title: Shear bond strength of veneering porcelain to zirconia: Effect of surface treatment by CNC-milling and composite layer deposition on zirconia.
abstract: The purpose of this study was to evaluate the shear bond strength of veneering feldspathic porcelain to zirconia substrates modified by CNC-milling process or by coating zirconia with a composite interlayer.
  
  
  
  Four types of zirconia-porcelain interface configurations were tested: RZ - porcelain bonded to rough zirconia substrate (n=16); PZ - porcelain bonded to zirconia substrate with surface holes (n=16); RZI - application of a composite interlayer between the veneering porcelain and the rough zirconia substrate (n=16); PZI - application of a composite interlayer between the porcelain and the zirconia substrate treated by CNC-milling (n=16). The composite interlayer was composed of zirconia particles reinforced porcelain (30%, vol%). The mechanical properties of the ceramic composite have been determined. The shear bond strength test was performed at 0.5mm/min using a universal testing machine. The interfaces of fractured and untested specimens were examined by FEG-SEM/EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The one-way ANOVA followed by Tukey HSD multiple comparison test was used to compare shear bond strength results (α=0.05).
  
  
  
  The shear bond strength of PZ (100±15MPa) and RZI (96±11MPa) specimens were higher than that recorded for RZ (control group) specimens (89±15MPa), although not significantly (p>0.05). The highest shear bond strength values were recorded for PZI specimens (138±19MPa), yielding a significant improvement of 55% relative to RZ specimens (p<0.05).
  
  
  
  This study shows that it is possible to highly enhance the zirconia-porcelain bond strength - even by ~55% - by combining surface holes in zirconia frameworks and the application of a proper ceramic composite interlayer.
authors.affiliation: Department of Materials Engineering, Federal University of Rio Grande do Norte (UFRN), Campus Lagoa Nova, 59078-970 Natal, Brazil.
authors.forename: R L P
authors.initials: RLP
authors.lastname: Santos
authors.affiliation: Center for MicroElectroMechanical Systems (CMEMS-UMinho), University of Minho, Campus Azurém, Guimarães 4800-058, Portugal.
authors.forename: F S
authors.initials: FS
authors.lastname: Silva
authors.affiliation: Department of Materials Engineering, Federal University of Rio Grande do Norte (UFRN), Campus Lagoa Nova, 59078-970 Natal, Brazil.
authors.forename: R M
authors.initials: RM
authors.lastname: Nascimento
authors.affiliation: Center for MicroElectroMechanical Systems (CMEMS-UMinho), University of Minho, Campus Azurém, Guimarães 4800-058, Portugal; Center for Research on Dental Implants (CEPID), Post-Graduation Program in Dentistry (PPGO), Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC, Brazil.
authors.forename: J C M
authors.initials: JCM
authors.lastname: Souza
authors.affiliation: Department of Materials Engineering, Federal University of Rio Grande do Norte (UFRN), Campus Lagoa Nova, 59078-970 Natal, Brazil.
authors.forename: F V
authors.initials: FV
authors.lastname: Motta
authors.affiliation: Center for MicroElectroMechanical Systems (CMEMS-UMinho), University of Minho, Campus Azurém, Guimarães 4800-058, Portugal.
authors.forename: O
authors.initials: O
authors.lastname: Carvalho
authors.affiliation: Center for MicroElectroMechanical Systems (CMEMS-UMinho), University of Minho, Campus Azurém, Guimarães 4800-058, Portugal; Laboratory of Ceramic and Composite Materials (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis, SC, Brazil. Electronic address: brunohenriques@dem.uminho.pt.
authors.forename: B
authors.initials: B
authors.lastname: Henriques
mesh_terms: D001840:Dental Bonding; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D033081:Shear Strength; D013499:Surface Properties; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: CNC-created surface holes; Composite interlayer; Feldspathic porcelain; Shear bond strength; Zirconia