title: Development of a new photoinitiation system for dental light-cure composite resins.
abstract: OBJECTIVE
  The purpose of this study is to explore the synergistic effect of combining camphorquinone (CQ) with 1-phenyl-1,2-propanedione (PPD) as a new photoinitiator.
  
  
  METHODS
  A BisGMA, UDMA, TEGDMA monomer mixture was made light-curing with CQ and/or PPD plus 0.2 wt.% N,N-cyanoethyl-methylaniline (CEMA). Seventeen groups, three specimens each, were tested in which the concentrations of PPD and CQ were varied. The effect of photosensitizer type (CQ or PPD) and ratio (PPD/CQ) on degree of conversion (DC) was investigated using FTIR spectrophotometry. The results were analyzed by ANOVA and Student-Newman-Keuls' multiple range comparison. The absorption spectra of PPD and CQ were recorded by UV-Vis spectrophotometry. A blind color comparison of specimens containing combinations of the two photosensitizers was also undertaken.
  
  
  RESULTS
  Alone, PPD induces a DC which is not significantly different from that of CQ alone. In combination, CQ + PPD produces a DC that generally exceeds that produced by the same concentration of either used alone. The maximum DC occurs between PPD/CQ = 1:1 and 1:4. At total photosensitizer concentrations above 1.8 wt.%, DC is increased by PPD but depressed by CQ, which is evidence that different mechanisms are involved. PPD (lambda max approximately 410 nm) and CQ (lambda max approximately 468 nm) have different wavelength absorption ranges, resulting in a perceptibly lighter shade of yellow for PPD.
  
  
  CONCLUSIONS
  1-phenyl-1,2-propanedione is a photosensitizer of potential value in reducing color problems associated with visible light cured dental resins. In combination with camphorquinone, it acts synergistically to produce a more efficient photoinitiation reaction.
authors.affiliation: Department of Restorative Dentistry, University of Texas Health Science Center, San Antonio 78284-7890, USA. yjpark@chonnam.ac.kr
authors.forename: Y J
authors.initials: YJ
authors.lastname: Park
authors.forename: K H
authors.initials: KH
authors.lastname: Chae
authors.forename: H R
authors.initials: HR
authors.lastname: Rawls
mesh_terms: D001565:Benzoates / Q000737:chemistry*; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D047188:Chalcones; D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry; D010777:Photochemistry / Q000379:methods*; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D013329:Structure-Activity Relationship; D013674:Technology, Dental; D013729:Terpenes / Q000737:chemistry*; D013997:Time Factors
chemical_list: D001565:Benzoates; D047188:Chalcones; D003188:Composite Resins; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D013729:Terpenes; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; C100349:1-phenyl-1,2-propanedione