title: An evaluation of the mechanical properties of 'hydrothermal' dental glass after water immersion and surface polishing.
abstract: OBJECTIVE
  To investigate claims that Duceram low-fusing ceramic (Duceram-LFC), a 'hydrothermal' dental veneer will increase in strength after hydrolytic testing and surface polishing.Methods. Using pre-determined powder/liquid slurry constituents, nominally identical Duceram-LFC disc-shaped specimens were fabricated to obtain mean bi-axial flexure strengths, standard deviations, Weibull modulus (m) and Vickers hardness. Thirty specimens were tested 'dry' (control), after 24 and 48h immersion in a water bath maintained at 37+/-1 degrees C and a further 30 samples polished to a 6 micrometer nap finish.
  
  
  RESULTS
  Mean bi-axial flexure strengths of specimens tested dry were found to be 67.04+/-13.87MPa (m=7.23+/-1.32) compared with 61.01+/-15.23MPa (m=4.29+/-0.78) and 68.42+/-23.36MPa (m=3.29+/-0.60) for 24 and 48h immersion, respectively. Following surface polishing, the bi-axial flexure strength was 95.91+/-22.4MPa (m=4.37+/-0.8). Vickers hardness numbers showed no significant difference between the dry control group and after 24 and 48h immersion (P>0.05).
  
  
  CONCLUSIONS
  Results obtained do not support claims for surface flaw and/or defect healing through the formation of an SiOH layer at the surface of Duceram-LFC specimens over time. However, the polishing regime interrupted the defect population associated with flaws present in dry (control) samples of Duceram-LFC which can be attributed to an associated reduction of initial surface flaws and/or defects.
authors.affiliation: Biomaterials Unit, School of Dentistry, University of Birmingham, St. Chad's Queensway, B4 6NN, Birmingham, UK.
authors.forename: William M
authors.initials: WM
authors.lastname: Palin
authors.forename: Garry J P
authors.initials: GJ
authors.lastname: Fleming
authors.forename: Peter M
authors.initials: PM
authors.lastname: Marquis
mesh_terms: D003775:Dental Polishing; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003801:Dental Veneers; D004548:Elasticity; D006244:Hardness; D007101:Immersion; D008422:Materials Testing; D018583:Pliability; D016062:Porosity; D013499:Surface Properties; D014867:Water; D017155:Wettability
chemical_list: C095718:Duceram; D014867:Water; D003776:Dental Porcelain