Comparison of the Effect of Two Experimental Varnishes Containing Nano- Hydroxyapatite with MI Varnish and Sodium Fluoride Varnish on Remineralization of Enamel White Spot Lesions: An In Vitro Study

Introduction: White Spot Lesions (WSLs), as the earliest clinical manifestation of enamel caries, result from subsurface mineral loss in the presence of dental biofilm and, if left untreated, may progress to cavitated lesions. The use of biomimetic remineralizing agents such as nano-hydroxyapatite (nano-HA) as an alternative or adjunct to fluoride has gained attention in recent years. This study aimed to compare two experimental varnishes containing nano-hydroxyapatite with MI varnish and sodium fluoride varnish on the remineralization of white spot lesions. Materials and Methods In this in-vitro study, fifty-five extracted human premolar teeth were divided into five groups (n = 11): experimental varnish containing nano-hydroxyapatite and fluoride, nano-hydroxyapatite varnish, MI varnish containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), 5% sodium fluoride varnish, and a control group. After inducing white spot lesions using a demineralizing solution, the specimens underwent a pH-cycling protocol for 10 days. Surface Microhardness (SMH) was measured using the Vickers microhardness test before demineralization, after demineralization, and after remineralization. One-way Analysis of Variance (ANOVA) with Tukey's post-hoc test and Repeated-measures ANOVA were used to compare SMH values (p < 0.05 in all tests). Results The results showed that after pH cycling, the highest SMH recovery was observed in the group receiving the varnish containing nano-hydroxyapatite with fluoride, whereas the group receiving sodium fluoride varnish and the control group exhibited the least remineralization (p < 0.05). Moreover, no statistically significant difference was observed between the nano-hydroxyapatite-containing groups and the MI varnish group. Conclusion Varnishes based on nano-hydroxyapatite, particularly in combination with fluoride, demonstrated greater remineralization potential compared to sodium fluoride varnish in initial enamel lesions and may serve as an effective approach for the non-invasive management of white spot lesions. Clinical studies are recommended to confirm the efficacy of these formulations.