title: Effect of thermal shock on mechanical properties of injection-molded thermoplastic denture base resins.
abstract: OBJECTIVE
  This study investigated the effect of thermal shock on the mechanical properties of injection-molded thermoplastic denture base resins.
  
  
  METHODS
  Four thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were tested. Specimens of each denture base material were fabricated according to ISO 1567 and were either thermocycled or not thermocycled (n = 10). The flexural strength at the proportional limit (FS-PL), the elastic modulus and the Charpy impact strength of the denture base materials were estimated.
  
  
  RESULTS
  Thermocycling significantly decreased the FS-PL of one of the polyamides and the PMMA and it significantly increased the FS-PL of one of the polyamides. In addition, thermocycling significantly decreased the elastic modulus of one of the polyamides and significantly increased the elastic moduli of one of the polyamides, the polyethylene terephthalate, polycarbonate and PMMA. Thermocycling significantly decreased the impact strength of one of the polyamides and the polycarbonate.
  
  
  CONCLUSIONS
  The mechanical properties of injection-molded thermoplastic denture base resins changed after themocycling.
authors.affiliation: Division of Removable Prosthodontics, Fukuoka Dental College, Fukuoka, Japan. ytakaha@college.fdcnet.ac.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Ippei
authors.initials: I
authors.lastname: Hamanaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimizu
mesh_terms: D003799:Dental Stress Analysis; D003819:Denture Bases; D055119:Elastic Modulus; D006358:Hot Temperature; D008422:Materials Testing; D055595:Mechanical Phenomena; D009757:Nylons / Q000737:chemistry; D018583:Pliability; D011076:Polycarboxylate Cement / Q000737:chemistry; D011093:Polyethylene Terephthalates / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry
chemical_list: D009757:Nylons; D011076:Polycarboxylate Cement; D011093:Polyethylene Terephthalates; D012117:Resins, Synthetic; C005506:polycarbonate