Tooth discoloration by blood: an in vitro histochemical study

An in vitro model, using a modification of a technique devised by Freccia & Peters, was developed to investigate tooth staining following pulpal haemorrhage. Samples of whole blood, erythrocytes, plasma and platelet concentrate and saline were individually placed in the pulp chambers of groups of five teeth and centrifuged twice daily for 25 min over a period of 3 consecutive days. This confirmed that the blood pigment responsible for the staining was found only in those samples containing erythrocytes. Teeth stained with packed red cells were then prepared for histological examination and subjected to four histochemical tests: (1) benzidine, (2) zinc leuco, (3) Perl's and (4) Turnbull Blue to analyse some of the biochemical changes following haemorrhage into the pulp chamber. These tests showed that, following haemolysis of erythrocytes within dentine, haemoglobin was found either intact or as one of the haematin molecules with no further breakdown of the haem structure and no evidence of any free ferric ions or haemosiderin.