title: Color stability, opacity and degree of conversion of pre-heated composites.
abstract: OBJECTIVE
  To assess color stability and opacity associated with the degree of conversion of a pre-heated nanohybrid composite (Tetric N-Ceram, Ivoclar/Vivadent, Schaan, Liechtenstein).
  
  
  METHODS
  Twenty-seven specimens were prepared (n=9) using a Teflon matrix following storage of compules containing the composite at temperatures of 8°C, 25°C or 60°C. After photoactivation and polishing, baseline readings of six specimens were taken regarding their color and opacity (Spectrophotometer PCB 6807, Byk Gardner, Geretsried, Germany). Then, the specimens were submitted to artificial ageing for 384 h (C-UV, Adexim Comexim, São Paulo, SP, Brazil), after which the final readings were taken. Three specimens for each temperature were submitted to analysis of degree of conversion (Nicolet 380, Thermo Scientific, Waltham, MA, USA). The results were analysed by 1-way ANOVA/Tukey (p<0.05).
  
  
  RESULTS
  There was no significant difference in color stability and opacity variation amongst the temperatures evaluated. The composite pre-heated at 60°C had a higher degree of conversion (65.13%), with statistically significant difference compared to the other temperatures (p<0.05).
  
  
  CONCLUSIONS
  Composite pre-heating does not promote changes in the optical properties, despite the increase in the degree of conversion.
authors.affiliation: Department of Dental Materials and Prosthodontics, Ribeirão Preto School of Dentistry, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Fabrício Mariano
authors.initials: FM
authors.lastname: Mundim
authors.forename: Lucas da Fonseca Roberti
authors.initials: Lda F
authors.lastname: Garcia
authors.forename: Diogo Rodrigues
authors.initials: DR
authors.lastname: Cruvinel
authors.forename: Fabrício Augusto
authors.initials: FA
authors.lastname: Lima
authors.forename: Luciano
authors.initials: L
authors.lastname: Bachmann
authors.forename: Fernanda de Carvalho Panzeri
authors.initials: Fde C
authors.lastname: Pires-de-Souza
mesh_terms: D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D008027:Light; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry; D058105:Polymerization; D013053:Spectrophotometry
chemical_list: D003188:Composite Resins