Abstract
In recent years, a number of studies have been atte mpted to explain the increase in tooth size within a considerably short period time. In Japan, although it had been previously reported that the lower first molar erupted at an earlier stage than the lower central incisor, the recent average eruption age of the lower central incisor tends to be earlier than that of the lower first molar. The purpose of the present study was to analyze the difference in tooth size and eruption pattern of permanent teeth between present and past generations in Japan. In order to do so, we compared the plaster models of permanent dentition obtained from 90 children who commuted to Kogasaki Elementary School in Chiba between 1997 and 2002 and those of 135 children who commuted to Asahi Elementary School in Shizuoka between 1975 and 1981.
At Kogasaki Elementary Sch ool, mesiodistal crown diameters of all of the permanent teeth measured were larger than those at Asahi. Furthermore, the eruption times of all of the permanent teeth observed were later in Kogasaki boys and girls than those of the boys and girls in Asahi. These Changes in tooth size seem to be related to the high level of nutrition, particularly, fats from the 1970s to 1990s. The late tooth eruption in Kogasaki seems to be due to enlargement of the tooth size. The lower first molar was the first tooth to erupt in Asahi, while the lower central incisor was the first to erupt in Kogasaki.
