Correlation between buccolingual inclination and wear of mandibular teeth in ancient and modern Japanese.

This study compared the correlation between the buccolingual inclination and the wear score of the mandibular teeth in Jomon (one of the ancestors of modern Japanese who lived from 5000 to 300 BC) and modern Japanese. Data were obtained from 40 modern male Japanese and 39 male Jomon skulls housed in the University Museum of the University of Tokyo and National Science Museum, Tokyo. For each specimen, three computed tomograms of coronal sections of the mandibular body were available. The second premolar, first molar and second molar of Jomon stood more vertically than those of modern Japanese. There were significant correlations between tooth wear and the buccolingual inclination of mandibular molars. When ancient and modern populations were compared, tooth wear was significantly greater and buccolingual tooth inclination was more vertical in the ancient people, who probably applied stronger masticatory forces than modern people. The results suggest that the mandibular molar orientation is more buccal and there is greater tooth wear in the first and second molars of people with strong masticatory function.