title: Assessment of exogenous pigmentation in colourless elastic ligatures.
abstract: BACKGROUND
  The aim of this study was to evaluate colour alteration of transparent elastic ligatures submitted to exogenous pigmentation.
  
  
  METHODS
  Forty test specimens were divided into eight groups corresponding to one commercial brand with five test specimens in each group. The test specimens were immersed into coffee and black tea solutions with the purpose of assessing colour alteration using a portable digital spectrophotometer (Vita Easyshade Compact). The surfaces of the ligatures under scanning electron microscope (SEM) at ×30, ×150 and ×20,000 magnification were evaluated with the purpose of observing the differences in porosity of the ligatures. The Kolmogorov-Smirnov test for normality was applied followed by the one-way analysis of variance (one-way ANOVA) and the level of significance adopted was 95%.
  
  
  RESULTS
  All the groups showed modified initial colour that was perceptible to the human eye. The brand that showed greater colour alteration, in comparison with its initial colour, was the American® pearl elastic ligature and the ligatures that presented the smallest colour variation were the Ortho-Organizer®. The surface evaluations of the ligatures showed differences with regard to the topography evidencing more porosity in the ligatures that showed greater staining.
  
  
  CONCLUSIONS
  The group that changed colour significantly was the one that presented the highest porosity, and the brand that was the least altered was the one that showed the lowest porosity.
authors: Department of Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Alline Birra Nolasco
authors: AB
authors: Fernandes
authors: Department of Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Antônio Carlos Oliveira
authors: AC
authors: Ruellas
authors: Department of Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Marcus Vinicius Almeida
authors: MV
authors: Araújo
authors: Department of Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Eduardo Franzotti
authors: EF
authors: Sant'Anna
authors: Department of Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: Carlos Nelson
authors: CN
authors: Elias
mesh_terms: D003069:Coffee; D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D020724:Elastomers / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning / Q000295:instrumentation; D009967:Orthodontic Appliances; D016062:Porosity; D013053:Spectrophotometry / Q000295:instrumentation; D013499:Surface Properties; D013662:Tea; D013696:Temperature; D013997:Time Factors
chemical_list: D003069:Coffee; D003764:Dental Materials; D020724:Elastomers; D013662:Tea
keywords: Orthodontic ligatures; exogenous pigmentation; orthodontic appliances