A comparison of surface roughness and composite/enamel bond strength of human enamel following the application of the Nd:YAG laser and etching with phosphoric acid

Abstract

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.