title: Influence of photoinitiator system and nanofiller size on the optical properties and cure efficiency of model composites.
abstract: OBJECTIVE
  To establish the relationship between photoinitiator system and nanofiller size on the optical properties and cure efficiency of model composites.
  
  
  METHODS
  Model composites based on BisGMA/TEGDMA (60:40mol%) were loaded with 40wt% of 7nm or 16nm-sized filler particles. One of the following photoinitiator systems was added: camphorquinone (CQ) associated with an amine (EDMAB), monoacylphosphine oxide (TPO), or bysacylphosphine oxide (BAPO). The optical properties of disk-shaped specimens were measured 24h after curing and repeated after storage in water for 90 days and coffee for 15 days. A large spectrum LED unit (Bluephase G2, Ivoclar Vivadent) was used for photoactivation. CIE L*a*b* parameters, color difference (ΔE), and translucency parameter (TP) were calculated. Knoop hardness readings were taken at top and bottom composite surfaces. Cure efficiency was determined by bottom/top hardness ratio. Data were statistically analyzed at α=0.05 significance level.
  
  
  RESULTS
  Composites formulated with 16nm particles had higher CIE L* than those with 7nm particles in all storage conditions. BAPO-based composites generally had lower CIE a* than the other composites. The group TPO+16nm before storage and all groups with 16nm-sized particles after storage had lower CIE b* (i.e. lower degree of yellowing) than the other groups. TPO-based materials had higher color stability. The cure efficiency was not significantly affected by photoinitiator system or particle size. CQ+7nm had the lowest and BAPO+16nm the highest hardness values.
  
  
  CONCLUSIONS
  Combination of photoinitiator system and filler particle size might affect the optical properties of composites, with low influence on cure efficiency.
authors.affiliation: Graduate Program in Dentistry, Federal University of Pelotas, Pelotas, RS, Brazil. Electronic address: salgadouff@gmail.com.
authors.forename: Vinícius E
authors.initials: VE
authors.lastname: Salgado
authors.affiliation: Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Pedro Paulo A C
authors.initials: PP
authors.lastname: Albuquerque
authors.affiliation: Department of Restorative Dentistry, Federal Fluminense University, Niterói, RJ, Brazil.
authors.forename: Larissa Maria
authors.initials: LM
authors.lastname: Cavalcante
authors.affiliation: Department of Biomaterials and Biomechanics, School of Dentistry, Oregon Health & Science University, Portland, OR, USA.
authors.forename: Carmem S
authors.initials: CS
authors.lastname: Pfeifer
authors.affiliation: Graduate Program in Dentistry, Federal University of Pelotas, Pelotas, RS, Brazil.
authors.forename: Rafael R
authors.initials: RR
authors.lastname: Moraes
authors.affiliation: Department of Restorative Dentistry, Federal Fluminense University, Niterói, RJ, Brazil; Graduate Program in Dentistry, School of Dentistry, Veiga de Almeida University, Rio de Janeiro, RJ, Brazil. Electronic address: felipefop@gmail.com.
authors.forename: Luis Felipe J
authors.initials: LF
authors.lastname: Schneider
mesh_terms: D003116:Color; D003188:Composite Resins; D055117:Curing Lights, Dental; D036103:Nanotechnology
chemical_list: D003188:Composite Resins
keywords: Alternative photoinitiators; BAPO; CIELAB; Camphorquinone; Fumed silica; Storage; TPO