title: Color stability of dental ceramics submitted to artificial accelerated aging after repeated firings.
abstract: BACKGROUND
  Color stability is an important factor to ensure the long-term clinical success of ceramic restorations. There is a lack of information on how color is affected by fabrication procedures, such as the number of firings.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effects that the number of firings and type of substrate have on the color stability of dental ceramic submitted to artificial accelerated aging.
  
  
  METHODS
  Sixty specimens were fabricated: 30 metal ceramic (Verabond II + IPS d.SIGN) and 30 all-ceramic (IPS d.SIGN). Specimens were divided into 3 groups (n=10), and submitted to 2, 3, or 4 firings (+/-900 degrees C), respectively, according to the manufacturer's instructions. Color readings were obtained with a spectrophotometer before and after artificial accelerated aging, and L*, a*, and b* coordinates and total color variation (Delta E) were analyzed (2-way ANOVA, Bonferroni, alpha=05).
  
  
  RESULTS
  For metal ceramic specimens, differences for the L* coordinates were significant (P<.05) only for the group submitted to 3 firings. With respect to the all-ceramic specimens, smaller L* coordinates were obtained for greater a* and b* coordinates, indicating that the greater the number of firings, the darker and more reddish/yellowish the specimen. All Delta E values, for all groups, were below 1.0. All-ceramic specimens submitted to 3 and 4 firings presented Delta E means differing statistically (P<.05) from those of the metal ceramic group.
  
  
  CONCLUSIONS
  The type of substrate and number of firings affected the color stability of the ceramic material tested. Artificial accelerated aging did not produce perceptible color stability changes (Delta E<1.0).
authors.affiliation: Department of Dental Materials and Prosthodontics, Ribeirão Preto School of Dentistry, University of São Paulo, São Paulo, Brazil. ferpanzeri@forp.usp.br
authors.forename: Fernanda de Carvalho Panzeri
authors.initials: Fde C
authors.lastname: Pires-de-Souza
authors.forename: Luciana Assirati
authors.initials: LA
authors.lastname: Casemiro
authors.forename: Lucas da Fonseca Roberti
authors.initials: Lda F
authors.lastname: Garcia
authors.forename: Diogo Rodrigues
authors.initials: DR
authors.lastname: Cruvinel
mesh_terms: D003116:Color; D003124:Colorimetry; D003735:Dental Casting Technique; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019554:Dental Restoration Wear; D006358:Hot Temperature; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D017797:Prosthesis Coloring; D013997:Time Factors
chemical_list: D016876:Metal Ceramic Alloys; D003776:Dental Porcelain