Discoloured primary incisors after an old injury

Correct answer: C. Pulp necrosis

• A. Reversible pulpitis is a vital pulp responding briefly to stimulus with no periapical change. There is no vitality here and there are periapical lesions.
• B. Internal resorption would show as an oval radiolucent expansion of the canal itself, and requires vital inflamed pulp tissue to drive it. Periapical lucencies with a non-vital tooth are a different process.
• C. CORRECT. Three findings converge on NECROSIS: no response to pulp testing, tenderness to percussion with periapical radiolucencies indicating that inflammation has passed beyond the apex, and a sinus tract confirming an established chronic infection with a drainage pathway. Crown discolouration completes the picture. The trauma a year ago severed the apical neurovascular supply, and the pulp died slowly and silently.
• D. Symptomatic irreversible pulpitis requires a VITAL pulp giving lingering pain. A non-responsive tooth with periapical radiolucency has moved past that stage.

Note: Pulp testing in a four-year-old is unreliable — cold and electric testing give inconsistent results in primary teeth. Weight the objective findings: sinus tract, percussion tenderness and radiographic lucency.

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.

Correct answer: B. Pulpectomy with a resorbable filling material and stainless steel crowns

• A. Observation is only acceptable where the tooth is close to exfoliation, unrestorable, or where infection threatens the permanent successor and extraction is indicated instead. Leaving established periapical infection in place risks damaging the developing permanent tooth bud.
• B. CORRECT. A NECROTIC primary tooth with periapical pathology and a sinus tract, where the root is not yet resorbing and the tooth is otherwise restorable, is treated by PULPECTOMY — the whole radicular pulp is removed and the canals filled with a RESORBABLE material such as zinc oxide eugenol or an iodoform paste, so the filling resorbs in step with the root. Full-coverage stainless steel crowns follow, because a pulpectomised primary incisor has lost too much structure to hold an intracoronal restoration.
• C. Indirect pulp capping is for a deep carious lesion with a VITAL, asymptomatic pulp. It has no application to a necrotic tooth with periapical disease.
• D. Pulpotomy removes only the CORONAL pulp and requires the radicular pulp to be VITAL and healthy. This pulp is necrotic throughout, so a pulpotomy would seal infection into the canals.

Note: The main alternative is EXTRACTION with space maintenance, chosen if the tooth is unrestorable, if there is significant root resorption or bone loss, or if the permanent successor's follicle is threatened. Both answers are defensible; the deciding factor is restorability and root status.