Improved Twin-Block Appliance With Mini-Screws For Mandibular Retrusion

This innovative approach combines a modified Twin-block (TB) appliance with mini-screws to treat skeletal Class II mandibular retrusion, optimizing vertical control and facial aesthetics. An 11-year-old girl presented with Class II Division 1 malocclusion, mandibular retrusion, and a convex facial profile. Her chief complaint was upper anterior tooth protrusion with a gummy smile (>5 mm). Pre-treatment evaluation revealed 6 mm overjet, deep overbite, and average mandibular plane angle (FH-MP). Cephalometric analysis confirmed a Class II skeletal pattern with growth acceleration (CVS2/CVS3). Treatment: Phase 1: A TB appliance with heightened incisor caps was used to promote mandibular protrusion and control vertical positioning of maxillary incisors and molars. Phase 2: Posterior resin-bonded blocks replaced the TB to stabilize the mandible. Mini-screws were placed between the mandibular incisors to intrude anterior teeth, addressing the gummy smile while rotating the occlusal plane counterclockwise. After leveling, posterior blocks were removed to enhance counterclockwise mandibular rotation, optimizing the facial profile. Traditional TB appliances promote sagittal mandibular growth but often cause unwanted clockwise rotation, leading to posterior displacement of the chin. The modified approach—using heightened incisor caps in Phase 1, mini-screws for protraction in Phase 2, and resin pads to avoid posterior extrusion—addresses these limitations, enhancing vertical and sagittal mandibular growth modification. For children with average-angle mandibular retrusion, this approach optimizes treatment outcomes, improves vertical control and facial aesthetics, and enhances patient satisfaction.