title: Residual monomer of autopolymerized acrylic resin according to different manipulation and polishing methods. An in situ evaluation.
abstract: OBJECTIVE
  To test the hypothesis that no difference exists in the in situ levels of residual monomer of an autopolymerized acrylic resin, irrespective of the method of manipulation and polishing.
  
  
  METHODS
  Forty volunteers received the test specimens. The residual monomer was evaluated by means of gas chromatography using methylethylketone as extraction solvent. The samples of autopolymerized acrylic resin were submitted to two methods of manipulation--mass and addition--as well as to two types of polishing-mechanical and chemical. Four test groups were determined according to manipulation and polishing techniques: mass-mechanical; mass-chemical; addition-mechanical; addition-chemical. The data obtained were analyzed by the Student's t-test for paired samples as well as by analysis of variance.
  
  
  RESULTS
  Residual methylmethacrylate was verified in high concentrations in the beginning of the testing as well as 24 hours after the test specimens had been worn. Mechanical polishing was associated with lower levels of residual monomer. The mass-mechanical group showed the lowest values. Mechanical polishing was associated with the lowest levels of residual monomer, and the lowest level of all occurred in mass-mechanical group.
  
  
  CONCLUSIONS
  The hypothesis is rejected. Variations of residual polymer were associated with variations in the manipulation and polishing, but high concentrations of residual monomer were present in all groups. These concentrations were reduced after 24 hours.
authors.affiliation: Department of Orthodontics, Pontifical Catholic University of Rio Grande do Sul, Rio Grande do Sul, Brazil. tatianasgoncalves@terra.com.br
authors.forename: Tatiana Siqueira
authors.initials: TS
authors.lastname: Gonçalves
authors.forename: Luciane Macedo
authors.initials: LM
authors.lastname: de Menezes
authors.forename: Luiz Ernani Aguiar
authors.initials: LE
authors.lastname: Silva
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002849:Chromatography, Gas; D003775:Dental Polishing; D006801:Humans; D008422:Materials Testing; D008768:Methylmethacrylates / Q000032:analysis*; D044367:Phase Transition; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D008768:Methylmethacrylates