Endodontics · patient case question
What was the original injury?
Patient case: A four-year-old who hit his front tooth
Patient: Male, 4 years old
Chief Complaint: Mother: “He fell at nursery and banged his front tooth, and now it has gone dark.”
Background: Fell onto a hard floor six weeks ago, striking tooth E (maxillary right primary central incisor). At the time the gum around the tooth bled a little. Healthy child, immunisations up to date.
Vital Signs: Afebrile · HR 96 bpm
Findings: At the time of injury: occlusion normal, no displacement, no increased mobility, tender to touch. Today: the tooth is grey, remains in normal position with normal mobility, is not tender to percussion, and there is no sinus tract or swelling. Radiograph shows no periapical or inter-radicular radiolucency and no root resorption.
Show answer and explanation
Correct answer: A. Concussion
- A. CORRECT. CONCUSSION is injury to the supporting structures WITHOUT abnormal loosening and WITHOUT displacement. The tooth is tender to touch or percussion but has normal mobility and remains in its normal position — exactly as described. The minor sulcular bleeding at the time indicates the periodontal ligament was injured, but the absence of both mobility and displacement is what makes this concussion rather than anything more severe.
- B. LATERAL LUXATION is displacement in a non-axial direction, with the tooth usually locked firmly in its new position and often an accompanying alveolar fracture. The occlusion would be altered, and the stem records a normal occlusion.
- C. SUBLUXATION is injury to the supporting structures with INCREASED MOBILITY but still no displacement, and sulcular bleeding is characteristic of it. The stem states explicitly that there was NO increased mobility — and mobility is the single discriminator between subluxation and concussion.
- D. AVULSION is complete displacement of the tooth out of its socket. Note the rule that follows: an avulsed PRIMARY tooth is NEVER replanted, because of the risk of damaging the developing permanent successor.
Note: The grey discoloration appearing weeks later is the EXPECTED sequel of the pulpal haemorrhage — blood breakdown products entering the dentinal tubules. On its own it does NOT establish that the pulp has become necrotic, which is the point of the next question. The full luxation spectrum in order of severity: concussion, subluxation, extrusive luxation, lateral luxation, intrusive luxation, avulsion.