MEDLINE is a federally-funded database of journal articles from over 3,600 medical journals.
The articles in MEDLINE are typically written by medical professionals for other medical professionals. The articles (and even the descriptions of the articles) tend to be hard for most people to understand.
An expert reads every article in MEDLINE and assigns one or more "subjects" that they think the article is mostly about. You can use these subject headings to help you find what you want.
Most of the time, when you search a database, you are trying to find articles that talk about the relationship between two (or more) distinct concepts -- smoking and cancer, alcohol and cirrhosis, biofilm and periodontal diseases, etc. If you're trying to find articles about ways that public health dentistry deals with [blank], then you'd search like this:
This can get a lot more complicated. Sometimes you don't know what terms the indexers used. Did they use "gums" or "gingiva," for instance?
Finally, this database will tell you about all sorts of articles to which you do not automatically have access. If you find an article that would be perfect for your project, but you see that we do not have online or printed access to the article, just use Interlibrary Loan to get the article delivered to you.
For more information about using MEDLINE, please see this YouTube tutorial: