The prevention of white spot lesions (WSLs) during orthodontic treatment with fixed appliances is of paramount importance to orthodontists. Numerous non-invasive techniques have been extensively researched to effectively manage WSLs. The objective of this study was to investigate the efficacy of MI varnish application, diode laser irradiation and their combination on remineralization of WSLs.

In this in vitro study, 40 enamel samples were divided randomly into 4 groups based on the applied treatment after demineralization. In Group I, MI varnish was applied to the enamel samples for a period of 7 days. In Group II, samples were irradiated with diode laser. In Group III, MI varnish was applied for 7 days, followed by diode laser irradiation. Whereas Group IV (control group) received no treatment and samples were stored in artificial saliva for 7 days. Microhardness assessments were performed at baseline, after demineralization and following the different treatment protocols. A representative sample from each group was randomly selected for scanning electron microscopy (SEM) analysis. One-way ANOVA, repeated measures ANOVA, and Tukey's Post Hoc tests were used for statistical analysis, with significance set at P≤0.05.

All treatment groups demonstrated significantly higher mean microhardness values compared to the control group (P<0.05). Group 1 (MI varnish) had a final microhardness mean value of 193.50 (P<0.001), Group 2 (diode laser) recorded the highest final mean of 214.20 (P=0.018), and Group 3 (MI varnish+diode laser) had a mean of 203.93 (P=0.011). SEM observations supported these findings by showing enhanced surface morphology in the treatment groups.

MI varnish application, laser irradiation, and their combination demonstrated enhanced microhardness of artificially demineralized enamel, highlighting their effectiveness in remineralization of WSLs.