title: Opalescence of all-ceramic core and veneer materials.
abstract: OBJECTIVE
  The enamel of natural teeth is opalescent, where there is light scattering of the shorter wavelengths of the visible spectrum, giving a tooth a bluish appearance in the reflected color and an orange/brown appearance in the transmitted color. The objective of this study was to determine the opalescence of all-ceramic core, veneer and layered specimens with a color measuring spectrophotometer.
  
  
  METHODS
  Colors of core (A2-corresponding shade), veneer (A2- and A3-corresponding shades) and layered (A2- and A3-layered) ceramics for all-ceramic restorations in clinically relevant thicknesses were measured in the reflectance and transmittance modes. The opalescence parameter (OP), which was calculated as the difference in blue-yellow coordinate (Deltab(*)) and red-green coordinate (Deltaa(*)), and the differences in blue-yellow coordinate (Deltab(*)) and in color (DeltaE(ab)(*)) between the reflected and transmitted colors were calculated. One-way ANOVA was performed for the OP values of the core, veneer and layered specimens by the kind of materials. Regression analysis was performed between the OP and Deltab(*), and the OP and DeltaE(ab)(*) values.
  
  
  RESULTS
  The range of the OP value was 1.6-6.1, 2.0-7.1, 1.3-5.0 and 1.6-4.2 for the core, veneer, A2- and A3-layered specimens, respectively, all of which were significantly influenced by the kind of materials (p<0.05). The OP and DeltaE(ab)(*) values showed significant correlations within each of the core and veneer ceramics.
  
  
  CONCLUSIONS
  Opalescence varied by kind of ceramics. The OP values of ceramics were lower than those of tooth enamel. All-ceramic materials that can simulate the opalescence of natural teeth should be developed.
authors.affiliation: Department of Dental Biomaterials Science and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.
authors.forename: Moon-Sang
authors.initials: MS
authors.lastname: Cho
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Yong-Keun
authors.initials: YK
authors.lastname: Lee
mesh_terms: D003442:Crowns; D003776:Dental Porcelain; D003801:Dental Veneers; D008422:Materials Testing; D055620:Optical Phenomena; D012542:Scattering, Radiation; D013053:Spectrophotometry / Q000379:methods
chemical_list: D003776:Dental Porcelain