Effects of zinc fluoride on inhibiting dentin demineralization and collagen degradation in vitro: A comparison of various topical fluoride agents

Root caries is developed because of demineralization followed by enzymatic collagen degradation. This in vitro study aimed to examine the inhibitory efficacy of ZnF2 on dentin demineralization and collagen degradation. Bovine dentin specimens were treated either with ZnF2 or HCl-acidified ZnF2 (ZnF2/HCl) and then demineralized. Anti-demineralization efficacy was assessed by TMR as mineral loss (AZ). The efficacy was compared with silver diammine fluoride (SDF), KF, and acidulated phosphate fluoride (APF). For evaluating anti-collagen degradation, EDTA-demineralized dentin specimens were treated by one of four fluoride agents [SDF, APF, ZnF2/HCl, NaF] followed by collagenase challenge. The eroded depth of collagen layer in the lesion was assessed using optical microscope. AZ of SDF, KF, ZnF2/HCl, and APF were significantly lower compared with ZnF2 and Control (no treatment). Regarding anti-collagen degradation, SDF and ZnF2/HCl demonstrated a significant difference in the eroded depth compared with Control. Although SDF possessed higher efficacy, ZnF2/HCl might be beneficial as a staining-free agent.