title: Fractal analysis of heterogeneous polymer networks formed by photopolymerization of dental dimethacrylates.
abstract: OBJECTIVE
  In this work the influence of the dimethacrylate monomer chemical structure on structural heterogeneity and physico-mechanical properties of the resulting polymer networks was investigated. Rigid aromatic dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and flexible aliphatic urethane-dimethacrylate (UDMA) were chosen for room-temperature homopolymerizations and copolymerizations induced by camphorquinone/N,N-dimethylaminoethyl methacrylate photoinitiating system.
  
  
  METHODS
  Atomic force microscopy (AFM) was used for visualizing the morphology of poly(dimethacrylate)s, which was described by: the fractal dimension (D(F)), the generalized fractal dimensions (D(q) and ΔD) as well as the modified fractal dimension (D(β)). Estimated fractal characteristics were correlated with polymer density, hardness and impact strength.
  
  
  RESULTS
  AFM images of fractured surfaces revealed the highly complex morphology of dimethacrylate polymer networks. They were found to possess the fractal character. The fractal parameters were observed to be proportional to the density, hardness and impact resistance of investigated polymers. ΔD appeared to be a good indicator of the structural heterogeneity of dimethacrylate networks. The results suggest that the fracture behavior of poly(dimethacrylate) matrix of dental materials can be controlled by the fractal morphology.
  
  
  CONCLUSIONS
  Correlating the morphological studies with the mechanical tests would be beneficial in defining the role of morphology in the mechanical behavior of dimethacrylate networks and consequently, lead to the development of a reliable method for identifying the cause of dental material failures under stress. Thus, fractal analysis could become one of the key elements in designing and developing dental materials.
authors.affiliation: Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, Gliwice, Poland. Izabela.Barszczewska-Rybarek@polsl.pl
authors.forename: Izabela M
authors.initials: IM
authors.lastname: Barszczewska-Rybarek
authors.forename: Monika
authors.initials: M
authors.lastname: Krasowska
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D017709:Fractals; D006244:Hardness; D008689:Methacrylates / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011108:Polymers / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate