title: Effect of Three Different Core Materials on Masking Ability of a Zirconia Ceramic.
abstract: OBJECTIVE
  Masking ability of a restorative material plays a role in hiding colored substructures; however, the masking ability of zirconia ceramic (ZRC) has not yet been clearly understood in zirconia-based restorations. This study evaluated the effect of three different core materials on masking ability of a ZRC.
  
  
  METHODS
  Ten zirconia disc samples, 0.5mm in thickness and 10mm in diameter, were fabricated. A white (W) substrate (control) and three substrates of nickel-chromium alloy (NCA), non-precious gold alloy (NPGA), and ZRC were prepared. The zirconia discs were placed on the four types of substrates for spectrophotometry. The L*, a*, and b* values of the specimens were measured by a spectrophotometer and color change (ΔE) values were calculated to determine color differences between the test and control groups and were then compared with the perceptual threshold. Randomized block ANOVA and Bonferroni test analyzed the data. A significance level of 0.05 was considered.
  
  
  RESULTS
  The mean and standard deviation values of ΔE for NCA, NPGA, and ZRC groups were 10.26±2.43, 9.45±1.74, and 6.70±1.91 units, respectively. Significant differences were found in the ΔE values between ZRC and the other two experimental groups (NCA and NPGA; P<0.0001 and P=0.001, respectively). The ΔE values for the groups were more than the predetermined perceptual threshold.
  
  
  CONCLUSIONS
  Within the limitations of this study, it was concluded that the tested ZRC could not well mask the examined core materials.
authors.affiliation: Assistant Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Tabatabaian
authors.affiliation: Graduate Student, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Faeze
authors.initials: F
authors.lastname: Masoomi
authors.affiliation: Assistant Professor of Biostatistics, Department of Community Oral Health, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mahshid
authors.initials: M
authors.lastname: Namdari
authors.affiliation: Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Minoo
authors.initials: M
authors.lastname: Mahshid
keywords: Color; Spectrophotometry; Visual Perception; Yttria Stabilized Tetragonal Zirconia