title: Thiol-ene functionalized siloxanes for use as elastomeric dental impression materials.
abstract: OBJECTIVE
  Thiol- and allyl-functionalized siloxane oligomers are synthesized and evaluated for use as a radical-mediated, rapid set elastomeric dental impression material. Thiol-ene siloxane formulations are crosslinked using a redox-initiated polymerization scheme, and the mechanical properties of the thiol-ene network are manipulated through the incorporation of varying degrees of plasticizer and kaolin filler. Formulations with medium and light body consistencies are further evaluated for their ability to accurately replicate features on both the gross and microscopic levels. We hypothesize that thiol-ene functionalized siloxane systems will exhibit faster setting times and greater detail reproduction than commercially available polyvinylsiloxane (PVS) materials of comparable consistencies.
  
  
  METHODS
  Thiol-ene functionalized siloxane mixtures formulated with varying levels of redox initiators, plasticizer, and kaolin filler are made and evaluated for their polymerization speed (FTIR), consistency (ISO4823.9.2), and surface energy (goniometer). Feature replication is evaluated quantitatively by SEM. The Tg, storage modulus, and creep behavior are determined by DMA.
  
  
  RESULTS
  Increasing redox initiation rate increases the polymerization rate but at high levels also limits working time. Combining 0.86 wt% oxidizing agent with up to 5 wt% plasticizer gave a working time of 3 min and a setting time of 2 min. The selected medium and light body thiol-ene formulations also achieved greater qualitative detail reproduction than the commercial material and reproduced micrometer patterns with 98% accuracy.
  
  
  CONCLUSIONS
  Improving detail reproduction and setting speed is a primary focus of dental impression material design and synthesis. Radical-mediated polymerizations, particularly thiol-ene reactions, are recognized for their speed, reduced shrinkage, and 'click' nature.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0596, USA.
authors.forename: Megan A
authors.initials: MA
authors.lastname: Cole
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0596, USA.
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Jankousky
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0596, USA; Biomaterials Research Center, School of Dentistry, University of Colorado Health Sciences Center, Aurora, CO 80045, USA. Electronic address: christopher.bowman@colorado.edu.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Bowman
mesh_terms: D000498:Allyl Compounds / Q000138:chemical synthesis*; D003432:Cross-Linking Reagents; D003760:Dental Impression Materials / Q000138:chemical synthesis*; D020724:Elastomers; D007616:Kaolin / Q000737:chemistry; D008422:Materials Testing; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis*; D012833:Siloxanes / Q000138:chemical synthesis*; D013439:Sulfhydryl Reagents / Q000138:chemical synthesis*
chemical_list: D000498:Allyl Compounds; D003432:Cross-Linking Reagents; D003760:Dental Impression Materials; D020724:Elastomers; D011108:Polymers; D012833:Siloxanes; D013439:Sulfhydryl Reagents; C036925:elastomeric polymer; D007616:Kaolin
keywords: Free radical; Impression material; Redox polymerization; Siloxane; Thiol-ene