Methods for making dental aligners from multilayer sheets

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.