RESUMO
Consumption of acidic carbonated beverages is the most important etiologic factor for dental erosion. Studies show that nano hydroxyl apatite can remineralize initial caries lesions. The aim of this study was to determine the effect of that nano hydroxy apatite on the micro hardness of enamel of permanent third molar after exposing to soft beer. This in vitro study was done on 18 permanent third molars without caries and crack. After measurement of the micro hardness of the teeth, these teeth were placed in the 40 cc of Delester and secondary micro hardness of them were measured. Then the teeth were divided in to two groups randomly and were exposed to nano hydroy apatite in treatment group and tap water in control group and finally micro hardness of the teeth was determined. Changes in micro hardness was analyzed with paired t test in each group and ANOVA between groups. The results showed that micro hardness of 18 samples after exposing to lemon Delester -Behnoosh- reduced to 92.5% of primary micro hardness and paired t test showed that this is significant statistically [P=0.009]. Micro hardness of 9 samples in water group after exposing to water was 99.3% of secondary micro hardness and paired t test showed there is not significant statistically [P=20.6]. Micro hardness of 9 samples in nano hydroxy apatite after exposing to nano hydroxy apatite was 98.2% of secondary micro hardness and paired t test showed there is significant statistically [P=0.012]. Based on the results of this study nano hydroxyl apatite can remineralize erosive lesion on the enamel of permanent teeth resulting from exposing to lemon Delester