title: Degree of conversion, depth of cure, and color stability of experimental dental composite formulated with camphorquinone and phenanthrenequinone photoinitiators.
abstract: OBJECTIVE
  This study evaluated the applicability of 9,10-phenanthrenequinone (PQ) in experimental dental composites.
  
  
  METHODS
  Camphorquinone (CQ), PQ, ethyl 4-N,N-dimethylaminobenzoate (EDMAB) and diphenyliodonium salt (DPI) were employed. A mixture of 2,2-bis(4-[2-hydroxy-3-methacryloxypropoxy]phenyl)-propane/triethylene glycol dimethacrylate (60:40%) and silanated glass filler at 60% were used. A two-peak-based light-emitting diode (LED) was used.
  
  
  METHODS
  The photoinitiator absorption and the light emission spectra were determined by a Ultraviolet-visible spectroscopy and a spectroradiometer, respectively. Relative photon absorption (RPabs) was calculated. Fourier-transformed infrared spectroscopy analysis was used to determine the degree of conversion (DC). The optical properties were determined with a spectrophotometer. Depth of cure was assessed from adapted International Organization for Standardization (ISO) 4049. Results were analyzed with descriptive analysis, analysis of variance, and Tukey's test (α = 5%).
  
  
  RESULTS
  PQ showed higher RPabs than CQ. Regarding the DC, CQ + EDMAB (control), CQ + EDMAB + DPI, PQ + DPI, and PQ + EDMAB + DPI produced statistically similar results. Groups formulated with CQ presented higher depth of cure. Only the group formulated with CQ + EDMAB presented satisfactory color stability (ΔE < 3.3).
  
  
  CONCLUSIONS
  PQ presented higher RPabs than CQ and it was able to produce DC similar to CQ + EDMAB, when used with DPI. However, groups formulated with PQ produced lower depth of cure, greater yellowing, and less color stability than the traditional combination CQ and amine.
  
  
  CONCLUSIONS
  Although research with novel photoinitiator systems should be encouraged, the traditional camphorquinone and amine pair remains as a reliable combination for the formulation of dental composites.
authors.affiliation: Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo-USP, São Paulo, Brazil.
authors.forename: Pedro Paulo A C
authors.initials: PP
authors.lastname: Albuquerque
authors.forename: Marcusv L
authors.initials: ML
authors.lastname: Bertolo
authors.forename: Larissa M A
authors.initials: LM
authors.lastname: Cavalcante
authors.forename: Carmem
authors.initials: C
authors.lastname: Pfeifer
authors.forename: Luis F S
authors.initials: LF
authors.lastname: Schneider
mesh_terms: D003116:Color; D003188:Composite Resins; D010616:Phenanthrenes / Q000737:chemistry*; D011809:Quinones / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013729:Terpenes / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D010616:Phenanthrenes; D011809:Quinones; D013729:Terpenes; C048339:camphoroquinone