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Evidence-Based Dentistry

Resources to support the practice of EBD

Finding Evidence

These sources provide clinical guidelines, clinical summaries, synopses, health technology assessments, and other forms of highly processed synthesis of evidence to inform clinical recommendations.  They take a step beyond a systematic review to offer recommendations for clinical practice. 


All Health Professions & Specialties

These sources offer select systematic reviews, synopses, and other integrations of primary study research from multiple sources into cohesive review articles.

These sources offer primary research studies.

Hierarchy of Evidence & Level of Processing

Efficient EBD searches start at the level of evidence with the highest level of “processing” available before moving down.

Individual primary research studies are processed via specific, structured methods into systematic reviews, which in turn are integrated with clinical expertise and review to become clinical guidelines. Clinical guidelines and summaries from trustworthy creators are the most efficient starting point for an EBD search.

This chart from JADA shows the hierarchy of evidence for single primary studies mapped to the level of processing to the types of appropriate EBD resources to search.  

JADA figure of Hierarchy of Evidence, Level of Processing, and Types of EBD Resources

Source: Brignardello-Petersen, Romina, et al. “A Practical Approach to Evidence-Based Dentistry: How to Search for Evidence to Inform Clinical Decisions.” Journal of the American Dental Association (1939), vol. 145, no. 12, Dec. 2014, pp. 1262–67, doi:10.14219/jada.2014.113

Hierarchy of Evidence for Research Studies

Preappraised and nonpreappraised research studies are research, and also have a hierarchy of evidence.  It is based on degree of assumed bias, based upon the evidence-based practice definition - "systematic deviation of study results from the ‘true’ results/effects on patients, because of the way(s) in which the study is conducted" (source)

Pre-Appraised Research


Non Pre-Appraised Research



Systematic Review

Randomized Control Trial (RCT)

Cohort Study

Case Control Study

Case Series/Case Report

Animal Research/Laboratory Study


Graphic of the Levels of Evidence

For more detailed information about the levels of evidence see the Oxford Centre for Evidence-based Medicine - Levels of Evidence (March 2009). Drawn from the UNC Chapel Hill Evidence-Based Dentistry Guide.

Research Study Design Types

Definitions of Study Types, in hierarchical order
(From BMJ’s Glossary of EBM terms)


A statistical technique that summarizes the results of several studies in a single weighted estimate, in which more weight is given to results of studies with more events and sometimes to studies of higher quality.

Systematic Review

A review in which specified and appropriate methods have been used to identify, appraise, and summarize studies addressing a defined question. I

  • May or may not involve meta-analysis.
Randomized Controlled Trial

Experimental study in which participants are randomly assigned to two or more groups: at least one (the experimental group) receiving an intervention that is being tested and another (the comparison or control group) receiving an alternative treatment or placebo.

  • Most effective for assessing the relative effects of interventions or treatments
Controlled Clinical Trial

Experimental study in which participants are assigned to two or more different treatment groups, typically by a method other than random allocation.

  • When the method of allocation is by random selection, the study is referred to as a randomized controlled trial (RCT).
  • Non-randomized controlled trials are more likely to suffer from bias than RCTs
Cohort Study

Observational study design that follows a group of people (a cohort), and then looks at how events differ among people within the group.

  • Useful for trying to ascertain whether exposure to specific is likely to cause specified events (e.g., lung cancer).
  • Prospective cohort studies (which track participants forward in time) are more reliable than retrospective cohort studies
Case control study

Observational study comparing a group of people who have experienced a specific event (usually an adverse event) and a group of people who have not experienced the same event, and looks at how exposure to suspect (usually noxious) agents differed between the two groups.

  • Most useful for identifying causes of rare events or factors
  • Can only generate odds ratios (OR) and not a relative risk (RR)
  • Provides weaker evidence than cohort studies but more reliable than a case series
Case Series

Observational analysis of a series of people with the disease (there is no comparison group in case series).

  • Provide weaker evidence than case-control studies