This investigation compared the effect of smear layer removal using various treatments with polyacrylic acid on the shear bond strength of glass ionomer restorative materials to dentin. Three brands of glass ionomer were applied to prepared dentin surfaces of extracted human molars, after one of four treatments with polyacrylic acid. Samples using dentin surfaces with the smear layer left intact served as controls. Comparison of mean shear bond strength values for all possible combinations of restorative material and polyacrylic acid treatment indicated that samples produced using 25% polyacrylic acid had lower (p less than 0.05) values in some instances. No other significant differences were found when test values were compared with each other or with control values. The authors concluded that removal of the smear layer does not enhance the dentin-glass ionomer restorative bond strength, as has been suggested by other investigators. Scanning electron photomicrographs indicate that treatment with higher concentrations of polyacrylic acid produces higher degrees of dentinal tubular orifice patency.
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