title: Evaluation of the effect of four surface conditioning methods on the shear bond strength of metal bracket to porcelain surface.
abstract: OBJECTIVE
  This study evaluated the effect of superpulse CO2 laser irradiation and deglazing of porcelain surfaces on the shear bond strength (SBS) of metal orthodontic brackets, and compared it with two conventional etching techniques.
  
  
  METHODS
  Forty-eight Feldspathic porcelain fused to metal specimens embedded in cylindrical acrylic resin tubes were fabricated, and all the specimens were divided into four groups. In Group 1, the specimens were roughened with a diamond bur and etched with hydrofluoric acid (HFA) gel for 4 min. In Group 2, the specimens were roughened with a bur and irradiated by a CO2 laser with a 2 W power setting for 20 sec. In Group 3, the specimens were only irradiated by a CO2 laser. In Group 4, the porcelain surface was sandblasted with 50 μm aluminum oxide. Before bonding, the bracket silane was applied on the porcelain surfaces. SBS was evaluated by a Universal testing machine (Zwickroll, Germany). The remaining adhesive after the bond failure was evaluated using an adhesive remnant index (ARI). Statistical analysis was conducted by analysis of variance (ANOVA), Tukey, and Kruskal-Wallis tests.
  
  
  RESULTS
  ANOVA revealed significant differences in SBS among the four groups (p<0.001). Group 1 demonstrated significantly higher bond strength (13.13±2.47) when compared with the other groups. Group 2 showed higher bond strength (9.60±1.91) when compared with group 4 (6.40±1.67) (p=0.016). Group 1 displayed the highest ARI scores among the groups.
  
  
  CONCLUSIONS
  Deglazing combined with HFA etching produced the highest bond strength, but CO2 laser irradiation provided adequate bond strength and allowed for elimination of the HFA step. Deglazing is not recommended as a preliminary step before CO2 laser conditioning.
authors.affiliation: 1 Orthodontic Research Center, Department of Orthodontic, School of Dentistry, Shiraz University of Medical Sciences , Shiraz, Iran .
authors.forename: Hooman
authors.initials: H
authors.lastname: Zarif Najafi
authors.forename: Morteza
authors.initials: M
authors.lastname: Oshagh
authors.forename: Sepideh
authors.initials: S
authors.lastname: Torkan
authors.forename: Bahareh
authors.initials: B
authors.lastname: Yousefipour
authors.forename: Raha
authors.initials: R
authors.lastname: Salehi
mesh_terms: D001840:Dental Bonding / Q000379:methods*; D045662:Dental Etching / Q000379:methods*; D003799:Dental Stress Analysis; D066298:In Vitro Techniques; D054020:Lasers, Gas; D016876:Metal Ceramic Alloys / Q000528:radiation effects*; D016910:Orthodontic Brackets; D033081:Shear Strength; D013499:Surface Properties
chemical_list: D016876:Metal Ceramic Alloys