ObjectiveDental caries in permanent teeth is one of the most common health issues—despite being preventable in early stages—due to inadequate regulation of preventive dental services in many countries. This study evaluates the association between regulation of preventive dental services and oral health outcomes.MethodsThis mixed-method study analysed data from 19 member countries of the Organisation for Economic Co-operation and Development (OECD). Oral health outcomes were measured using decayed missing and filled teeth (DMFT) indexes for children aged 12 to 18 years. Oral health expenditures were measured as a percentage of each country's gross domestic product (GDP). We conducted web-based research and systematically extracted and coded data on dental policy regarding children's preventive dental services. Preventive care was assessed based on legal policy mandating children receive preventive services, availability of free services for children, and regulation of the services provided. We assessed the relationship amongst oral health policy, outcomes, and expenditure using bivariate regression analysis.ResultsThe most common preventive policy category is the availability of free dental services for children (78.95%), and the least common is policy mandating dental services for children (26.32%). The oral health expenditure is correlated with DMFT index (−4.42,P< 0.05). The legal policy mandating dental services for children is correlated with DMFT index (−1.32,P< 0.05) and correlated with average oral health expenditure (0.16,P< 0.05).ConclusionsA percentage increase in oral health expenditure is associated with a 4.42 reduction in DMFT. The existence of legal policy mandating dental care for children is associated with a 1.32 reduction in mean DMFT score and a 0.16% increase in oral health expenditure. These findings highlight the importance of preventive care and may aid policymaking and health system reforms.