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

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. 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. 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). 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.