title: Residual monomer of reline acrylic resins. Effect of water-bath and microwave post-polymerization treatments.
abstract: OBJECTIVE
  This study compared the residual monomer (RM) in four hard chair-side reline resins (Duraliner II-D, Kooliner-K, Tokuso Rebase Fast-TRF and Ufi Gel hard-UGH) and one heat-polymerized denture base resin (Lucitone 550-L), which was processed using two polymerization cycles (short-LS and long-LL). It was also investigated the effect of two after polymerization treatments on this RM content.
  
  
  METHODS
  Specimens (n=18) of each material were produced following the manufacturers' instructions and then divided into three groups. Group I specimens were left untreated (GI-control). Specimens of group II (GII) were given post-polymerization treatment by microwave irradiation. In group III (GIII), specimens were submitted to immersion in water at 55 degrees C (reline resins-10 min; denture base resin L-60 min). The RM was analyzed using high performance liquid chromatography (HPLC) and expressed as a percentage of RM. Data were analyzed by two-way ANOVA followed by Tukey's test (alpha=0.05).
  
  
  RESULTS
  Comparing control specimens, statistical differences were found among all materials (p<0.05), and the results can be arranged as K (1.52%)>D (0.85%)>UGH (0.45%)>LL (0.24%)>TRF (0.14%)>LS (0.08%). Immersion in hot water (GIII) promoted a significant (p<0.05) reduction in the RM for all materials evaluated compared to control (GI), with the exception of LL specimens. Materials K, UGH and TRF exhibited significantly (p<0.05) lower values of RM after microwave irradiation (GII) than in the control specimens.
  
  
  CONCLUSIONS
  The reduction in RM promoted by water-bath and microwave post-polymerization treatments could improve the mechanical properties and biocompatibility of the relining and denture base materials.
authors.affiliation: Department of Dental Materials and Prosthodontics, Araraquara Dental School, R. Humaita, No. 1680, São Paulo State University, CEP 14801-903 Araraquara, São Paulo, Brazil.
authors.forename: Vanessa M
authors.initials: VM
authors.lastname: Urban
authors.forename: Ana L
authors.initials: AL
authors.lastname: Machado
authors.forename: Regina V
authors.initials: RV
authors.lastname: Oliveira
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Vergani
authors.forename: Ana C
authors.initials: AC
authors.lastname: Pavarina
authors.forename: Quezia B
authors.initials: QB
authors.lastname: Cass
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry* / Q000528:radiation effects; D000704:Analysis of Variance; D002851:Chromatography, High Pressure Liquid; D003822:Denture Liners; D003823:Denture Rebasing; D008689:Methacrylates / Q000032:analysis*; D008872:Microwaves; D044367:Phase Transition; D014867:Water
chemical_list: D000180:Acrylic Resins; D008689:Methacrylates; D014867:Water