Pathology · patient case question
Why have the crowns become discoloured?
Patient case: Discoloured primary incisors after an old injury
Patient: Female, 4 years old, accompanied by her father
Chief complaint: Father: “Her two front teeth have gone dark and now she says they hurt.”
History: Fell against a coffee table about a year ago. Teeth E and F were bruised but not displaced and were not treated at the time.
Findings: Teeth E and F are grey-brown. Both are tender to percussion. Neither responds to pulp testing. A sinus tract is present buccal to tooth E. Radiographs show periapical radiolucencies on both, with roots not yet resorbing.
Show answer and explanation
Correct answer: D. Breakdown of red blood cells within the dentinal tubules
- A. Tertiary dentine deposition narrows the pulp chamber and gives a YELLOW, opaque appearance — the picture of pulp canal obliteration, which indicates a surviving, reactive pulp rather than a dead one.
- B. Enamel hypoplasia from an injury to the underlying permanent successor produces defective, pitted or discoloured enamel on that SUCCESSOR — Turner tooth — not on the injured primary tooth itself.
- C. Extrinsic dietary staining sits on the enamel surface, affects all exposed teeth rather than two traumatised ones, and polishes away.
- D. CORRECT. Trauma ruptures pulpal blood vessels and blood enters the dentinal tubules. Haemoglobin breaks down to haemosiderin, haematin and other iron-containing pigments, which stain the dentine from within. The colour follows a recognised sequence: an initial PINK from fresh haemorrhage, then GREY-BROWN or BLACK as the pigments degrade and the pulp necroses. Because the stain is intrinsic and within dentine, external bleaching or polishing cannot remove it.
Note: A pink or grey discolouration appearing within days to weeks of trauma sometimes reverses if the pulp revascularises. Grey-brown persisting for months, as here, means necrosis.