Regional Inequality in Dental Care Utilization in Japan: An Ecological Study Using the National Database of Health Insurance Claims

BACKGROUND: This study examined regional inequalities in dental care utilization in Japan and the association of dental care utilization with socioeconomic factors. METHODS: Using the Fourth National Database of Health Insurance Claims and Specific Health Checkups of Japan Open data, this ecological study analyzed 216 million pieces of aggregated data from April 2017 to March 2018. Nine indicators of dental care utilization were used: outpatient visits, outreach services, cavity fillings, pulpectomies, dental calculus removals, periodontal surgeries, tooth extractions, dental bridges, and dentures. Standardized claim ratios (SCRs) for these indicators were calculated for Japan's 47 prefectures, which were divided into three groups based on the number of dental clinics per population, average income per capita, and the proportion of university enrollments. Associations of the dental care utilization with dental supply and regional socioeconomic factors were examined. FINDINGS: The ratios of maximum to minimum of SCRs were 1·4 for outpatient visits, 19·3 for outreach services, and 17·6 for periodontal surgeries. Dental supply was positively associated with outpatient visits, outreach services, dental calculus removal, and periodontal surgeries. Regional average income and educational level were positively associated with dental calculus removals, and negatively associated with pulpectomies, tooth extractions, dental bridges, and dentures. INTERPRETATION: In Japan, regional inequalities in dental care utilization exist for periodontal care and outreach services but are smaller for urgent and substantial dental care. Regional income and educational levels appear to have influence on dental care utilization. FUNDING: Ministry of Health, Labour and Welfare of Japan (H31–19FA1001).