Canine substitution of congenitally missing maxillary lateral incisors in Class I and Class III malocclusions by using skeletal anchorage Elie William Amm, a Joanna Antoszewska-Smith, b and Jim Boley c Beirut, Lebanon, and Wroclaw, Poland, and Dallas, Tex Introduction: This prospective cohort study aimed to evaluate canine substitution supported by skeletal anchorage as a viable treatment protocol for patients with maxillary lateral incisor agenesis (MLIA) and skeletal Class I or Class III. Methods: Patients (n 5 30) who met the following criteria were recruited: (1) bilateral MLIA or unilateral MLIA with a riziform contralateral incisor with a planned extraction; (2) skeletal Class I or Class III; and (3) dentoalveolar discrepancy in the mandible \5 mm. The archwire sequence routine was administered, com- bined with a rapid palatal expander, temporary intraoral skeletal anchorage device, and intermaxillary traction with Class III elastics. The results of the cephalometric analyses, peer assessment rating indexes, and the pa- tient's smile self-evaluation using the visual analog scale were compared between initial and final treatments. Results: This study indicated that closing the space in patients with Class I or Class III malocclusion by using temporary intraoral skeletal anchorage devices in the mandible, along with Class III elastics, yielded satisfactory outcomes. Proper occlusion was established by mesialization of the maxillary teeth and correction of the inter- maxillary discrepancy, thereby yielding beneficial and significant cephalometric changes after the treatment. The soft tissue profile was maintained when it was harmonious before the treatment and improved posttreatment in patients in whom the profile was initially inharmonious. All occlusions improved, as evidenced by the peer assessment rating index. Smile esthetics were also enhanced after orthodontic treatment for all patients. Conclusions: Canine substitution may be safely offered to patients with Class I and Class III skeletal pattern and MLIA. (Am J Orthod Dentofacial Orthop 2019;156:512-21) T ooth agenesis affects 20% of the world's popula- tion, and maxillary lateral incisor agenesis (MLIA) is one of the most frequent subtypes. The preva- lence of MLIA varies from 1.15% to 5% in different pop- ulations. 1-3 It is characterized by a lack of formation of the deciduous or the permanent lateral incisors because of impaired odontogenesis. The latter process is a complex mechanism regulated by sequential and reciprocal epithelial-mesenchymal interactions, controlled by activators and inhibitors involved in several pathways. Disturbances in these signaling cas- cades can lead to abnormalities in odontogenesis and alterations in the standard number of teeth. Alves-Ferre- ira 1 reported the first evidence of the involvement of sprouty genes in MLIA susceptibility; however, it is not uncommon for MLIA to be associated with multiple den- toalveolar and skeletal malformations. The aforementioned malocclusion may develop in a unilateral MLIA (UMLIA) or bilateral MLIA (BMLIA) form. In UMLIA, the left and right sides are both affected, with no significant differences between them. The prevalence of microdontic contralateral lateral inci- sors is higher in patients with UMLIA than in patients with no MLIA. 4 Microdontia of the contralateral maxil- lary incisor occurs in approximately 38.8%-52.4% of pa- tients. 5,6 Multiple treatment options are available for congen- itally missing lateral incisors such as canine substitution, single-tooth implant, and tooth-supported restorations. a Department of Orthodontics, School of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon. b Department of Maxillofacial Orthopaedics and Orthodontics, Wroclaw Medical University, Wroclaw, Poland. c Department of Orthodontics, Baylor College of Dentistry, Dallas, Tex. All authors have completed and submitted the ICMJE Form for Disclosure of Po- tential Conflicts of Interest, and none were reported. This research did not receive any specific grant from funding agencies in the pub- lic, commercial, or not-for-profit sectors. Address correspondence to: Elie William Amm, Saint Antoine Building, GF, Selsal Street Rue 402, Jbeil, Lebanon; e-mail, elieamm@hotmail.com. Submitted, June 2018; revised and accepted, October 2018. 0889-5406/$36.00 Ó 2019 by the American Association of Orthodontists. All rights reserved. https://doi.org/10.1016/j.ajodo.2018.10.027 512 ORIGINAL ARTICLE