title: Zirconia-porcelain bonding: effect of multiple firings on microtensile bond strength.
abstract: OBJECTIVE
  To determine the bond strength between zirconia and porcelain with varying numbers of veneer firing cycles.
  
  
  METHODS
  Fifty specimens of zirconia veneered with feldspathic ceramic were submitted to one (1-firing), two (2-firings), three (3-firings), four (4-firings), or five (5-firings) firing cycles to sinter the porcelain. After the respective number of firings, the specimens were embedded into acrylic resin and sectioned into bars with a 1-mm2 cross-sectional area. The microbars were bonded to a special device and attached to a universal testing machine (Emic DL 1000). Microtensile bond strength testing (MTBS) was performed at 0.5 mm/min. The maximum load for fracture was recorded (N) and the microtensile bond strength was calculated in MPa. Data were analyzed using one-way ANOVA and Tukey's test (α = 0.05). The Weibull modulus and characteristic strength was also calculated for each experimental group.
  
  
  RESULTS
  Specimens submitted to a single firing cycle presented the lowest bond strength values (14.1 MPa), two firing cycles provided intermediate bond strength values (15 MPa) and the other groups presented equivalently high values (18.1 - 18.4 MPa). The Weibull modulus did not change between the groups.
  
  
  CONCLUSIONS
  More than three firing cycles of a veneer ceramic provided higher bond strengths between zirconia and the veneering ceramic.
authors.forename: Flávia Z
authors.initials: FZ
authors.lastname: Trindade
authors.forename: Marina
authors.initials: M
authors.lastname: Amaral
authors.forename: Renata M
authors.initials: RM
authors.lastname: Melo
authors.forename: Marco A
authors.initials: MA
authors.lastname: Bottino
authors.forename: Luiz Felipe
authors.initials: LF
authors.lastname: Valandro
mesh_terms: D000268:Adhesiveness; D000538:Aluminum Silicates / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D055119:Elastic Modulus; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D017680:Potassium Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D003764:Dental Materials; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar; D015040:Zirconium; C028541:zirconium oxide