title: Double-layer porcelain veneers: effect of layering on resulting veneer color.
abstract: BACKGROUND
  Densely sintered aluminum oxide veneered with feldspathic porcelain seems to be a promising technology for the fabrication of porcelain laminate veneers, which provide both strength and esthetics. To effectively use this approach for porcelain veneers, practitioners should know how the resulting color is affected by adding a layer of veneering porcelain onto the aluminum oxide.
  
  
  OBJECTIVE
  This study compared changes in CIE L*a*b* color coordinates of simulated stained teeth when covered with the aluminum oxide core disks alone and after the disks had been veneered with 3 different shades of porcelain.
  
  
  METHODS
  Fifteen aluminum oxide disks were divided into 3 groups. Each of 5 disks was veneered with porcelain of the Vita shades A1, A2, and B4, respectively. The colors of the substrate covered with the nonveneered disks and the veneered disks were measured separately, and the color differences were calculated. Measurements of the disks on a white background were also performed and used as controls. The extracted data were compared with Vita shade values available from the literature.
  
  
  RESULTS
  Statistically significant differences in color coordinates of dark substrates were recorded between the substrate covered by an aluminum oxide disk and the addition of veneering porcelain to the aluminum oxide disks. Veneering the aluminum oxide disks with A1, A2, and B4 porcelain produced significant differences in the resulting color when placed on a dark substrate. The direction of the color modifications correlated with values obtained from the literature. The resulting color was also affected by the color of the underlying structures.
  
  
  CONCLUSIONS
  Although aluminum oxide alone does have a degree of masking capability, the resulting color of porcelain veneers with the use of this material can successfully be modified with the veneering porcelain.
authors.affiliation: Nanjing Medical University, Nanjing, China.
authors.forename: F
authors.initials: F
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Heydecke
authors.forename: M E
authors.initials: ME
authors.lastname: Razzoog
mesh_terms: D000537:Aluminum Oxide; D000704:Analysis of Variance; D003116:Color / Q000592:standards; D003124:Colorimetry; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003801:Dental Veneers; D017797:Prosthesis Coloring
chemical_list: D003776:Dental Porcelain; D000537:Aluminum Oxide