Although the phosphoric acid etching method are using widely for the bonding between enamel and resin, problems such as demineralization, depth of etch, softening are reported. Evaluations of etching efficacy of other acids are necessary- to improve it. The purpose of this study was an evaluation of the possibility of substitution; of pyruvic acid for phopphoric acid. Aqueous solutions of pyruvic and phosphoric acid with 5%, 10%, 20%, 40%, 60%, 85% concentration were prepared and used as etchants on bovine enamel surface. 11 experimental groups Nvere planned including 0% distilled water, a control group was 40% phosphoric acid solution. Shear bond strength between etched enamel and an experimental BIS-GMA composite resin were measured using Instron, surface roughness and depth of etch were measured using profilometer, and surface topography were observed using SEM.
1. A concentration of pyruvic acid groups which showed the highest shear bond strength and surface roughness, and the sigrvficant irregular surface was 20%.
2. Shear bond strength of 20% pyruvic acid group was same with it of 40% phosphoric acid group, however
values of surface roughness and depth of etch were smaller than those- of 409e´ phosphoric acid group.
3. Depth of etch of phosphoric acid groups were increased until to 40% group and then it was decreased, depth
of etch oT pyruvic acid groups were increased with the rise of concentration.
x RTnivic acid could be considered as a substitute etchant for phosphric acid with same bond strength and smaller surface roughness and depth of etch, and its optimal´ concentration was assumed smaller than 20%.
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