The aim of this study is to determine the hardness and roughness of glass ionomer cement, glass carbomer, and compomer by nanoindentation. Three different dental restorative materials: glass ionomer cement, glass carbomer cement, and compomer were used. Disc specimens (10 mm × 1 mm) were prepared from each material using teflon mold. All specimens were light cured according to the manufacturer's instructions. The specimens were then mounted in polyacrilic resin. After grinding and polishing the specimens were stored in distilled water at 37• C for 1 day. The specimens were investigated using nanoindenter. The highest nanohardness was measured for glass ionomer cement and the lowest for glass carbomer. Regarding roughness, glass ionomer cement and compomer showed the highest mean values. Glass ionomer cement and compomer exhibited similar nanomechanical properties. Glass carbomer had superior ability to be polished up.

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To produce good adhesion between composite resin and etched enamel surface, it is necessary to form a microscopically intimate contact between them. Contaminants, like saliva, may interfere with such bonding. Salivary contamination may reduce the bond strength between composite resin and the enamel by 40 to 60%. Recent studies have suggested that only rewashing and drying of the etched and saliva contaminated enamel surface is sufficient in restoring bond strength to the normal ideal condition. Purpose:To evaluate the effect of saliva contamination on the shear bond strength of composite resin to enamel by using different parameters. Materials and methods:The highest mean shear bond strength of composite resin was obtained on the uncontaminated enamel surface, and the lowest mean shear bond strength was obtained on the saliva contaminated moist enamel surface. Results:The mean shear bond strength of composite resin to saliva contaminated, washed and air-dried enamel surface was less than the mean shear bond strength to the dry enamel surface. Conclusion:This suggests that only rewashing of the saliva contaminated enamel surface is not enough in achieving bond strength equal to that of the uncontaminated enamel surface.