A longitudinal study of changes in tooth size and dental arch dimensions from the mixed to permanent dentitions in Australian aboriginals.

Abstract

Objectives: (i) To investigate tooth size and dental arch dimensional changes from the mixed to permanent dentitions in Australian Aboriginals using a three-dimensional imaging system. (ii) To investigate the extent to which tooth size and dental arch dimensions contribute to dental crowding. Design: Longitudinal retrospective study. Participants/setting: Serial dental models of 49 Australian Aboriginals (28 males and 21 females) from the Yuendumu Study at ages 8, 12 and 15 years (or within a 1 year range). Main Outcome Measures: All the dental models were digitised using a 3D scanner (Optix 400S) and analysed with a 3D modeling software (Rhinoceros ® 3D 4.0). Study variables included mesiodistal tooth widths, arch widths, arch lengths, arch depths and tooth size arch length discrepancy (TSALD). Subjects at age 15 years were then subdivided into crowded (TSALD≤-1mm) and non-crowded (TSALD>-1mm) groups for analysis. Results: The changes in tooth size and dental arch dimensions from the mixed dentition to permanent dentitions are summarized as follows: 1) There was a mean reduction in mesiodistal widths of teeth ranging from 0.07mm to 0.24mm. 2) The intercanine and intermolar widths increased in males and females from the age of 8 to 15 years. 3) Arch length and arch depth showed a progressive reduction between 8 and 15 years of age. 4) Sexual dimorphism was observed whereby males had larger tooth size and dental arch dimensions than females. In crowded subjects, tooth 15 in males and teeth 31, 36 and 42 in females were statistically significantly larger than the non-crowded subjects. The lower intercanine width in males and upper intercanine width in females were significantly smaller in crowded subjects. Conclusions: The findings of the present study showed significant changes in the dentition from the age of 8 to 15 years. No clear distinction could be made in the present study as to whether tooth size or dental arch dimensions play a greater role in contributing to dental crowding.