Young adult left Class III subdivision with wide buccal corridors and a missing mandibular first molar treated with MARPE and unilateral molar protraction using fixed appliances and reinforced anchorage: A case report

A missing mandibular first molar in a young adult may be restored prosthetically or managed by orthodontic protraction, but long-distance unilateral space closure is biomechanically demanding. This case report describes an 18-year-old woman with a mandibular left first molar lost to caries, mesial tipping of the second molar, a developing third molar, mandibular midline deviation, a left Class III subdivision, wide buccal corridors, and lingually inclined mandibular buccal segments without posterior crossbite. The patient selected orthodontic protraction of the mandibular left second and third molars. Miniscrew-assisted rapid palatal expansion was used to improve maxillary transverse dimension and buccal corridors, while the mandibular arch was coordinated by dentoalveolar expansion. The mandibular incisor brackets were inverted to provide positive torque and reinforce anterior anchorage. The second molar was derotated with buccal fixed-appliance mechanics and sectional lingual brackets and protracted using a unilateral Class II elastic. The developing third molar was surgically exposed and incorporated into the arch. Active treatment lasted 21 months. The edentulous space was completely closed, bilateral Class I canine and molar relationships and coincident dental midlines were achieved, and normal overjet and overbite were established. Buccal corridors were clinically reduced without posterior crossbite. Panoramic imaging showed satisfactory root parallelism, maintained alveolar bone levels, and no severe root resorption. Positive anterior torque, together with asymmetric Class II elastic mechanics, contributed to reinforced anterior anchorage and extensive unilateral molar protraction while maintaining controlled mandibular incisor position.