title: Glass transition and degree of conversion of a light-cured orthodontic composite.
abstract: OBJECTIVE
  This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite.
  
  
  METHODS
  Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s).
  
  
  RESULTS
  Fill Magic presented lower Tg than Concise (35-84 masculineC versus 135 masculineC), but reached a higher DC.
  
  
  CONCLUSIONS
  The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm(2) is necessary to reach adequate conversion level and obtain satisfactory adhesion.
authors.affiliation: Department of Physics and Chemistry, São Paulo State University, Ilha Solteira, Brazil.
authors.forename: Michela M D S
authors.initials: MM
authors.lastname: Sostena
authors.forename: Renata A
authors.initials: RA
authors.lastname: Nogueira
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Grandini
authors.forename: João Carlos Silos
authors.initials: JC
authors.lastname: Moraes
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D055117:Curing Lights, Dental / Q000145:classification; D055119:Elastic Modulus; D004735:Energy Transfer; D017276:Friction; D005898:Glass / Q000737:chemistry* / Q000528:radiation effects; D006358:Hot Temperature; D006801:Humans; D008027:Light; D008422:Materials Testing; D016910:Orthodontic Brackets; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry* / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis; D013997:Time Factors; D044366:Transition Temperature
chemical_list: D003188:Composite Resins; C481898:Fill Magic; D011108:Polymers; D019279:Resin Cements; D017438:Bisphenol A-Glycidyl Methacrylate