A method of making an orthodontic appliance for repositioning teeth or as a retainer according to the present invention includes preparing a dental model for the fabrication of an orthodontic aligner, placing the dental model on a thermo-forming machine, thermoforming a soft flexible material onto the dental model, the soft flexible material having adhesive material covered by release liner, on the side facing away from the portion of the dental model to which it is thermoformed, trimming off excess soft flexible material from the dental model, peeling off the release liner to expose the adhesive material, applying a predetermined length of flexible tension strain material to the adhesive side of the soft flexible material, thermoforming a harder, more rigid material over the soft flexible material which has the flexible tension strain material attached, and trimming the excess hard material from the dental model. In a preferred form of the method, the soft flexible material has a pressure sensitive film on the patients palate side, covered by a release liner. The method further includes the steps of removing the finished orthodontic appliance from the dental model, removing the remaining release liner from the soft flexible material, and placing the dental appliance into a patients mouth.
