Objective To explore the relationship between the oxidative balance score OBS and periodontitis. Method A retrospective analysis of clinical data from 5980 participants in the National Health and Nutrition Examination Survey NHANES database from 2009 to 2012 was conducted. We described the nonlinear relationship between OBS and the risk of periodontitis using restricted cubic splines. Logistic regression analysis was used to further describe the association between OBS and its components with the risk of periodontitis. Subgroup and interaction analyses were employed to explore this relationship across different groups. Result The study included 5980 patients with an average age of 51. 91 ± 14. 19 years. Of these 3301 participants had periodontitis. Compared to participants with a low OBS those with a high OBS had a reduced risk of periodontitis OR = 0. 80 95% CI = 0. 68-0. 93 . In patients with cancer this relationship was more pronounced OR = 0. 66 95% CI = 0. 48- 0. 89 . Subgroup and interaction analysis showed that the relationship between OBS and periodontitis was moderated by age with a stronger protective effect of OBS observed in older participants age ≥ 65 years OR = 0. 61 95%CI = 0. 43-0. 87 . Conclusion This study indicates that an increased OBS is associated with a reduced risk of periodontitis and this relationship is influenced by age. In older individuals a higher OBS has a stronger protective effect against the risk of periodontitis. Improving OBS-related diet and lifestyle may help reduce the occurrence and progression of periodontitis.