Dental Public Health, Prevention and Epidemiology
This domain tests measurement, survey methods, prevention at population level and the arithmetic of screening. Expect questions that ask you to interpret a number rather than recall a definition.
Measurement
- Prevalence is the proportion of cases at one point in time; incidence is the rate of new cases over a period. DMFT and dmft count lifetime caries experience, not current activity; ICDAS records lesion severity and activity.
- WHO Basic Methods for oral health surveys defines sampling, examiner calibration and recording; kappa above 0.8 indicates good inter-examiner agreement.
Prevention
- Fluoride acts mainly topically: it promotes remineralisation as fluorapatite, inhibits demineralisation and interferes with bacterial metabolism. Water fluoridation is effective at about 1 mg per litre.
- The common risk factor approach links oral disease to sugar, tobacco, alcohol and hygiene, sharing determinants with other non-communicable diseases.
- Prevention levels: primordial, primary, secondary and tertiary. The Ottawa Charter frames health promotion as public policy, supportive environments, community action, personal skills and reorientation of services.
Worked example
A caries screening test has sensitivity 90 percent and specificity 95 percent, and prevalence in the target group is 10 percent. Positive predictive value equals (0.9 times 0.1) divided by [(0.9 times 0.1) plus (0.05 times 0.9)], which is 0.09 divided by 0.135, or 0.67. Even with strong test properties, one third of positives are false when prevalence is low, which is why screening programmes must target high-risk groups.
Traps
- Confusing prevalence with incidence.
- Quoting DMFT as if it measured present caries activity.
- Ignoring examiner calibration when comparing surveys.
- Citing national Lebanese figures without naming a published survey.