Abstract
Background & aim: Surface micro-hardness measurements are a suitable technique for investigating the effect of these materials on the amount of enamel remanization.The aim of this study was to compare the effect of sodium fluoride mouthrinse, nano hydroxyapatite solution, resin infiltration Icon and combination of nanohydroxy apatite solution and sodium fluoride mouthrinse on the micro-hardness of demineralized enamel lesions.
Materials and Method:  In this in vitro study 50 specimens of intact human premolar enamel were chosen and randomly divided to 5 groups of 10. After the initial measurement of micro-hardness, the specimens were immersed in demineralizing solution and then the measurement were recorded again. G1 group was immersed in sodium fluoride mouthrinse, G2 group was immersed in nano hydroxyapatite solution, G3 group was treated with resin infiltration Icon according to manufacturer’s instruction and G4 group was immersed in combination of nanohydroxy apatite solution and sodium fluoride mouthrinse. The G5 group was kept in distilled water as control. After the treatments of all specimens the micro-hardness for each one were measured again. For the statistical comparison between the groups, ANOVA and LSD tests were performed.
Results: In all groups, surface micro hardness after dimerization was significantly lower than that of enamel (P= 0.01) and in groups G1, G2, G3 and G4 after treatment the microhardness increased significantly after demineralization (P = 0.005) and in groups G1, G2, G4 and G5, microhardness decreased significantly before demineralization (P <0.03) But in G3 group there was no significant difference (P=0.2).
Conclusion: Sodium fluoride mouthwash and nano-hydroxyapatite solution both increase the surface microhardness of primary carious lesions. Infiltration resin showed the best result in increasing the surface microcrystallinity of primary carious lesions compared to other products.
 
Keywords: Tooth Remineralization, Tooth Demineralization, hardness test, hydroxyapatite,resin infiltration