BACKGROUND: Antimicrobial use (AMU) in Japan is characterized by a high prevalence of oral third-generation cephalosporin prescriptions, especially in dental medicine. However, few studies have examined the time trends and factors influencing AMU in older individuals seeking dental care. Therefore, in this study, we aimed to investigate AMU, particularly third-generation cephalosporin, in a cohort of older adults. METHODS: This retrospective study analyzed the dental prescription health insurance claims data of patients aged ≥75 years in one metropolitan area from 2018 to 2021. The antimicrobials were categorized, and the number of defined daily doses (DDDs) per 1000 inhabitants per day (DID) was calculated to assess trends over this period. Multivariate logistic regression analysis was performed to identify factors associated with third-generation cephalosporin prescriptions. RESULTS: This database contains 58,655 patients, of whom 15,038 were prescribed antimicrobials from dentistry. Our findings suggest that third-generation cephalosporins accounted for 44.8 % of all antimicrobial prescriptions, with a noticeable decreasing trend in DID over the study period. Factors significantly associated with third-generation cephalosporin prescriptions included dental association membership (adjusted odds ratio [AOR] 0.72, 95 % confidence interval [CI] 0.63-0.82), fiscal year (AOR 0.86, 95 % CI 0.83-0.89), and their interaction. CONCLUSIONS: The findings suggest that the pattern of prescribing third-generation cephalosporins in dental medicine might be shifting owing to heightened awareness of antimicrobial resistance (AMR) and educational initiatives by groups, such as dental associations. Effective educational and policy interventions by professional associations could reduce inappropriate antimicrobial prescriptions, thereby mitigating AMR on a large scale.