Topographical characteristics and shear bond strength of tooth surfaces cut with a laser-powered hydrokinetic system

Abstract

Statement of problem. Erbium lasers, specifically Er;YAG and Er,Cr;YSGG that emit in the near red wavelengths, cut both enamel and dentine. Bonding to these cut surfaces with composites has not been assessed for all laser systems. Purpose. This investigation assessed the shear bond strength of composite bonded to tooth structure treated with an Er,Cr;YSGG–powered hydrokinetic system (HKS, Millennium system) and then was compared with surfaces treated with a carbide bur. Material and methods. Extracted human molars were cut into enamel and dentin with both systems. Nonetched and acid-etched subgroups were evaluated. Shear bond strength was measured with an Instron test machine with a knife-edge loading head. In addition, SEMs were evaluated. Results. There were no significant differences in shear bond strength between etched bur cut (23.3 ± 2.5 MPa), etched laser-cut enamel (23.7 ± 4.5 MPa), and nonetched laser-cut enamel (20.5 ± 2.8 MPa). For nonetched enamel, bond strength values for laser-cut surfaces were significantly higher than the bur-cut surfaces (8.7 ± 4.3 MPa). Bond strength differences for dentin between bur (14.3 ± 1.7 MPa) and laser cuts (11.5 ± 4.3 MPa) were not significant ( P =.03). SEM revealed that laser cutting of enamel did not cause formation of a smear layer. Conclusion. There were no significant differences in shear bond strength between etched bur-cut, etched laser-cut, and nonetched laser-cut enamel. With nonetched enamel, bond strength values for nonetched laser-cut surfaces were significantly higher than for the bur-cut surfaces. No bond strength differences between bur and laser cutting existed for dentin. Similar topography was observed for bur and laser prepared surfaces of etched enamel and nonetched dentin. (J Prosthet Dent 1999:82:451-5.)