Background and Aim : High consumption of carbonated diet soda is the most common etiologic factor for dental erosion. This study aimed to assess the efficacy of addition of Xylitol to carbonated diet soda to prevent enamel microhardness reduction in permanent teeth .

  Materials and Methods : This in-vitro experimental study was conducted on 40 human impacted third molars that had been surgically extracted and were free from caries, erosion, cracks or hypocalcification. For correct measurement of microhardness, surface of samples was polished with 5000 grit abrasive paper and microhardness was measured usingVickers microhardness testing machine. The teeth were then divided into 4 groups and immersed in 40 ml of 4 different solutions for 5 minutes (regular coke as the first control, coke zero, coke zero plus 10 g Xylitol and tap water as the second control). Understudy surface was a 5x5 mm square on the distal surface of teeth. At the end of experiment, microhardness of teeth was measured again. Changes in microhardness were compared in each group with paired t-test and between groups with ANOVA .

  Results : Based on the obtained results, microhardness decreased after immersion of specimens in regular coke, coke zero and coke zero plus 25% Xylitol by -38.66 ± 24.87, -26.1 ± 16.65 and -19.5 ± 23.52, respectively and these reductions were statistically significant (P1=0.001)(P2=0.001)(P3=0.005). Change in microhardness was -7.4 ± 9.17 in specimens immersed in tap water and was not statistically significant (P4=0.5). The reduction in microhardness of enamel exposed to Xylitol was significantly less than the other two test groups .

  Conclusion: Addition of Xylitol to carbonated diet soda reduced the amount of tooth erosion but could not prevent it .