Background. Many types of
toothpastes contain substances that can remineralize initial enamel caries. This study aimed to assess the effect of nano-
hydroxyapatite (NHA) on microhardness of artificially created
carious lesions. Methods. In this in vitro study, NHA was prepared using
sol-gel technique and added to the
toothpaste with 7% concentration. A total of 80 extracted sound teeth were collected. The
crowns were polished using 500-grit abrasive paper. The specimens were randomly coded from 1 to 80. Number 1 to 40 were assigned to group A and numbers 41 to 80 to group B. The microhardness was measured using HVS-1000 Vickers microhardness tester. The specimens were demineralized using 37%
phosphoric acid for 3 minutes in order to create artificial
carious lesions and then were rinsed with water, air-sprayed for 3 minutes and dried. Microhardness was measured again. Next, the specimens were brushed for 15 days, twice daily, for 15 seconds. After 15 days, microhardness was measured again.
Toothpaste A contained NHA and
fluoride and
toothpaste B contained
fluoride alone. Data were analyzed using SPSS 16, with one-sample Kolmogorov-Smirnov test and ANOVA at a significance level of P<0.05. Results. The microhardness of specimens significantly decreased following
acid exposure (P<0.01) but increased again in both groups after exposure to
toothpastes. The increase in microhardness was significantly greater in group A (P<0.01). Conclusion. The
toothpaste containing NHA was more effective than the
toothpaste without NHA for the purpose of remineralization.