Effects of Medicaid expansion on self-reported use of dental services in socioeconomically vulnerable subgroups.

OBJECTIVE Research suggests Medicaid expansion led to modest increases in the use of dental services among low-income adults, especially in states with more generous Medicaid dental benefits. We expand upon this research by examining whether the effect of Medicaid expansion differed across important socioeconomic subgroups. METHODS Using Behavioral Risk Factor Surveillance System data from 2012 to 2016, we employed a difference-in-differences framework to estimate the effect of Medicaid expansion on annual use of dental services overall and by whether states offered more-than-emergency Medicaid dental benefits. We used generalized linear mixed-effects model trees to estimate effects across socioeconomic subgroups (e.g., age, education, race, income). RESULTS The effect of Medicaid expansion varied by state's generosity of Medicaid dental coverage and combinations of socioeconomic subgroups. Overall, there was no significant association between Medicaid expansion and probability of using dental services (-0.1 pp percentage points [pp], p = 0.914). Medicaid expansion was associated with a modest increase in the probability of using dental services in states with more-than-emergency Medicaid dental benefits (2.3 pp, p < 0.001) and with a modest decrease in states with no or emergency-only benefits (-4.3 pp, p < 0.001). Among adults aged 21-35 without a high school diploma, Medicaid expansion was associated with an 8.1 pp (p = 0.003) increase in dental use probability, but there were no associated effects of Medicaid expansion for other subgroups. CONCLUSIONS While Medicaid expansion alone is not sufficient to ensure adults receive recommended dental care, some vulnerable subgroups appear to have benefited. Efforts to mitigate barriers to dental care may be needed to increase uptake of dental services by low-income adults.