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Pathology · patient case with 2 questions

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.

Question 1

The fistula of a chronic abscess produces an exudate mainly composed of which cells?

  1. Neutrophils
  2. Eosinophils
  3. Lymphocytes
  4. Plasma cells
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Correct answer: A. Neutrophils

  • A. Correct. The material draining through a sinus tract is PUS, and pus is composed predominantly of NEUTROPHILS (polymorphonuclear leukocytes) — living and degenerating — together with tissue debris and bacteria. Even in a 'chronic' abscess, the actively draining exudate is neutrophil-rich because the suppurative process is ongoing.
  • B. Eosinophils are elevated in parasitic infection and allergic/type I hypersensitivity reactions.
  • C. Lymphocytes dominate CHRONIC granulomatous inflammation in the surrounding tissue (as in a periapical granuloma), but they are not the main cell in the purulent exudate itself.
  • D. Plasma cells are the antibody-producing effectors of chronic inflammation, prominent in periapical granulomas and chronic periodontitis — again in the tissue, not the pus.

Note: Useful distinction: the periapical GRANULOMA (the surrounding tissue) is a chronic inflammatory lesion rich in lymphocytes, plasma cells and macrophages, while the PUS draining out of it is acute and neutrophil-rich.

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Question 2

The patient asks why his tooth is black. What is the cause of the discoloration?

  1. Breakdown of white blood cells
  2. Extrinsic staining from chromogenic bacteria
  3. Bacterial endotoxin staining
  4. Breakdown of red blood cells
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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.

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