title: Optical properties of CAD-CAM ceramic systems.
abstract: OBJECTIVE
  To evaluate the direct transmittance (T%), translucency, opacity and opalescence of CAD-CAM ceramic systems and the correlation between the translucency parameter (TP) and the contrast ratio (CR).
  
  
  METHODS
  Specimens of shades A1, A2 and A3 (n=5) were fabricated from CAD-CAM ceramic blocks (IPS e.max(®) CAD HT and LT, IPS Empress(®) CAD HT and LT, Paradigm™ C, and VITABLOCS(®) Mark II) and polished to 1.0±0.01mm in thickness. A spectrophotometer (Lambda 20) was used to measure T% on the wavelength range of 400-780nm. Another spectrophotometer (VITA Easyshade(®) Advance) was used to measure the CIE L(*)a(*)b(*) coordinates and the reflectance value (Y) of samples on white and black backgrounds. TP, CR and the opalescence parameter (OP) were calculated. Data were statistically analysed using VAF (variance accounting for) coefficient with Cauchy-Schwarz inequality, one-way ANOVA, Tukey's test, Bonferroni correction and Pearson's correlation.
  
  
  RESULTS
  T% of some ceramic systems is dependent on the wavelength. The spectral behaviour showed a slight and constant increase in T% up to approximately 550nm, then some ceramics changed the behaviour as the wavelength gets longer. TP and CR values ranged, respectively, from 16.79 to 21.69 and from 0.52 to 0.64 (r(2)=-0.97). OP values ranged from 3.01 to 7.64.
  
  
  CONCLUSIONS
  The microstructure of CAD-CAM ceramic systems influenced the optical properties. TP and CR showed a strong correlation for all ceramic systems evaluated. Yet, all ceramics showed some degree of light transmittance.
  
  
  CONCLUSIONS
  In addition to shade, this study showed that other optical properties influence on the natural appearance of dental ceramics.
authors.affiliation: Post-graduate Program in Dentistry, Dental School, University of Passo Fundo, Campus I, BR 285, Km 171, PO Box 611, 99001-970 Passo Fundo, RS, Brazil. Electronic address: dbona@upf.br.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Della Bona
authors.affiliation: Post-graduate Program in Dentistry, Dental School, University of Passo Fundo, Campus I, BR 285, Km 171, PO Box 611, 99001-970 Passo Fundo, RS, Brazil.
authors.forename: Audrea D
authors.initials: AD
authors.lastname: Nogueira
authors.affiliation: Post-graduate Program in Dentistry, Dental School, University of Passo Fundo, Campus I, BR 285, Km 171, PO Box 611, 99001-970 Passo Fundo, RS, Brazil.
authors.forename: Oscar E
authors.initials: OE
authors.lastname: Pecho
mesh_terms: D000465:Algorithms; D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D006801:Humans; D008027:Light; D008422:Materials Testing; D055620:Optical Phenomena; D017680:Potassium Compounds / Q000737:chemistry; D013053:Spectrophotometry / Q000295:instrumentation
chemical_list: D000538:Aluminum Silicates; C520133:IPS e.max CAD LT; C075815:IPS-Empress ceramic; D017680:Potassium Compounds; C493120:lithia disilicate; D003776:Dental Porcelain; C016447:feldspar; C078519:leucite; C023506:Glass ceramics
keywords: Dental ceramics; Opacity; Opalescence; Translucency; Transmittance