Correction of severe Class II malocclusion remains a challenge to clinical orthodontics. A typical phenotype of skeletal Class II malocclusion is characterized by prognathism of the maxilla and retruded positioning of the mandible, leading to a typical clinical manifestation of increased overjet and overbite coupled with excessive Curve of Spee. It has been shown that the reduction of severe overjet, overbite and Curve of Spee is hard to achieve by the use of fixed appliances only. The emergence of sagittally guided twin-block (SGTB) is intended to address this particular skeletal anomaly. SGTB consists of the upper component which is permanently bonded to the maxilla, and its lower removable counterpart, providing the forcible advancement of the mandible. The musculature force generated from the mandible is transferred to the maxilla which is therefore retracted backward. The lengthy period of forward positioning of the mandible also allows for the TMJ to adapt to stabilize the new positioning of the mandible. The ultimate treatment effects of SGTB include the minimization of jaw discrepancy, the restoration of Class I molar relationship, reduction of overjet and overbite, flattening of the Curve of Spee, and improvement of facial profile. This lecture will provide convincing evidence of SGTB effects based on a wealth of relevant research, extensive literature review and successfully finished cases.
Clarify the working mechanism of SGTB, i.e. retraction of the maxilla and sustainable repositioning of the mandible.
Define the indications of SGTB, i.e. skeletal Class II malocclusion with retruded mandible.
Verify the efficacy of SGTB, i.e. reduction of deep overjet, overbite and Curve of Spee combined with facial profile improvement.