title: Masking Colored Substrates Using Monolithic and Bilayer CAD-CAM Ceramic Structures.
abstract: OBJECTIVE
  To evaluate the masking ability and translucency of monolithic and bilayer CAD-CAM ceramic structures.
  
  
  METHODS
  Discs of high translucency (HT) and low translucency (LT) lithium disilicate-based ceramic (IPS e.max CAD) with different thicknesses (0.7, 1, 1.5, and 2 mm) were evaluated as a monolithic structure or combined (bilayer) with a 0.5-mm-thick zirconia framework (IPS e.max ZirCAD). The masking ability and translucency were calculated based on CIE L*a*b* color coordinates measured with a spectrophotometer (SP60, X-Rite). The translucency parameter (TP) was calculated using color coordinates measured over standard white-and-black backgrounds. The masking ability was calculated by CIEDE2000 color difference metric (ΔE00) for each specimen measured over a tooth-colored substrate (shade A2) compared to three darker backgrounds (shade C4 and two metal substrates). Confidence intervals (CI) for the means (95% CI) were calculated for TP and ΔE00. The Pearson correlation between ΔE00and TP was investigated for monolithic and bilayer structures over all backgrounds.
  
  
  RESULTS
  The thinner the lithium disilicate layer, the greater the translucency and the higher the ΔE00values. The effect of ceramic thickness on both translucency and masking ability was more pronounced for the monolithic structures. In addition, monolayers always presented a greater color variation than their bilayer counterparts. The metallic background produced greater ΔE00than the C4-shaded substrate.
  
  
  CONCLUSIONS
  Monolithic veneers were able to mask C4-shaded background but did not mask metallic backgrounds. Bilayer structures showed greater shade masking ability than monolithic structures.
authors.forename: G R
authors.initials: GR
authors.lastname: Basso
authors.forename: A B
authors.initials: AB
authors.lastname: Kodama
authors.forename: A H
authors.initials: AH
authors.lastname: Pimentel
authors.forename: M R
authors.initials: MR
authors.lastname: Kaizer
authors.forename: A Della
authors.initials: AD
authors.lastname: Bona
authors.forename: R R
authors.initials: RR
authors.lastname: Moraes
authors.forename: N
authors.initials: N
authors.lastname: Boscato
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D003116:Color; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D008027:Light; D008422:Materials Testing; D013053:Spectrophotometry; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; C520133:IPS e.max CAD LT; C075815:IPS-Empress ceramic; C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide