title: Effect of abutment shade, ceramic thickness, and coping type on the final shade of zirconia all-ceramic restorations: in vitro study of color masking ability.
abstract: OBJECTIVE
  The aim of the study was to evaluate the effect of abutment shade, ceramic thickness, and coping type on the final shade of zirconia all-ceramic restorations.
  
  
  METHODS
  Three different types of disk-shaped zirconia coping specimens (Lava, Cercon, Zirkonzahn: ø10 mm × 0.4 mm) were fabricated and veneered with IPS e.max Press Ceram (shade A2), for total thicknesses of 1 and 1.5 mm. A total of sixty zirconia restoration specimens were divided into six groups based on their coping types and thicknesses. The abutment specimens (ø10 mm × 7 mm) were prepared with gold alloy, base metal (nickel-chromium) alloy, and four different shades (A1, A2, A3, A4) of composite resins. The average L*, a*, b* values of the zirconia specimens on the six abutment specimens were measured with a dental colorimeter, and the statistical significance in the effects of three variables was analyzed by using repeated measures analysis of variance (α=.05).The average shade difference (ΔE) values of the zirconia specimens between the A2 composite resin abutment and other abutments were also evaluated.
  
  
  RESULTS
  The effects of zirconia specimen thickness (P<.001), abutment shade (P<.001), and type of zirconia copings (P<.003) on the final shade of the zirconia restorations were significant. The average ΔE value of Lava specimens (1 mm) between the A2 composite resin and gold alloy abutments was higher (close to the acceptability threshold of 5.5 ΔE) than th ose between the A2 composite resin and other abutments.
  
  
  CONCLUSIONS
  This in-vitro study demonstrated that abutment shade, ceramic thickness, and coping type affected the resulting shade of zirconia restorations.
authors.affiliation: Department of Prosthodontics, Graduate School of Clinical Dental Science, The Catholic University of Korea, Seoul, Republic of Korea.
authors.forename: Seon-Hee
authors.initials: SH
authors.lastname: Oh
authors.affiliation: Department of Prosthodontics, Samsung Medical Center, College of Medicine, Sungkyunkwan University, Seoul, Republic of Korea.
authors.forename: Seok-Gyu
authors.initials: SG
authors.lastname: Kim
keywords: Abutment; Restoration; Zirconia