Traditional Medicare does not cover routine dental care, but little is known about transitions in dental outcomes upon reaching Medicare eligibility at age sixty-five. Using data from the 2010-19 Medical Expenditure Panel Surveys, we examined dental insurance, utilization, and outcomes among US adults before and after age sixty-five, using a regression discontinuity design and segmented regression analysis. Among 97,108 US adults representing a weighted population of 104,787,300 people, complete edentulism, or the loss of all teeth, increased by 4.8 percentage points at age sixty-five, and the percentage of people receiving restorative dental care decreased by 8.7 percentage points. Enrollment in Medicare Advantage, which may offer a dental benefit, was not associated with greater use of dental services relative to traditional Medicare, and Medicare Advantage enrollees had a significantly larger drop in dental spending from private insurance at age sixty-five than traditional Medicare enrollees. Expanding Medicare to cover dental services may help counteract these effects among all enrollees.