title: Quantum yield of conversion of the photoinitiator camphorquinone.
abstract: The primary absorber in dental resins is the photoinitiator, which starts the photo polymerization process. We studied the quantum yield of conversion of camphorquinone (CQ), a blue light photoinitiator, in dental resin composites using a LED lamp (3M FreeLight) and a Quartz Tungsten Halogen (QTH) lamp (VIP) as the light curing units at five different irradiances. The molar extinction coefficient, epsilon(469), of CQ was 46+/-2 cm(-1)/(mol/L) at 469 nm. The reciprocity of irradiance and exposure time holds for changes of CQ absorption coefficient, that is, irradiance x exposure time (=radiant exposure)=constant. Both LED and QTH lamps yielded the same curing threshold (the radiant exposure when CQ absorption drops to 1/e) and the same quantum yield conversion under different irradiances. In our dental resin formulation (0.7 wt.% CQ with reducing agents 0.35 wt.% dimethylaminoethyl methacrylate (DMAEMA) and 0.05 wt.% butylated hydroxytoluene (BHT)) the quantum yield was measured as 0.07+/-0.01 CQ conversion per absorbed photon.
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Yin-Chu
authors.initials: YC
authors.lastname: Chen
authors.forename: Jack L
authors.initials: JL
authors.lastname: Ferracane
authors.forename: Scott A
authors.initials: SA
authors.lastname: Prahl
mesh_terms: D000042:Absorption; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D003188:Composite Resins / Q000528:radiation effects*; D008027:Light; D044367:Phase Transition / Q000528:radiation effects*; D017785:Photons; D011092:Polyethylene Glycols / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000528:radiation effects; D011874:Radiometry / Q000379:methods*; D013674:Technology, Dental / Q000379:methods*; D013729:Terpenes
chemical_list: D003188:Composite Resins; D011109:Polymethacrylic Acids; D013729:Terpenes; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone