title: The effect of cycling deflection on the injection-molded thermoplastic denture base resins.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of cycling deflection on the flexural behavior of injection-molded thermoplastic resins.
  
  
  METHODS
  Six injection-molded thermoplastic resins (two polyamides, two polyesters, one polycarbonate, one polymethyl methacrylate) and, as a control, a conventional heat-polymerized denture based polymer of polymethyl methacrylate (PMMA) were used in this study. The cyclic constant magnitude (1.0 mm) of 5000 cycles was applied using a universal testing machine to demonstrate plasticization of the polymer. Loading was carried out in water at 23ºC with eight specimens per group (n = 8). Cycling load (N) and deformation (mm) were measured.
  
  
  RESULTS
  Force required to deflect the specimens during the first loading cycle and final loading cycle was statistically significantly different (p < 0.05) with one polyamide based polymer (Valplast) and PMMA based polymers (Acrytone and Acron). The other polyamide based polymer (LucitoneFRS), polyester based polymers (EstheShot and EstheShotBright) and polycarbonate based polymer (ReigningN) did not show significant differences (p > 0.05). None of the materials fractured during the loading test. One polyamide based polymer (Valplast) displayed the highest deformation and PMMA based polymers (Acrytone and Acron) exhibited the second highest deformation among the denture base materials.
  
  
  CONCLUSIONS
  It can be concluded that there were considerable differences in the flexural behavior of denture base polymers. This may contribute to the fatigue resistance of the materials.
authors.affiliation: a 1 Division of Removable Prosthodontics, Fukuoka Dental College , Fukuoka, Japan.|b 2 Department of Biomaterials Science and Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku , Turku, Finland.
authors.forename: Ippei
authors.initials: I
authors.lastname: Hamanaka
authors.affiliation: a 1 Division of Removable Prosthodontics, Fukuoka Dental College , Fukuoka, Japan.|b 2 Department of Biomaterials Science and Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku , Turku, Finland.
authors.forename: Misa
authors.initials: M
authors.lastname: Iwamoto
authors.affiliation: b 2 Department of Biomaterials Science and Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku , Turku, Finland.
authors.forename: Lippo Vj
authors.initials: LV
authors.lastname: Lassila
authors.affiliation: b 2 Department of Biomaterials Science and Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku , Turku, Finland.|c 3 City of Turku, Division for Welfare , Turku, Finland.
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
authors.affiliation: d 4 Division of Biomaterials, Kyushu Dental University , Fukuoka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimizu
authors.affiliation: a 1 Division of Removable Prosthodontics, Fukuoka Dental College , Fukuoka, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003819:Denture Bases; D006801:Humans; D008422:Materials Testing; D009757:Nylons / Q000737:chemistry; D010969:Plastics / Q000737:chemistry*; D018583:Pliability; D011076:Polycarboxylate Cement / Q000737:chemistry; D011091:Polyesters / Q000737:chemistry; D011093:Polyethylene Terephthalates / Q000737:chemistry; D058105:Polymerization; D011108:Polymers / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D013314:Stress, Mechanical; D013450:Sulfones / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; C000601794:Acrytone; D003764:Dental Materials; D009757:Nylons; D010969:Plastics; D011076:Polycarboxylate Cement; D011091:Polyesters; D011093:Polyethylene Terephthalates; D011108:Polymers; D013450:Sulfones; C005506:polycarbonate; C040291:Lucitone; C045672:Reigning resin; D019904:Polymethyl Methacrylate
keywords: Denture base resin; PMMA; polyamide; polycarbonate; polyester