Standardized cylinders of light-cured composite resin were bonded to the ground labial enamel surface of bovine incisor teeth that had been immersed in double-distilled water for 7 days after having been (a) immersed in hydrogen peroxide for 5, 30, or 60 min, then etched for 60 s with 37% phosphoric acid; (b) immersed in saline for 5, 30, or 60 min, then etched for 60 s with 37% phosphoric acid; (c) etched with 37% phosphoric acid for 60 s, then immersed in hydrogen peroxide for 5, 30, or 60 min; or (d) etched with 37% phosphoric acid for 60 s, then immersed in saline for 5, 30, or 60 min. The enamel surface was washed with water for 1 min and dried with compressed air for 30 s prior to applying the resin. The tooth and applied resin were stored in water at 37 degrees C for 1 day prior to shear and tensile testing. A total of 192 specimens was used, 8 for each enamel preparation mode, for each time period, and for each test. Test values were tabulated and statistically analyzed. Analysis of variance revealed significantly higher bond strength values (p less than 0.005) for hydrogen peroxide-treated as compared with saline-treated specimens. A significant interaction was also noted between test solution and etching order. Scanning electron microscopic examination of failed shear- and tensile-tested specimens revealed no significant solution-related differences in the fracture pattern or the resin quality.(ABSTRACT TRUNCATED AT 250 WORDS)