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Endodontics · single question

A tooth has been non-vital following trauma one year ago. What causes the dark DISCOLORATION of the tooth?

  1. Breakdown of white blood cells
  2. Pulp calcification
  3. Bacterial endotoxins
  4. Breakdown of red blood cells (hemoglobin degradation products)
Show answer and explanation

Correct answer: D. Breakdown of red blood cells (hemoglobin degradation products)

  • A. WBC breakdown does not produce significant chromogenic pigments.
  • B. Pulp calcification (dystrophic calcification) causes radiographic opacity, not external discoloration.
  • C. Bacterial endotoxins contribute to pulp necrosis but are not the primary cause of discoloration.
  • D. Tooth discoloration following pulp necrosis from trauma is caused by the BREAKDOWN OF RED BLOOD CELLS (RBCs) within the pulp. When trauma causes pulpal hemorrhage, RBCs lyse and release hemoglobin, which breaks down into iron compounds (hemosiderin, hematoidin) and other chromogenic byproducts. These penetrate the dentinal tubules and cause the characteristic gray-brown discoloration.

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