Multilayer polymer sheets

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

providing a multilayer sheet comprising three polymer layers, the three polymer layers comprising:

a first layer consisting of a co-polyester, the co-polyester having a flexural modulus greater than 150,000 psi, an elongation at yield of greater than 4%, a tensile modulus greater than 150,000 psi, a tensile strength at yield of 4000-6500 psi, and an elongation at break of greater than 70%; and

a second layer consisting of a thermoplastic polyurethane elastomer, the thermoplastic polyurethane elastomer having an ultimate tensile strength of greater than 5000 psi, an elongation at break of greater than 200%, and a hardness of 60A to 85D; and

a third layer;

wherein the co-polyester has an elastic modulus greater than the thermoplastic polyurethane elastomer;

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 light transmission between 400 nm and 800 nm of greater than about 75%.

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

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

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

6. The method of claim 1 , wherein the multilayer sheet further comprises a fourth layer comprising a same or different thermoplastic polyurethane elastomer.

7. The method of claim 6 , wherein the first layer and the third layer are disposed between the second layer and the fourth layer.

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

9. The method of claim 1 , wherein the thermoplastic polyurethane elastomer comprises a light transmission between 400 nm and 800 nm of greater than about 75%.

10. 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%.

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