Alterations in the size, morphology and number of teeth are among the many inherited disorders that have been reported in individuals with Down syndrome. By contrast, third molar agenesis and tooth transposition have been largely ignored and the prevalence of canine impaction has not been reported. The intention of this study was to quantify the occurrence of these anomalies in a group of individuals with Down syndrome, using standardized records, which included a clinical examination, dental casts, and a panoramic radiograph. The results show a notably high prevalence of third molar agenesis (74% of individuals older than 14 years), canine impaction (15%), and maxillary canine/first premolar transposition (15%), compared to published figures from random population samples. These anomalies should not be seen as separate, independent entities, but as associated phenomena. The slow rate of cell growth and a consequent reduced cell number that characterize this syndrome may be responsible for the underdevelopment of the upper jaw, the delayed dental development, the reduction in teeth number and size, and the altered path of canine eruption. No explanation, other than genetics, is immediately available to explain why the maxillary canine/first premolar transposition should represent another phenotypic expression of this trisomy.

The custom of canine bud removal has detrimental consequences on children’s general health and dental care. The objective of this study was to assess whether the prevalence of missing primary canines and dental defects in offspring of emigrants from Ethiopia is greater than in offspring of native Israeli parents of similar socioeconomic class. 477 children of Ethiopian descent and 317 offspring of native Israeli parents, from 21 nursery schools and kindergartens, underwent dental examinations aimed to determine the presence or absence of primary canines and of developmental enamel defects on adjacent teeth to the primary canines. For purposes of analysis, children were classified into two age groups: younger (ages 18–48 months) and older (ages 49–82 months). Canines were present in more Israeli than Ethiopian younger children, 87.5% vs. 42.3%, p=0.0001; and in more Israeli than Ethiopian older children, 92.6% vs. 40.4%, p=0.0001. More dental defects were detected in Ethiopian than in Israeli younger children, 32% vs. 3.9%, p=0.0001; and in more Ethiopian than Israeli older children, 31.2% vs. 5.8%, p=0.0001. The prevalence of missing primary canines and dental defects was greater among offspring of parents who had emigrated from Ethiopia 15–20 years earlier than among offspring of native Israeli parents living in the same low socioeconomic neighborhoods.