The effect of smear layer removal on the in vitro cytotoxicity of four dental restorative materials

Abstract

Smear layer removal has been advocated in vivo by some authors to increase the bonding of certain dental restorative materials and to remove any bacteria remaining after cavity preparation. The possibility of an increase in the chemical toxicity of restorative materials after smear layer removal is difficult to evaluate in vivo due to the effect of other variables such as an increase in bacterial penetration and possible toxicity of the conditioners employed. Therefore, the present study set out to determine whether smear layer removal would influence the in vitro cytotoxicity of four dental restorative materials. The model cavity system was employed using dentine slices 100 μm and 500 μm thick with or without a smear layer present. After an initial study to determine the effect of a range of conditioners on eugenol release through treated dentine phosphoric acid was used for smear layer removal. With 100-μm dentine slices the cytotoxicity of Kalzinol, AquaCem and Poly-F Plus was significantly increased after smear layer removal but not zinc phosphate cement. With 500-gmm slices only the cytotoxicity of Kalzinol increased after smear layer removal. Therefore, it appears that smear layer removal, particularly if the intervening dentine is thin, will increase the cytotoxicity of some dental restorative materials.