Destructive effects of citric acid, lactic acid and acetic acid on primary enamel microhardness

  Objective: This study aimed to assess the destructive effects of citric acid, lactic acid and acetic acid produced from the fermentation of foods on primary teeth enamel.   Methods: This in vitro, experimental study was conducted on 24 sound primary teeth. The teeth were polished with a fine abrasive paper under running water. Tooth pieces measuring 3 × 4 × 3mm were cut out of the teeth and stored in 100% humidity until the experiment. The specimens were divided into 3 groups (n=8) and immersed in acetic acid, citric acid and lactic acid, respectively. The enamel microhardness of specimens was measured by Vickers microhardness tester at baseline and 5 and 30min after immersion in the freshly prepared acid solutions.   Results: Repeated measures ANOVA showed that the effect of immersion time on microhardness was significant (p<0.001). Pairwise comparison among 0, 5 and 30 minutes time points using Bonferroni adjustment showed significant differences in microhardness at different time points (p<0.001). Evaluation of the effect of type of acid on microhardness revealed that the microhardness was not significantly different in the three groups of acids (p=0.915). Among the three understudy acids, only the reduction in microhardness from time 0 to 30 minutes was significantly different between lactic acid and acetic acid (p=0.042).   Conclusion: Citric acid, lactic acid and acetic acid were all capable of demineralization and reduction of enamel microhardness. A significant difference existed in the demineralization potential of acids (the highest for lactic acid). However, this effect was more significant early after exposure.