Preventive and Community Dentistry
What this domain tests
Preventive and community dentistry tests levels of prevention, epidemiology and population strategies. The exam asks you to interpret rates and choose appropriate prevention.
Core rules
- Primordial prevention avoids risk factors before they occur, such as sugar policy. Primary prevention prevents disease, for example fluoride and sealants. Secondary prevention is early detection through screening. Tertiary prevention limits disability through restoration and rehabilitation.
- DMFT counts decayed, missing and filled teeth; dmft is used for primary teeth. DMFS counts surfaces.
- Prevalence is existing cases divided by the total population. Incidence is new cases divided by the population at risk over time.
- Water fluoridation is a population measure. Fluoride varnish and sealants are targeted measures.
- High-risk groups include low socioeconomic status, dry mouth, orthodontic appliances and special needs.
- Screening uses visual examination and risk assessment; not every lesion needs a radiograph.
- Health promotion uses education, policy and environmental change, not leaflets alone.
Worked example
A school survey finds 300 children; 120 have untreated caries, 60 have filled teeth and 20 are missing teeth due to caries. DMFT = (120 + 60 + 20) divided by 300 = 0.67 teeth per child. If 40 new caries cases occur in the next year, incidence = 40 divided by 300 = 13.3% per year. Baseline prevalence = 200 divided by 300 = 66.7%.
Traps
- Do not mix DMFT and dmft; primary and permanent dentitions are counted separately.
- Prevalence is not incidence.
- Sealants are for caries-free pits and fissures, not open cavities.
- Community water fluoridation is not the same as individual fluoride supplements.