MJDF Dental Public Health & Evidence-Based Dentistry 2

Question 1

What is a systematic review in the hierarchy of evidence?

Accepted Answer

A rigorous synthesis of all available evidence on a defined question using pre-specified methods, typically including meta-analysis — highest quality evidence for clinical decisions

Answer

Systematic reviews use transparent, reproducible methodology to identify, appraise, and synthesise evidence from all relevant studies on a clinical question, reducing bias; meta-analysis statistically pools data when appropriate.

Question 2

What is the difference between relative risk reduction (RRR) and absolute risk reduction (ARR)?

Accepted Answer

RRR is the proportional reduction in risk; ARR is the absolute difference in event rates between groups — ARR is clinically more meaningful

Answer

ARR is the actual difference in risk (e.g., 2% vs. 1% = 1% ARR); RRR expresses this as a proportion of the control group risk (e.g., 50% RRR). ARR is more clinically meaningful — a 50% RRR with a very small ARR may not justify treatment.

Question 3

What is 'number needed to treat' (NNT) in evidence-based dentistry?

Accepted Answer

Reciprocal of ARR — how many patients must be treated to prevent one additional event; lower NNT = more effective treatment

Answer

NNT = 1/ARR; if ARR is 10% (0.10), NNT = 10 — you treat 10 patients to prevent one adverse outcome. NNT is a practical measure of treatment effectiveness in clinical decision-making.

Question 4

What is 'publication bias' in the context of systematic reviews?

Accepted Answer

The tendency for positive studies to be published more readily than negative studies, skewing systematic review conclusions towards overestimated treatment effects

Answer

Publication bias occurs because studies showing positive results are more likely to be published; negative or null results remain unpublished, causing systematic reviews to overestimate treatment benefits.

Question 5

What is the Bradford Hill criterion of 'biological plausibility' in epidemiological causal inference?

Accepted Answer

A plausible mechanism exists by which the exposure could cause the outcome — supports but does not prove causality

Answer

Biological plausibility means there is a known or hypothesised mechanism that could explain the exposure-outcome relationship; it is one of Hill's nine criteria for assessing causality but is not sufficient alone.

MJDF Part 1 Practice Test

MJDF Part 1 Practice Test

MJDF Dental Public Health & Evidence-Based Dentistry 2