title: Polymerization shrinkage-strain kinetics of temporary crown and bridge materials.
abstract: OBJECTIVE
  The purpose of this study was to measure the polymerization shrinkage kinetics of four commercially available polymer-based temporary crown and bridge materials, including the effect of ambient temperature.
  
  
  METHODS
  Three dimethacrylate-based materials and one monomethacrylate-based material were investigated. The polymerization shrinkage-strains were measured by using the Bonded-disk method with initial specimen temperature at both 23 and 37 degrees C, with values particularly noted at 5, 10, and 120 min after mixing. Five recordings were taken for each material. The progress of the setting reaction and its temperature-dependence were evaluated by the kinetic curves, and net shrinkage and total shrinkage (inclusive of expansion magnitude) of each material were compared by independent sample t-test and one-way ANOVA.
  
  
  RESULTS
  Most shrinkage occurred in the first 10 min after mixing although there was an early expansion especially with the monomethacylate in the first 5 min. At 120 min, the net shrinkage-strain at 23 and 37 degrees C of the materials used in this test ranged from 3.54 to 4.13%. The fastest setting dimethacrylate-based material and the monomethacrylate-based material showed higher shrinkage-strain than other materials. No significant differences of net shrinkage-strain were found between 23 and 37 degrees C, but higher shrinkage rates were measured at 37 degrees C than at 23 degrees C.
  
  
  CONCLUSIONS
  The Bonded-disk method is a suitable method for measuring temperature-dependence of shrinkage-strain of polymer-based temporary materials. The dimethacrylate-based materials are preferable to monomethacrylates for temporary restoration as judged by the magnitude of polymerization shrinkage-strain, the majority of which is apparent within 10 min from the start of mixing and may affect the clinical outcome.
authors.affiliation: Biomaterials Science Unit, Department of Restorative Dentistry, University of Manchester Dental School, Higher Cambridge Street, Manchester M15 6FH, UK. ksh1250@yahoo.co.kr
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: D C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D000180:Acrylic Resins / Q000528:radiation effects; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D003188:Composite Resins / Q000528:radiation effects; D003442:Crowns; D018772:Dental Marginal Adaptation; D003794:Dental Restoration, Temporary; D003799:Dental Stress Analysis / Q000295:instrumentation / Q000379:methods; D003830:Denture, Partial, Fixed; D006358:Hot Temperature; D007700:Kinetics; D008422:Materials Testing; D008689:Methacrylates / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000528:radiation effects; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; C483029:Temphase; C098586:luxatemp; C091347:vinyl ethyl methacrylate; D017438:Bisphenol A-Glycidyl Methacrylate; D019904:Polymethyl Methacrylate; C069714:Protemp