title: Contrast ratio of six zirconia-based dental ceramics.
abstract: OBJECTIVE
  The objective of this study was to determine the effect of thickness and brands on the contrast ratio of six zirconia dental ceramics.
  
  
  METHODS
  Six brands of yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics (ZENO® Translucent, Lava™ Plus High Translucency, inCoris TZI, Cercon® Base, Zeno®Zr, Lava™) were used in this study. Disc-shaped specimens with 15 mm diameter were prepared in five thickness levels (0.3, 0.6, 0.9, 1.2, 1.5 mm, n = 10) for each brand. The contrast ratio (CR = Y(b) /Y(w) ) was determined from the luminous reflectance over black (Y(b) ) and white (Y(w) ) backgrounds using a spectrophotometer. Two-way ANOVA was performed to determine the significant differences among thicknesses and brands at α = 0.05.
  
  
  RESULTS
  The mean contrast ratio values of six zirconia ceramics were significantly different and influenced by both the thickness and brand. The mean contrast ratio values of all groups increased as their thickness increased from 0.3 to 1.5 mm. inCoris TZI was the most translucent, with the lowest contrast ratio at a thickness of 0.6 to 1.5 mm. The mean contrast ratio values of Lava™ and Lava™ Plus were significantly lower than those of Zeno®Zr, ZENO® Translucent, and Cercon® Base.
  
  
  CONCLUSIONS
  The thickness and brands had significant effects on the contrast ratio of six zirconia dental ceramics. The mean contrast ratio values of inCoris TZI, Lava™, and Lava™ Plus High Translucency were significantly lower than those of Cercon® Base, Zeno®, and ZENO® Translucent at all thicknesses.
authors.affiliation: Prosthodontic Department, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
authors.forename: Widchaya
authors.initials: W
authors.lastname: Kanchanavasita
authors.forename: Premwara
authors.initials: P
authors.lastname: Triwatana
authors.forename: Kallaya
authors.initials: K
authors.lastname: Suputtamongkol
authors.forename: Alisa
authors.initials: A
authors.lastname: Thanapitak
authors.forename: Mathura
authors.initials: M
authors.lastname: Chatchaiganan
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008027:Light; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016062:Porosity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation; D013499:Surface Properties; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium
keywords: Zirconium dioxide; thickness; translucency