Background: In 2009, the South Korean government expanded universal health insurance to include oral health services. In the present study, we sought to examine whether improved access resulted in a reduction in income-based self-reported oral health inequalities. Methods: We analyzed repeated cross-sectional data from the Korea National Health and Nutrition Examination Survey (KNHANES) waves IV through VI (2007-2015). We analyzed self-reported oral health status among 68,431 subjects. Changes in oral health inequalities across four income levels (low, middle-low, middle-high, and high) were assessed with the Slope Index of Inequality (SII) and the Relative Index of Inequality (RII). Results: The average oral health status of children and adolescents improved the most over the observation period. The absolute magnitude of oral health inequalities (measured by the SII) improved for most groups, with the notable exception of young male adults. By contrast, the ratio of poor oral health between high-and low-income groups (measured by the RII) changed little over time, indicating that relative inequalities remained resistant to change. Conclusions: The expansion of dental health insurance may not be sufficient to move the needle on self-reported oral health inequalities among adults.

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.

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This study investigates whether workers with long working hours as well as shift workers perceive higher unmet dental care needs, and whether there is a gender difference in the associations. We used the Korea Health Panel (2009, 2011–2014) involving 20,451 person-wave observations from 5567 individuals. Perceived unmet dental care needs was defined when the participants reported that they perceived a need for dental treatment or check-up but had failed to receive dental care services during the past year. Fixed effects logit models were applied to examine how changes in weekly working hours or shift work status were linked to changes in perceived unmet dental needs within each individual. Among participants, 15.9–24.7% reported perceived unmet dental needs and the most common reason was time scarcity. We found that long working hours (>52 h/week) was significantly associated with perceived unmet dental needs due to time scarcity in both men (OR = 1.42, 95% CI 1.13–1.78) and women (OR = 1.35, 95% CI 1.03–1.79) compared workers working 40–52 h per week. Shift work was also a significant risk factor, but only in women (OR = 1.57, 95% CI 1.06–2.32). These findings provide evidence for labor policies to reduce working hours in order to improve access to dental care services.