title: Comparative effect of different polymerization techniques on residual monomer and hardness properties of PMMA-based denture resins.
abstract: OBJECTIVE
  The aim of this study was to compare the residual monomer and microhardness of poly(methyl methacrylate) (PMMA)-based denture resins processed by using autoclave and conventional water bath techniques.
  
  
  METHODS
  To determine the amount of residual methyl methacrylate (MMA) monomer, disk-shaped specimens (n=5) were prepared from 3 different acrylic resins (Meliodent, Paladent and Qc-20). Control groups were polymerized in water bath for 30 minutes at 100°C. The study groups were prepared in an autoclave device for 60°C/30 min followed 130°C/10 min and the other group for 60°C/30 min followed by 130°C/20 min. According to standard calibration curves, ultraviolet spectrophotometry at 230 nm was used to determine the residual monomer. For the Vickers hardness measurements, disk-shaped specimens (n=5) were prepared for each test group. Hardness measurements were performed with a Vickers hardness tester under a 4.91-N press load for a 30 seconds, after immersion in distilled water at 37ºC for 48 hours. The data were analyzed by ANOVA and Tukey HSD test (p<0.05).
  
  
  RESULTS
  Autoclave polymerization produced a significant decrease in the amount of residual monomers for all resin groups (p<0.05). This procedure also showed a significant increase in hardness for all resin groups (p<0.05). For the 3 resin groups, no significant differences were found between autoclave polymerization for 10 minutes and for 20 minutes (p>0.05).
  
  
  CONCLUSIONS
  The autoclave polymerization technique exhibited significantly lower residual monomer content and greater hardness than conventional heat polymerization.
authors.affiliation: 1 Department of Prosthodontics, Faculty of Dentistry, Karadeniz Technical University, Trabzon - Turkey.
authors.forename: Elif Aydogan
authors.initials: EA
authors.lastname: Ayaz
authors.forename: Rukiye
authors.initials: R
authors.lastname: Durkan
authors.forename: Ayşegul
authors.initials: A
authors.lastname: Koroglu
authors.forename: Bora
authors.initials: B
authors.lastname: Bagis
mesh_terms: D001843:Bone Cements / Q000737:chemistry*; D003764:Dental Materials / Q000138:chemical synthesis*; D003819:Denture Bases; D006244:Hardness; D006361:Heating / Q000379:methods; D008422:Materials Testing; D018583:Pliability; D058105:Polymerization; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D012117:Resins, Synthetic / Q000138:chemical synthesis*
chemical_list: D001843:Bone Cements; D003764:Dental Materials; D012117:Resins, Synthetic; D019904:Polymethyl Methacrylate