Microscopic investigation of artificially demineralized surface enamel exposed to controlled intra-oral periods

BACKGROUND: Arrest and regression of enamel caries is generally followed by clinical surface changes in enamel. The aim of this study was to evaluate microscopic surface changes in demineralized enamel submitted to toothbrushing with a fluoridated dentifrice or to a fluoridated gel in situ. METHODS: Enamel blocks demineralized by an acidic gel, were built in plates of five volunteers during three periods of 14 days each: exposure to the oral cavity (C+); brushing with a fluoridated dentifrice three times a days (B); application of a 2 per cent sodium fluoride gel and exposure to the oral cavity (F). Eight blocks were kept in 100 per cent humidity under refrigeration as negative controls (C-). RESULTS: Stereomicroscopic examination revealed that 15, 47.4 and 30 per cent of samples from C+, B and F presented enamel cavitation after the experimental period. The demineralized enamel area in these groups decreased considerably compared to C-, both in cavitated and non-cavitated samples, although it was statistically significant only in cavitated samples from B (p=0.003; t test). Scanning electron microscopy revealed that C+ and F retained irregularities caused by the acid challenge, while B presented a more leveled profile of the enamel surface. CONCLUSIONS: Exposure of demineralized enamel to intra-oral periods reduced the demineralized enamel area. Tooth brushing enhanced this reduction, because of surface abrasion.