A 5-year-old fell and injured her front teeth one month ago. She now presents with a swelling on the gingiva overlying tooth E that appeared three days ago. What is the most likely explanation?

Correct answer: D. A parulis draining a necrotic pulp following the earlier trauma

• A. A pyogenic granuloma is a red, vascular, easily bleeding overgrowth of granulation tissue in response to chronic irritation. It does not follow this trauma-then-infection sequence, and the trauma here was a month earlier.
• B. An eruption cyst is a bluish, fluctuant, dome-shaped swelling directly over an ERUPTING tooth crown. Tooth E is a primary maxillary lateral incisor, already erupted; its permanent successor is years away at age 5.
• C. Normal healing does not produce a NEW swelling a month after the injury. A lesion appearing after an asymptomatic interval signals pathology, not healing.
• D. CORRECT. The timeline is the whole question. Trauma one month ago, symptoms three days ago — that gap is the interval during which the pulp became necrotic and the infection reached the periapex and then perforated the cortical plate. A parulis (gum boil) is the soft-tissue opening of a sinus tract draining a necrotic pulp, and it is the expected sequela of luxation or concussion injury to a primary incisor. Treatment is pulpectomy or extraction, with a radiograph to assess the permanent successor.

Note: Post-traumatic pulp necrosis in primary teeth commonly declares itself weeks to months later. Warn parents at the time of injury to watch for swelling, a sinus tract, discolouration or pain, and arrange follow-up rather than discharging after the acute visit.