Journal of the Anthropological Society of Nippon

The dental arches of the siblings apparently resemble one another in their form and measurement values. How about the dimension of tooth crown? This question stimulated the present authors to look into their relation. The materials used in this study are the plaster casts of upper and lower jaws obtained from the inhabitants in Kamiina District, Nagano Prefecture. On these plaster casts mesiodistal and buccolingual crown diameters were measured, and rectangle (mesiodistal diameter×buccolingual diameter) was calculated.

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This paper has discussed about the quantitative development of the third digital and metacarpal bones in Japanese. The materials are right hand radiographs of 28 boys and 24 girls, collected longitudinally from 12 to 16 years of age.
Growth of the length : In boys, the growth of digital bones becomes slower about at and after 14 or 15 years. This retardation appears earlier in the more distal phalanx. The total length of digit continues to growth untill the oldest age in this series, 16 years, decreasing the growth rate after 14 years. The metacarpal bone increase distinctly the length till 15 years and retards after then.
In girls, the retardation of growth in digital bones appears about from 13 years and is later in the middle phalanx the other phalanges. Comparing the mean values of both sexes, the girls are generally longer than the boys at 12 years, both sexes are nearly equal each other at 13 years, and after then the girls are shorter than the boys with age.
Growth of the breadth: As for both the digital and metacarpal bones, a constant increase is noticeable in the boy but in the girls, and the boys are wider than the girls over these years of age. The sex difference becomes larger with age.
Growth of the breadth of compact substance and bone cavity in the metacrapal: The growth curve of compact substance is almost parallel with that of metacarpal itself, while no increase is noticed on the breadth of bone cavity through these ages. In boys, as for the proportion of the breadth of compact substance with that of bone cavity, the compact substance is smaller than the bone cavity at 12 years, but the difference of them becomes decreasing with age and both the breadthes are almost identical each other at 16 years. While, in girls, both breadthes .are nearly equal each other at 12 years, but the compact substance exceeds little by little the bone cavity with age by the growth of the breadth of compact substance. The breadth of compact substance and bone cavity seems to change the proportion of relative size at an age point, that is, 16 years in the boys and 12 or 13 years in the girls.

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