Effects of universal oral healthcare coverage in an adult population: A long-term nationwide natural experiment.

OBJECTIVES: A large and long-term natural experiment occurred in Finland from the late 1980s-2000, when adults' entitlement to subsidized oral healthcare was strongly dependent on the arbitrary classification based on their year of birth: people born in 1956 or later were entitled to subsidized care, while people born before 1956 were not. The aim of this study was to investigate the effect of this expanded universal oral healthcare coverage on service use and oral health outcomes. METHODS: Data from annual nationally representative cross-sectional postal surveys among 15-64-year-olds between 1990 and 2014 were used. For this study, the following outcome variables were formed: experiencing toothache during the past month (yes/no), the number of missing teeth with three different thresholds (over 10, over 5 or at least 1 missing tooth), brushing more than once a day and the number of visits to the dentist. Regression discontinuity plots and bias-corrected local polynomial regression discontinuity estimators measuring the effect of the extended universal coverage on the outcomes at the year-of-birth cut-off of 1956 were generated separately from the data from 1990 to 2000 and from 2002 to 2014. RESULTS: Between 1990 and 2000, the number of visits to the dentist (0.2 visits, 95% CI, confidence intervals: -0.03; 0.43) and the proportion of those who visited the dentist during the past 12 months (4.2%, 95% CI: 0.1%; 8.3%) increased at the year-of-birth cut-off of 1956. There were minor drops (1.5%-1.9%) in the number of missing teeth across all thresholds (over 10, over 5, or at least 1 missing teeth) at the cut-off. Analyses with the data from the surveys from 2002 to 2014 showed that there were no discontinuities in these outcomes at the cut-off of 1956. Regression discontinuity estimates related to toothache experience and toothbrushing frequency were inconclusive due to high variability in the underlying data and the likely small effect of the more universal coverage on these outcomes. CONCLUSIONS: The current study provided evidence of the beneficial effects of universal oral healthcare coverage on the oral healthcare service use and teeth preservation from a large and long-term natural experiment occurred in Finland from the late 1980s to 2000.