title: [Effect of veneering technologies on color and translucency of Y2O3 stabilized tetragonal zirconia polycrystals all-ceramic restorations].
abstract: OBJECTIVE
  To compare color parameters and transmittance of Y2O3 stabilized tetragonal zirconia polycrystals (Y-TZP) all-ceramic restorations using different veneering technologies.
  
  
  METHODS
  Fifteen disc specimens with 10 mm in diameter and (0.50 +/- 0.01) mm in thickness were fabricated of IPS e. max ZirCAD core material, and ZL1 IPS e. max ZirLiner was layered in 0.10 mm thickness. The specimens were divided into three groups randomly (n=5 per group). Group ZP was veneered 0.60 mm by heat-pressing; group ZC was veneered 0.60 mm by layering; group ZPC was veneered 0.30 mm by heat-pressing and then 0.30 mm by layering. Color parameters L*, a*, b* and transmittance of zirconia specimens were measured before and after veneering with ShadeEye NCC dental chromameter and spectrophotometer. Color saturation C* ab and color difference deltaE were calculated in the following formulae: C* ab = [(a*)2 + (b*)2](1/2), deltaE = [(deltaL*)2 + (deltaa*)2 + (deltab*)2](1/2) One-way analysis of variance and Turkey's multiple comparison test were used to analyze data (alpha = 0.05) by SPSS 10.0 statistic software. Color parameters of A2 shade tabs were measured, and color differences between each group and tab were calculated.
  
  
  RESULTS
  As to ZP,ZPC,ZC groups, the value of a* increased (-1.35 +/- 0.07, -0.64 +/- 0.06, -0.36 +/- 0.05) (P < 0.05), the value of b* decreased (27.01 +/- 0.07, 25.48 +/- 0.11, 23.28 +/- 0.25) (P < 0.05), and the value of C* ab decreased (27.04 +/- 0.08, 25.49 +/- 0.11, 23.28 +/- 0.25) (P < 0.05). L* and transmittance were maximum in ZP group (87.53 +/- 0.48, 1.64 +/- 0.03) and minimum in ZPC group (82.14 +/- 0.18, 1.47 +/- 0.01) (P < 0.05). Compared with standard A2 shade tab, the color difference of ZC group was minimum (delta = 1.04), and the color difference of ZP group was maximum (deltaE = 4.86).
  
  
  CONCLUSIONS
  Y-TZP all-ceramic restoration veneered by heat-pressing was the most transparent and lightest; while veneered by both heat-pressing and layering, the restoration was worst in translucency and the least light. The color of zirconia all-ceramic restoration veneered by layering was the most similar to standard shade tab, and the color difference was minimum.
authors.affiliation: Department of Prosthodontics, Nanjing Stomatological Hospital, The Affiliated Hospital of Medical School, Nanjing, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Xiao-ping
authors.initials: XP
authors.lastname: Luo
authors.forename: Yu-juan
authors.initials: YJ
authors.lastname: Shi
mesh_terms: D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D006358:Hot Temperature; D008422:Materials Testing; D017797:Prosthesis Coloring; D013674:Technology, Dental / Q000379:methods*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide