Commonly referred to as the Bionator I, this appliance is designed to open a closed bite in Class I and Class II malocclusions and to correct Class II skeletal relationships. The lower anterior teeth are covered with acrylic to act as a bite plane, to hold the bite open, and to prevent anterior super-eruption. The posterior acrylic is carefully ground-in to permit controlled eruption of the molars and bicuspids until the closed bite is corrected. Opening the midline expansion screw aids in posterior eruption by relieving tight interproximal contacts -- also allowing for a limited amount of arch development (when necessary).