Distribution of dentists in the Greater Tokyo Area, Japan.

Japan is considered to have an overabundance of dentists; however, there are scarce data on regional inequalities in the ratio of dentists to patients. We examined these inequalities in Japan's Greater Tokyo Area - otherwise known as the Kanto region, and the world's most populous metropolitan area - by subdividing it into small- and medium-sized medical care zones. We calculated the number of dentists per 100,000 population using the 2012 Survey of Physicians, Dentists, and Pharmacists for the three medical district tiers [primary medical care zones: municipalities (cities, towns, villages and special wards); secondary medical care zones: multiple adjacent municipalities; and tertiary care zones: prefectures]. We also estimated the influence of having a dental school in the district or an adjacent district on the number of dentists. The number of dentists per 100,000 population was 79.2 across the whole Kanto region; the range for each type of medical care zone was as follows: 65.3-126.4 at the tertiary level; 38.0-929.6 at the secondary level; and 0-3,087.6 at the primary level. The median Gini coefficient among tertiary medical care zones was 0.16 (range 0.11-0.36). The median number of dentists per 100,000 population was 273.8 in primary medical care zones that had a dental school, 79.9 in adjacent zones, and 59.6 in other zones. We identified significant inequalities in the number of dentists among the medical care zones, and the presence of a dental school had a major influence on this number.

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