Evaluation of NaOCl application prior to resin infiltrant or fluoride-containing resin varnish in the treatment of white spot lesions: An in vitro study.

OBJECTIVE: The aim of this in vitro study is to investigate the effect of NaOCl (5.25 %) prior to resin infiltration and resin varnish on microhardness, surface roughness, and DIAGNOdent Pen values in the treatment of white spot lesions (WSLs). METHODS: The artificial initial caries lesions were created in 160 human enamel samples. The demineralizated samples were divided into five groups: resin infiltration (ICON; DMG, Hamburg, Germany), NaOCl + ICON, resin varnish (Clinpro XT; 3M ESPE, Seefeld, Germany), NaOCl + Clinpro XT, and a negative control group. Enamel samples that underwent thermocycling aging were subjected to 5.000 cycles between 5-55 degrees C (N = 32, n = 16 for aging subgroups). Surface roughness (Ra), Vicker's microhardness (VHN), and DIAGNOdent Pen (Kavo, Biberach, Germany) (DDP) values were recorded at the baseline, after demineralization, after treatment, and after the thermal aging stages. The micro-CT analysis, microleakage, and Scanning Electron Microscope images were evaluated after treatment procedures and thermal aging. Robust ANOVA, Pearson's chi-square, and McNemar tests were used for statistical analysis. The significance level was p < 0.05. RESULTS: The main effect of both group and stage was statistically significant for DDP, Ra, VHN, and micro-CT values. All treatment procedures improved the demineralized enamel compared to the negative control group (p < 0.001). The application of NaOCl (5.25 %) before resin infiltration increased microhardness but also in roughness. The resin-infiltrated groups showed less microleakage than the resin-varnish-treated groups (p < 0.001). CONCLUSION: The application of NaOCl prior to resin infiltration or resin varnish did not result in any important alterations in the examined parameter values.