title: Effect of post-polymerization heat-treatments on degree of conversion, leaching residual MMA and in vitro cytotoxicity of autopolymerizing acrylic repair resin.
abstract: OBJECTIVE
  This study evaluated the effect of post-polymerization heat-treatments on degree of conversion (DC), residual methyl methacrylate concentration (MMA(r)) and in vitro cytotoxicity of autopolymerizing acrylic repair resin.
  
  
  METHODS
  A total of 336 specimens were prepared by bench- and hydroflask-curing and subjected to post-polymerization heat-treatments: a) water immersion at 60°C for 30 min, b) microwaving at 500 W for 3 min, c) combined use of water immersion and microwaving d) no treatment (as control). Specimens were eluted in cell culture medium for 1, 2, 5 and 7 days. DC and MMA(r) in eluates were measured by FTIR spectrometry and HPLC, respectively. In vitro cytotoxicity of eluates on L-929 fibroblasts was determined by XTT assay. Data were statistically analyzed with Dunn's multiple comparison and Pearson correlation tests (p≤0.05).
  
  
  RESULTS
  DC was highest (99.9%) in bench- and hydroflask-cured groups which were subjected to water immersion. At all elution periods, MMA(r) was detected in eluates of all treatment groups and were higher in bench-cured groups than hydro-flask cured groups. Cell proliferation values indicated slightly cytotoxic effect throughout 7 days; regardless of the curing method or post-polymerization treatment. The correlation between MMA(r) and cell proliferation was negative after elution of 1, 2, 5 days and was only statistically significant (p<0.05) at 5 days. At elution of 7 days, the correlation was positive with no significance.
  
  
  CONCLUSIONS
  Post-polymerization heat-treatment of autopolymerizing acrylic repair resin by immersion in water at 60°C for 30 min is clinically recommended to improve the DC while reducing the leaching residual MMA.
authors.affiliation: Department of Removable Prosthodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey. cbural@istanbul.edu.tr
authors.forename: Canan
authors.initials: C
authors.lastname: Bural
authors.forename: Esin
authors.initials: E
authors.lastname: Aktaş
authors.forename: Günnur
authors.initials: G
authors.lastname: Deniz
authors.forename: Yeşim
authors.initials: Y
authors.lastname: Ünlüçerçi
authors.forename: Nilgün
authors.initials: N
authors.lastname: Kızılcan
authors.forename: Gülsen
authors.initials: G
authors.lastname: Bayraktar
mesh_terms: D000180:Acrylic Resins / Q000633:toxicity; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D058250:Dental Restoration Repair; D006244:Hardness; D006358:Hot Temperature; D007101:Immersion; D007739:L Cells; D020366:Methylmethacrylate / Q000032:analysis*; D051379:Mice; D008872:Microwaves; D058105:Polymerization; D055116:Self-Curing of Dental Resins / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water
chemical_list: D000180:Acrylic Resins; D014867:Water; D020366:Methylmethacrylate