Effects of salivary proteinase 3 and oxidative stress markers on secondary caries following pit-and-fissure sealants in patients with S-ECC.

Objective: To investigate the effects of salivary proteinase 3 (PR3) and levels of oxidative stress markers on the development of secondary caries following pit-and-fissure sealant application in patients with severe early childhood caries (S-ECC). Methods: This prospective, single-center cohort study included 200 children aged 3-5 years, comprising 60 caries-free healthy controls for baseline biomarker comparison and 140 children with S-ECC receiving pit and fissure sealants for longitudinal outcome analysis. The S-ECC cohort was divided into the no secondary caries group (No-SC, Results: PR3 and MDA levels were significantly lower in the SC group, whereas TAC and SOD levels were significantly higher. After adjustment, each standard deviation increase in PR3 and in MDA was associated with 70% and 44% lower odds of secondary caries, respectively, while each standard deviation increase in TAC and in SOD was associated with 168% and 116% higher odds, respectively. The combined PR3 and TAC model showed the highest discriminatory performance for predicting secondary caries (AUC = 0.835) and provided favorable clinical net benefit within a 0.1-0.7 threshold range. Conclusion: Reduced salivary PR3 and MDA levels, together with elevated TAC and SOD levels, were associated with post-sealant secondary caries in children with S-ECC. Impaired antimicrobial defenses and oxidative stress imbalance may contribute to secondary caries through distinct pathways, although external validation is still needed before routine clinical application.