Oral and Maxillofacial Surgery
The Oral and Maxillofacial Surgery domain tests judgement rather than operative technique: whether a third molar must be removed, how far an odontogenic infection has spread, which facial injury needs urgent referral, and when a biopsy cannot be deferred. Items are vignette-based, so the immediate next step and the safe disposition earn more marks than eponyms.
Assessing the lower third molar
- Absolute indications: recurrent pericoronitis, unrestorable caries, caries on the distal surface of the second molar, a cystic lesion, a tooth in the line of a mandibular fracture, and impaction blocking orthodontic or prosthetic treatment.
- Radiographic nerve-risk signs: radicular radiolucency overlapping the canal, interruption of the white line of the canal, deflection or narrowing of the canal, and a darkened or bifid apex. Two or more signs justify CBCT before surgery.
- Coronectomy may be offered when roots are intimately related to the canal and the tooth is asymptomatic and vital; it is contraindicated with active infection, horizontal impaction or a mobile root.
Odontogenic infection
- Spread follows the path of least resistance: buccal space from maxillary posteriors, submandibular when mandibular molar apices lie below the mylohyoid, sublingual when above it, canine space from the long canine root.
- Ludwig angina is bilateral submandibular and sublingual cellulitis with floor-of-mouth elevation, drooling and airway threat; treat with airway control, intravenous antibiotics and surgical decompression. Frank pus is often absent.
- The definitive treatment of an odontogenic abscess is elimination of the source plus incision and drainage; antibiotics are adjuncts and never replace drainage.
Facial trauma priorities
- Airway, cervical spine, haemorrhage and head injury precede any dental repair.
- Zygomatic complex: malar flattening, infraorbital numbness, diplopia, restricted upward gaze and subconjunctival haemorrhage.
- Mandible: displacement follows muscle pull, with the ramus fragment drawn superiorly by masseter, medial pterygoid and temporalis.
Worked example
A 26-year-old has a mesioangular impacted 38 with recurrent pericoronitis. The radiograph shows a radiolucency over the root overlapping the canal and an interrupted white line. The next step is not immediate extraction: these nerve-risk signs mandate CBCT to map the canal, then consent for extraction with documented nerve risk, or coronectomy if the tooth is vital. During an acute episode, drain and irrigate first.
Traps
- Prescribing antibiotics for pericoronitis without drainage.
- Calling a spreading infection a periapical abscess when the floor of the mouth is raised; reassess the airway.
- Omitting distal caries of the second molar as an indication.