Comparisons of tooth sizes, dental arch dimensions, tooth wear, and dental crowding in Amazonian indigenous people.

INRODUCTION: Our objective was to assess tooth wear, arch dimensions, tooth sizes, and dental crowding in 4 remote indigenous villages on the Xingu River in Brazil. These populations have similar patterns of dietary habits and practice exclusive breast-feeding, whereas studies in human genetics show large intertribal genetic distances and low intratribal variations.

METHODS: Dental casts of 107 subjects in the permanent dentition were evaluated. Tooth wear, arch dimensions, mesiodistal tooth widths, and the irregularity index of the incisors were obtained and compared using analysis of variance or the Kruskal-Wallis test (P <0.05).

RESULTS: Tooth wear and tooth size in the mandible were similar among villages. Three groups were discriminated. The first group included the Xicrin-Kayapó and Arara-Laranjal villages, since no significant difference was found between them. Larger tooth sizes and arch dimensions (P <0.001) were found in both jaws in the Assurini village compared with the Xicrin-Kayapó and Arara-Laranjal villages; this resulted in similar dental crowding index values in these groups. The Arara-Iriri village, where a high coefficient of inbreeding had been reported, showed intermediate arch dimensions, with the mesiodistal tooth widths similar to those in the Xicrin-Kayapó and Arara-Laranjal villages. This scenario resulted in a group with the lowest irregularity index, close to 0.

CONCLUSIONS: These Amazonian indigenous villagers, who have been genetically studied previously, showed large intergroup genetic variations and similar patterns of tooth wear. Thus, we suggest from the findings in this study that the etiology of dental crowding among the inhabitants of the Xingu River area is predominantly associated with variations in the dimensions of dental arches, related to genetic influences.