This study evaluated the effects of the short-term use of a dentifrice containing nano-sized carbonate apatite (n-CAP) on the occlusion of the dentinal tubules using a scanning electron microscope (SEM) and an image analyser in vitro. One hundred human dentine specimens were wet ground with a silicone carbide papers and etched with 6% citric acid for 1 min to allow complete opening of the dentinal tubule. Specimens showing complete opening tubules were used as the baseline. The specimens were divided randomly into five groups: G1: 0% n-CAP, G2: 5% n-CAP, G3: 10% n-CAP, G4: 20% n-CAP and G5: 10% strontium chloride (SrCl2). Five specimens from each group were brushed by applying 50, 100, 250 and 500 strokes, respectively. All the specimens were evaluated by a SEM (×3000), and the degree of occlusion of the dentinal tubules was quantified using an image analyser. The results were analysed by one-way anova and a Tukey's test using the spss 12.0 statistical package program. The dentifrice containing 20% n-CAP for 50 strokes, which indicated 2-day use, showed the highest tubular occlusion than the other groups (P < 0.05). Moreover, this group showed 79.5% and 77.4% less open tubular area than the baseline and 0% n-CAP group, respectively. The groups containing various concentrations of n-CAP showed significant differences in the SrCl2 group after tooth-brushing for 500 strokes, which indicated 17-day use. According to this examination of the short-term use of desensitizing dentifrices in vitro, the dentifrice containing 20% n-CAP was the most effective in occluding the dentinal tubules.
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