Preventive Dentistry and Oral Public Health: Community Dentistry, Epidemiology, Oral Health Education
This domain tests epidemiology, indices, fluoride, sealants, oral health education and community programme design - including the arithmetic candidates most often lose marks on.
Indices and epidemiology
- DMFT/dmft counts Decayed, Missing (due to caries) and Filled teeth; prevalence is the proportion affected, incidence is new cases over time.
- The CPI uses index teeth (11, 16, 26, 31, 36, 46) and scores bleeding, calculus, 4–5 mm and ≥6 mm pockets; it does not measure attachment loss.
- Dean's index grades fluorosis and the community fluorosis index summarises it.
- Cross-sectional studies give prevalence; case-control is efficient for rare outcomes; cohort studies give incidence and relative risk.
Fluoride and prevention
Fluoride acts mainly topically, through a calcium fluoride-like reservoir, enhanced remineralisation and inhibited demineralisation. Community water fluoridation at 0.7–1.0 ppm reduces caries by roughly 20–40%. Sealants are indicated for deep pits and fissures of permanent molars, especially in the first two years after eruption. Fluoride varnish (5% NaF, about 22,600 ppm) is the evidence-based professional application.
Worked example
A screening test has sensitivity 90% and specificity 95%; disease prevalence is 10%. PPV = (0.90 × 0.10) / [(0.90 × 0.10) + (0.05 × 0.90)] = 0.09 / 0.135 ≈ 0.67. Even a good test predicts poorly in a low-prevalence population, which is why screening should target high-risk groups.
Traps
Reporting DMFT without separating decayed from filled teeth; using CPI scores to claim attachment loss; describing water fluoridation as a purely systemic benefit; sealing already-cavitated or poorly isolated teeth.