title: Effect of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin.
abstract: OBJECTIVE
  The aim of this research was to investigate the effects of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin.
  
  
  METHODS
  PMMA powder was applied after heat treatment at 100°C for 2h (code: HT100) or 130°C for 2h (code: HT130). The test specimens were fabricated from autopolymerizing resin to investigate the flexural properties of denture base resin cross-linked with methacrylated dendrimer, the surface microhardness of PMMA beads, and the thickness of the swollen layer of PMMA beads. The specimens were autopolymerized, and all specimens were stored in 37°C water for 24h. Half of the specimens were immersed in 37°C water for an additional 6 months (water storage period: 24h and 6 months). The flexural strength and flexural modulus (n=10/group) were measured with a three point bending test. Statistical analysis was performed using ANOVA and the Newman-Keuls test at a significance level of 0.05.
  
  
  RESULTS
  Heat treatment and the water storage period had a significant effect on flexural strength. The flexural strength of HT130 showed significantly higher values than in other groups. The surface microhardness of PMMA beads of HT130 showed a significantly greater microhardness than other groups. The thickness of a swollen layer of PMMA beads of HT100 and HT130 was significantly decreased.
  
  
  CONCLUSIONS
  The flexural strength and the surface microhardness were increased after heat treatment at 130°C. The thickness of a swollen layer of PMMA beads was decreased after heat treatment.
authors.affiliation: Department of Biomaterials Science, Institute of Dentistry, University of Turku, BioCity Turku Biomaterials Research Program, Turku, Finland; Division of Removable Prosthodontics, Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka, Japan. Electronic address: tomokawa@college.fdcnet.ac.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kawaguchi
authors.affiliation: Department of Biomaterials Science, Institute of Dentistry, University of Turku, BioCity Turku Biomaterials Research Program, Turku, Finland.
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.affiliation: Division of Removable Prosthodontics, Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka, Japan.
authors.forename: Hirono
authors.initials: H
authors.lastname: Sasaki
authors.affiliation: Division of Removable Prosthodontics, Department of Oral Rehabilitation, Fukuoka Dental College, Fukuoka, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Biomaterials Science, Institute of Dentistry, University of Turku, BioCity Turku Biomaterials Research Program, Turku, Finland.
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D000180:Acrylic Resins; D001672:Biocompatible Materials / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003778:Dentures; D006244:Hardness; D006358:Hot Temperature; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011208:Powders; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D001672:Biocompatible Materials; D003764:Dental Materials; D011108:Polymers; D011208:Powders; D019904:Polymethyl Methacrylate
keywords: Denture base polymer; Flexural property; Heat treatment; Interpenetrating polymer network; PMMA