Geographic distribution of dentists in Japan: 1980-2000

Objective: In the late 1950s and 1960s, Japan recognized that it had a shortage of dentists and that they were unevenly distributed. To solve these problems, four national and eight private dental schools were established, leading to a significant increase in the number of dental students in the 1970s and 1980s. The purpose of this study was to investigate the effects of this increased supply on the geographic distribution of dentists in Japan. Method: We determined the number of dentists and the population in each of Japan's 3,252 municipalities. The ratio of the number of dentists to the population of an area was assessed using Gini coefficients calculated from Lorenz curves. Results: From 1980 to 2000, the average number of dentists per 100,000 persons in Japan increased from 44 to 70. The Lorenz curve plotted for 1980-1990 appeared as a nearly diagonal line, with the Gini coefficient decreasing from 0.310 to 0.263. The Gini coefficient in the year 2000 was 0.255, indicating only a slight improvement in 10 years from 1990 to 2000. Conclusions: The results suggest that the geographical distribution of dentists in Japan is influenced by municipalities' population size. While the number of dentists in municipalities with populations of less than 5,000 increased during the years from 1980 to 2000, 25.9 percent of these municipalities still had no dentists at the end of this period. This is an important issue that warrants prompt corrective action.