title: Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.
abstract: OBJECTIVE
  This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions.
  
  
  METHODS
  Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 ºC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05).
  
  
  RESULTS
  Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic.
  
  
  CONCLUSIONS
  Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.
authors.affiliation: Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos Campos, Brazil.
authors.forename: A M M
authors.initials: AM
authors.lastname: Mesquita
authors.forename: M
authors.initials: M
authors.lastname: Ozcan
authors.forename: R O A
authors.initials: RO
authors.lastname: Souza
authors.forename: A N
authors.initials: AN
authors.lastname: Kojima
authors.forename: R S
authors.initials: RS
authors.lastname: Nishioka
authors.forename: E T
authors.initials: ET
authors.lastname: Kimpara
authors.forename: M A
authors.initials: MA
authors.lastname: Bottino
mesh_terms: D002516:Ceramics; D001840:Dental Bonding; D003776:Dental Porcelain; D003801:Dental Veneers; D004868:Equipment Failure; D005898:Glass; D006358:Hot Temperature; D006813:Humidity; D066298:In Vitro Techniques; D008422:Materials Testing; D011897:Random Allocation; D033081:Shear Strength; D013997:Time Factors
chemical_list: C483026:In-Ceram Alumina; C485633:In-Ceram Zirconia; C556625:VITA VM7; D003776:Dental Porcelain