Public Health Dentistry
Public Health Dentistry tests epidemiology, oral health indices, prevention at community level, and national oral health programs. Questions require correct use of rates, indices, and study designs.
Core rules
- Prevalence is the proportion with disease at a point in time; incidence is new cases over a period.
- DMFT counts decayed, missing, and filled permanent teeth; dmft is used for primary teeth.
- A cross-sectional study measures exposure and outcome at one time and cannot establish temporality.
- Community water fluoridation is effective at about 1 ppm, adjusted to climate; it reduces caries safely.
- Health education should be targeted, culturally appropriate, and evaluated.
Worked example
Five children have DMFT scores of 2, 3, 0, 1, and 4. The mean DMFT is (2+3+0+1+4) divided by 5, which equals 2.0. The reasoning is to sum individual index values and divide by the number of children. This is a group measure, not a caries severity classification for an individual. If the question asked for prevalence of caries experience, count children with DMFT greater than zero, which is four out of five, or 80 percent.
Traps
- Do not report incidence from a single cross-sectional survey.
- DMFT and dmft are not interchangeable; use the correct dentition.
- Water fluoride concentration must be adjusted for climate and local baseline.
- Screening is not the same as diagnosis; screen positives need confirmatory examination.