title: Effect of resin shades on opacity of ceramic veneers and polymerization efficiency through ceramics.
abstract: OBJECTIVE
  The aim of this study was to assess the effect of different resin cement shades on the opacity and color difference of ceramics and to determine the polymerization efficiency of the resin cement at different shades after curing through ceramics.
  
  
  METHODS
  Two different ceramics (IPS e.max Press and IPS Empress(®)CAD, Ivoclar Vivadent) were used for this study. A light-cured veneer luting resin (Variolink Veneer, Ivoclar Vivadent) in four different shades of HV+1, HV+3, LV-1, and LV-3 was used for the colorimetric measurements. The color and spectral reflectance of the ceramics were measured according to the CIELab color scale relative to the standard illuminant D65 on a reflection spectrophotometer (ColorEye7000A, USA). Color differences (ΔE values) and the contrast ratios (CR) of the different groups of samples were calculated. In order to analyse the polymerization efficiency of the resin cements, the micromechanical properties of the resins were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). The results were analysed using one-way ANOVA and Tukey's HSD post hoc tests (SPSS 18.0).
  
  
  RESULTS
  The one-way ANOVA test showed that the values of ΔE and CR of the different specimen groups were significantly different (p<0.05). Group 1 (20.7 ± 0.5) (IPS-CAD without resin cement) exhibited the highest and group 10 (14.8 ± 0.5) (e.max:HV+3) exhibited the lowest ΔE value. Significant differences in the micromechanical properties were identified among the tested resin cements in different shades (p<0.05).
  
  
  CONCLUSIONS
  Resin cement shade is an important factor for the opacity of a restoration. Furthermore, the resin shade affects the micromechanical properties of the underlying resin cement.
authors.affiliation: Hacettepe University, Faculty of Dentistry, Department of Restorative Dentistry, Sıhhiye, 06100 Ankara, Turkey. Electronic address: dtelifoz@gmail.com.
authors.forename: Elif
authors.initials: E
authors.lastname: Öztürk
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Chiang
authors.forename: Erdal
authors.initials: E
authors.lastname: Coşgun
authors.forename: Şükran
authors.initials: Ş
authors.lastname: Bolay
authors.forename: Reinhard
authors.initials: R
authors.lastname: Hickel
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Ilie
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003116:Color; D003124:Colorimetry / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D055119:Elastic Modulus; D004548:Elasticity; D006244:Hardness; D006801:Humans; D008027:Light; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008689:Methacrylates / Q000737:chemistry; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; C508050:IPS e.max Press; C075815:IPS-Empress ceramic; D008689:Methacrylates; D019279:Resin Cements; C493120:lithia disilicate; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink; C023506:Glass ceramics
keywords: CAD/CAM; Ceramics; Color change; Light polymerization; Luting resin cement; Opacity; Veneers; Vickers hardness