Multiple choice Questions - Evidence Based Orthodontics

Test your knowledge on The Role of Evidence in Orthodontics (Graber 7th Edition, Chapter 8) with these 30 high-yield MCQs.

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1. Evidence-Based Orthodontics (EBO) is best defined as the integration of:

• A. Best research evidence and clinical expertise only
• B. Best research evidence and patient values only
• C. Clinical expertise and patient values only
• D. Best research evidence, clinical expertise, and patient values/preferences

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Correct Answer: D

Explanation: According to Sackett et al., Evidence-Based Medicine (and Orthodontics) is the integration of the best available research evidence with clinical expertise and patient values.

2. In the hierarchy of evidence, which study design is generally considered to provide the highest level of evidence for treatment efficacy?

• A. Case-control study
• B. Cohort study
• C. Randomized Controlled Trial (RCT)
• D. Expert opinion

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Correct Answer: C

Explanation: RCTs are considered the gold standard for assessing treatment efficacy because randomization minimizes selection bias and confounding variables, unlike observational studies.

3. Which component of the PICO format represents the alternative treatment or standard of care being compared?

• A. P (Patient/Population)
• B. I (Intervention)
• C. C (Comparison)
• D. O (Outcome)

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Correct Answer: C

Explanation: PICO stands for Patient/Population, Intervention, Comparison, and Outcome. 'C' refers to the control group or alternative intervention against which the primary intervention is measured.

4. The primary purpose of "allocation concealment" in an RCT is to prevent:

• A. Detection bias
• B. Selection bias
• C. Attrition bias
• D. Performance bias

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Correct Answer: B

Explanation: Allocation concealment ensures that the person enrolling participants does not know which group the next patient will be assigned to, preventing them from influencing the assignment (Selection Bias).

5. A study that follows a group of patients with a specific exposure (e.g., thumb sucking) forward in time to observe an outcome (e.g., open bite) is known as a:

• A. Case-control study
• B. Cross-sectional study
• C. Prospective Cohort study
• D. Randomized clinical trial

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Correct Answer: C

Explanation: Cohort studies are observational studies where groups are defined by exposure status and followed longitudinally to assess outcomes. Since it looks forward in time, it is prospective.

6. Which type of bias occurs if the outcome assessors know which treatment group a patient belongs to?

• A. Selection bias
• B. Detection (or Observer) bias
• C. Attrition bias
• D. Publication bias

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Correct Answer: B

Explanation: Detection bias (or observer bias) arises when the person measuring the outcome is influenced by their knowledge of the intervention. Blinding of assessors mitigates this.

7. In a meta-analysis, the "Forest plot" graphically displays:

• A. The randomization process
• B. The results of individual studies and the pooled estimate
• C. The risk of bias in each study
• D. The publication date of studies

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Correct Answer: B

Explanation: A forest plot shows the effect estimates and confidence intervals for each included study (usually as squares with lines) and the overall combined result (usually as a diamond at the bottom).

8. If the 95% Confidence Interval (CI) for a mean difference includes the value "0", this implies:

• A. The result is statistically significant
• B. The result is not statistically significant
• C. The sample size was too small
• D. There is a large treatment effect

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Correct Answer: B

Explanation: For continuous data (mean difference), if the CI crosses 0 (the line of no effect), it means there is no statistically significant difference between the groups at the chosen level (p > 0.05).

9. Heterogeneity in a systematic review refers to:

• A. Variability in the results of the included studies
• B. Similarity in study designs
• C. The use of different statistical software
• D. The bias present in the review process

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Correct Answer: A

Explanation: Heterogeneity describes the variation in study outcomes. It can be clinical (different populations/treatments) or statistical (variability in data beyond chance), often measured by the I² statistic.

10. Which study design is most prone to "recall bias"?

• A. RCT
• B. Prospective Cohort study
• C. Case-control study
• D. Laboratory study

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Correct Answer: C

Explanation: Case-control studies are retrospective. Participants (cases) are asked to remember past exposures, and those with the condition may remember differently than those without (controls), leading to recall bias.

11. The "diamond" shape at the bottom of a forest plot represents:

• A. The result of the largest study
• B. The weighted mean difference of the control group
• C. The pooled (combined) effect estimate of all studies
• D. The point of no significance

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Correct Answer: C

Explanation: The diamond represents the overall result of the meta-analysis. Its width represents the confidence interval of the pooled estimate.

12. "Attrition bias" in a longitudinal study is caused by:

• A. Poor randomization
• B. Loss of participants (dropouts) during the study
• C. Inaccurate measurement tools
• D. Funding source influence

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Correct Answer: B

Explanation: Attrition bias occurs when participants who drop out of the study differ systematically from those who remain, potentially skewing the results (e.g., if treatment failures drop out).

13. Which of the following is a "secondary" source of evidence?

• A. Randomized Controlled Trial
• B. Systematic Review
• C. Cohort Study
• D. Case Series

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Correct Answer: B

Explanation: Systematic reviews (and meta-analyses) are secondary research because they filter, synthesize, and analyze primary research studies (like RCTs and Cohorts).

14. The main limitation of a "cross-sectional study" is its inability to:

• A. Measure prevalence
• B. Establish causality (temporal sequence)
• C. Be conducted quickly
• D. Study multiple variables

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Correct Answer: B

Explanation: Cross-sectional studies measure exposure and outcome at the same single point in time ("snapshot"). Therefore, you cannot determine if the exposure preceded the outcome (causality).

15. To minimize "performance bias", a study should ideally be:

• A. Randomized
• B. Double-blinded
• C. Multi-centered
• D. Large in sample size

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Correct Answer: B

Explanation: Performance bias occurs if patients or clinicians behave differently because they know who is in which group. Blinding (masking) both parties prevents this.

16. The CONSORT statement is a guideline used for reporting:

• A. Observational studies
• B. Systematic reviews
• C. Randomized Controlled Trials
• D. Case reports

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Correct Answer: C

Explanation: CONSORT (Consolidated Standards of Reporting Trials) provides an evidence-based set of recommendations for reporting randomized trials to ensure transparency.

17. In statistical hypothesis testing, the p-value represents:

• A. The probability that the results are due to chance assuming the null hypothesis is true
• B. The probability that the alternative hypothesis is true
• C. The clinical significance of the finding
• D. The power of the study

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Correct Answer: A

Explanation: The p-value measures the strength of evidence against the null hypothesis. A low p-value (typically < 0.05) indicates that the observed data would be unlikely if there were truly no effect.

18. Which database is considered the premier source for Systematic Reviews?

• A. PubMed
• B. Google Scholar
• C. The Cochrane Library
• D. Embase

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Correct Answer: C

Explanation: The Cochrane Library is renowned for producing high-quality, independent systematic reviews used to inform healthcare decision-making.

19. What is "publication bias"?

• A. Studies with positive/significant results are more likely to be published than negative ones
• B. Bias introduced by the funding agency
• C. Bias in the statistical analysis of data
• D. Reviewers rejecting papers based on author reputation

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Correct Answer: A

Explanation: This is a major issue where "negative" studies (showing no difference) often remain unpublished (the "file drawer" problem), causing systematic reviews to overestimate treatment effects.

20. The PRISMA statement provides guidelines for reporting:

• A. RCTs
• B. Systematic Reviews and Meta-Analyses
• C. Observational studies
• D. Animal studies

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Correct Answer: B

Explanation: PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) is the standard checklist and flow diagram used to report systematic reviews.

21. In an RCT, "Intention-to-Treat" (ITT) analysis means:

• A. Analyzing only patients who completed the full treatment protocol
• B. Analyzing patients in the groups they were originally randomized to, regardless of adherence
• C. Excluding dropouts from the final analysis
• D. Analyzing based on the treatment actually received

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Correct Answer: B

Explanation: ITT preserves the benefits of randomization. By analyzing everyone in their original groups (even if they switched or dropped out), it provides a more realistic (pragmatic) estimate of effectiveness.

22. An "I-squared" (I²) value of 0% in a meta-analysis suggests:

• A. High heterogeneity
• B. Moderate heterogeneity
• C. No observed heterogeneity
• D. Significant publication bias

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Correct Answer: C

Explanation: I² ranges from 0% to 100%. A value of 0% indicates that the variation across studies is likely due to chance alone (consistency), whereas high values (>75%) suggest considerable heterogeneity.

23. Which level of evidence is traditionally at the base (lowest level) of the evidence pyramid?

• A. Case Series
• B. Animal research / In vitro studies
• C. Expert opinion / Editorials
• D. Cross-sectional studies

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Correct Answer: B

Explanation: While Expert Opinion is the lowest form of clinical evidence involving humans, foundational research like animal or lab studies sits at the very bottom, as findings often do not translate directly to humans.

24. A "confounding variable" is a factor that:

• A. Is the main outcome of interest
• B. Distorts the association between exposure and outcome
• C. Is used to randomize patients
• D. Is removed during blinding

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Correct Answer: B

Explanation: A confounder is associated with both the exposure and the outcome (e.g., age or smoking status) and can make it look like there is a relationship when there isn't, or mask a true relationship.

25. Which risk of bias tool is most commonly used for assessing Randomized Controlled Trials?

• A. ROBINS-I
• B. Newcastle-Ottawa Scale
• C. Cochrane Risk of Bias tool (RoB 2)
• D. QUADAS-2

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Correct Answer: C

Explanation: The Cochrane Risk of Bias tool (RoB 2) is the standard for RCTs. ROBINS-I and Newcastle-Ottawa are used for observational/non-randomized studies.

26. A 95% Confidence Interval (CI) implies that if the study were repeated 100 times:

• A. The true population value would lie within this range 95 times
• B. 95% of the patients will improve
• C. The result is 95% correct
• D. There is a 5% chance of bias

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Correct Answer: A

Explanation: A CI is a range of values that likely contains the true population parameter. It indicates the precision of the estimate.

27. Which of the following is an example of a "Patient-Reported Outcome Measure" (PROM)?

• A. Cephalometric ANB angle
• B. Little's Irregularity Index
• C. Oral Health-Related Quality of Life (OHRQoL)
• D. Bond failure rate

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Correct Answer: C

Explanation: PROMs capture the patient's perspective on their health status. OHRQoL scores (like CPQ or OHIP) measure the impact of oral health on daily life, unlike clinician-measured angles or indices.

28. The "Null Hypothesis" (H0) generally states that:

• A. The experimental treatment is superior
• B. There is no difference between the groups being compared
• C. The study has low power
• D. The results are biased

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Correct Answer: B

Explanation: The null hypothesis is the default position that there is no relationship between two measured phenomena or no difference among groups.

29. When searching for evidence, using "AND" between two search terms (e.g., "Orthodontics AND Corticotomy"):

• A. Broadens the search to include articles with either term
• B. Narrows the search to include only articles with both terms
• C. Excludes the second term
• D. Finds synonyms for both terms

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Correct Answer: B

Explanation: Boolean operator "AND" is used to refine/narrow a search, ensuring that the results must contain both keywords.

30. Why is randomization essential in clinical trials?

• A. To ensure the sample size is large enough
• B. To balance known and unknown confounders between groups
• C. To ensure patients do not know their treatment allocation
• D. To make statistical analysis easier

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Correct Answer: B

Explanation: The unique power of randomization is that it creates comparable groups by distributing both known (measured) and unknown (unmeasured) confounding variables equally, isolating the treatment effect.