Nanoparticle-Enriched Sodium Fluoride Gel with and Without Er, Cr: YSGG Laser Activation: Effects on Enamel Microhardness and Sealant Bond Performance on Demineralized Enamel

This study aimed to assess the remineralization efficacy of NaF gel enriched with hydroxyapatite nanoparticles (HANPs) and bioactive glass nanoparticles (BAGNPs), with and without adjunctive Er, Cr: YSGG laser irradiation (ECL; 0.5 W, 5 Hz, 20 mJ/pulse, 60 µs pulse duration, water–air spray), on artificially demineralized enamel by evaluating enamel microhardness (MH), resin tag length (RTL), and shear bond strength (SBS) of pit and fissure sealants (PFSs). A total of 168 extracted human third molars free from cracks, fractures, erosion, enamel hypoplasia, surface irregularities, and any history of prior chemical or fluoride treatment were included in the study. All samples underwent continuous immersion in a demineralizing solution until specific DIAGNOdent values of 10-25 were achieved. Samples were randomly allocated into six groups (n = 28): Group 1 (untreated control), Group 2 (NaF gel), Group 3 (NaF + HANPs), Group 4 (NaF + BAGNPs), Group 5 (NaF + HANPs-ECL), and Group 6 (NaF + BAGNPs-ECL). Enamel MH was assessed using a Vickers MH tester (n = 8). RTL was evaluated using scanning electron microscopy (SEM) (n = 8). SBS was measured using a universal testing machine (n = 12), followed by failure mode analysis. Data were analyzed using ANOVA and Tukey’s post hoc test (p < 0.05). Group 5 (NaF + HANPs-ECL) exhibited the highest values for MH (366.20 ± 26.11 HV), RTL (70.34 ± 2.57 µm), and SBS (13.67 ± 0.35 MPa), whereas the untreated control group exhibited the lowest values for all the outcomes. Groups 1 and 2 demonstrated comparable RTL and SBS values (p > 0.05). The remaining groups exhibited significantly different MH, RTL, and SBS values (p < 0.05). The ECL-assisted nanoparticle-integrated NaF gel significantly enhanced enamel MH, RTL, and shear SBS of PFS compared to NaF gel alone. HANPs demonstrated superior remineralization outcomes compared to BAGNPs across all tested parameters. The present findings support the adjunctive use of laser activation with nanoparticle-modified NaF gel as a promising strategy for optimizing sealant performance on demineralized enamel.