title: Effects of the type and thickness of ceramic, substrate, and cement on the optical color of a lithium disilicate ceramic.
abstract: BACKGROUND
  Reproducing the characteristics of natural teeth in ceramic crowns remains a complex and difficult process.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the effect of the substrate, cement, type, and thickness of the ceramic on the resulting color of a lithium disilicate ceramic.
  
  
  METHODS
  Forty ceramic disks were prepared from IPS e.max Press LT (low translucency) and HO (high opacity) in 2 different thicknesses (1.5 and 2 mm). The LT groups were composed of monolithic ceramic disks, and the HO groups were composed of disks fabricated with a 0.5-mm thickness combined with a 1- or 1.5-mm veneering ceramic thickness. Disks made of composite resin (R) and alloy (A) were used as substrate structures. The resin cement used was Variolink II. Color was measured with a spectrophotometer and expressed in CIELAB coordinates. Color differences (ΔE) were calculated. The data were analyzed with ANOVA and the Tukey HSD test (α=.05).
  
  
  RESULTS
  When the ΔE of ceramic disks with both substrates, with and without cement, were compared, the lowest value (3) was obtained for ceramic HO with a 2-mm thickness/alloy substrate/without cement; the highest value (10) was obtained for ceramic LT with a1.5-mm thickness/alloy substrate/with cement. This difference was statistically significant. When the effect of cement on the ΔE of ceramics in both substrates was compared, the lowest value (1.1) occurred with ceramic HO with a 1.5-mm thickness/resin substrate, and the highest was observed for ceramic LT with a 1.5-mm thickness/alloy substrate (6.4). This difference was statistically significant.
  
  
  CONCLUSIONS
  The substrate color, type and thickness of ceramic, and presence of the cement significantly influenced the resulting optical color. The ΔE values of cemented HO ceramics were lower than that of the LT ceramic.
authors.affiliation: Doctoral student, Department of Prosthodontics, University of São Paulo, Bauru School of Dentistry, São Paulo, Brazil. Electronic address: lais_pires@hotmail.com.
authors.forename: Laís A
authors.initials: LA
authors.lastname: Pires
authors.affiliation: Professor, Faculty of Professional Masters in Dentistry, University of Fortaleza, Ceará, Brazil.
authors.forename: Pollyanna M R
authors.initials: PM
authors.lastname: Novais
authors.affiliation: Professor, University Federal Rural of Pernambuco, Academic Unit of the Cabo of Santo Agostinho, Pernambuco, Brazil.
authors.forename: Vinícius D
authors.initials: VD
authors.lastname: Araújo
authors.affiliation: Professor, Department of Prosthodontics, University of São Paulo, Bauru School of Dentistry, São Paulo, Brazil.
authors.forename: Luiz F
authors.initials: LF
authors.lastname: Pegoraro
mesh_terms: D002516:Ceramics / Q000737:chemistry / Q000627:therapeutic use; D003442:Crowns; D003738:Dental Cements / Q000627:therapeutic use*; D003776:Dental Porcelain / Q000627:therapeutic use*; D006801:Humans; D066298:In Vitro Techniques; D017797:Prosthesis Coloring
chemical_list: D003738:Dental Cements; C493120:lithia disilicate; D003776:Dental Porcelain