title: The Effect of two Shading Techniques on Value of Zirconia-Based Crowns.
abstract: BACKGROUND
  By introducing the coloring liquids, it is claimed that it is possible to make the color of frameworks fabricated from zirconium oxide extremely close to the natural tooth color.
  
  
  OBJECTIVE
  The purpose of this research was to evaluate the effect of two staining techniques on value changing in zirconia crowns.
  
  
  METHODS
  Three groups A, B, and C, each containing ten zirconia crowns, were used. The zirconium cores samples were fabricated by a CAD/CAM device. Group A was left uncolored, Groups B was submerged for two minutes in A2 coloring liquid and Group C was stained with brush. Then all cores were sintered and the porcelain was applied by using the layering technique. Ultimately, the crowns color was determined using a spectrophotometer. Their color changing (∆E) and value changing (∆L) in relation to A2 color were also assessed. The data were analyzed with one-sample t-test, post-hoc Tukey, and one-way ANOVA tests with significant level set at 0.05.
  
  
  RESULTS
  The mean value in all groups was higher than the value obtained from A2 color samples (p= 0.001). The highest mean value was 78.31±1.22 belonging to group C (staining with brush) and the lowest mean value was 76.99±0.65 belonging to group B (submerging). The results of post-hoc Tukey regarding both ∆E and ∆L variables showed a significant difference between groups A (uncolored) and C (staining with brush) with P∆E=0.006 and P∆L=0.039, respectively. A significant difference between group B (submerging technique) and C (staining with brush) were shown when these two variables were compared (P∆E=0.001, P∆L=0.015).
  
  
  CONCLUSIONS
  Due to the higher value increase in surface staining (brush), it is recommended to use the submerging technique for staining zirconia cores.
authors.affiliation: Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Ahmad
authors.initials: A
authors.lastname: Hassan Ahangari
authors.affiliation: Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Kianoosh
authors.initials: K
authors.lastname: Torabi Ardakani
authors.affiliation: Postgraduate Student in Prosthodontics, Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran;
authors.forename: Farideh
authors.initials: F
authors.lastname: Mahdavi
authors.affiliation: Private Dentist, Shiraz, Iran;
authors.forename: Mahshid
authors.initials: M
authors.lastname: Torabi Ardakani
keywords: Color; Crown; Spectrophotometer; Value; Zirconia