title: Effect of water storage and surface treatments on the tensile bond strength of IPS Empress 2 ceramic.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of water storage (24 hours and 1 year) on the tensile bond strength between the IPS Empress 2 ceramic and Variolink II resin cement under different superficial treatments.
  
  
  METHODS
  One hundred and eighty disks with diameters of 5.3 mm at the top and 7.0 mm at the bottom, and a thickness of 2.5 mm were made, embedded in resin, and randomly divided into six groups: Groups 1 and 4 = 10% hydrofluoric acid for 20 seconds; Groups 2 and 5 = sandblasting for 5 seconds with 50 microm aluminum oxide; and Groups 3 and 6 = sandblasting for 5 seconds with 100 microm aluminum oxide. Silane was applied on the treated ceramic surfaces, and the disks were bonded into pairs with adhesive resin cement. The samples of Groups 1 to 3 were stored in distilled water at 37 degrees C for 24 hours, and Groups 4 to 6 were stored for 1 year. The samples were subjected to a tensile strength test in an Instron universal testing machine at a crosshead speed of 1.0 mm/min, until failure. The data were submitted to analysis of variance and Tukey's test (5%).
  
  
  RESULTS
  The means of the tensile bond strength of Groups 1, 2, and 3 (15.54 +/- 4.53, 10.60 +/- 3.32, and 7.87 +/- 2.26 MPa) for 24-hour storage time were significantly higher than those observed for the 1-year storage (Groups 4, 5, and 6: 10.10 +/- 3.17, 6.34 +/- 1.06, and 2.60 +/- 0.41 MPa). The surface treatments with 10% hydrofluoric acid (15.54 +/- 4.53 and 10.10 +/- 3.17 MPa) showed statistically higher tensile bond strengths compared with sandblasting with 50 microm(10.60 +/- 3.32 and 6.34 +/- 1.06 MPa) and 100 microm (7.87 +/- 2.26 and 2.60 +/- 0.41 MPa) aluminum oxide for the storage time 24 hours and 1 year.
  
  
  CONCLUSIONS
  Storage time significantly decreased the tensile bond strength for both ceramic surface treatments. The application of 10% hydrofluoric acid resulted in stronger tensile bond strength values than those achieved with aluminum oxide.
authors.affiliation: Division of Dental Meterials, Department of Restorative Dentistry, Piracicaba School of Dentistry, State University of Campinas, Av. Limeira 901, Piracicaba, São Paulo, CEP 13414-903, Brazil.
authors.forename: Luciana A
authors.initials: LA
authors.lastname: Salvio
authors.forename: Lourenço
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: Simonides
authors.initials: S
authors.lastname: Consani
authors.forename: Mário A C
authors.initials: MA
authors.lastname: Sinhoreti
authors.forename: Mario F
authors.initials: MF
authors.lastname: de Goes
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Knowles
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000009:adverse effects*
chemical_list: D000538:Aluminum Silicates; D003764:Dental Materials; C075815:IPS-Empress ceramic; D019279:Resin Cements; D014867:Water; D003776:Dental Porcelain; C103502:Variolink