Twin Block Functional Therapy

The Twin Block is a removable, two-piece orthodontic appliance designed to correct Class II Division 1 malocclusion by posturing the lower jaw forward, typically worn full-time to leverage growth during the pubertal spurt. Through its interlocking inclined bite blocks, it encourages approximately 6 mm of mandibular growth while modestly restraining maxillary development-known as the "headgear effect"-and achieving significant overjet reduction (~5-6 mm) alongside improved molar relationships. Skeletal changes include enhanced SNB and reduced ANB, while dental effects involve upper molar distalization (~1 mm), lower molar advancement (~4-5 mm), and modest lower incisor proclination (~2-3°). Patients also typically experience improved facial convexity, chin projection, and airway dimensions, contributing to functional and aesthetic benefits. Treatment is most effective when started around the peak adolescent growth phase and averages 10-14 months of active correction followed by several months of retention and possible transition to fixed braces-a protocol with compliance rates hindered by 25-35% dropout or appliance breakage.The Twin Block is an evidence-based, patient-friendly alt.