A comparative study of three etching solutions. Effects on contact angle, rate of etching and tensile bond strength

Summary Conditioning of the enamel surface is an accepted procedure in several disciplines of dentistry to obtain increased bonding of dental materials to tooth surfaces. Three etching solutions commonly in use are 50% phosphoric acid, 50% phosphoric acid attenuated with 7% zinc oxide by weight and 50% citric acid. The effects of these solutions on the contact angle of an uncured epoxy resin on, and the bond strength of an epoxy resin formulation to polished enamel surfaces were investigated and compared with the results obtained on polished, unconditioned surfaces. In addition, the rates of etching of enamel surfaces by these acids were determined. The attenuated phosphoric acid produced the greatest reduction in contact angles and the most marked increase in bond strengths. 50% phosphoric acid etched the enamel surface to a greater extent than the other conditioning solutions.