Income-Related Inequalities in Access to Dental Care Services in Japan.

: This study aimed to evaluate whether income-related inequalities in access to dental care services exist in Japan. : The subjects included beneficiaries of the National Health Insurance (NHI) in Chiba City, Japan, who had been enrolled from 1 April 2014 to 31 March 2015. The presence or absence of dental visits and number of days spent on dental care services during the year were calculated using insurance claims submitted. Equivalent household income was calculated using individual income data from 1 January to 31 December 2013, declared for taxation. : Of the 216,211 enrolled subjects, 50.3% had dental care during the year. Among those with dental visits, the average number of days (standard deviation) spent on dental care services per year was 7.7 (7.1). Low income was associated with a decreased rate of dental care utilization regardless of age and sex. However, there was a significant inverse linear association between the number of days spent on dental care services and income levels for both sexes. : There were income-related inequalities in access to dental care services, regardless of the age group or sex, within the Japanese universal health insurance system.