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Article: Volume 14 Number 4 Page 195 - October 2021

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  Orth Update 2021; 14: 195-199

Orthodontics:  Unusual case report: ectopic canines, resorption and hypodontia in monozygotic twins

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Abstract: Ectopic maxillary canines are present in 1–3% of the population and may consequentially cause root resorption in 66.7% of lateral incisors. Ectopic canines are thought to be of polygenic and multifactorial origin, although Msx1 and Pax9 are suggested genetic candidates. Hypodontia is present in up to 11.3% of the population and is associated with mutations in Msx1, Pax9 and Axin2. Previous studies have separately demonstrated similarities in hypodontia and ectopic canines in monozygotic twins. This report discusses similarities clinically and using cone beam computed tomography in 14-year-old male genetically identical twins. While hypodontia and ectopic canines have both previously been linked with a genetic origin, this report suggests there is also a genetic predisposition to root resorption. The association between hypodontia and ectopic canines is usually associated with the guidance theory and hypodontia of upper lateral incisors; however, this report highlights the occurrence of ectopic canines and hypodontia of premolar teeth. It also presents the sequelae of severe root resorption associated with ectopic canines and idiopathically in areas of non-impacted canines

Clinical relevance: The role of the general dental practitioner in early recognition of hypodontia and ectopic canines and the importance of referral for an orthodontic opinion is emphasized.

Author notes: Dayna Rosenthal, BDS (Hons), Dental Core Trainee in Oral and Maxillofacial Surgery, Royal Free London NHS Foundation Trust. Paroo Mistry, BDS, MFDS, RCS (Eng), MSc, MOrth RCS (Eng), FDS (Orth) RCS (Eng), Consultant Orthodontist, Royal Free London NHS Foundation Trust. Email:

Objective: The reader should understand and consider the role of genetics in hypodontia, ectopic canines and root resorption, as well as the importance of early recognition of ectopic canines and referral.