Pharmacology, Anesthesia, and Emergency Medicine in Dentistry
What the exam tests
Maximum-dose calculations, correct choice of local anesthetic and vasoconstrictor in medically complex patients, and instant recognition of dental office emergencies.
Core rules
- Lidocaine 2% with 1:100,000 epinephrine: 36 mg lidocaine and 18 micrograms epinephrine per 1.8 mL cartridge. Maximum lidocaine 7 mg/kg (adult cap 500 mg). Articaine 4%: maximum about 7 mg/kg; prilocaine and benzocaine can cause methaemoglobinaemia.
- Maximum epinephrine for a healthy adult is about 0.2 mg (roughly 11 cartridges of 1:100,000). In controlled cardiac disease keep it low but do not withhold it absolutely; aspiration and slow injection matter more than avoidance.
- Local anesthetic toxicity starts with CNS excitation (perioral tingling, tinnitus, agitation) then depression and seizures. Stop injecting, manage the airway, give oxygen and call for help.
- Syncope is the most common emergency: lay the patient flat, raise the legs, ensure airway. Anaphylaxis: adrenaline 0.5 mg intramuscularly for an adult (0.01 mg/kg in children), oxygen, fluids, call for emergency services.
- Antibiotic prophylaxis is reserved for defined cardiac conditions and is not routine for joint prostheses. NSAIDs are the analgesic of choice unless contraindicated.
Worked example
A 60 kg patient needs a mandibular block and infiltration. Reasoning: maximum lidocaine = 7 x 60 = 420 mg. Each 1.8 mL cartridge of 2% lidocaine contains 36 mg, so 420/36 = about 11 cartridges by drug, while the epinephrine limit of 0.2 mg allows about 11 cartridges too. Practical limit is therefore around 11 cartridges, and a typical procedure uses far fewer - but the calculation must be shown.
Traps that cost marks
- Saying adrenaline is absolutely contraindicated in all cardiac patients.
- Treating a fainting patient by sitting them upright.
- Calculating dose per cartridge without converting percentage to milligrams.