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Dentistry for MOSDOH: Evidence-Based Dentistry

Toolkit to support the study and research of dentistry

Textbooks & Reference by Subject

Levels of Evidence

Hierarchy of evidence for clinical questions related to therapy, prevention, etiology or harm

Levels of Evidence

Always start an EBD search looking for the highest level of evidence that matches your query needs. If a meta-analysis is not available on the topic, look next for systematic reviews without statistical synthesis, next for randomized control trials, next for cohort studies, next for case control studies, etc.

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.

EBD Tutorials

Using PICO to create a Search

PICO is the framework most commonly used in Evidence-Based Practice to structure clinical questions, adjusted to fit the specific type of question.

The question types are : Therapy/Treatment, Prevention, Diagnosis, Prognosis, and Etiology

  • Patient Problem or Population
  • Intervention or Impact
  • Comparison or Control
  • Outcome
  • (T)ype

Creating a Database Search Strategy Based Upon PICO (T)

Note: This type of strategy works for larger databases such as PubMed, Cochrane Library, etc. Smaller useful banks of evidence such as the ADA Evidence Database or the National Guideline Clearinghouse may be more suitable for category browsing.

  1. Do NOT search for your complete PICO sentence
  2. Identify key terms
  3. Identify any synonyms or broader terms that closely relate to your terms if applicable
    1. Find useful synonyms by browsing articles that match your search for their listed keywords, by consulting a thesaurus, by consulting your textbooks' glossaries or indices, or by searching a medical thesaurus such as PubMed's MeSH database
  4. Leave out adjectives, connecting words, punctuation, etc.
  5. Leave out any words that can be implied by other search terms
  6. Use Boolean coding (AND OR NOT) and punctuation to structure your search
    1. To get fewer results:
      1. Add more terms using Boolean code AND to limit your search
    2. To get more results:
      1. Remove terms to expand your search 
      2. Add synonyms for your terms using Boolean punctuation and Boolean code OR
  7. Consult the ADA Clinical Practice Guidelines Handbook, 2013 Update for more detail and useful search aids

Example Search Based on PICO Therapy/Treatment Question:

PICO Question : For patients with halitosis [Patient Problem], are probiotics [Intervention] as effective as chlorhexidine mouthwash [Comparison] in reducing measurable Volatile Sulfer Compound levels [Outcome]?

Identify Important Keywords : halitosis, probiotics, chlorhexidine, mouthwash, volatile sulfur compound

Simple PubMed Search : halitosis AND probiotics AND sulfur

The Boolean connector AND tells the database that all articles you find must include each of those words. 

Sulfur is unique enough that it is useful to try searching without the rest of the phrase first. If you find too many irrelevant articles, then add the entire phrase.

This search finds less than 20 articles, many of which appear relevant. This may be a good point to browse abstracts to find the best articles, or to find further useful specific terms to further narrow your question or search. 

Pubmed Search Part Two : halitosis AND sulfur AND chlorhexidine

In this case, you can better organize and consider your search results by running a new but related searches. 

Run a new search to find the same sort of articles focused on chlorhexidine mouthwash.  Ideally, you will be able to find the data necessary to perform a thorough analysis in the two sets of results.


Example Search Based on PICO Prevention Question:

PICO Question : In adolescent athletes [Patient Population], does the use of facial protection [Intervention] reduce the risk of maxillofacial injury [Outcome]?

Note: Prevention or prognosis questions sometimes do not include a specific Comparison or Control aspect.

Identify Important Keywords : adolescent, athletes, facial protection, maxillofacial injuries

Simple PubMed Search : athletes AND "maxillofacial injuries" AND "facial protection"

For this search, you want to make sure that it looks for the phrases maxillofacial injuries and facial protection, and not just those several words in any position in the article, so you must enclose them in quotation marks. This will always tell a database that you want to find exactly the enclosed phrase.

This search finds only one article. You must broaden your search. You can do this by dropping off one of your terms, which will mean that you find more articles. Or, you can do it by adding more synonyms for some of the terms:

Pubmed Search Part Two : athletes AND "maxillofacial injuries" AND ("facial protection" OR mouthguard OR "mouth guard" OR "face mask" OR "face guard" OR "Mouth Protectors")

Facial protection is a broad category term that isn't very commonly used, so it is a good choice to consider for adding synonyms to your search. You can find useful synonyms or names of specific types of facial protection by browsing articles that match your search, consulting a thesaurus, or by searching a medical thesaurus such as PubMed's MeSH database.

Adding the Boolean code word OR in between terms means that you will find all articles that contain either or both terms; the parentheses ensure that the AND part of the search is unaffected. 

Changing your search this way quadruples your useful search results.

Pubmed Search Part Threeathletes AND ("maxillofacial injuries" OR "jaw injuries" OR "jaw fractures" OR maxillofacial fractures" OR  "dental fracture" OR "mandibular fracture") AND ("facial protection" OR mouthguard OR "mouth guard" OR "face mask" OR "face guard" OR "Mouth Protectors")

Maxillofacial injuries is also a good term to expand upon - while it is more standard than facial protection, it has many subcategories or variants.

This nearly doubles your search results.

PubMed Search Part Four : athletes AND ("maxillofacial injuries" OR "jaw injuries" OR "jaw fractures" OR maxillofacial fractures" OR  "dental fracture" OR "mandibular fracture") AND ("facial protection" OR mouthguard OR "mouth guard" OR "face mask" OR "face guard" OR "Mouth Protectors") , with the addition of the Ages : Adolescent : 13-18 years filter

Use one of the filters on the left side of the screen to limit your results to your desired population age, or alternatively, manually add it as an AND term. 

This will reduce your results to only those directly applicable to your query.