title: Effect of CO2 and Nd:YAG Lasers on Shear Bond Strength of Resin Cement to Zirconia Ceramic.
abstract: OBJECTIVE
  Because of poor bond between resin cement and zirconia ceramics, laser surface treatments have been suggested to improve adhesion. The present study evaluated the effect of CO2 and Nd:YAG lasers on the shear bond strength (SBS) of resin cement to zirconia ceramic.
  
  
  METHODS
  Ninety zirconia disks (6×2 mm) were randomly divided into six groups of 15. In the control group, no surface treatment was used. In the test groups, laser surface treatment was accomplished using CO2 and Nd:YAG lasers, respectively (groups two and three). Composite resin disks (3×2 mm) were fabricated and cemented to zirconia disks with self-etch resin cement and stored in distilled water for 24 hours. In the test groups four-six, the samples were prepared as in groups one-three and then thermocycled and stored in distilled water for six months. The SBS tests were performed (strain rate of 0.5 mm/min). The fracture modes were observed via stereomicroscopy. Data were analyzed with one and two-way ANOVA, independent t and Tukey's tests.
  
  
  RESULTS
  The SBS values of Nd:YAG group (18.95±3.46MPa) was significantly higher than that of the CO2 group (14.00±1.96MPa), but lower than that of controls (23.35±3.12MPa). After thermocycling and six months of water storage, the SBS of the untreated group (1.80±1.23 MPa) was significantly lower than that of the laser groups. In groups stored for 24 hours, 60% of the failures were adhesive; however, after thermocycling and six months of water storage, 100% of failures were adhesive.
  
  
  CONCLUSIONS
  Bonding durability of resin cement to zirconia improved with CO2 and Nd:YAG laser surface treatment of zirconia ceramic.
authors.affiliation: Professor, Dental Research Center, Department of Restorative Dentistry, Dental School, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Shahin
authors.initials: S
authors.lastname: Kasraei
authors.affiliation: Associate Professor, Dental Research Center, Department of Operative Dentistry, Dental School, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Loghman
authors.initials: L
authors.lastname: Rezaei-Soufi
authors.affiliation: Assistant Professor, Department of Operative Dentistry, Dental School, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Yarmohamadi
authors.affiliation: Postgraduate Student, Department of Restorative Dentistry, Dental School, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Amanj
authors.initials: A
authors.lastname: Shabani
keywords: Lasers, Gas; Lasers, Solid-State; Resin Cements; Yttria Stabilized Tetragonal Zirconia