Background <p>Oral health has a significant effect on longevity and quality of life. Periodontal diseases and dental caries are the primary causes of tooth loss, with the former being more prevalent than the latter. Antioxidants are associated with periodontal diseases. However, comprehensive analyses of this association are limited in literature, especially when focusing on circulating antioxidants. This study analyzed the association between antioxidant levels in the blood and skin along with periodontal diseases in populations with normal occlusion.</p> Methods <p>This cross-sectional study was conducted as part of the Iwaki Health Promotion Project in 2022. Overall, 456 individuals aged ≥ 20 years with healthy occlusion were included. Multivariate logistic regression analyses were performed, with periodontal disease defined as the primary outcome variable, circulating antioxidant levels as the exposure, and the following covariates: age, sex, smoking and drinking status, sugar intake, educational background, and oral care habits. In addition, the potential causal direction between antioxidant levels and periodontal diseases were explored using Bayesian network analysis.</p> Results <p>Individuals with the fifth quintile of blood and skin carotenoid levels had a lower odds ratio (OR) for periodontal diseases compared with those with the first quintile (blood: adjusted OR = 0.32 [95% confidence interval (CI), 0.16–0.64], skin: adjusted OR = 0.45 [95% CI, 0.23–0.88]). In particular, blood lutein and lycopene levels, but not vitamin A, C, and E levels, were significantly associated with periodontal diseases. Bayesian network analysis suggested that carotenoid levels may be a potential causal factor for periodontal diseases, and this association may be mediated by salivary immunoglobulin A and oral dysbiosis.</p> Conclusions <p>Blood and skin carotenoid levels are associated with the prevalence of periodontal diseases.</p>