title: Influence of the cross-linking agent on mechanical properties of PMMA powder with compromised particle morphology.
abstract: OBJECTIVE
  To investigate the effect of a cross-linking agent on the mechanical properties of self-cured orthodontic acrylic resin using PMMA powder (CPM-PMMA) with a compromised microstructure.
  
  
  METHODS
  The mechanical properties of three sample groups were investigated in this study: CPM-PMMA, orthocryl and orthoplast. CPM-PMMA powder was prepared by suspension polymerization. It was mixed with a commercially available liquid (orthocryl) to yield a test specimen and to compare its flexural properties and Vicker hardness with the two commercial products. Molecular weight and particle size distribution of all groups were examined. Particle morphology was observed using scanning electron microscopy (SEM) and optical microscopy (OM).
  
  
  RESULTS
  The average molecular weight of the CPM-PMMA powder was similar to that of the industrial products. Its particle size distribution was narrow and limited to large sizes (91.1-149μm). SEM and OM presented the compromise particle morphology. However, the flexural properties and Vicker hardness of CPM-PMMA powder mixed with orthocryl liquid showed no significant difference compared with orthocryl sample group. In addition, the CPM-PMMA had higher flexural properties than the orthoplast samples.
  
  
  CONCLUSIONS
  Although the CPM-PMMA powder presented a compromised particle morphology and narrow particle size distribution, when mixed with orthocryl liquid, the cured resin produced acceptable mechanical properties due to the large amount of cross-linking agent. This result could indicate that the mechanical properties of self-cured acrylic resins are mainly dependent on the amount of cross-linking agent in the liquid component.
authors.affiliation: Department of orthodontics, research office, faculty of dentistry, Mahidol university, No. 6, Yothi Road, Ratchathewi District, 10400 Bangkok, Thailand.
authors.forename: Tassanaporn
authors.initials: T
authors.lastname: Saen-Isara
authors.affiliation: Department of orthodontics, research office, faculty of dentistry, Mahidol university, No. 6, Yothi Road, Ratchathewi District, 10400 Bangkok, Thailand. Electronic address: surachai.dec@mahidol.ac.th.
authors.forename: Surachai
authors.initials: S
authors.lastname: Dechkunakorn
authors.affiliation: Department of orthodontics, research office, faculty of dentistry, Mahidol university, No. 6, Yothi Road, Ratchathewi District, 10400 Bangkok, Thailand.
authors.forename: Niwat
authors.initials: N
authors.lastname: Anuwongnukroh
authors.affiliation: Department of physics, faculty of science, Mahidol university, 272 Rama VI Road, Ratchathewi District, 10400 Bangkok, Thailand.
authors.forename: Toemsak
authors.initials: T
authors.lastname: Srikhirin
authors.affiliation: Biomedical engineering research unit, National Metal and Materials Technology Center (MTEC), Pahonyothin Road, KlongNueng, KlongLuang, 12120 Pathumtani, Thailand.
authors.forename: Siriporn
authors.initials: S
authors.lastname: Tanodekaew
authors.affiliation: Department of orthodontics, research office, faculty of dentistry, Mahidol university, No. 6, Yothi Road, Ratchathewi District, 10400 Bangkok, Thailand.
authors.forename: Wassana
authors.initials: W
authors.lastname: Wichai
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D055595:Mechanical Phenomena; D008970:Molecular Weight; D010316:Particle Size; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011208:Powders
chemical_list: D000180:Acrylic Resins; D003432:Cross-Linking Reagents; D003764:Dental Materials; D011208:Powders; D019904:Polymethyl Methacrylate
keywords: Cross-linking agent; Mechanical properties; Orthodontic acrylic resins