title: Effect of surface conditioning modalities on the repair bond strength of resin composite to the zirconia core / veneering ceramic complex.
abstract: OBJECTIVE
  This study evaluated the effect of different surface conditioning protocols on the repair strength of resin composite to the zirconia core / veneering ceramic complex, simulating the clinical chipping phenomenon.
  
  
  METHODS
  Forty disk-shaped zirconia core (Lava Zirconia, 3M ESPE) (diameter: 3 mm) specimens were veneered circumferentially with a feldspathic veneering ceramic (VM7, Vita Zahnfabrik) (thickness: 2 mm) using a split metal mold. They were then embedded in autopolymerizing acrylic with the bonding surfaces exposed. Specimens were randomly assigned to one of the following surface conditioning protocols (n = 10 per group): group 1, veneer: 4% hydrofluoric acid (HF) (Porcelain Etch) + core: aluminum trioxide (50-µm Al2O3) + core + veneer: silane (ESPE-Sil); group 2: core: Al2O3 (50 µm) + veneer: HF + core + veneer: silane; group 3: veneer: HF + core: 30 µm aluminum trioxide particles coated with silica (30 µm SiO2) + core + veneer: silane; group 4: core: 30 µm SiO2 + veneer: HF + core + veneer: silane. Core and veneer ceramic were conditioned individually but no attempt was made to avoid cross contamination of conditioning, simulating the clinical intraoral repair situation. Adhesive resin (VisioBond) was applied to both the core and the veneer ceramic, and resin composite (Quadrant Posterior) was bonded onto both substrates using polyethylene molds and photopolymerized. After thermocycling (6000 cycles, 5°C-55°C), the specimens were subjected to shear bond testing using a universal testing machine (1 mm/min). Failure modes were identified using an optical microscope, and scanning electron microscope images were obtained. Bond strength data (MPa) were analyzed statistically using the non-parametric Kruskal-Wallis test followed by the Wilcoxon rank-sum test and the Bonferroni Holm correction (α = 0.05).
  
  
  RESULTS
  Group 3 demonstrated significantly higher values (MPa) (8.6 ± 2.7) than those of the other groups (3.2 ± 3.1, 3.2 ± 3, and 3.1 ± 3.5 for groups 1, 2, and 4, respectively) (p < 0.001). All groups showed exclusively adhesive failure between the repair resin and the core zirconia. The incidence of cohesive failure in the ceramic was highest in group 3 (8 out of 10) compared to the other groups (0/10, 2/10, and 2/10, in groups 1, 2, and 4, respectively). SEM images showed that air abrasion on the zirconia core only also impinged on the veneering ceramic where the etching pattern was affected.
  
  
  CONCLUSIONS
  Etching the veneer ceramic with HF gel and silica coating of the zirconia core followed by silanization of both substrates could be advised for the repair of the zirconia core / veneering ceramic complex.
authors.affiliation: University of Zurich, Zurich, Switzerland. mutluozcan@hotmail.com
authors.forename: Mutlu
authors.initials: M
authors.lastname: Ozcan
authors.forename: Luiz Felipe
authors.initials: LF
authors.lastname: Valandro
authors.forename: Sarina Maciel
authors.initials: SM
authors.lastname: Pereira
authors.forename: Regina
authors.initials: R
authors.lastname: Amaral
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Bottino
authors.forename: Gurel
authors.initials: G
authors.lastname: Pekkan
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods*; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D017269:Dental Prosthesis Repair; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D006801:Humans; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D058105:Polymerization; D017680:Potassium Compounds / Q000737:chemistry; D033081:Shear Strength; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D003764:Dental Materials; D017680:Potassium Compounds; D012821:Silanes; C556625:VITA VM7; D003776:Dental Porcelain; C016447:feldspar; D017438:Bisphenol A-Glycidyl Methacrylate; C081713:Visio-Bond; D015040:Zirconium; D000537:Aluminum Oxide; D006858:Hydrofluoric Acid; C028541:zirconium oxide