Science and Practice of Dentistry
What you must know
The domain is deliberately broad, so expect questions that integrate several sciences at once. Core areas: head and neck anatomy (trigeminal divisions, fascial spaces and the route of spread of odontogenic infection, lingual nerve and inferior alveolar canal relationships), oral histology and tooth development, dental materials (polymerisation shrinkage, coefficient of thermal expansion, wear, fluoride release, bond strength), cariology and periodontal microbiology, general and oral pathology, pharmacology (local anaesthetics, analgesics, antibiotic stewardship, drug interactions), radiography (physics, ALARA, interpretation) and infection control (sterilisation, hand hygiene, sharps).
Traps in questions
- Concentration arithmetic: percentage x 10 = mg/mL. A 2% solution is 20 mg/mL, so a standard 2.2 mL cartridge holds 44 mg.
- Mixing weight-based maximum doses with absolute ceilings; children, the elderly and hepatic impairment lower the limit.
- Assuming a material is universally superior rather than matching properties to the site (e.g. composite in a wet, subgingival field).
- Treating caries as static: arrested lesions and remineralisation are real, and not every white spot needs a bur.
- Eruption and exfoliation timing; primary molars normally exfoliate around 9-12 years.
Worked example
A 60 kg adult needs a mandibular molar extracted. Lidocaine 2% with 1:80,000 adrenaline: at 7 mg/kg the ceiling is 420 mg, about 9 cartridges. But adrenaline at 1:80,000 is 0.0125 mg/mL, i.e. 0.0275 mg per cartridge; a 0.2 mg healthy-adult limit caps you near 7 cartridges. The lower figure governs - you are limited by the vasoconstrictor, not the anaesthetic. Show the working.