Salivary Oxidative Stress and Dental Caries in Adolescents With Type 1 Diabetes Mellitus: A Cross-Sectional Study

Introduction: Adolescents with type 1 diabetes mellitus (T1DM) may experience alterations in salivary function and oral health, potentially accompanied by increased oxidative stress.This study evaluated salivary oxidative stress biomarkers and their relationship with dental caries in adolescents with T1DM.Materials and methods: This hospital-based observational cross-sectional study included 56 adolescents aged 12-18 years, comprising 28 participants with T1DM and 28 age-and sex-matched healthy controls.Unstimulated whole saliva was collected and analyzed for malondialdehyde (MDA) and 8-hydroxy-2′deoxyguanosine (8-OHdG) levels, which were normalized to total salivary protein.Salivary flow rate, pH, plaque index, gingival index, and dental caries experience were also assessed.Between-group comparisons, correlation analyses, multivariate linear regression, and binary logistic regression were performed.Correlations were compared between groups, and an MDA × T1DM interaction was tested in the logistic model.Results: Adolescents with T1DM had significantly higher salivary MDA and 8-OHdG concentrations than controls (both p < 0.001).Salivary flow rate and pH were significantly lower in the T1DM group (p < 0.001 and p = 0.007, respectively).Active caries were more prevalent among adolescents with T1DM (p = 0.003), whereas the difference in overall decayed, missing, and filled teeth (DMFT) scores was not statistically significant (p = 0.087).MDA was positively correlated with DMFT in the T1DM group (ρ = 0.659, p < 0.001), but not in controls (ρ = 0.117, p = 0.554); the difference between correlations was significant (p = 0.025).In adjusted logistic regression, each 1 nmol/mg increase in salivary MDA was associated with higher odds of high caries experience (DMFT > 2; adjusted OR = 5.00, 95% CI: 1.68-14.87;p = 0.004).A significant MDA × T1DM interaction was observed (OR = 44.81,95% CI: 1.50-1337.40;p = 0.028), indicating that the association between MDA and high caries experience differed according to diabetes status.The MDA association was not significant in controls (OR = 1.04, 95% CI: 0.21-5.26;p = 0.962).Addition of the interaction term significantly improved model fit (likelihood-ratio χ² = 7.06, p = 0.008).The wide CI indicated substantial imprecision in the interaction estimate.8-OHdG was not significantly correlated with DMFT.Conclusion: Adolescents with T1DM demonstrated increased salivary oxidative stress, impaired salivary parameters, and a greater active caries burden.Salivary MDA was associated with caries experience only among adolescents with T1DM, suggesting a diabetes-specific link that requires confirmation in larger prospective studies.