title: Effects of low-energy electron beam irradiation on flexural properties of self-curing acrylic resin.
abstract: OBJECTIVE
  The purpose of this study was to confirm the effectiveness of LEB irradiation onto the polymer powder for improving the mechanical properties of self-curing acrylic resin.
  
  
  METHODS
  The polymer powder of self-curing acrylic resin was irradiated with total LEB doses of 25, 50, 75 or 100kGy. Non-irradiated powder was used as a control. After LEB irradiation, ESR measurement, weight-average molecular weight measurement and three-point bending test were performed.
  
  
  RESULTS
  ESR spectrum of control had no peaks. After LEB irradiation, nine peaks were observed in each ESR spectrum, which indicates the presence of free radicals from main polymer chain. The quantity of free radicals increased linearly up to 100kGy. Calibrated weight-average molecular weights were as follows: control, 960,000; 25kGy, 500,000; 50kGy, 440,000; 75kGy, 410,000; and 100kGy, 390,000. Molecular weight decreased with increasing LEB irradiation dose. The mean values of flexural strength (MPa) were as follows: control, 61.5±3.0; 25kGy, 68.1±4.0; 50kGy, 73.0±1.9; 75kGy, 70.4±3.6; and 100kGy, 67.7±2.3. The flexural strength of the specimens cured with the LEB-irradiated powder was significantly higher than that of control (p<0.01). These results indicate that flexural strength of polymer materials cured with the LEB-irradiated powder increases because of increase in cross-linking structure.
  
  
  CONCLUSIONS
  It is confirmed that LEB irradiation onto the polymer powder of self-curing acrylic resin improves the flexural strength.
authors.affiliation: Division of Comprehensive Prosthodontics, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata city, Niigata 951-8514, Japan. Electronic address: kyoitou@dent.niigata-u.ac.jp.
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Ito
authors.affiliation: Department of Dental Technology, Meirin College, 3-16-10 Masago, Niigata city, Niigata 950-2086, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Nomura
authors.affiliation: Division of Comprehensive Prosthodontics, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata city, Niigata 951-8514, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Nomura
authors.affiliation: Division of Biomaterial Science, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata city, Niigata 951-8514, Japan.
authors.forename: Kouichi
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000180:Acrylic Resins; D004583:Electrons; D008970:Molecular Weight; D011108:Polymers; D011208:Powders; D011829:Radiation Dosage; D012117:Resins, Synthetic; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D011108:Polymers; D011208:Powders; D012117:Resins, Synthetic
keywords: Cross-linking; Flexural strength; Low-energy electron beam; Polymer powder; Self-curing acrylic resin