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 ZnF(2) on dentin demineralization and collagen degradation. Bovine dentin specimens were treated either with ZnF(2) or HCl-acidified ZnF(2) (ZnF(2)/HCl) and then demineralized. Anti-demineralization efficacy was assessed by TMR as mineral loss (DeltaZ). 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, ZnF(2)/HCl, NaF] followed by collagenase challenge. The eroded depth of collagen layer in the lesion was assessed using optical microscope. DeltaZ of SDF, KF, ZnF(2)/HCl, and APF were significantly lower compared with ZnF(2) and Control (no treatment). Regarding anti-collagen degradation, SDF and ZnF(2)/HCl demonstrated a significant difference in the eroded depth compared with Control. Although SDF possessed higher efficacy, ZnF(2)/HCl might be beneficial as a staining-free agent.