RESUMEN
INTRODUCTION: Dental caries is the most common chronic disease worldwide, and various forms of fluoride are considered useful preventive tools. The production of nanoscale materials can significantly improve their mechanical and chemical properties. The present study compared the microhardness of primary tooth enamel after applying sodium fluoride varnish (conventional) and nano-sodium fluoride varnish. MATERIALS AND METHODS: Sixty-eight sound canine teeth were selected in this experimental study. The teeth were mounted so that the buccal surface was exposed. A 3 × 3 mm square was obtained on the buccal surface of the crown of each tooth. Enamel surfaces were polished using sandpaper in the presence of water as a coolant. The samples were randomly divided into four groups (n = 17): G1, conventional 5% NaF; G2, 1% nano-NaF; G3, 5% nano-NaF; G4, control. The initial microhardness was measured. Before surface treatment with different fluoride compounds, the samples were placed in a demineralizing solution for two days, and the microhardness of all the samples was re-measured. Then G1, G2, and G3 were treated with the fluoride type specified for each group, and G4 was treated as a control (without treatment). Finally, pH cycling was applied, and the microhardness was measured again. Data were analyzed with SPSS 20, using Repeated measure ANOVA and post-hoc Tukey tests. P < 0.05 was considered significant. RESULTS: Repeated measure ANOVA showed that microharness of G1, G2, G3, and G4 was statistically significant different. Tukey tests showed that the microhardness of G1, G2, and G3 were not significantly different. However, these three groups exhibited significantly more microhardness than the control group (P = 0.024, P = 0.027, and P = 0.010). CONCLUSION: There was no significant differences in enamel microhardness of deciduous teeth between conventional 5% NaF,1% nano-NaF and 5% nano-NaF.