title: The effect of a coupling medium on color and translucency of CAD-CAM ceramics.
abstract: OBJECTIVE
  To evaluate color and translucency of ceramics and the influence of a coupling medium (G - glycerin) on these optical properties, testing the hypothesis that glycerin influences the translucency values regardless the evaluation method.
  
  
  METHODS
  Five specimens from A2-shaded ceramics (IPS e.max CAD HT and LT, IPS Empress CAD HT and LT, Paradigm C, and Vita Mark II) were fabricated from ceramic blocks and polished to 1.0 ± 0.01mm in thickness. A spectrophotometer (Vita Easys hade) was used to measure the CIELAB coordinates and the reflectance value (Y) of specimens placed on white and black backgrounds. The translucency parameter (TP) and the contrast ratio (CR) were calculated. Another spectrophotometer (Lambda 20) was used to measure the direct light transmittance (T%) of the specimens. The color and the CIELAB coordinates were evaluated using the Vita Easy shade on neutral grey background and values were used to calculate difference in color (ΔE). All evaluations were repeated using G and values were recorded. Data were statistically analyzed using Anova, Tukey and Student's t-test (α=0.05) and Pearson's correlation.
  
  
  RESULTS
  Although the mean translucency values were significantly different for each method (TP and CR), they were strongly correlated (r²=0.97), even when G was used (r²=0.96).
  
  
  CONCLUSIONS
  The coupling medium significantly influenced the mean values of ΔE and translucency.
  
  
  CONCLUSIONS
  Color and translucency values cannot be compared if measured using different coupling media (e.g. air and liquid glycerin).
authors: Post-graduate Program in Dentistry, Dental School, University of Passo Fundo, Brazil.
authors: Audrea Dallazem
authors: AD
authors: Nogueira
authors: Alvaro
authors: A
authors: Della Bona
mesh_terms: D000388:Air; D000465:Algorithms; D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003116:Color; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry; D008027:Light; D017680:Potassium Compounds / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet / Q000295:instrumentation
chemical_list: D000538:Aluminum Silicates; C520133:IPS e.max CAD LT; D017680:Potassium Compounds; C082340:Vita Mark II; C493120:lithia disilicate; D003776:Dental Porcelain; C016447:feldspar; C078519:leucite; C023506:Glass ceramics; D005990:Glycerol
keywords: CAD–CAM technology; Ceramics; Color; Glycerin; Translucency