Fluoride varnishes and caries development in primary tooth enamel: an in vitro study

This in vitro study evaluated the effect of fluoride varnishes on caries development in primary tooth enamel using polarized light microscopic techniques. A total of forty extracted or exfoliated primary teeth with intact, caries-free smooth surfaces underwent a fluoride-free prophylaxis and soft tissue were assigned to one of the following groups: 1) duraphat (5 percent sodium fluoride, vanish, Colgate, n=10); 2) Duraflor (5 percent sodium fluoride, Pharmascience, n = 10); 3 Cavity Shield (5 percent sodium fluoride varnish, Omni, n=10); and 4) Control (n=10). An acid-resistant coating was applied to the specimens leaving an exposed window of sound enamel (5mm x 1mm). The fluoride varnishes were applied to the primary teeth according to the manufacturer's recommendation. Following thermocycling (500 cycles, 5-50 degrees C) of the fluoride varnish-treated and control teeth, a fluoride-free pumice toothbrushing was performed to remove visible and macroscopically (dissecting microscope at 16x) detectable fluoride varnish. An acid resistant coating was reapplied where necessary, leaving the fluoride varnish treated sound enamel window exposed. Following in vitro caries formation (2.2mM Ca, 2.2mM PO4 50mM acetic acid, 0.5ppm fluoride, pH 3.90), longitudinal sections (5 per specimen) were obtained and evaluated by polarized light microscopy for mean lesion depth. Comparisons were made among treatment and control groups.