Effect of an S-PRG filler-containing varnish on enamel remineralization: an in vitro comparative study

Abstract Background Interest in biologically active remineralization systems has increased in recent years for the management of early enamel carious lesions, which represent potentially reversible subsurface mineral loss. The objective of this study was to compare the remineralization efficacy of sodium fluoride (NaF), casein phosphopeptide–amorphous calcium phosphate combined with fluoride (CPP-ACP + F), and surface pre-reacted glass-ionomer (S-PRG)–containing varnishes on artificially induced enamel lesions using quantitative light-induced fluorescence (QLF) and optical coherence tomography (OCT). Methods Forty standardized enamel specimens were subjected to artificial demineralization and randomly allocated into four groups ( n = 10): NaF varnish, CPP-ACP + F varnish, S-PRG varnish, and untreated negative control. Following varnish application and 24-hour storage in artificial saliva, specimens underwent an 8-day pH-cycling protocol. Remineralization was assessed using QLF parameters (ΔF, ΔQ) and OCT-derived optical lesion depth (OLD) after demineralization and post-treatment. Data were analyzed using mixed-design repeated-measures ANOVA with Bonferroni-adjusted post-hoc comparisons (α = 0.05). Results Significant Group × Time interactions were observed for ΔF, ΔQ, and OLD ( p < 0.001), indicating that the magnitude of change from post-demineralization to post-treatment differed among the experimental groups. No significant intergroup differences were observed before treatment ( p > 0.05). The S-PRG group demonstrated the greatest remineralization effect, showing the greatest improvements in ΔF (10.16 ± 0.62%) and ΔQ (138.50 ± 5.87) and the greatest reduction in OLD (92.00 ± 3.59 μm). NaF and MI Varnish groups showed moderate remineralization effects, whereas the untreated control group demonstrated minimal structural recovery. Conclusion S-PRG–containing varnish showed a favorable remineralization profile across QLF and OCT outcomes under pH-cycling conditions. QLF and OCT provided complementary insights into mineral and structural lesion recovery. These findings support the potential of multi-ion–releasing bioactive systems in non-invasive caries management; however, clinical validation is warranted.