title: Effect of Er,Cr:YSGG laser parameters on shear bond strength and microstructure of dentine.
abstract: OBJECTIVE
  The objective of this study was to investigate the effect of different Er,Cr:YSGG laser parameters on the morphology of irradiated dentine and the shear bond strength between resin composites and irradiated dentine.
  
  
  METHODS
  Dentine specimens prepared from extracted human third molars were randomly assigned to six groups, including one receiving phosphoric acid etching, and five others with different laser parameters: 5 W for 30 sec, 2.5 W for 30 sec, 2.5 W for 60 sec, 1.5 W for 30 sec, and 1.5 W for 100 sec. Surface morphology was examined using a scanning electron microscope (SEM). Average roughness (Ra) was determined with a profilometer. Bonding of resin composites to the dentine specimens was tested in shear mode.
  
  
  RESULTS
  The dentine surfaces irradiated by the Er,Cr:YSGG laser showed a scaly and rugged appearance and open dentinal tubules without smear layer production. The 5-W-irradiated group had the highest roughness value (p < 0.05). One-way ANOVA revealed that the shear bond strength of resin composites to the laser-irradiated dentine ranged from 12.35-15.61 MPa, and was not significantly (p > 0.05) different from the bond strength seen in the acid-etched dentine of 19.06 MPa. However, the surface roughness of the laser-irradiated dentine was significantly (p < 0.05) higher than that of the acid-etched dentine.
  
  
  CONCLUSIONS
  The 5-W power setting may be suitable for dental restoration applications in terms of shear bond strength and activation area.
authors.affiliation: Department of Dentistry, Chung-Shan Medical University Hospital, Taichung, Taiwan, ROC.
authors.forename: Jang-Ching
authors.initials: JC
authors.lastname: Chou
authors.forename: Chun-Cheng
authors.initials: CC
authors.lastname: Chen
authors.forename: Shinn-Jyh
authors.initials: SJ
authors.lastname: Ding
mesh_terms: D000134:Acid Etching, Dental; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000295:instrumentation / Q000379:methods; D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008963:Molar; D016369:Smear Layer; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents