title: Effects of postpolymerization microwave irradiation on provisional dental acrylics: physical and mechanical properties.
abstract: BACKGROUND
  This study aimed to evaluate the effects of microwave irradiation on the physical and mechanical properties of poly(methyl methacrylate) (PMMA) provisional resins.
  
  
  METHODS
  Twenty bars and 20 disc-shaped specimens were fabricated for each selected provisional restorative material (Dencor and Duralay). Test groups were subjected to microwave irradiation (3 minutes at 600 W) after polymerization. Bar specimens were subjected to a flexural strength test. Disc-shaped specimens were used to evaluate microhardness. Backscattered Raman spectroscopy was employed for each group to define the degree of conversion of the monomer/polymer. The frequency bands corresponding to C = C and C = O groups were used to determine the conversion of methyl methacrylate (MMA) monomers into polymers. Glass transition temperature was determined using a differential scanning calorimeter.
  
  
  RESULTS
  Microwave irradiation of both tested autopolymerizing PMMA provisional materials resulted in a statistically significant increase in microhardness, degree of conversion and glass transition temperature values. Also, the results demonstrated a significant increase in flexural strength after postpolymerization microwave irradiation for the Dencor specimens.
  
  
  CONCLUSIONS
  It is concluded that mechanical and physical properties are positively influenced by microwave irradiation.
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Dentistry, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre - Brazil.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Ozkomur
authors.affiliation: Department of Conservative Dentistry, Faculty of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre - Brazil.
authors.forename: Carmen Beatriz Borges
authors.initials: CB
authors.lastname: Fortes
mesh_terms: D020366:Methylmethacrylate / Q000737:chemistry*; D008872:Microwaves; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry*
chemical_list: D012117:Resins, Synthetic; D020366:Methylmethacrylate; D019904:Polymethyl Methacrylate