Insurance coverage expansion and inequalities in unmet oral healthcare needs in Korea: Repeated cross‐sectional analysis, 2007‐2015

Objectives This study aimed to evaluate whether Korea's 2012 health insurance expansion of adult dental care coverage reduced income‐based oral health inequalities. Methods This study analysed nationally representative repeated cross‐sectional data from waves IV to VI (2007‐2015) of the Korean National Health and Nutrition Examination Survey. The main outcome variable is unmet dental needs due to cost, and the independent variable is household income. Further, the slope index of inequality (SII) and the relative index of inequality (RII) were calculated. Calculations were adjusted for income and stratified by age group, gender and survey period. Data from the three waves were pooled to estimate the SII and RII trend coefficients between survey years. These were tested using two‐way interaction terms for each age group and gender. Results Some changes in income‐based inequality trends were identified. Relative and absolute inequalities in unmet needs (indicated by the RII and SII) decreased over time for most age groups. However, this trend was not observed for older women. Conclusions Income‐based inequalities in unmet dental needs persisted among older women in Korea despite the insurance expansion. By contrast, after the 2012 insurance expansion, the absolute and relative inequality in unmet dental needs decreased for young and middle‐aged as well as older adults.