Evolving Trends in Dental Services in Aging Japan: An Age–Period–Cohort Analysis Using Nationwide Data from Fiscal Years 2016 to 2023

<b>Background/Objectives</b>: Understanding changes in dental service utilization is vital for planning effective oral health strategies in aging societies. In this study, we aimed to elucidate nationwide trends in major dental procedures in Japan from fiscal year (FY) 2016 to FY2023, and to assess the age, period, and cohort effects underlying these trends. <b>Methods</b>: Using open data from Japan's National Database of Health Insurance Claims, five procedure types were analyzed: cavity filling, dental calculus removal, tooth extraction, dental crown procedures, and denture procedures. Descriptive analyses were performed to examine the annual and age-specific changes in the number of procedures per 1000 population. Age-period-cohort (APC) analyses were conducted using Poisson regression with spline functions, applying 10-year age groups. <b>Results</b>: From FY2016 to FY2023, restorative and prosthetic procedures, including cavity fillings, crowns, and dentures, demonstrated a steady decline, whereas preventive procedures, such as dental calculus removal increased, particularly among younger age groups. The APC analysis revealed distinct age-, period-, and cohort-related patterns in dental service utilization. Age effects indicated relatively higher rates of prosthetic procedures among older adults, whereas cohort effects suggested generational improvements in oral health. Period effects showed a downward shift beginning in FY2020, temporally aligned with the coronavirus disease pandemic. <b>Conclusions</b>: The combined descriptive and APC analyses indicate evolving patterns in dental service utilization in Japan, characterized by increased preventive care among younger generations and persistent age-related differences in prosthetic service use. These findings provide population-based evidence relevant for planning sustainable oral healthcare systems in aging societies.