Effects of various acids on the buccal surface of human permanent teeth: a study using scanning electron microscopy.

Contradictory evidence exists as to the acid necessary for producing optimum enamel etching on buccal tooth surfaces. The aims of this study were to (1) compare the etching abilities of four different acids; (2) identify the acid concentrations required for optimum etching; and (3) determine the concentration stability of phosphoric acid solutions. Crowns of caries-free molar teeth were pumiced, sectioned mesiodistally, washed, and dried. Study groups of 10 specimens were etched with either phosphoric, lactic, citric, or pyruvic acid prepared in concentrations from 5 to 70%. Etching was performed for 1, 11/2, or 5 minutes. Specimens were prepared and examined with scanning electron microscopy. To simulate clinical conditions, the final part of the experiment exposed 37% HAP04 to room air for various time periods. Stability of the acid concentration was determined. Phosphoric acid produced the most desirable etching effects when applied for either 60 or 90 seconds. Investigations of different concentrations of phosphoric acid suggested that a superior etching result is obtained within the range of 30 to 40%. Titration experiments revealed that 37% phosphoric acid was reasonably stable under normal clinical conditions. Introduction Using 85% phosphoric acid, Buonoeore 1 demonstrated that treating enamel surfaces with acid enhanced adhesion of resins to tooth surfaces. The adhe sion was improved by etching the enamel surface with the acid. However, as various resin materials were introduced to the commercial market, other acids were suggested as etchants. 2-4 This has led to controversy as to the type of acid necessary for producing optimum enamel etching on buccal tooth surfaces. Therefore, the initial aim of this investigation was to compare the etching abilities of four different acids on human buc* This study was supported by the Ontario Ministry of Health