title: Cytotoxicity of orthodontic separating elastics.
abstract: BACKGROUND
  Separating elastics may be cytotoxic to the interdental gingival tissues. Both latex and non-latex separating elastics are widely used and both types should be biocompatible.
  
  
  OBJECTIVE
  To determine if latex and non-latex orthodontic separating elastics are cytotoxic.
  
  
  METHODS
  The cytotoxicity of natural latex (Groups A, D and O) and non-latex (Group M) orthodontic separating elastics were determined by incubating 15 elastics of each type in Eagle's essential medium (MEM), removing the supernatant after 24, 48, 72 and 168 hours and adding it to cultures of L-929 mouse fibroblasts in growth medium (MEM plus glutamine, garamicine, fungizone, sodium bicarbonate, buffered saline and foetal calf serum). To verify the cell response in extreme situations, three additional groups were included: Group CC (cell control), consisting of L-929 cells not exposed to supernatants from the maintenance medium with the elastics; Group C+ (positive control), consisting of Tween 80; Group C- (negative control), consisting of phosphate buffered saline solution. The positive and negative controls were incubated in MEM maintenance medium for 24, 48, 72 and 168 hours and the extracted elutes were added to L-929 line cells incubated in the growth medium. The viability of the cells was determined with neutral red (dye-uptake method) at 24, 48, 72 and 168 hours. The data were analysed with the analysis of variance (ANOVA) and Tukey's multiple comparison test. The significance level was p < or = 0.05.
  
  
  RESULTS
  The elastics in Groups A, D and O induced greater cell lysis at 72 hours compared to the other experimental times. There were statistically significant differences between the cytotoxicity of the elastics in Groups A, D and O in relation to Group CC for experimental times of 24, 48, 72 and 168 hours (p > 0.05). There was not, however, a statistically significant difference between Groups D and CC at 24 hours.
  
  
  CONCLUSIONS
  The latex and non-latex orthodontic separating elastics tested were considered to be biocompatible.
authors.affiliation: Federal University of Rio de Janeiro-UFRJ, Rio de Janeiro, Brazil.
authors.forename: Matheus Melo
authors.initials: MM
authors.lastname: Pithon
authors.forename: Rogério Lacerda
authors.initials: RL
authors.lastname: dos Santos
authors.forename: Fernanda Otaviano
authors.initials: FO
authors.lastname: Martins
authors.forename: Maria Teresa Villela
authors.initials: MT
authors.lastname: Romanos
authors.forename: Mônica Tirre de Souza
authors.initials: MT
authors.lastname: Araújo
mesh_terms: D000818:Animals; D016923:Cell Death; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D003764:Dental Materials / Q000633:toxicity*; D020724:Elastomers / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects; D007840:Latex / Q000633:toxicity; D008422:Materials Testing; D051379:Mice; D009499:Neutral Red; D009967:Orthodontic Appliances; D012826:Silicone Elastomers / Q000633:toxicity; D013997:Time Factors
chemical_list: D004396:Coloring Agents; D017077:Culture Media, Conditioned; D003764:Dental Materials; D020724:Elastomers; D007840:Latex; D012826:Silicone Elastomers; D009499:Neutral Red