title: Effects of light-curing time on the cytotoxicity of a restorative composite resin on odontoblast-like cells.
abstract: This in vitro study evaluated the cytotoxicity of an experimental restorative composite resin subjected to different light-curing regimens.
  
  
  METHODS
  Forty round-shaped specimens were prepared and randomly assigned to four experimental groups (n=10), as follows: in Group 1, no light-curing; in Groups 2, 3 and 4, the composite resin specimens were light-cured for 20, 40 or 60 s, respectively. In Group 5, filter paper discs soaked in 5 µL PBS were used as negative controls. The resin specimens and paper discs were placed in wells of 24-well plates in which the odontoblast-like cells MDPC-23 (30,000 cells/cm²) were plated and incubated in a humidified incubator with 5% CO2 and 95% air at 37ºC for 72 h. The cytotoxicity was evaluated by the cell metabolism (MTT assay) and cell morphology (SEM). The data were analyzed statistically by Kruskal-Wallis and Mann-Whitney tests (p<0.05).
  
  
  RESULTS
  In G1, cell metabolism decreased by 86.2%, indicating a severe cytotoxicity of the non-light-cured composite resin. On the other hand, cell metabolism decreased by only 13.3% and 13.5% in G2 and G3, respectively. No cytotoxic effects were observed in G4 and G5. In G1, only a few round-shaped cells with short processes on their cytoplasmic membrane were observed. In the other experimental groups as well as in control group, a number of spindle-shaped cells with long cytoplasmic processes were found.
  
  
  CONCLUSIONS
  Regardless of the photoactivation time used in the present investigation, the experimental composite resin presented mild to no toxic effects to the odontoblast-like MDPC-23 cells. However, intense cytotoxic effects occurred when no light-curing was performed.
authors.affiliation: Department of Biology Science, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
authors.forename: Andreza Maria Fábio
authors.initials: AM
authors.lastname: Aranha
authors.forename: Elisa Maria Aparecida
authors.initials: EM
authors.lastname: Giro
authors.forename: Josimeri
authors.initials: J
authors.lastname: Hebling
authors.forename: Fernanda Campos Rosetti
authors.initials: FC
authors.lastname: Lessa
authors.forename: Carlos Alberto de Souza
authors.initials: CA
authors.lastname: Costa
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003188:Composite Resins / Q000528:radiation effects / Q000633:toxicity*; D055117:Curing Lights, Dental; D008855:Microscopy, Electron, Scanning; D009804:Odontoblasts / Q000187:drug effects* / Q000378:metabolism; D058105:Polymerization; D011897:Random Allocation; D051381:Rats; D013997:Time Factors; D018675:Toxicity Tests
chemical_list: D003188:Composite Resins