title: Degree of conversion and flexural properties of a dendrimer/methyl methacrylate copolymer: design of experiments and statistical screening.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of photosensitive initiator and activator concentrations on the degree of conversion and flexural properties of an experimental photopolymerized dental copolymer containing dendrimer.
  
  
  METHODS
  The experimental resin system consisted of a dendrimer with 12 methacrylate groups and methyl methacrylate in a mass ratio of 80:20. The initiator and activator used were camphorquinone and 2-(N,N-dimethylamino)ethyl methacrylate, whose concentrations varied individually from 1 to 4 wt%. The degree of conversion was determined with FTIR spectroscopy, and flexural strength and flexural modulus with the three-point bending test. The experiments were designed and analyzed, and the results plotted with Modde 5.0 software.
  
  
  RESULTS
  The highest degree of conversion was obtained with 2.5 wt% initiator and activator concentrations, the highest flexural strength with 2.5 wt% initiator and 1.0 wt% activator concentration, and the highest flexural modulus with 1.0 wt% initiator and activator concentrations.
  
  
  CONCLUSIONS
  The results indicated that the degree of conversion increased, and flexural strength and flexural modulus decreased, with increasing initiator and activator concentrations. The high concentrations of initiator probably inhibited the transmittance of the active wavelengths to the depths of the samples (the inner filter effect), resulting in inhomogeneous conversion and thus decreased mechanical properties.
authors.affiliation: Department of Prosthetic Dentistry and Biomaterials Research, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, FIN-20520 Turku, Finland. eeva.viljanen@utu.fi
authors.forename: Eeva K
authors.initials: EK
authors.lastname: Viljanen
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: Mikael
authors.initials: M
authors.lastname: Skrifvars
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D004548:Elasticity; D006801:Humans; D008027:Light; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D020366:Methylmethacrylate / Q000737:chemistry* / Q000528:radiation effects; D018583:Pliability; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D019163:Reducing Agents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013729:Terpenes / Q000737:chemistry
chemical_list: D008689:Methacrylates; D011108:Polymers; D019163:Reducing Agents; D013729:Terpenes; D020366:Methylmethacrylate; C048339:camphoroquinone; C049840:2-(dimethylamino)ethyl methacrylate