title: Effect of CAD-CAM porcelain veneers thickness on their cemented color.
abstract: OBJECTIVE
  To determine the effect of thickness of porcelain veneers constructed from CAD-CAM on their final color when two resin cements were used.
  
  
  METHODS
  Buccal surfaces of extracted sound human molars with shade 3M2 [verified using digital spectrophotometer (Vita Easyshade-Vident)] were reduced to expose flat enamel surfaces. CAD-CAM blocks (Vitablokcs Mark II) of the same shade were sectioned into three groups of 0.3, 0.5 and 0.7mm thickness. Each group was subdivided into two subgroups; one subgroup was cemented to enamel using an etch-and-rinse resin cement (Calibra/Prime and bond-NT, Dentsply) and the other was cemented to enamel using a self-etching resin cement (Panavia-F, Kuraray). The shade of the two resin cements was "light". Change in color (ΔE) between the selected shade (3M2) and the resulted shade was measured for each specimen using a digital spectrophotometer (Vita Easyshade-Vident). Means and SDs were calculated and data was statistically analyzed using ANOVA and post hoc tukey's.
  
  
  RESULTS
  Change in color (ΔE) between the selected and the produced shade for the Calibra subgroups was 2.8 (0.3) for the 0.3mm, 1.67 (0.2) for the 0.5mm thick specimens and 1.26 (0.3) for the 0.7mm. Panavia F subgroups showed ΔE of 2 (0.4) for the 0.3mm, 1.13 (0.23) for the 0.5mm thick specimens and 1.21 (0.31) for the 0.7mm. The 0.7mm subgroups showed no significant difference in color change among the two cements (P>.05), however, Calibra resulted in significantly higher change in color values for the 0.5mm thick specimens (P<.05). In spite of the presence of significant difference for the Calibra 0.5mm thick subgroup, the color change was considered to be within the clinically acceptable range. The 0.3mm showed high significant difference for the two tested cements with the Panavia showing less change in color and Calibra showing clinically detectable change in color.
  
  
  CONCLUSIONS
  Increasing porcelain veneer thickness from 0.5 to 0.7mm did not significantly affect the final color of cemented veneers. Whilst the color was significantly affected at the thickness of 0.3mm.
authors.affiliation: School of Dentistry, International Medical University, Kuala Lumpur, Bukit Jalil, Malaysia. hanan_omar@imu.edu.my
authors.forename: Hanan
authors.initials: H
authors.lastname: Omar
authors.forename: Osama
authors.initials: O
authors.lastname: Atta
authors.forename: Omar
authors.initials: O
authors.lastname: El-Mowafy
authors.forename: Saad A
authors.initials: SA
authors.lastname: Khan
mesh_terms: D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design / Q000295:instrumentation* / Q000379:methods; D003793:Dental Restoration, Permanent; D003801:Dental Veneers; D004955:Esthetics, Dental; D006801:Humans; D017797:Prosthesis Coloring; D019279:Resin Cements / Q000737:chemistry
chemical_list: D019279:Resin Cements; D003776:Dental Porcelain