title: Surface treatment with a fractional CO2 laser enhances shear bond strength of resin cement to zirconia.
abstract: OBJECTIVE
  The present study investigated the effect of different surface treatments on shear bond strength (SBS) of resin cement to zirconia.
  
  
  METHODS
  Ninety zirconia blocks were prepared and divided into 6 groups of 15 by treatment. Group 1 served as the control group, whereas groups 2 and 3 were treated with air abrasion and a universal primer (Monobond plus), respectively. The remaining zirconia copings were treated with a fractional CO2 laser for 10 seconds using 10 W/10 mJ (group 4), 10 w/14 mJ (group 5) or 20 W/10 mJ (group 6). A luting cement (Clearfil SA) was bonded to the treated zirconia surfaces and cured for 40 seconds. SBS was measured with a universal testing machine and the type of bond failure was determined.
  
  
  RESULTS
  There was a statistically significant difference in SBS among the study groups (p<0.001). The highest SBS values were observed in the groups treated with the fractional CO2 laser at settings of 20 W/10 mJ (28.1 MPa) or 10 W/14 mJ (27.4 MPa), followed by the specimens treated with the universal primer (22.8 MPa). The control specimens exhibited the lowest SBS (9.4 MPa) among the study groups (p<0.05). There was no significant difference in the distribution of failure modes among the groups (p=0.871).
  
  
  CONCLUSIONS
  The application of fractional CO2 laser can improve bond strength of resin cement to zirconia ceramic, and thus it could be considered as an appropriate alternative to conventional methods of zirconia surface treatment.
authors.affiliation: Assistant Professor of Orthodontics, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Farzaneh
authors.initials: F
authors.lastname: Ahrari
authors.affiliation: Assistant Professor of Restorative Dentistry, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Boruziniat
authors.affiliation: School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Mehrnoosh
authors.initials: M
authors.lastname: Alirezaei
keywords: CO2; Zirconia; bond strength; ceramic; fractional; laser; porcelain; resin cement; surface treatment