Public Health, Prevention and Dental Practice Management
What you must know
Epidemiology: prevalence versus incidence, DMFT/dmft (teeth, not surfaces), and the care index. Screening: sensitivity, specificity, positive and negative predictive values, and why predictive values shift with disease prevalence - link this to Wilson and Jungner screening criteria. Prevention: Delivering Better Oral Health guidance, twice-yearly fluoride varnish from age 2, higher-fluoride toothpaste for elevated risk, fissure sealants, diet and sugar frequency, smoking and alcohol brief advice, and water fluoridation at about 1 ppm. Service delivery: risk-based recall intervals (commonly 3–12 months), the NHS band/UDA system, and access. Governance: clinical audit against standards with a repeating cycle, significant event analysis, infection prevention and control, and registration requirements.
Traps
Sensitivity and positive predictive value are routinely swapped; PPV depends on prevalence while sensitivity does not. DMFT is misread as surfaces (that is DMFS). Fluoride questions catch candidates who recommend varnish below the licensed age or who forget that high-strength toothpaste is an adjunct, not a substitute for varnish. Audit is confused with research: audit compares practice to an existing standard and re-audits.
Worked example: predictive value
In 1,000 people with 10% disease prevalence, a test with 90% sensitivity and 90% specificity gives 90 true positives (from 100 diseased) and 90 false positives (from 900 healthy). PPV = 90 ÷ 180 = 50%. Halve the prevalence and the PPV falls further, even though sensitivity is unchanged. Rule of thumb: sensitivity and specificity belong to the test; predictive values belong to the population.