title: [The effect of firing times on the chroma of tetragonal zirconia polycrystal by adding rare-earth oxides].
abstract: OBJECTIVE
  The aim of this study is to evaluate whether the firing times affect the chroma of zirconia by adding rare-earth oxides.
  
  
  METHODS
  Six kinds (S1, S2, S3, S4, S5, S6) of tooth-like yttria stabilized tetragonal zirconia polycrystal (Y-TZP) were available by introducing internal colorating technology, the color were gauged with ShadeEye NCC chromatometry instrument, and one-way ANOVA was used to analysis the color of each kind of tooth-like zirconia after 1, 2, 3, 4, 5 times firing individually.
  
  
  RESULTS
  After 1, 2, 3, 4, 5 times firing respectively, the chromatic aberration ranged between 0.10-1.47 merely. The luminosity of three kinds (S1, S2, S6) of tooth-like zirconia were decreased (P < 0.05), the luminosity of the other three kinds (S3, S4, S5) of tooth-like zirconia were not obviously changed (P > 0.05), as for the hue and chroma, no significant differences were found (P > 0.05).
  
  
  CONCLUSIONS
  There are no significant influence on the color of tooth-like Y-TZP after 1, 2, 3, 4, 5 times firing respectively, the chroma of yttria stabilized tetragonal zirconia polycrystal by adding rare-earth oxides are with high stability.
authors.affiliation: Dept. of Prosthodontics, The Ninth People's Hospital, School of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gao
authors.forename: Fu-qiang
authors.initials: FQ
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Huang
authors.forename: Lin-hua
authors.initials: LH
authors.lastname: Gui
mesh_terms: D003776:Dental Porcelain; D003799:Dental Stress Analysis; D008422:Materials Testing; D010087:Oxides; D013499:Surface Properties; D015019:Yttrium; D015040:Zirconium
chemical_list: D010087:Oxides; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide