Ambient Air Pollution and Outpatient Visits for Odontogenic Inflammatory Diseases in Shanghai: A Case-Crossover Study

Introduction and aims Ambient air pollution is a major environmental health risk, and its impact on odontogenic inflammatory oral diseases remains unclear. We investigated the association between short-term air pollution and outpatient visits for odontogenic inflammatory oral diseases. Methods We conducted a time-stratified case-crossover study using individual-level outpatient data from the Dental Hospital of Fudan University in Shanghai, China, from 2013 to 2025 (n = 253,773). Daily concentrations of PM 2.5 , PM 2.5-10 , NO 2 , SO 2 , CO, and O 3 were obtained from fixed monitoring stations. Conditional logistic regression combined with distributed lag non-linear models was used to estimate exposure-response associations and lag effects. Stratified analyses were performed by sex, age, and season. Results Short-term exposure to PM 2.5 , PM 2.5-10 , NO 2 , SO 2 , and CO was associated with increased outpatient visits for odontogenic inflammatory diseases, with percentage increases of 1.31%, 1.19%, 7.39%, 0.94%, and 1.47% per IQR increment, respectively, and NO 2 showing the strongest association. In contrast, O 3 was inversely associated with outpatient visits, with a percentage change of -6.61% (95% CI: -8.08%, -5.11%). Most pollutants exhibited immediate effects (lag 0 or lag 0-1), whereas O 3 showed more prolonged lag patterns (lag 0-6). Stronger associations were observed for chronic apical periodontitis than for pulpitis, and the associations were more pronounced during the cold season. Conclusion Short-term air pollution was associated with increased risk of outpatient visits for odontogenic inflammatory oral diseases. These findings highlight the potential association between air pollution and short-term increases in outpatient visits for odontogenic inflammatory oral diseases. Clinical Relevance Reducing short-term exposure to ambient air pollution, particularly traffic-related pollutants such as NO 2 , may help decrease the acute outpatient burden of odontogenic inflammatory oral diseases.