A 7-year-old child had a stainless steel crown placed the day before and arrived with swelling in the lower lip at the level of mandibular occlusion. What is the most likely cause?

Correct answer: D. Trauma (lip bite during anesthesia)

• A. INCORRECT — While nickel allergy can occur with stainless steel, it typically manifests as mucosal lichenoid reactions, not acute lip swelling at the occlusal level the day after placement.
• B. INCORRECT — Post-crown infection presenting as lip swelling within 24 hours would be an extremely rapid progression and atypical presentation.
• C. INCORRECT — Abscess formation within 24 hours of crown placement is not a realistic timeline.
• D. CORRECT — The most likely cause is self-inflicted trauma from lip biting while the local anesthesia was still effective after crown placement. Children often bite their lips/cheeks when numb, causing significant swelling, bruising, or ulceration. The location (lower lip at mandibular occlusion level) is classic.