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/

Objectives. This study was conducted to evaluate enamel morphology aft er laser etching and acid etching and to determine the shear bond stre ngth of composite to acid-etched and laser-treated enamel. Methods. En amel from freshly extracted permanent molar teeth was subjected to eit her laser treatment with an Nd:YAG laser in different laser parameters or was exposed to 37% phosphoric acid for 60 s (Gluma Gel, Bayer Dent al). Surface profile analysis of the enamel was undertaken with a Pert hometer (S8P, Feinpruif). The results were analyzed by SPSS/PC multipl e range test and Student-Newman Keuls procedure. Specimens were examin ed in a scanning electron microscope (SEM). Shear bond strengths of ac id-etched and laser-etched enamel/composite (Brilliant Dentin, Coltene AG and Pekalux, Bayer Denial) were also determined. These results wer e compared by SPSS/PC multiple range test. Results. The acid-etched sp ecimens exhibited a qualitatively different type of enamel surface mor phology when compared with the laser-treated specimens. Laser treatmen t at higher exposures resulted in the formation of microcracks and fis sures. No significant difference in surface roughness was observed bet ween 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, t he mean bond strengths of all laser-treated specimens, regardless of t he test parameters, were significantly lower (p < 0.05) than the acid- etched enamel specimens. Significance. Although the laser roughened th e 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 descri bed cannot be recommended as a viable alternative to acid etching.