title: Effect of different bonding conditions on the shear bond strength of two compomers to bovine dentin.
abstract: OBJECTIVE
  Despite the improvements to compomer materials, the bond strength of these materials remains inferior to "composite/resin bonding" systems and limits their clinical use. The purpose of this study was to evaluate the effect of acidic conditioning with phosphoric acid and Prompt L-Pop (PLP) on the shear bond strength of two compomers Dyract AP (DAP) and Composan Glass (CG) to dentin.
  
  
  METHODS
  Sixty extracted bovine teeth were used to test the shear bond strength of two compomers to flat dentin labial surfaces. The dentin specimens were randomly assigned to six groups of ten specimens each: Group 1: DAP and Prime & Bond NT (PBNT); Group 2: DAP/PBNT with a 15 second dentin etch prior to bonding; Group 3: DAP placed with PLP adhesive; Group 4: CG and Compobond NE (CBNE); Group 5: CG/CBNE with a 15 second dentin etch; and Group 6: CG placed with PLP adhesive. The specimens were stored at 37 masculineC with 100% humidity for 24 hours then mounted and sheared using an Instron Universal Testing Machine at a cross head speed of 0.5 mm/min. The results were recorded in Mega Pascals (MPa). The sheared specimens were examined under a light microscope, and the type of failure (adhesive, cohesive, or mixed) was recorded.
  
  
  RESULTS
  The mean dentin shear bond strength value (MPa) for the groups was: Group 1 (11.6+/-3.9); Group 2 (13.2+/-3.3); Group 3 (12.4+/-2.0); Group 4 (13.0+/-4.3); Group 5 (19.3+/-3.7); and Group 6 (13.1+/-3.0). One way analysis of variance (ANOVA) and Tukey HSD post-hoc tests detected a significantly higher bond strength (P = 0.003) for group 5. For groups 1, 3, 4, and 6, the mode of failure was mostly adhesive. When acid etching of dentin was performed (groups 2 and 5), cohesive fracture within dentin was the predominant mode of failure. Acid etching and the use of PLP significantly reduced the number of adhesive fractures and reduced variability in the shear bond strength results.
  
  
  CONCLUSIONS
  Acid etching significantly increased the shear bond strength of CG to dentin but did not affect DAP. The application of PLP resulted in a shear bond strength not statistically different from PBNT or CPNE. CG bond to dentin is improved with acid etching using phosphoric acid. However, PLP provided no significant improvement in the shear bond strength of DAP and CG.
authors.affiliation: Division of Operative Dentistry, Department of Restorative Dental Sciences in the College of Dentistry at King Saud University in Riyadh, Saudi Arabia. h_nahed@yahoo.com
authors.forename: Hend
authors.initials: H
authors.lastname: Al-Nahedh
authors.forename: Nasrien Z
authors.initials: NZ
authors.lastname: Ateyah
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D020770:Compomers; D001840:Dental Bonding; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents; D008422:Materials Testing; D010756:Phosphoric Acids; D019279:Resin Cements; D033081:Shear Strength; D018709:Statistics, Nonparametric
chemical_list: D020770:Compomers; D017220:Dentin-Bonding Agents; C088486:Dyract; D010756:Phosphoric Acids; D019279:Resin Cements; C513778:composan glass compobond; C030242:phosphoric acid