title: The degree of conversion of fiber-reinforced composites polymerized using different light-curing sources.
abstract: OBJECTIVE
  Fiber-reinforced composites (FRC) with different polymer matrix compositions are available on the market. The aim of this study was to compare the degree of monomer conversion of FRC that contained either dimethacrylate resin matrix or semi-IPN resin matrix. In addition, the effect of different types of light-curing units and durations of light irradiation on the degree of conversion was evaluated.
  
  
  METHODS
  Continuous unidirectional fibers impregnated with dimethacrylate or semi-IPN resin were compared. As control materials, a particulate filler composite resin and an unfilled resin were used. The materials were photopolymerized using various irradiation times and different types of light-curing units (quartz-tungsten-halogen with standard or turbo tip, light-emitting diode and plasma-arc). Degree of monomer conversion (DC%) was determined by FT-IR spectrometry. The infrared spectra were recorded at seven different time points after polymerization.
  
  
  RESULTS
  ANOVA showed significant differences between the materials tested, and the curing units (P<0.05). The DC% of semi-IPN and dimethacrylate matrix FRC was not statistically different (P>0.05) compared to that of unfilled resin. Conventional quartz-tungsten halogen with turbo tip showed the highest DC% (69-72.3%), whereas the plasma-arc curing unit showed the lowest degree of conversion (47-62%).
  
  
  CONCLUSIONS
  Within the limitations of this study, it can be concluded that semi-IPN matrix of FRC did not show a difference in the degree of conversion compared to dimethacrylate resin FRC when quartz-tungsten or a light-emitting diode polymerization unit was used. The plasma-arc light-curing unit showed a lower degree of conversion with all materials compared to the light-emitting diode and quartz-tungsten-halogen lamps.
authors.affiliation: Faculty of Dentistry, Suleyman Demirel University, Isparta, Turkey.
authors.forename: S
authors.initials: S
authors.lastname: Uctasli
authors.forename: A
authors.initials: A
authors.lastname: Tezvergil
authors.forename: L V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: P K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003748:Dental Equipment; D003799:Dental Stress Analysis; D005898:Glass; D006219:Halogens; D008027:Light; D008422:Materials Testing; D044367:Phase Transition; D019904:Polymethyl Methacrylate; D012666:Semiconductors; D017550:Spectroscopy, Fourier Transform Infrared; D013674:Technology, Dental; D014978:Xenon
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D006219:Halogens; C485628:Stick resin; C009753:fiberglass; D014978:Xenon; D019904:Polymethyl Methacrylate