title: Residual compressive surface stress increases the bending strength of dental zirconia.
abstract: To assess the influence of surface treatment and thermal annealing on the four-point bending strength of two ground dental zirconia grades.
  
  
  
  Fully-sintered zirconia specimens (4.0×3.0×45.0mm3) of Y-TZP zirconia (LAVA Plus, 3M ESPE) and Y-TZP/Al2O3zirconia (ZirTough, Kuraray Noritake) were subjected to four surface treatments: (1) 'GROUND': all surfaces were ground with a diamond-coated grinding wheel on a grinding machine; (2) 'GROUND+HEAT': (1) followed by annealing at 1100°C for 30min; (3) 'GROUND+Al2O3SANDBLASTED': (1) followed by sandblasting using Al2O3; (4) 'GROUND+CoJet SANDBLASTED': (1) followed by tribochemical silica (CoJet) sandblasting. Micro-Raman spectroscopy was used to assess the zirconia-phase composition and potentially induced residual stress. The four-point bending strength was measured using a universal material-testing machine.
  
  
  
  Weibull analysis revealed a substantially higher Weibull modulus and slightly higher characteristic strength for ZirTough (Kuraray Noritake) than for LAVA Plus (3M ESPE). For both zirconia grades, the 'GROUND' zirconia had the lowest Weibull modulus in combination with a high characteristic strength. Sandblasting hardly changed the bending strength but substantially increased the Weibull modulus of the ground zirconia, whereas a thermal treatment increased the Weibull modulus of both zirconia grades but resulted in a significantly lower bending strength. Micro-Raman analysis revealed a higher residual compressive surface stress that correlated with an increased bending strength.
  
  
  
  Residual compressive surface stress increased the bending strength of dental zirconia. Thermal annealing substantially reduced the bending strength but increased the consistency (reliability) of 'GROUND' zirconia.
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Kapucijnenvoer 7, blok a bus 7001, B-3000 Leuven, Belgium; Tokyo Medical and Dental University, Graduate School of Medical and Dental Sciences, Gerodontology and Oral Rehabilitation, 1-5-45 Yushima, Bunkyo, Tokyo 113-8510, Japan.
authors.forename: Masanao
authors.initials: M
authors.lastname: Inokoshi
authors.affiliation: KU Leuven (University of Leuven), Department of Materials Engineering, Kasteelpark Arenberg 44, B-3001 Heverlee, Belgium.
authors.forename: Fei
authors.initials: F
authors.lastname: Zhang
authors.affiliation: KU Leuven (University of Leuven), Department of Materials Engineering, Kasteelpark Arenberg 44, B-3001 Heverlee, Belgium.
authors.forename: Kim
authors.initials: K
authors.lastname: Vanmeensel
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Kapucijnenvoer 7, blok a bus 7001, B-3000 Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.affiliation: Tokyo Medical and Dental University, Graduate School of Medical and Dental Sciences, Gerodontology and Oral Rehabilitation, 1-5-45 Yushima, Bunkyo, Tokyo 113-8510, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Minakuchi
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Kapucijnenvoer 7, blok a bus 7001, B-3000 Leuven, Belgium.
authors.forename: Ignace
authors.initials: I
authors.lastname: Naert
authors.affiliation: KU Leuven (University of Leuven), Department of Materials Engineering, Kasteelpark Arenberg 44, B-3001 Heverlee, Belgium.
authors.forename: Jozef
authors.initials: J
authors.lastname: Vleugels
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Kapucijnenvoer 7, blok a bus 7001, B-3000 Leuven, Belgium. Electronic address: bart.vanmeerbeek@kuleuven.be.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D003764:Dental Materials; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D008422:Materials Testing; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013499:Surface Properties; D015019:Yttrium; D015040:Zirconium
chemical_list: D003764:Dental Materials; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide
keywords: Alumina sandblasting; Grinding; Mechanical properties; Stress; Tribochemical silica sandblasting; Zirconia