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Public Health: INBDE study notes and practice questions

Public health and prevention questions cover how oral disease is prevented and measured in populations, how fluoride works, and how care is organised and paid for.

102 practice questions · 3 patient cases

Practice Public Health

Where it fits in the official INBDE blueprint

Practice and Profession (prevention, population oral health). Nearest foundation knowledge areas: FK 9, FK 10. See the content outline for the official weights. This mapping is approximate: real items combine a clinical area with a foundation area.

What this area tests

High-yield checklist

Common traps

These notes are original study aids, not official exam content. Confirm clinical details against current guidelines.

Sample questions

1. A drug with LOW LD50 and HIGH ED50 has a:

  1. High therapeutic index u2014 very dangerous
  2. High therapeutic index u2014 relatively safe
  3. Low therapeutic index u2014 very dangerous
  4. Low therapeutic index u2014 relatively safe
Show answer and explanation

Correct answer: C. Low therapeutic index u2014 very dangerous

TI = LD50/ED50. Low LD50 (numerator) u00f7 High ED50 (denominator) = LOW TI. A low TI means the drug has a NARROW safety margin u2014 the effective dose is dangerously close to the lethal dose. Classic narrow-TI drugs: warfarin, lithium, digoxin, phenytoin.

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2. What is the recommended community water fluoridation level in the United States?

  1. 0.7 mg/L (ppm)
  2. 1.5 mg/L (ppm)
  3. 0.3 mg/L (ppm)
  4. 1.0 mg/L (ppm)
Show answer and explanation

Correct answer: A. 0.7 mg/L (ppm)

The U.S. Public Health Service recommends 0.7 mg/L (0.7 ppm) of fluoride in community water — updated in 2015 from the previous range of 0.7–1.2 ppm. This level provides optimal caries prevention while minimizing fluorosis risk. If the natural fluoride level is 0.3 ppm, supplemental fluoride is needed. A child in an area with 0.3 ppm water would need supplemental fluoride — typically 0.50 mg/day for ages 3–6.
  • A. ✅ CORRECT – 0.7 mg/L is the current USPHS optimal community water fluoride recommendation.
  • B. ❌ 1.5 ppm or above can cause fluorosis — exceeds the safe recommendation.
  • C. ❌ 0.3 ppm is below the optimal level — areas with this level may need supplementation.
  • D. ❌ 1.0 ppm was the previous upper limit — the 2015 guideline consolidated this to 0.7 ppm.

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3. Why is fluoride varnish beneficial?

  1. High bioavailability and substantivity
  2. Only pH buffering
  3. Only mechanical protection
  4. Antibacterial effect only
Show answer and explanation

Correct answer: A. High bioavailability and substantivity

FLUORIDE VARNISH advantages: (1) HIGH BIOAVAILABILITY — sustained fluoride release at high concentrations at the tooth surface; (2) SUBSTANTIVITY — prolonged retention/contact time with tooth structure compared to rinses; (3) Favorable pH — acidic pH promotes fluoride incorporation into enamel as fluorapatite; (4) Easy professional application. The combination of high bioavailability AND substantivity makes varnish superior to other topical fluoride forms for caries prevention. A is correct.

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4. All of the following are sources of systemic fluoride EXCEPT:

  1. Fluoridated toothpaste (swallowed by children)
  2. Community water fluoridation
  3. Professionally applied topical fluoride (in-office)
  4. Infant formula reconstituted with fluoridated water
Show answer and explanation

Correct answer: C. Professionally applied topical fluoride (in-office)

C) Professionally applied topical fluoride — CORRECT (NOT a systemic source).
Professional in-office fluoride (varnish, gel, foam) is a TOPICAL application — it acts locally on the tooth surface and is NOT a source of SYSTEMIC fluoride. Even when swallowed in small amounts, the intention and primary action is topical. Systemic fluorosis develops from INGESTED fluoride during tooth development.
A) Swallowed toothpaste: Young children who swallow fluoride toothpaste ingest meaningful amounts — a recognized source of systemic fluoride and fluorosis risk.
B) Water fluoridation: The primary systemic fluoride source — ingested daily, the classic source of systemic fluoride and dental fluorosis when excessive.
D) Infant formula with fluoridated water: A recognized source of excess fluoride intake in infants — associated with fluorosis risk.

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5. Which of the following is NOT a risk factor for dental fluorosis?

  1. Race/ethnicity
  2. Age during fluoride exposure
  3. Bottled milk consumption
  4. Fluoride supplement use
Show answer and explanation

Correct answer: C. Bottled milk consumption

Bottled milk (formula made with bottled water) is NOT a recognized risk factor for fluorosis — milk itself does not contain significant fluoride, and bottled water without added fluoride has lower fluoride than fluoridated tap water. Risk factors FOR fluorosis include: age (6 months–8 years, when teeth are developing), total fluoride intake (fluoridated water + supplements + toothpaste ingestion), geographic region (naturally high fluoride areas), and race/ethnicity (some studies show differential prevalence). Bottled milk actually REDUCES fluorosis risk compared to formula made with fluoridated tap water.
  • A. ❌ Race/ethnicity is a recognized epidemiologic variable in fluorosis prevalence studies.
  • B. ❌ Age is a key risk factor — fluorosis only occurs during tooth development (before eruption).
  • C. ✅ CORRECT – Bottled milk is NOT a risk factor for fluorosis; it does not contain significant fluoride levels.
  • D. ❌ Fluoride supplement use IS a risk factor, especially when combined with fluoridated water.

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6. A patient discloses that they currently smoke cigarettes. What is the FIRST thing the dentist should do under the 5 A's framework?

  1. Prescribe varenicline (Chantix) immediately
  2. Refer to a smoking cessation program
  3. Advise the patient to quit
  4. Ask the patient about their smoking habits
Show answer and explanation

Correct answer: D. Ask the patient about their smoking habits

The 5 A's for tobacco cessation: Ask → Advise → Assess → Assist → Arrange. ASK is always the FIRST step — screen every patient at every visit before any intervention.
  • A. Prescribing without asking about readiness to quit skips essential steps.
  • B. Referral (Arrange) is the 5th step — not the first.
  • C. Advise is the 2nd A — comes after asking.
  • D. CORRECT. FIRST step = ASK. Establish tobacco use status. Can't intervene without screening.

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7. What is the ideal fluoride concentration in community drinking water?

  1. 0.7 ppm
  2. 0.7 ml
  3. 1.0 ppm
  4. 1.2 ppm
Show answer and explanation

Correct answer: A. 0.7 ppm

The CDC-recommended optimal fluoride level in community water is 0.7 mg/L (ppm) — updated in 2015 from the previous 0.7–1.2 range. 'ml' is a volume unit, not a concentration unit, so option B is nonsensical. 1.0 and 1.2 ppm are outdated and above current recommendations.

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8. Which dental index is NOT reversible?

  1. Periodontal score (CPITN)
  2. Gingival score (GI)
  3. DMFT
  4. OHI-S
Show answer and explanation

Correct answer: C. DMFT

DMFT (Decayed, Missing, Filled Teeth) is irreversible u2014 once a tooth is decayed, extracted, or restored, that status cannot change. OHI-S measures removable debris; gingival index measures reversible inflammation; CPITN scores can improve with treatment.

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Patient cases

All Public Health questions (102)