title: Influence of dentin and core porcelain thickness on the color of fully sintered zirconia ceramic restorations.
abstract: BACKGROUND
  The influence of the thickness of dentin and core porcelain, and the glazing procedure on the color of computer-aided design and computer-aided manufacturing ceramic restorations has not been investigated.
  
  
  OBJECTIVE
  This study evaluated the influence of the thickness of dentin and core porcelain and glazing on the color of fully sintered zirconia ceramic restorations.
  
  
  METHODS
  Fully sintered zirconia core material was cut into 90 specimens of 0.3 mm (n=30, group ZC1), 0.4 mm (n=30, group ZC2), and 0.5-mm thickness (n=30, group ZC3). On a dentin disk obtained from an extracted molar, the L*, a*, b* values of the specimens were measured at different steps in the laboratory procedures (Zirconia core, Effect Bonder, Effect Liner, dentin porcelain, glazing) with a spectrophotometer. One millimeter dentin porcelain was applied on half of the specimens of each group and 1.5-mm dentin porcelain on the rest. To assess the ability of porcelain substructures to mask the underlying dark colored tooth structure, color difference (ΔE) values between the steps were calculated. Results were statistically analyzed with ANOVA.
  
  
  RESULTS
  Glazing caused a decrease in the L* values and an increase in the a* and b* values (P<.05). Increasing the thickness of dentin porcelain decreased the L*, a*, and b* values (P<.05). Increasing the zirconia core thickness resulted in an increase in the L* values and a decrease in the a* and b* values (P<.05). Increasing the dentin porcelain thickness from 1 mm to 1.5 mm resulted in a color change below the perceptibility threshold (ΔE<2.6). In the ZC1 group, glazing resulted in a color change perceptible to 50% of observers, whereas, in the ZC2 and ZC3 groups with 1-mm dentin porcelain, the ΔE value was higher than 5.5. However, the color change was perceptible to 50% of the observers in all of the groups with 1.5-mm dentin porcelain.
  
  
  CONCLUSIONS
  Although the thicknesses of the dentin and core porcelain did not influence the final shade of the restoration, glazing resulted in a perceptible color difference.
authors.affiliation: Associate Professor, Department of Dental Technology, Vocational School of Health Related Professions, Marmara University, Istanbul, Turkey. Electronic address: gsinmazisik@marmara.edu.tr.
authors.forename: Gulden
authors.initials: G
authors.lastname: Sinmazisik
authors.affiliation: Assistant Professor, Department of Dental Technology, Vocational School of Health Related Professions, Marmara University, Istanbul, Turkey.
authors.forename: Bulent
authors.initials: B
authors.lastname: Demirbas
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, Faculty of Dentistry, Marmara University, Istanbul, Turkey.
authors.forename: Bilge
authors.initials: B
authors.lastname: Tarcin
mesh_terms: D003116:Color; D003118:Color Perception / Q000502:physiology; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003804:Dentin / Q000033:anatomy & histology; D006801:Humans; D008422:Materials Testing; D012684:Sensory Thresholds / Q000502:physiology; D013053:Spectrophotometry; D013499:Surface Properties; D013696:Temperature; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide