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Library Research Guides

Dental Hygiene

Provides resources, strategies, and information on conducting research in Dental Hygiene.

Clinical Scenario

You will usually begin your research with a clinical scenario:

Mark McGee – a 70-year-old male – is concerned about his bad breath.  You tell him that he wouldn’t have much to be concerned about if he only brushed his teeth. He doesn’t believe you and says, “show me the evidence!”  

Then you should use PICO, synonyms, & boolean operators to create a well-defined, searchable question.


The PICO model helps you create an answerable question from a clinical scenario by identifying search terms & their relationships so that you can conduct an effective literature search.

P =   patient/population/problem
Who is the patient?  What are the significant characteristics (age, gender, dental problem)?
I =    Intervention
What will you do:  educate the patient, provide a dental device, drug? 
C =   Comparison
Is  there a comparison to the intervention?  Optional. 
O =   Outcome
What do you want to achieve:  Improve oral health, reduce symptoms, improve patient compliance?


Based on the clinical scenario above:

  • P =   bad breath, male, adult
  • I =     toothbrushing
  • C =   doing nothing
  • O =   reduction in bad breath

Not all of these terms will be used directly in the search, but it's good to be aware of all potential search terms.

Research Question

Here's the question that you'll base your search on.

Does toothbrushing, in comparison with doing nothing [i.e., what the patient is currently doing], decrease bad breath in older male adults?


Synonyms, words that mean the same thing or are closely related to each other, can help expand your search appropriately. 

For this search, the synonyms are:

bad breath      



oral hygiene


You could also use terms such as mouth rinses or toothpaste.

Boolean Operators

Boolean operators such as AND & OR are used to connect synonyms & concepts.

  • Use OR to connect synonyms to appropriately expand your search for a concept. Your search results will contain citations for each term.  Place parentheses around the search terms when you use OR so that the database searches them together. 
  • Use AND to connect concepts.  This will narrow your search results, giving you just the articles that include all terms, that is,  the intersection of the search terms you've used.  Remember:  Databases assume AND between terms, so you don't have to use it.
  • Always capitalize boolean operators; if you don't, they'll be ignored.

Putting It All Together

Here are the terms (also known as a "search string") that will be used to search the database:

  (bad breath OR halitosis) AND (toothbrushing OR oral hygiene)

Bad breath & halitosis are synonyms for one concept, so they're connected by OR & placed within parentheses.

Toothbrushing & oral hygiene are synonyms for the second concept.  They're connected to the first concept with AND.