Dental Public Health, Epidemiology, and Preventive Dentistry
Core concepts
Public health questions test measurement and prevention logic. Understand incidence (new cases over time) versus prevalence (all cases at a point), and how each is calculated. Know measures of oral disease: DMFT/dmft indices, plaque and gingival indices, and CPITN/periodontal screening. Learn study designs - cross-sectional (prevalence, association), cohort (incidence, risk), case-control (rare outcomes, odds ratios), and randomised controlled trials (causality).
Screening principles matter: a suitable test with acceptable sensitivity and specificity, a treatable condition, and an acceptable cost. Understand sensitivity (true positives detected) versus specificity (true negatives excluded) and how prevalence affects predictive values.
Prevention
Know the evidence base for prevention: fluoride toothpaste, water fluoridation, fluoride varnish, fissure sealants, and dietary sugar control. Understand the concept of the common risk factor approach - diet, smoking, alcohol, and hygiene affect multiple chronic diseases. Learn about inequalities in oral health and the role of commissioning and workforce planning.
Traps
- Confusing incidence with prevalence.
- Assuming a highly sensitive test is always best; the choice depends on the purpose.
- Forgetting that predictive values change with disease prevalence.
- Choosing a screening programme without evidence of benefit or treatability.
Worked example
A test detects 90 of 100 diseased people and correctly identifies 80 of 100 healthy people. Rule of thumb: sensitivity = 90/100 = 90%; specificity = 80/100 = 80%. If the same test is used where disease is rare, the positive predictive value falls sharply even though sensitivity and specificity are unchanged.