Endodontics · patient case question
The patient asks why his tooth is black. What is the cause of the discoloration?
Patient case: Trauma to #8 and #9 with a discoloured tooth and sinus tract
Scenario: A patient had trauma and FRACTURED #8 and #9. Tooth #9 has a PULP EXPOSURE, an ABSCESS WITH A SINUS TRACT, and a DARK COLOUR.
Show answer and explanation
Correct answer: D. Breakdown of red blood cells
- A. White blood cell breakdown does not release the pigmented haem products that cause this discoloration.
- B. Extrinsic staining from chromogenic bacteria sits on the tooth SURFACE and is removed by prophylaxis; this discoloration is intrinsic, from within the tooth.
- C. Bacterial endotoxin (lipopolysaccharide) drives periapical inflammation and bone resorption, but it is not the chromogen responsible for the colour change.
- D. Correct. After trauma, haemorrhage into the pulp chamber is followed by HAEMOLYSIS of red blood cells. Haemoglobin breakdown products — iron-containing pigments that combine with pulpal putrefaction products to form iron sulphide — penetrate the DENTINAL TUBULES and produce the grey-black intrinsic discoloration of a non-vital traumatised tooth.
Note: This is exactly why SODIUM PERBORATE internal bleaching works — it oxidises those haem breakdown products lodged in the dentinal tubules.