Formable sheets for medical applications and methods of manufacture thereof

1. An appliance for use in an oral cavity, wherein the appliance comprises a stain resistant polymeric shell that has cavities designed to receive teeth, and wherein the shell comprises a thermoplastic polymeric mixture that comprises a polycarbonate and a cycloaliphatic polyester, wherein the polycarbonate is present in an amount of about 50 wt % to about 90 wt % and wherein the weight percents are based on a total weight of a mixture that comprises polycarbonate and cycloaliphatic polyester.

2. The appliance of claim 1 , wherein the polymeric mixture further comprises an additional thermoplastic polymer.

3. The appliance of claim 2 , wherein the thermoplastic polymer is a polyolefin, polyamide, polyarylate, polyimide, polyacetal, polyacrylic, polystyrene, polyamideimide, polyacrylate, polymethacrylate, polyurethane, polyarylsulfone, polyethersulfone, polyarylene sulfide, polysulfone, polyetherimide, polytetrafluoroethylene, polyetherketone, polyether etherketone, polyarylene ether, polydimethylsiloxane, liquid crystalline polymer, polybenzoxazole, polyoxadiazole, polybenzothiazinophenothiazine, polybenzothiazole, polypyrazinoquinoxaline, polypyromellitimide, polyquinoxaline, polybenzimidazole, polyoxindole, polyoxoisoindoline, polydioxoisoindoline, polytriazine, polypyridazine, polypiperazine, polypyridine, polypiperidine, polytriazole, polypyrazole, polypyrrolidine, polycarborane, polyoxabicyclononane, polydibenzofuran, polyphthalide, polyacetal, polyanhydride, polyvinyl ether, polyvinyl thioether, polyvinyl alcohol, polyvinyl ketone, polyvinyl halide, polyvinyl nitrile, polyvinyl ester, polysulfonate, polythioester, polysulfonamide, polyurea, polyphosphazene, polysilazane, or a combination comprising at least one of the foregoing thermoplastic polymers.

4. The appliance of claim 1 , wherein the cycloaliphatic polyester has recurring units of formula (VIII)

5. The appliance of claim 1 , wherein the cycloaliphatic polyester is polyethelene terephthalate, polybutylene terephthalate, poly(1,4-cyclohexane-dimethanol-1,4-cyclohexanedicarboxylate), poly(trimethylene terephthalate), poly(cyclohexanedimethanol-co-ethylene terephthalate), poly(ethylene naphthalate), poly(butylene naphthalate), or a combination comprising at least one of the foregoing cycloaliphatic polyesters.

6. The appliance of claim 1 , wherein the polycarbonate has a number average molecular weight of about 500 to about 1,000,000 grams/mole and the cycloaliphatic polyester has a molecular weight of about 500 to about 1,000,000 grams/mole.

7. The appliance of claim 6 , wherein polycarbonate has a number average molecular weight of about 9,000 to about 38,000 grams/mole and the cycloaliphatic polyester has a molecular weight of about 40,000 g/mole to about 55,000 grams/mole.

8. The appliance of claim 1 , wherein the polymeric mixture has an elastic modulus of greater than or equal to about 1,500 Newton/square millimeter when measured in tensile deformation at a rate of 2 millimeters/minute at room temperature, prior to use in an oral cavity.

9. The appliance of claim 1 , wherein the polymeric mixture has a percent stress retention of greater than or equal to about 40%, prior to use in an oral cavity.

10. The appliance of claim 1 , wherein the polymeric mixture has a stain resistance Delta F of less than or equal to about 2, prior to use in the oral cavity.

11. The appliance of claim 1 , wherein the polymeric mixture has a yellowness index of less than or equal to about 1 and a percent haziness of less than or equal to about 0.5, prior to use in an oral cavity.

12. The appliance of claim 1 , wherein the polymeric mixture has a percent stress retention of greater than or equal to about 40%, an elastic modulus of greater than or equal to about 1,500 Newton/square millimeter when measured in tensile deformation at a rate of 2 millimeters/minute at room temperature, a stain resistance Delta E of less than or equal to about 2, a yellowness index of less than or equal to about 1 and a percent haziness of less than or equal to about 0.5, prior to use in an oral cavity.

13. The appliance of claim 1 , wherein the polymeric shell has a thickness of about 125 to about 1,250 micrometers.

14. The appliance of claim 1 , wherein the polymeric shell comprises two or more layers.

15. The appliance of claim 14 , wherein one layer comprises an elastomer.

16. The appliance of claim 1 , wherein the appliance is part of a system of appliances designed to reposition teeth.

17. A method for maintaining or repositioning teeth in the oral cavity comprising:

placing an appliance in a patient's mouth, wherein the appliance comprises a stain resistant polymeric shell having cavities designed to receive teeth, and wherein the appliance comprises a polymeric mixture, that comprises a polycarbonate and a cycloaliphatic polyester; wherein the polycarbonte is present in an amount of about 50 wt % to about 90 wt %; and wherein the weight percents are based on a total weight of the polymeric mixture.

18. The method of claim 17 , wherein additional appliances may be placed in a patient's mouth, and wherein a tooth position defined by a single cavity in each successive appliance differs from that defined in a prior appliance by an amount of no more than 2 millimeters.