co-polyester.

10. The method of claim 1 , wherein the third layer comprises a same or different thermoplastic polyurethane elastomer.

11. The method of claim 1 , wherein the third layer has a hardness from 60 A to 85 D.

12. The method of claim 1 , wherein the third layer is disposed between the first layer and the second layer.

13. The method of claim 1 , wherein the first layer is disposed adjacent to the third layer.

14. The method of claim 1 , wherein the multilayer sheet further comprises a fourth layer.

15. The method of claim 1 , wherein the first layer is thicker than the second layer.

16. A multilayer dental aligner for positioning a patient's teeth from a first arrangement toward a second arrangement, the multilayer dental aligner comprising:

a multilayer sheet comprising:

a first layer;

a second layer; and

a third layer;

wherein the first layer consists of a co-polyester, the co-polyester having an elongation at break of greater than 70%;

wherein the second layer consists of a thermoplastic polyurethane elastomer, the thermoplastic polyurethane elastomer having an elongation at break of greater than 200% and a hardness of about 60 A to about 85 D; and

wherein the first layer has a hardness greater than the hardness of the second layer; and

wherein the multilayer sheet forms a plurality of tooth-receiving cavities configured to receive and reposition the patient's teeth from the first arrangement toward the second arrangement.

17. The multilayer dental aligner of claim 16 , wherein the co-polyester has a tensile strength at yield of between about 4000 psi and 6500 psi, and wherein the thermoplastic polyurethane elastomer has an ultimate tensile strength of greater than about 5000 psi.

18. The multilayer dental aligner of claim 16 , wherein the thermoplastic polyurethane elastomer has a flexural modulus greater than 35,000 psi.

19. The multilayer dental aligner of claim 16 , wherein the co-polyester has a flexural modulus greater than 150,000 psi.

20. The multilayer dental aligner of claim 16 , wherein the co-polyester and the thermoplastic polyurethane elastomer both have a light transmission between 400 nm and 800 nm of greater than about 75%.

21. The multilayer dental aligner of claim 16 , wherein the thermoplastic polyurethane elastomer has a compression set at about 70° C. of greater than 40% after 24 hours.

22. The multilayer dental aligner of claim 16 , wherein the first layer is coextruded with or laminated to the third layer.

23. The multilayer dental aligner of claim 16 , wherein the co-polyester has a stress relaxation at 24 hours in a wet environment of between 90-100% humidity of greater than 10%.

24. The multilayer dental aligner of claim 16 , wherein the third layer comprises a same or different co-polyester.

25. The multilayer dental aligner of claim 16 , wherein the third layer comprises a same or different thermoplastic polyurethane elastomer.

26. The multilayer dental aligner of claim 16 , wherein the third layer has a hardness from 60 A to 85 D.

27. The multilayer dental aligner of claim 16 , wherein the third layer is disposed between the first layer and the second layer.

28. The multilayer dental aligner of claim 16 , wherein the first layer is disposed adjacent to the third layer.

29. The multilayer dental aligner of claim 16 , wherein the multilayer sheet further comprises a fourth layer.

30. The multilayer dental aligner of claim 16 , wherein the first layer is thicker than the second layer.