Dentistry: Applied Clinical Decision-Making
This domain tests applied clinical dentistry: caries and endodontic diagnosis, periodontal staging and grading, oral medicine, minor oral surgery, prosthodontics, paediatric care, dental materials, radiology and infection control. Items reward the reasoning behind a decision - the classification arithmetic, the dose calculation - rather than recalled slogans.
Core rules to have ready
- Caries: judge lesion activity and depth first. Remineralise non-cavitated lesions (1,450 ppm fluoride toothpaste, varnish), seal susceptible pits, and operate only when the lesion is cavitated or prevention has failed.
- Periodontitis: diagnose on interdental clinical attachment loss (CAL) ≥2 mm at ≥2 non-adjacent teeth; stage on the worst site, grade on progression.
- Endodontics: confirm pulpal and apical diagnosis, take working length with an apex locator verified radiographically, irrigate with NaOCl plus EDTA, and obturate when canals are dry and symptom-free.
- Local anaesthetic: lidocaine 2% with 1:100,000 adrenaline is 4.4 mg/kg (adult cap about 500 mg, roughly seven 1.8 mL cartridges). Dose by weight, not by cartridge count.
- Odontogenic infection: amoxicillin 500 mg three times daily is first-line; metronidazole 400 mg three times daily adds anaerobic cover. Avoid tetracyclines under 12 years and in pregnancy.
- Sterilisation: validated steam cycles - 134 °C for ≥3 minutes or 121 °C for 15 minutes - with cycle monitoring; handpieces reprocessed between patients.
Worked example
A 52-year-old non-smoker (HbA1c 6.4%) has probing depths of 4–6 mm. The worst site shows 6 mm CAL and 50% radiographic bone loss, with no teeth lost to periodontitis. Severity places this in Stage III (CAL ≥5 mm, bone loss to the middle third and beyond); tooth loss ≤4 and probing depth ≥6 mm fit Stage III complexity. Grade: 50% ÷ 52 years = 0.96, inside the 0.25–1.0 band, so Grade B; the controlled HbA1c does not shift it to Grade C. Answer: Stage III, Grade B.
Traps that cost marks
- Averaging CAL across the mouth instead of using the worst site.
- Grading from smoking habit alone - calculate bone loss ÷ age first, then apply modifiers by one step.
- Calling a site healthy because radiographs show bone, ignoring CAL from treated disease.
- Prescribing antibiotics for irreversible pulpitis; drainage or pulpectomy is the treatment.
- Counting caries-related tooth loss when staging periodontitis, which counts only periodontitis-related loss.