title: Color stability and polymerization behavior of direct esthetic restorations.
abstract: OBJECTIVE
  The current study evaluated the effect of accelerated artificial aging (AAA) on the color stability (CS) and degree of conversion (DC) of nanofilled and nanohybrid resin composites associated to different adhesive systems in direct esthetic restorations.
  
  
  METHODS
  Eighty bovine incisors were used to obtained dentin blocks (4 × 4 × 1 mm). The restorative systems were bonded to the blocks and photoactivated according to the manufacturer's instructions. Three adhesive systems were used: Adper Scotchbond Multi-Purpose (conventional of three steps), Tetric N-Bond (conventional of two steps) and ClearFill SE Bond (self-etching). Also, two composites were used: Filtek Z350 XT (nanofilled) and IPS Empress Direct (nanohybrid). The restorations were made using a silicone mold placed on top of the prepared dentin blocks (N = 10). CS was measured after 300 hours of AAA by means of ultraviolet light using a spectrophotometer and CIE L*a*b* parameters on the top surface of the composite and at the bonded interface. The DC was performed using Fourier transform infrared spectroscopy (N = 10). Data were analyzed using two-way analysis of variance and Tukey's test (α = 0.05).
  
  
  RESULTS
  The adhesive systems had no significant influence on the color stability (ΔE) of either the restoration surface (α = 0.90) or the bonded interface (α = 0.78). However, composite influenced the color as measured by ΔE and isolated coordinates (α < 0.001). The nanohybrid composite showed increased DC values (67%) compared with the nanofilled (61%) with statistically significant differences (α < 0.001).
  
  
  CONCLUSIONS
  The adhesive system did not affect the final color of direct esthetic restorations. The nanohybrid composite demonstrated a higher DC and increased color stability after AAA compared to the nanofilled composite.
  
  
  CONCLUSIONS
  The long-term color stability of composite restorations is a critical aspect of esthetic restorative procedures. Optimal Polymerization behavior of resin composite as indicated by the degree of conversion also influence on the color stability after artificial aging of composite restorations.
authors: Restorative Dentistry Department, Piracicaba Dental School - State University of Campinas, 901 Limeira Ave, Areião, Piracicaba, 13414-903, SP, Brazil.
authors: Dayane Carvalho Ramos Salles de
authors: DC
authors: Oliveira
authors: Eduardo José
authors: EJ
authors: Souza-Júnior
authors: Lúcia Trazzi
authors: LT
authors: Prieto
authors: Erick Kamiya
authors: EK
authors: Coppini
authors: Rodrigo Rocha
authors: RR
authors: Maia
authors: Luís Alexandre Maffei Sartini
authors: LA
authors: Paulillo
mesh_terms: D003116:Color; D003188:Composite Resins; D003793:Dental Restoration, Permanent; D004955:Esthetics, Dental; D058105:Polymerization; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003188:Composite Resins