Did expansion of insurance coverage for major diseases in Korea induce a positive spillover effect on dental service utilization?

Although people with serious major diseases are disproportionately likely to have poor oral health, they are also more likely to defer treatment for oral health conditions due to financial constraints. The South Korean government introduced a comprehensive benefit expansion policy covering four major disease categories in 2013: cancer, cardiac diseases, cerebrovascular diseases, and rare diseases. Meanwhile, a policy expanding benefits for dental prosthetic services for the elderly was also introduced during the same period. Using nationally representative Korean Health Panel data from 2012 to 2017, we performed a difference-in-difference (DID) analysis to examine the positive spillover effect of insurance expansion for the four major disease categories on encouraging dental service utilization (frequency of dental visits and dental out-of-pocket payments) or decreasing unmet dental needs. Additionally, a triple-difference (TD) analysis was performed to examine whether the effect of coverage expansion of dental prosthetic services on dental service utilization was larger among the beneficiaries of the expansion for the four major disease categories. Benefit expansion for the four major disease categories did not significantly affect dental service utilization among the beneficiaries (DID model) during all study years and slightly increased unmet dental needs in 2014 and 2015. However, the effect of expanded coverage for dental prosthetic services on encouraging dental service utilization was larger (TD model) among the beneficiaries of the policy for the four major disease categories than among non-beneficiaries when we defined the beneficiaries as individuals with two or more household members who had one of the four major diseases. Our results suggest a need to provide more intense coverage for those with comorbidities by embracing the concept of proportionate universalism in the coverage of dental services.