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Evidence-Based Dentistry: ACQUIRE - Find the Evidence

Evidence Pyramid

The evidence pyramid is used to illustrate the evolution of the literature.

As you move up the pyramid the amount of available literature decreases, but increases in its relevance to the clinical setting.

Source: “EBM Pyramid.” Digital Image. Eli M. Oboler Library, 22, February 2017


Filtered or Secondary Resources :  Are summaries and analyzes of the evidence derived from and based on  unfiltered (primary sources) They provide an appraisal of the quality of studies and often make recommendations for practice.

Unfiltered or Primary Resources : Provide evidence concerning a topic under investigation. Primary resources are generally articles that appear in peer-reviewed journals and are found primarily by searching databases.


Evidence Types

You will encounter many types of evidence, it is important to distinguish between these different categories of scholarly literature.

Peer-reviewed (or refereed):  Refers to articles that have undergone a rigorous review process, often including revisions to the original manuscript, by peers in their discipline, before publication in a scholarly journal.  This can include empirical studies, review articles, meta-analysis among others.

Empirical study (or primary article):  An empirical study is one that aims to gain new knowledge on a topic through direct or indirect observation and research.  These include quantitative or qualitative data and analysis. In science, an empirical article will often include the following sections:  Introduction, Methods, Results, and Discussion.

Review article:  In the scientific literature, this is a type of article that provides a synthesis of existing research on a particular topic.  These are useful when you want to get an idea of a body of research that you are not yet familiar with.  It differs from a systematic review in that it does not aim to capture ALL of the research on a particular topic.

Systematic review:  This is a methodical and thorough literature review focused on a particular research question.  It's aim is to identify and synthesize all of the scholarly research on a particular topic in an unbiased, reproducible way to provide evidence for practice and policy-making.  It may involve a meta-analysis (see below). 

Meta-analysis:  This is a type of research study that combines or contrasts data from different independent studies in a new analysis in order to strengthen the understanding of a particular topic.  There are many methods, some complex, applied to performing this type of analysis.

Filtered Resource Examples

Filtered or secondary resources are summaries and analysis of the evidence derived from and based on unfiltered ( primary sources) . They provide an appraisal of the quality of studies and often make recommendations for practice.

What kinds of studies are relevant?

  • Clinical Practice Guidelines
  • Meta-Analysis
  • Systematic Reviews
  • Critically-Appraised Topics
  • Critically-Appraised Individual Articles



Unfiltered Resource Examples

Filtering Unfiltered Resources

Open Access Journals

Peer Review in 3 Minutes

How to Tell if Article is Peer-Reviewed?

Here are some methods to tell if a journal is peer-reviewed:

  • If it's online, go to the journal home page and check under About This Journal. Often the brief description of the journal will note that it is peer-reviewed or refereed or will list the Editors or Editorial Board.
  • Go to the database Ulrich's and do a Title Keyword search for the journal. If it is peer-reviewed or refereed, the title will have a little umpire shirt symbol by it.
  • BE CAREFUL! A journal can be refereed/peer-reviewed and still have non-peer reviewed articles in it. Generally if the article is an editorial, brief news item or short communication, it's not been through the full peer-review process. Databases like Web of Science will let you restrict your search only to articles (and not editorials, conference proceedings, etc).

Journal Impact Factor

The Journal Citations Reports (JCR)  provides quantitative tools for ranking, evaluating, categorizing, and comparing journals.  One measurement used is the Impact Factor.  The Impact Factor is a measure of the frequency with which the "average article" in a journal has been cited in a particular year or period. The Impact Factor is calculated by dividing the number of current year citations to the source items published in that journal during the previous two years.  The Impact Factor should be used with caution as there are many factors that can influence citation rates.


To learn more about Impact Factor read this article: The Agony and the Ecstasy—The History and Meaning of the Journal Impact Factor



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