title: [Study on the mechanism of discoloration and the efficacy of bleaching in non-infected traumatically discolored teeth].
abstract: OBJECTIVE
  To investigate the mechanism of discoloration and the efficacy of bleaching in non-infected traumatically discolored teeth.
  
  
  METHODS
  In vitro model of discolored teeth: sample of fresh erythrocytes was placed in the pulp cavity of 20 extracted teeth and centrifuged for 3 consecutive days. These discolored teeth were divided equally and randomly into two groups: group A (control group); group B (bleaching group), bleached with 10% carbamide peroxide gel for 4 weeks. And then all teeth were prepared for histological examination and subjected to a series of histochemical tests to analyze some of the biochemical changes following haemorrhage into the pulp chamber and post-bleaching.
  
  
  RESULTS
  Haemoglobin and haematin were detected in the dentinal tubules of discolored teeth from group A and no evidence of ferric or haemosiderin. Specimens from group B demonstrated a negative response to histochemical tests.
  
  
  CONCLUSIONS
  In the absence of bacterial invasive, haemoglobin and haematin could cause discoloration of non-infected traumatized teeth. Peroxide bleaching agent can effectively remove haemoglobin and haematin.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Wuhan University, Wuhan 430079, China. wangyn@public.wh.hb.cn
authors.forename: Yi-Ning
authors.initials: YN
authors.lastname: Wang
authors.forename: Feng-Ying
authors.initials: FY
authors.lastname: Chen
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
mesh_terms: D000293:Adolescent; D002648:Child; D006801:Humans; D066298:In Vitro Techniques; D011897:Random Allocation; D014073:Tooth Bleaching / Q000379:methods*; D014075:Tooth Discoloration / Q000209:etiology / Q000628:therapy*