Functional Appliances Bionator/Orthopedic Corrector The functional appliances include Activators, Frankels, Bionators, Orthopedic Correctors, Twin Block™ and Herbst® designs. The doctor can choose from various removable and fixed appliance designs. All functional appliance designs address Skeletal Class II problems by advancing the mandible forward to a corrected Class I position. Bionator I to Open click for larger view Bionator II to Close click for larger view Orthopedic Corrector click for larger view Neutral Bionator click for larger view How To Send A Case: All Functional Appliance designs require accurate working models. A construction bite should be provided to indicate the amount of mandibular advancement. Acrylic designs require a posterior opening of 2mm to 3mm to allow for proper appliance fabrication.