The Aetiology of Ectopic Maxillary Canine Teeth

Objectives: To elucidate the mode of inheritance of ectopic canines. Introduction: The aetiology of ectopic maxillary canines has been proposed to be genetic and is associated with incisor-premolar hypodontia as well as with various other anomalies. The Maltese population has a high prevalence of ectopic teeth, especially ectopic canines, as compared to other populations. This has been ascribed to the ‘Founder Effect' phenomenon, the population having grown from under 20,000 to over 400,000 in the past 500 years. Methods: Probands with ectopic maxillary canines were identified during routine clinical examination. The inclusion criteria were a positive family history of ectopic canines, peg incisors or missing teeth in more than one generation or with an affected first cousin. Families with a member affected by a genetic syndrome were excluded. Ectopic or missing teeth were identified by clinical examination or from existing records. Radiographic investigation was undertaken where necessary. Twenty-two families were examined, comprising a total of 98 individuals. Pedigrees were constructed and the percentages of affected first-degree relatives determined. Results: Analysis suggests autosomal dominant transmission. 12% of first degree relatives had ectopic canines, 4% had transposed canines and a further 12% exhibited hypodontia, in particular upper lateral and lower central incisors. Penetrance is highly variable between families and there seems to be no clear pattern of augmentation or attenuation of symptoms. One concordant pair of fraternal twins and one discordant pair of identical twins were included in the sample. Conclusion: The genetic aetiology of ectopic canines is supported by this study, as is its close association with incisor-premolar hypodontia. Expressivity is also highly variable with other eruption anomalies such as maxillary and mandibular canine transposition forming part of the phenotype. The discordant identical twins suggest the possibility of epigenetic factors influencing eruption of teeth.