Contours of maxillary molars studied in Australian Aboriginals

Abstract

Distances from the central pit to the perimeter of the crown of permanent upper molars were measured on standardized occlusal photographs of dental casts representing 210 male and 181 female Aboriginals from Yuendumu in the Northern Territory of Australia. In both males and females the first molar was the largest tooth but it showed least variability. Variabilities of the distances tended to be greater for radii constructed in the buccolingual direction than for the transverse mesiodistal radii. The most marked size reduction in the molar series from first to third related to the distolingual part of the crown, which was also the most variable region. Size differences between molars in the mesial contour radii were not marked. Sexual dimorphism was evident in most crown radii, being most marked for the second molar.

Shape components of the maxillary molars in Australian Aboriginals

“…The significance of differences in component scores between molars and between sexes were assessed by student's t-test. By treating the crown radii collectively rather than individually, the principal components analysis disclosed sources of common variability that were not revealed so readily by the purely descriptive univariate analysis reported previously (Yamada and Brown, 1988).…”

“…As the largest contour radii of the first molar were associated with the hypocone region (Yamada and Brown, 1988), the main influence leading to elevated scores for component I1 was hypocone reduction. The average scores increased in a gradient along the molar series, implying progressively greater hypocone reduction, but there were no significant sex differences in the average scores.…”

“…The photographic and measurement procedures and an estimate of the experimental error have been detailed previously (Yamada and Brown, 1988); they are given in brief outline here. Contour radii of the molar crowns were constructed at 10-degree intervals on tracings of photographic prints prepared at a magnification of x 4 (Fig.…”

“…It is our belief that scores derived from com onents that can be identified with observe i Y morphological variability among the molars will provide a more complete assessment of size and shape differences between teeth and between males and females. We use the same raw data reported for Australian Aboriginals previously (Yamada and Brown, 1988) in a descri tive study or size gradients and sex dimorp K ism among the maxillary molars.known, their quanti P ication requires more …”

Sexual dimorphism of cusp dimensions in human maxillary molars

“…Further investigations are warranted to clarify the relation between cusp diameters and areas. Yamada and Brown (1988) chose the central pit as the origin for measuring maxillary molars on standardized occlusal photographs. The central pit is formed by a convergence of ridges terminating in a central point at the base of the occlusal surface.…”