Changes in alveolar prognathism and anterior teeth protrusion in Japan

Abstract

Temporal changes in alveolar prognathism and anterior protrusion of the anterior teeth were examined using adult Japanese skeletal materials from the following periods: Jomon, Yayoi, protohistoric Kofun, early medieval Kamakura, late medieval Muromachi, early modern Edo, and Recent. These samples are mainly from the Kanto region except for the Yayoi which derives from the northern Kyushu and Yamaguchi regions and the Recent whose geological origin is unknown. The results indicated the existence of a subtle but nearly monotonous increase in alveolar prognathism through time, which is different from the previous interpretation. In contrast, the maxillary anterior teeth showed drastic changes toward a more protrusive condition from the Jomon to Kofun periods. The changes of this trait after the Yayoi period are small but it tends to become stronger through time. Causative factors of changes in anterior teeth protrusion were discussed.