title: Ester-free thiol-ene dental restoratives--Part B: Composite development.
abstract: OBJECTIVE
  To assess the performance of thiol-ene dental composites based on selected ester-free thiol-ene formulations. Further, to point out the benefits/drawback of having a hydrolytically stable thiol-ene matrix within a glass filled composite.
  
  
  METHODS
  Composite samples containing 50-65wt% of functionalized glass microparticles were prepared and photopolymerized in the presence of a suitable visible light photoinitiator. Shrinkage stress measurements were conducted as a function of the irradiation time. Degrees of conversion were measured by FT-IR analysis by comparing the double bond signals before and after photopolymerization. Mechanical tests were carried out on specimens after curing as well as after extended aging in water. Dynamic mechanical analysis was employed to track the changes in storage modulus near body temperature. The properties of the thiol-ene composites were compared with those of the BisGMA/TEGDMA control.
  
  
  RESULTS
  Depending on the resin type, similar or higher conversions were achieved in thiol-ene composites when compared to the dimethacrylate controls. At comparable conversions, lower shrinkage stress values were achieved. Although exhibiting lower initial elastic moduli, the thiol-ene composites' flexural strengths were found to be comparable with the controls. Contrary to the control, the mechanical properties of the ester-free thiol-ene composites were shown to be unaffected by extensive aging in water and at least equaled that of the control after aging in water for just five weeks.
  
  
  CONCLUSIONS
  Employing non-degradable step-growth networks as organic matrices in dental composites will provide structurally uniform, tough materials with extended service time.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA; Department of Polymer Chemistry, Faculty of Chemistry, MCS University, Gliniana St. 33, 20-614 Lublin, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Podgórski
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA.
authors.forename: Eftalda
authors.initials: E
authors.lastname: Becka
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA.
authors.forename: Mauro
authors.initials: M
authors.lastname: Claudino
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Flores
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA.
authors.forename: Parag K
authors.initials: PK
authors.lastname: Shah
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA; Department of Craniofacial Biology, School of Dental Medicine, University of Colorado, Denver, Anschutz Medical Campus, Mail Stop 8310, 12800E. 19th Avenue, Aurora, CO 80045, USA.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Stansbury
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, 3415 Colorado Ave, JSC Biotech Building, Boulder, CO 80309, USA. Electronic address: christopher.bowman@colorado.edu.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Bowman
mesh_terms: D003188:Composite Resins; D003764:Dental Materials; D055119:Elastic Modulus; D008422:Materials Testing; D008689:Methacrylates; D018583:Pliability; D011092:Polyethylene Glycols; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013438:Sulfhydryl Compounds
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D013438:Sulfhydryl Compounds; D011092:Polyethylene Glycols
keywords: Dental composites; Photopolymerization; Shrinkage stress; Thiol-ene resins