Effect of 38% ammonia-free silver fluoride solution, with and without potassium iodide, on surface microhardness loss: An in vitro study.

OBJECTIVE: To evaluate the effect of 38% silver fluoride (AgF) solution, with and without potassium iodide (KI) application, on surface microhardness loss. DESIGN: Bovine enamel blocks were analyzed for initial surface microhardness and allocated into 4 groups (G) (n = 10 per group): G1 - Sterility control, G2 - Growth control, G3 - AgF without KI application, and G4 - AgF with KI application. G3 and G4 received treatments according to manufacturers. G2, G3 and G4 were exposed to dual-species biofilms of Candida albicans and Streptococcus mutans. During the cariogenic challenge, 5 specimens per group were removed after 24 h and after 48 h. At each point, the pH of the culture medium and the percentage of surface microhardness loss (%SML) were evaluated. Data were analyzed using two-way ANOVA with Tukey post hoc tests (p < 0.05), considering group and time as fixed factors, and their interaction. RESULTS: For %SML, the group × time interaction was not significant (p = 0.064). A group effect was observed (p = 0.001), whereas time had no significant effect (p = 1.000). G3 (5.29 ± 10.88) showed lower %SML than G2 (27.09 ± 12.10; p = 0.003), while G4 (20.19 ± 18.74) did not differ significantly from either G2 (p = 0.626) or G3 (p = 0.063). Significant effects of group (p < 0.001) and time (p = 0.001) on culture-medium pH were observed; however, the group × time interaction was not significant (p = 0.306). No significant difference in pH was found between G3 (5.41 ± 0.27) and G4 (5.40 ± 0.20) (p = 0.998). CONCLUSION: Under these in vitro dual-species biofilm conditions, the 38% ammonia-free AgF treatments with and without KI showed similar effects on surface microhardness loss.