In vitro demineralization prevention by fluoride and silver nanoparticles when applied to sound enamel and enamel caries-like lesions of varying severities

Objectives: To investigate the effect of fluoride and silver nanoparticles on the prevention of in vitro demineralization of sound enamel and enamel caries-like lesions of varying severities. Methods: Caries-like lesions of different severities (1/6/15 days) were created in bovine enamel specimens. One group remained sound. All specimens were demineralized again using a partially saturated acetic acid solution. Mimicking the intra-oral retention of fluoride and silver in vitro, this solution was supplemented with fluoride (0/1/10 ppm) and/or silver nanoparticles (0/10 ppm) in a factorial design. Changes in lesion depth (Delta L) and integrated mineral loss (Delta Delta Z) were evaluated by digital transverse microradiography. Data was analyzed using three-way ANOVA. Results: Lesion severity significantly affected Delta Delta Z and Delta L, after no treatment and after the treatment of fluoride and silver independently (p = 0.012 and p = 0.037, respectively). Fluoride and the fluoride x lesion severity interaction were shown to be significant (p < 0.001) on Delta Delta Z and Delta L. Silver nanoparticles significantly affected Delta Delta Z (p = 0.041), but not Delta L (p = 0.15). The silver nanoparticles x lesion severity interaction was significant for Delta Delta Z and Delta L (p = 0.032 and p = 0.024, respectively). No interaction was observed for Delta Delta Z and Delta L between fluoride and silver (p = 0.962 and p = 0.971, respectively) as well as lesion severity and the use of fluoride and silver combined (p = 0.722 and p = 0.158, respectively). Conclusion: Fluoride and silver nanoparticles had a significant effect on the prevention of in vitro demineralization of sound enamel and enamel caries-like lesions of varying severities.