Fluoride varnish: Effect on in vitro enamel caries formation

Objective: This in vitro study evaluated the effect of a fluoride varnish containing amorphous calcium phosphate (Enamel ProVarnish), an acidulated phosphate fluoride gel (Minute-Gel) and foam (Minute-Foam) on in vitro enamel caries formation. Methods: 15 teeth with caries-free enamel surfaces were divided into 5 portions. Each portion was assigned to a treatment group: (1) No Treatment Control; (2) APF Foam (Minute-Foam, Oral-B Laboratories, Boston MA 02199); (3) APF Gel (Minute-Gel, Oral-B Laboratories, Boston MA 02199); (4) Enamel ProVarnish (Premier Products Co, Plymouth Meeting, PA 19462). The agents were applied to the tooth portions per the manufacturers' recommendations. The tooth portions were exposed to synthetic saliva for 30 days with daily replenishing. Fluoride-free pumice mechanical toothbrushing was performed with the Enamel ProVarnish groups to remove visibly and macroscopically (dissecting microscope at 16x) detectable varnish. In vitro enamel caries were created using a modified demineralization solution (2.2 mM calcium, 2.2 mM phosphate, 1.0 mM fluoride, pH 3.90, 10 days). Longitudinal sections (5 sections per tooth portion for each group) were evaluated for mean lesion depths using polarized light microscopy and analyzed with ANOVA and DMR. Results: Mean lesion depths were: Control 287+31µm; APF Foam 189+24µm; APF Gel 162+27µm; Enamel ProVarnish 89+22µm. Significant difference in mean lesion depths was found between the Control Group and all treatment groups (P<0.05). Mean lesion depths for the varnish group were significantly less than the APF groups (P<0.05). Conclusions: Fluoride delivery to sound enamel surfaces provides a means to improve resistance to an in vitro caries challenge (P<.05). With in vitro caries formation, fluoride varnish application provided a greater protection than topical application of an APF foam or gel (P<0.05).