Facial swelling and odontogenic infection — formative SAQs

SAQ 1 (10 marks)

A 6-year-old boy presents with three days of right-sided facial swelling and toothache. He has a fever of 38.6 degrees Celsius and has refused solid food today. On examination there is a firm, warm, tender swelling of the right cheek, tender right cervical lymphadenopathy, and a badly carious right lower molar that is tender to percussion. He has no trismus, drooling or airway compromise. ^{[1] [4]}

1. What is the most likely diagnosis and source, and what anatomical principle explains the cheek swelling? (3) ^[4]
2. Outline your management plan, including the role of source control and antibiotic choice with doses. (4) ^{[1] [5]}
3. Describe your safety-net advice and the features that would require immediate reassessment. (3) ^[2]

Model answer — SAQ 1

(1) Diagnosis and anatomy (3). The most likely diagnosis is a spreading odontogenic cellulitis arising from the carious right lower molar, with the periapical abscess having perforated the cortical bone into the buccal space. The anatomical principle is that the buccinator muscle attachment on the mandible determines the direction of spread: pus from a root apex that tracks buccally passes into the buccal space and presents as cheek swelling, whereas an apex below the mylohyoid line tracks into the submandibular space. Here the cheek swelling localises the collection to the buccal space. ^{[4] [1]}

(2) Management plan (4). The curative step is source control — the offending tooth must be extracted or undergo endodontic treatment and any collection drained; antibiotics alone cannot sterilise an established abscess and will fail without this. I would arrange urgent dental or oral-maxillofacial review for extraction or drainage. For analgesia and fever I would give paracetamol 15 mg/kg orally every four to six hours (maximum 60 mg/kg/day) and ibuprofen 5 to 10 mg/kg every six to eight hours. For the spreading cellulitis with systemic features I would give amoxicillin-clavulanate 45 mg/kg/day (amoxicillin component) orally in two divided doses, which covers oral streptococci and anaerobes. If he were unable to tolerate oral intake or were more unwell, I would admit for intravenous ampicillin-sulbactam 150 mg/kg/day (ampicillin component) in four divided doses, or clindamycin if penicillin-allergic. ^{[1] [5]}

(3) Safety-net advice (3). Give a concrete written plan: return immediately — even overnight — if he develops drooling or cannot swallow his saliva, difficulty opening his mouth, a changed or muffled voice, swelling under the chin or floor of the mouth, fast breathing or stridor, or if he simply looks more unwell. These are the red flags of Ludwig angina or deep space spread. Also arrange planned review at 48 to 72 hours if the swelling or fever has not improved, because failure to improve signals an undrained collection needing repeat dental and imaging assessment. Emphasise the need for dental follow-up to address the underlying caries and prevent recurrence. ^[2]