title: Cytotoxicity of denture base resins: effect of water bath and microwave postpolymerization heat treatments.
abstract: OBJECTIVE
  This study compared the effect of two postpolymerization heat treatments on the cytotoxicity of three denture base resins on L929 cells using 3H-thymidine incorporation and MTT assays.
  
  
  METHODS
  Sample disks of Lucitone 550, QC 20, and Acron MC resins were fabricated under aseptic conditions and stored in distilled water at 37 degrees C for 48 hours. Specimens were then divided into three groups: (1) heat treated in microwave oven for 3 minutes at 500 W; (2) heat treated in water bath at 55 degrees C for 60 minutes; and (3) no heat treatment. Eluates were prepared by placing three disks into a sterile glass vial with 9 mL of Eagle's medium and incubating at 37 degrees C for 24 hours. The cytotoxic effect from the eluates was evaluated using the 3H-thymidine incorporation and MTT assays, which reflect DNA synthesis levels and cell metabolism, respectively.
  
  
  RESULTS
  The components leached from the resins were cytotoxic to L929 cells when 3H-thymidine incorporation assay was employed. In contrast, eluates from all resins revealed noncytotoxic effects as measured by MTT assay. For both MTT assay and 3H-thymidine incorporation, the heat treatments did not decrease the cytotoxicity of the materials tested.
  
  
  CONCLUSIONS
  Resins were graded by 3H-thymidine incorporation assay as slightly cytotoxic and by MTT assay as noncytotoxic. Cytotoxicity of the denture base materials was not influenced by microwave or water bath heat treatment.
authors.affiliation: Department of Dental Materials and Prosthodontics, São Paulo State University, Araraquara Dental School, São Paulo, Brazil.
authors.forename: Janaina Habib
authors.initials: JH
authors.lastname: Jorge
authors.forename: Eunice Teresinha
authors.initials: ET
authors.lastname: Giampaolo
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Vergani
authors.forename: Ana Lúcia
authors.initials: AL
authors.lastname: Machado
authors.forename: Ana Cláudia
authors.initials: AC
authors.lastname: Pavarina
authors.forename: Iracilda Zeppone
authors.initials: IZ
authors.lastname: Carlos
mesh_terms: D000180:Acrylic Resins / Q000633:toxicity*; D000704:Analysis of Variance; D000818:Animals; D004396:Coloring Agents / Q000378:metabolism; D003819:Denture Bases / Q000009:adverse effects*; D006358:Hot Temperature; D007739:L Cells / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008872:Microwaves; D015394:Molecular Structure; D044367:Phase Transition; D013778:Tetrazolium Salts / Q000378:metabolism; D014316:Tritium / Q000378:metabolism; D014867:Water
chemical_list: D000180:Acrylic Resins; D004396:Coloring Agents; C488492:QC 20 (denture base resin); D013778:Tetrazolium Salts; C042207:4-anisyltetrazolium blue; D014867:Water; D014316:Tritium; C075051:Acron MC; C040291:Lucitone