Efficacy of topical strategies to prevent the onset of root caries lesions: an in vitro study.

This study evaluated the efficacy of several topical dental products in preventing the initiation of root caries lesions using a validated biological caries model. Biofilms of Streptococcus mutans UA159 were formed on bovine root dentin slabs treated with one of five agents: 1% chlorhexidine (CHX) gel, 22,600 ppm fluoride varnish, 5000 ppm fluoride toothpaste, 38% silver diamine fluoride (SDF), or a negative control (0.9% NaCl). The model simulated a highly cariogenic environment through repeated sucrose challenges for 4 days. After the experimental period, biofilms were assessed for biomass, viable bacterial counts, and soluble protein content. Dentin demineralization was quantified through laser fluorescence measurements and percentage surface Knoop microhardness loss. SDF-treated slabs showed the lowest demineralization values, with surface microhardness loss comparable to CHX but significantly lower than fluoride varnish, 5000 ppm fluoride toothpaste, and the control group (p < 0.05). Laser fluorescence results supported these findings, showing significantly reduced lesion development in the SDF group. SDF also produced the greatest reduction in viable bacterial counts and biomass, indicating a pronounced antimicrobial effect, whereas CHX demonstrated an intermediate impact. Fluoride varnish and high-fluoride toothpaste showed limited preventive effects under the severe cariogenic challenge imposed. Under the experimental conditions of this in vitro model, SDF demonstrated the greatest preventive effect among the evaluated agents in limiting early root caries formation, both by limiting biofilm activity and reducing dentin demineralization. CHX also demonstrated a preventive effect, though to a lesser extent. Further clinical studies are warranted to determine the extent to which these findings translate to clinically relevant preventive strategies.