title: Adhesion of dental porcelain to cast, milled, and laser-sintered cobalt-chromium alloys: shear bond strength and sensitivity to thermocycling.
abstract: BACKGROUND
  New technologies have led to the introduction of new materials, so an evaluation of the adhesion of ceramics to these materials is needed.
  
  
  OBJECTIVE
  The purpose of this study was to compare the shear bond strength of dental porcelain to cast, milled, and laser-sintered cobalt-chromium alloys, and to investigate the adhesive bond and failure type after thermocycling, 90 metal cylinders (10 mm diameter and 10 mm height) were prepared from cast (30 specimens), milled (30 specimens), and laser-sintered (30 specimens) alloys.
  
  
  METHODS
  Ceramic cylinders (2.5 mm diameter and 4 mm length) were fused to the alloy cylinders. For each group, 15 specimens were thermocycled 5500 times at temperatures between 4°C and 60°C before testing. After testing, the specimen surfaces were visually examined to determine the failure mode. Differences in adhesion values according to manufacturing method, testing condition (thermocycling or no thermocycling), and interaction between the factors were evaluated with a 2-way ANOVA. The χ(2) test (95% confidence level) was performed to determine whether the failure mode was associated with the testing condition.
  
  
  RESULTS
  Adhesion strengths for the nonthermocycled specimens were 42.79 ±14.14 MPa (cast), 37.56 ±9.18 MPa (milled), and 29.09 ±6.95 MPa (laser-sintered), and, for the thermocycled specimens, 16.52 ±8.96 MPa (cast), 22.21 ±13.25 MPa (milled), and 24.28 ±10.13 MPa (laser-sintered). Two-way ANOVA results indicated no statistically significant differences in adhesion among the manufacturing methods (P=.257), but statistically significant differences were observed according to both testing conditions (P<.001) and interaction between the factors (P=.015). The χ(2) test indicated that the failure mode was not associated with the testing condition (thermocycled, P=.280; nonthermocycled, P=.240).
  
  
  CONCLUSIONS
  The porcelain adhesion values for all the materials were adequate for clinical applications. No significant adhesion differences were observed between cast, milled, and laser-sintered specimens, or among thermocycled and nonthermocycled laser-sintered specimens. However, significant adhesion differences were observed among the thermocycled and nonthermocycled cast and the milled specimens.
authors.affiliation: Graduate student, Dentistry Laboratory and Clinical Technique Research, International University of Catalunya, Barcelona, Spain. Electronic address: pep@denteklab.net.
authors.forename: Josep
authors.initials: J
authors.lastname: Serra-Prat
authors.affiliation: Research Collaborator, Department of Prosthodontics, International University of Catalunya, Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Cano-Batalla
authors.affiliation: Professor, Chairman of Department of Prosthodontics, International University of Catalunya, Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Cabratosa-Termes
authors.affiliation: Professor, Faculty of Department of Prosthodontics, International University of Catalunya, Barcelona, Spain.
authors.forename: Oscar
authors.initials: O
authors.lastname: Figueras-Àlvarez
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry*; D017076:Computer-Aided Design; D001840:Dental Bonding; D003735:Dental Casting Technique; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006358:Hot Temperature; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D033081:Shear Strength; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
chemical_list: D000538:Aluminum Silicates; D002858:Chromium Alloys; D016876:Metal Ceramic Alloys; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar