OBJECTIVES: This study was conducted to evaluate enamel morphology after laser etching and acid etching and to determine the shear bond strength of composite to acid-etched and laser-treated enamel. METHODS: Enamel from freshly extracted permanent molar teeth was subjected to either laser treatment with an Nd:YAG laser in different laser parameters or was exposed to 37% phosphoric acid for 60 s (Gluma Gel, Bayer Dental). Surface profile analysis of the enamel was undertaken with a Perthometer (S8P, Feinpruif). The results were analyzed by SPSS/PC multiple range test and Student-Newman Keuls procedure. Specimens were examined in a scanning electron microscope (SEM). Shear bond strengths of acid-etched and laser-etched enamel/composite (Brilliant Dentin, Coltene AG and Pekalux, Bayer Dental) were also determined. These results were compared by SPSS/PC multiple range test. RESULTS: The acid-etched specimens exhibited a qualitatively different type of enamel surface morphology when compared with the laser-treated specimens. Laser treatment at higher exposures resulted in the formation of microcracks and fissures. No significant difference in surface roughness was observed between laser-treated enamel in three different parameters (10 pps, 0.8 W; 15 pps, 1.0 W; 20 pps, 1.25 W) and acid-etched specimens. However, the mean bond strengths of all laser-treated specimens, regardless of the test parameters, were significantly lower (p < 0.05) than the acid-etched enamel specimens. SIGNIFICANCE: Although the laser roughened the surface of the enamel, it did not provide a surface as retentive as a surface treated with conventional acid etching. It is concluded from this study that the Nd:YAG laser operated under the conditions described cannot be recommended as a viable alternative to acid etching.
OBJECTIVES: This study was conducted to evaluate enamel morphology after laser etching and acid etching and to determine the shear bond strength of composite to acid-etched and laser-treated enamel. METHODS: Enamel from freshly extracted permanent molar teeth was subjected to either laser treatment with an Nd:YAG laser in different laser parameters or was exposed to 37% phosphoric acid for 60 s (Gluma Gel, Bayer Dental). Surface profile analysis of the enamel was undertaken with a Perthometer (S8P, Feinpruif). The results were analyzed by SPSS/PC multiple range test and Student-Newman Keuls procedure. Specimens were examined in a scanning electron microscope (SEM). Shear bond strengths of acid-etched and laser-etched enamel/composite (Brilliant Dentin, Coltene AG and Pekalux, Bayer Dental) were also determined. These results were compared by SPSS/PC multiple range test. RESULTS: The acid-etched specimens exhibited a qualitatively different type of enamel surface morphology when compared with the laser-treated specimens. Laser treatment at higher exposures resulted in the formation of microcracks and fissures. No significant difference in surface roughness was observed between laser-treated enamel in three different parameters (10 pps, 0.8 W; 15 pps, 1.0 W; 20 pps, 1.25 W) and acid-etched specimens. However, the mean bond strengths of all laser-treated specimens, regardless of the test parameters, were significantly lower (p < 0.05) than the acid-etched enamel specimens. SIGNIFICANCE: Although the laser roughened the surface of the enamel, it did not provide a surface as retentive as a surface treated with conventional acid etching. It is concluded from this study that the Nd:YAG laser operated under the conditions described cannot be recommended as a viable alternative to acid etching.