The use of medial axis transformation to examine evolutionary changes in mandibular shape

Traditional osteometric studies serve to combine both size and shape together, so whether contrasts in mandibular form during recent times reflect predominantly size, or shape, changes remains controversial. In order to examine specific changes in morphological shape, mandibular outline form was subjected to medial axis transformation. This technique was performed on museum mandibles derived from Romano-British, Anglo-saxon and modern (19th century) samples. The lengths of the derived component medial axes, and angles subtended by pairs of medial axes, were subsequently subjected to univariate and multivariate statistical analysis. The data indicated that there were contrasts in mandibular shape between the 3 samples, predominantly reflecting a more vertical ramus, closer approximation between both coronoid and condylar processes with a more prominent mental region in the modern compared with the two older samples. Although the causes of such mandibular changes remain obscure, this study provided objective data on mandibular shape differences in recent times.