Methods: Bovine enamel and root dentin specimens were divided into 9 groups according to the surface hardness: control, 20 Nanop paste (20% Ca/P), 20 Nanop paste plus (20% Ca/P + 0.2% NaF),10 Nanop paste (10% Ca/P), 10 Nanop paste plus (10% Ca/P+ 0.2% NaF), placebo paste, Fluoride paste (0.2% NaF), MI paste (CPP-ACP, RECALDENT, GC America, USA) and MI paste plus (CPP-ACP + 0.2% NaF). Fifteen enamel and dentin specimens in each group were subjected to pH-cycles (demineralization–6h/ remineralization-18h a day) for 7 days. The pastes were applied twice a day, before and after the demineralization process, using microbrush for 1 minute. The excess of paste was removed and the specimens were washed in deionized water for 5 s before being immersed in the de- or remineralizing solution. The dental subsurface demineralization was analyzed by cross-sectional hardness (KgF/mm2, depth 10-220µm). Data were tested using two-way ANOVA and Bonferroni’s test (p<0.05).
Results: The only treatment able to reduce the loss of enamel and dentin subsurface hardness was Fluoride paste, which significantly differed from the control at 30 and 50 µm depth: enamel (F paste: 186±51 and 253±49, Control: 16±24 and 91±89 KgF/mm2, respectively) and dentin (F paste: 6.7±5.8 and 9.9±4.8, Control: 1.2±3.3 and 4.9±4.6 KgF/mm2, respectively).
Conclusions: The experimental Nanop pastes, regardless of the presence of fluoride, were unable to reduce dental demineralization in vitro.