title: Porcelain thickness and cement shade effects on the colour and translucency of porcelain veneering materials.
abstract: OBJECTIVE
  Purposes of this in vitro study include evaluating colour changes in combinations of feldspathic porcelain and cement resulting from different thicknesses of porcelain and different shades of composite luting agent, and evaluating relative translucency parameter (RTP) values.
  
  
  METHODS
  Porcelain discs of shade A1 at nominal thicknesses of 0.5 and 1.0mm were bonded to cements of three shades in a factorial design. Colours were calculated for CIE D65 Illuminant and Standard Human Observer on black, grey and white backings. A colour difference (CD) was calculated of each possible pair of different porcelain thickness values for the same cement shade and each possible pair of different cement shades for the same porcelain thickness. RTP was analyzed by ANOVA and selected pairwise comparisons.
  
  
  RESULTS
  All mean CDs studied were perceptible and most were at or greater than the clinical acceptability threshold, with the notable exception that the mean CDs and their confidence limits were below the clinical acceptability threshold for a change in porcelain thickness when utilizing the Clear cement shade. Variation in the shade of the resin luting cement will result in CDs which are near or beyond clinical acceptability. A decrease in porcelain thickness did significantly increase RTP when bonded to the resin cement shades studied.
  
  
  CONCLUSIONS
  Changes in porcelain thickness or cement shade may adversely affect basic aesthetic properties of these materials. Development of methods for analyzing aesthetic effects over greater ranges of thickness for these materials would improve the prognosis for using these materials.
authors.affiliation: The Ohio State University, College of Dentistry, Division of Restorative, Prosthetic and Primary Care Dentistry, Columbus, OH, USA; Atatürk University, Faculty of Dentistry, Prosthodontics Department, Erzurum, Turkey.
authors.forename: Duygu
authors.initials: D
authors.lastname: Kürklü
authors.forename: Shereen S
authors.initials: SS
authors.lastname: Azer
authors.forename: Burak
authors.initials: B
authors.lastname: Yilmaz
authors.forename: William M
authors.initials: WM
authors.lastname: Johnston
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000538:Aluminum Silicates / Q000737:chemistry; D003116:Color; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D004955:Esthetics, Dental; D006801:Humans; D006858:Hydrofluoric Acid / Q000737:chemistry; D008027:Light; D008422:Materials Testing; D017680:Potassium Compounds / Q000737:chemistry; D011874:Radiometry / Q000295:instrumentation; D019279:Resin Cements / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D017680:Potassium Compounds; D019279:Resin Cements; D014867:Water; D003776:Dental Porcelain; C016447:feldspar; D006858:Hydrofluoric Acid
keywords: Colour; Dental cement shades; Porcelain thickness; Porcelain veneering materials; Translucency