Oral and Maxillofacial Surgery: Exodontia, Anesthesia, Trauma, Infections, Tumors, TMJ
This domain tests exodontia, local anaesthesia, odontogenic infection, maxillofacial trauma, tumours and TMJ disorders, with emphasis on emergencies and dose calculation.
Exodontia and anaesthesia
- Straight forceps for upper anteriors, bayonet for upper third molars, cow-horn for lower molars; assess sinus proximity and buccal bone before elevating upper molars.
- Mandibular third molars risk inferior alveolar and lingual nerve injury; radiographic assessment of root proximity is mandatory.
- Maximum lidocaine dose is 4.4 mg/kg without vasoconstrictor and 7 mg/kg with it; 2% lidocaine = 20 mg/mL; one 1.8 mL cartridge holds 36 mg.
Infection
Ludwig's angina is bilateral submandibular, sublingual and submental cellulitis with a board-like floor of mouth and airway threat: secure the airway, give intravenous antibiotics, and drain surgically. Mandibular molar apices lie below the mylohyoid line, which is why they spread to the submandibular space.
Trauma and TMJ
Le Fort I is a low dentoalveolar fracture, II is pyramidal through the nasal bones, III is craniofacial. Mandibular fractures occur most often at the angle and condyle; bilateral condylar fracture produces an anterior open bite. Anterior disc displacement with reduction gives a reciprocal click; without reduction, limited opening with deviation.
Worked example
A 60 kg patient needs 2% lidocaine with 1:100,000 epinephrine. Maximum lidocaine = 7 mg/kg × 60 = 420 mg; at 20 mg/mL that is 21 mL, about 11.6 cartridges. But epinephrine at 1:100,000 = 0.01 mg/mL, and a 0.2 mg cardiac limit gives 20 mL. The practical limit is therefore about 20 mL, set by the vasoconstrictor, not the cartridge count.
Traps
Treating cartridge number as the dose limit; ignoring the epinephrine ceiling; prescribing antibiotics instead of draining an abscess; mislabelling Le Fort II as Le Fort I.