Some effects on the teeth, dental arches and jows in man-made environment

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 10671954
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 矯正・小児・社会系歯学
• Research Institution: Nihon University
• Principal Investigator: ABE Misao Nihon University Dental school at Matsudo, Orthodontics, Research Assistant, 松戸歯学部, 助手 (70130416)
• Project Period (FY): 1998 – 2000
• Keywords: Macaca fuskata yakui / Roentgenographic cephalometry / Dietary consistency

Research Abstract

The purpose of this study was to investigate the influence on jaw, dental arch and tooth size of the change in habitat and diet ecology over multiple generations of Yakushima macaques. The materials used were the skulls of adult female Yakushima macaques. They had been reared at the Japan Monkey Center (JMC), Inuyama Japan. The sample set consisted of 1st generation animals captured on the island of Yakushima and their 2nd to 4th generation offspring born at JMC.Examination using lateral and frontal cephalographs of these skulls were performed and liner and angular measurements on these films were made. Teeth and primate spaces were measured by dental caliper. Dental arches were measured by dental caliper and model measuring instrument. Measurements of each generations were statistically compared with that of the 1st generation using the t-test and principal components analysis.
The results were showed a reduction in morphology of jaw bones which reduced in size over several generations from the 1st generation over proceeding generations. An especially remarkable reduction of the front part of face was noted. A reduction in morphology of dental archs which reduced in size over several generations from the 1st generation. The shape of lower dental arch tended to become narrowed. The ratio of upper 2nd molar to upper lateral incisor and lower 2nd molar to lower canine were seemed to have reduced.
On Yakushima, the wild population's diet consists of fruits, leaves, seeds, flowers, insects and mushrooms (sic. Agetsuma, 1995). At JMC, the macaques were fed sweet potatoes, apples, chrysalides, wheat, fruits and peanuts. It seems that these morphological changes are mainly dependent on the change of diet which is softened under captivity compared to the food eaten in their natural environment.