title: The influence of metal substrates and porcelains on the shade of metal-ceramic complex: a spectrophotometric study.
abstract: BACKGROUND
  The final esthetic outcome of a metal-ceramic restoration is influenced by several factors including the type of the underlying metal as well as the brand of the ceramic.
  
  
  METHODS
  An in vitro study.
  
  
  OBJECTIVE
  The purpose of the in vitro study was to investigate the influence of four types of metal-ceramic alloys and two porcelain systems on the color co-ordinates of the metal-ceramic complex. It also aimed at establishing a color index which correlated the color of the metal-ceramic combination to the yellow-blue axis.
  
  
  METHODS
  Twenty-four disc-shaped metal specimens of 12 mm × 1 mm were cast from base metal alloys, nickel-chromium (Ni-Cr) (Wiron 99), cobalt-chromium (Co-Cr) (Wirobond C), a palladium (Pd)-rich noble metal alloy (Spartan Plus), and a high noble gold (Au) alloy (Pontostar). These discs were covered with two commercially available feldspathic porcelains (Vita Omega and Shofu Vintage) of A3 shade to a total thickness of 1.2 mm. Each group had six specimens, of which three were coated with Vita Omega and the remaining with Shofu Vintage. Opaque and dentin layers were applied to a standardized thickness of 0.2 mm ± 0.05 mm and 1 mm ± 0.05 mm, respectively onto the metal surface after air abrasion with 50 μm alumina particles. The reflectance spectra were measured with a spectrophotometer and data were recorded in L*, a* and b* coordinates in the CIE Lab Color Order System.
  
  
  METHODS
  Analysis of variance (ANOVA) and path analysis were the statistical tools employed to analyze the data. A critical difference (CD) value was calculated for each color co-ordinate to make comparisons between each metal-ceramic combination. A color index for each metal-ceramic complex was also calculated from the color co-ordinates obtained.
  
  
  RESULTS
  ANOVA revealed that significant differences existed between the metal-porcelain combination at 0.01 ( P < 0.01) level. The L* value was significantly higher for Au and Co-Cr alloys with Vita Omega porcelain. The a* value was highest for Ni-Cr alloy when combined with Shofu Vintage ceramic. The b* value of Au alloy with Vita Omega porcelain was significantly higher than any other metal-ceramic combination. The color co-ordinates of Pd alloy with both porcelain systems did not show any significant differences. Gold alloy with Vita Omega showed the highest color index value.
  
  
  CONCLUSIONS
  The variations in metal-ceramic alloy and porcelain can influence the shade of a metal-ceramic restoration. Color index value was the highest for gold alloy.
authors: Department of Prosthodontics, Sree Mookambika Institute of Dental Sciences, Kulasekharam, Tamilnadu, India.
authors: Kavitha
authors: K
authors: Janardanan
authors: Sreelal Thankappan
authors: ST
authors: Pillai
authors: Harshakumar
authors: H
authors: Karunakaran
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003116:Color; D045662:Dental Etching / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D006047:Gold Alloys / Q000737:chemistry; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D017797:Prosthesis Coloring; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D002858:Chromium Alloys; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar; D010165:Palladium; D000537:Aluminum Oxide