title: Evaluation of the optical properties of CAD-CAM generated yttria-stabilized zirconia and glass-ceramic laminate veneers.
abstract: BACKGROUND
  When feldspathic porcelain (FP) laminate veneers are used to mask tooth discoloration that extends into the dentin, significant tooth reduction is needed to provide space for the opaque layer and optimize the bonding of the restoration.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the color effect of trial insertion paste (TP), composite resin abutment (CRA), and veneer regions on the optical properties of feldspathic porcelain (FP), yttria-stabilized zirconia (Y-TZP), and IPS e.max CAD HT (IEC) veneers.
  
  
  METHODS
  A melamine tooth was prepared for a laminate veneer on a model, and a definitive cast was made. The definitive die was scanned by using the TurboDent System (TDS), then 30 CRA were machined and 10 veneers were fabricated for each ceramic material (FP, Y-TZP, IEC). The optical properties of different veneer materials, CRA (A(1), A(2), A(3)) and TP (bleach XL, opaque white, transparent, and yellow) were evaluated in the cervical, body, and incisal regions with a spectrophotometer. Results were analyzed by using 1-way ANOVA (.05).
  
  
  RESULTS
  The color difference for all the veneers was affected by TP and CRA colors in different regions. The mean values for the Y-TZP veneer color coordinates (L*: 74 ±0.34, a*: 0.09 ±0.20, and b*: 17.43 ±0.44) were significantly different (P<.001) from those of IEC veneers (L*: 70.15 ±0.23, a*: -0.69 ±0.073, and b*:11.48 ±0.30) and FP veneers (L*: 70.00 ±0.86, a*: - 0.28 ±0.203, and b*: 13.86 ±1.08). There was no difference between IEC for L* and FP. Significant difference was detected (P<.001) in color coordinates among the 3 veneer materials for a* and b*.
  
  
  CONCLUSIONS
  The TP color affected the color difference for all veneer materials except the Y-TZP, while there was no effect on the CRA color. The magnitude of color coordinates changed as a function of TP color and veneer material.
authors.affiliation: The University of Alabama at Birmingham, Birmingham, Alabama, USA. tghazzawi@taibah.edu.sa
authors.forename: Tariq F
authors.initials: TF
authors.lastname: Alghazzawi
authors.forename: Jack
authors.initials: J
authors.lastname: Lemons
authors.forename: Perng-Ru
authors.initials: PR
authors.lastname: Liu
authors.forename: Milton E
authors.initials: ME
authors.lastname: Essig
authors.forename: Gregg M
authors.initials: GM
authors.lastname: Janowski
mesh_terms: D000538:Aluminum Silicates; D000704:Analysis of Variance; D002516:Ceramics; D003116:Color; D003188:Composite Resins; D017076:Computer-Aided Design; D000044:Dental Abutments; D003738:Dental Cements; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D003765:Models, Dental; D055620:Optical Phenomena; D017680:Potassium Compounds; D013053:Spectrophotometry; D015019:Yttrium; D015040:Zirconium
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D003738:Dental Cements; D017680:Potassium Compounds; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; C016447:feldspar; D015019:Yttrium; C023506:Glass ceramics; D015040:Zirconium