Twin Block

The Standard Twin Block is a removable functional appliance with upper and lower bite blocks set at a 70° angle to posture the mandible forward, reducing overjet and correcting Class II malocclusion. As the upper block is selectively trimmed, the lower first molars erupt, helping address deep overbite. Treatment typically lasts 7–9 months, ensuring a stable bite and preventing dual occlusion. Effective in both mixed and permanent dentition, the appliance relies on proper retention and minimum block thickness (5–6 mm) to maintain interlock and guide eruption. An expansion screw may be added for transverse development. Once functional correction is achieved, a Phase 2 "Support Appliance" is recommended to maintain results.