Management of Unilateral Maxillary Lateral Incisor Agenesis With Canine Substitution and Mandibular Canine-Lateral Incisor Transposition: A Case Report

This clinical case report presents the orthodontic diagnosis and management of a 15-year-old female patient with two rare concurrent dental anomalies - unilateral agenesis of the maxillary left lateral incisor and complete transposition of the mandibular right canine and lateral incisor. The absence of tooth #22 was managed by canine substitution, with tooth #23 reshaped and positioned to simulate a lateral incisor, while tooth #24 was adapted to function as a canine. The mandibular transposition between teeth #42 and #43 was accepted and aligned in the transposed position, with careful biomechanical control of torque and angulation to optimize periodontal health. A comprehensive non-extraction strategy was chosen, employing fixed orthodontic appliances in both arches, followed by Essix clear retainers and fixed lingual retention for long-term stability. The treatment plan emphasized esthetic recontouring, functional adaptation, and periodontal protection. Treatment was completed in 36 months, resulting in space closure in the upper arch, a good occlusion, improved smile esthetics, and functional guidance without the need for prosthetic replacement. This case underlines the importance of early diagnosis, conservative treatment planning, and multidisciplinary coordination in managing complex anomalies. It further highlights that canine substitution, combined with the acceptance of transposition, can provide a predictable and esthetic long-term outcome when implants or restorative approaches are contraindicated or challenging.