An orthodontic appliance made by a thermal forming process is provided. The thermal forming process can include heating a thermoformable material using a plurality of independently controllable heat sources. The plurality of independently controllable heat sources can produce at least one overlapping heating zone. The thermal forming process can further include monitoring one or more temperatures from a plurality of temperature sensing elements operably coupled to different areas of the thermoformable material. The thermal forming process can further include adjusting power of one or more of the plurality of independently controllable heat sources based on the one or more monitored temperatures such that each of the different areas of the thermoformable material reaches a respective desired temperature. The thermal forming process can further include disposing the heated thermoformable material over at least a portion of a mold to form the orthodontic appliance.

A forming device has a machine frame and a forming apparatus disposed on the machine frame. At least one heating chamber is disposed on the machine frame. A heatable support is received in the at least one heating chamber in a position of use for preheating semi-finished products and can be moved in a movement direction out of the at least one heating chamber into a removal position for removal of preheated semi-finished products from the support. In the removal position, the support is at least partially located adjacent to the machine frame and enables access to preheated semi-finished products. At least one heating device is associated with the at least one heating chamber and has one or more convection heating devices that discharge at least one directable heating air flow.

A heat-shrinkable polyester film that has (1) a hot-water heat shrinkage of 40% or more in a main shrinkage direction of the film when immersed in hot water of 98 C. for 10 seconds; (2) a planar orientation coefficient of 0.035-0.070; (3) ethylene terephthalate as a main constituent component and 6-25 mol % diethylene glycol (DEG) constituent in 100 mol % of polyhydric alcohol in all the polyester resin constituting the film; (4) a maximum shrinkage stress of 2-17 MPa in the main shrinkage direction of the film when measured in hot air of 90 C.; and (5) a tensile elongation at break of 20% or more in a direction orthogonal to the main shrinkage direction after the film is aged in an atmosphere with an atmospheric temperature of 40 C. and a relative humidity of 85% for 28 days.

Methods of forming a dental appliance. The methods may include partially curing a prepolymer mixture into a semi-solid polymer material having a first shape that is a sheet. The semi-solid polymer material may be placed over a dentition mold, wherein the semi-solid polymer material may take on a second shape corresponding to a shell having one or more cavities for receiving one or more teeth. The semi-solid polymer material may be fully cured by exposure to energy until the semi-solid polymer material thermosets in the second shape.

Methods of forming a dental appliance. The methods may include partially curing a prepolymer mixture into a semi-solid polymer material having a first shape. The first shape may include a channel in accordance with a dental arch of a patient. A positive dentition mold corresponding to the patient may be used to modify the first shape of the partially cured prepolymer mixture to form a shell having cavities shaped to receive teeth of the patient. The semi-solid polymer material may be fully cured by exposing the semi-solid polymer material to energy until the semi-solid polymer material sets.