Find Less
This section of the tutorial will teach you how to focus a search when the first words you use find more results than you can reasonably browse.
Searching is an iterative process. When the first search you try finds a very large number of results it is usually a good idea to focus on a more specific aspect of the topic.
When looking for articles related to the use of fluoride in the prevention of caries your initial search, fluoride AND caries, finds over 7500 results!
On reflection you realize that adding the word prevention may help focus your search. Yet, the search fluoride AND caries AND prevention still finds over 5200 results.
You decide to narrow the focus of your question by looking at a specific vehicle for the administration of fluoride. After reviewing some of the titles in the intial results you decide to focus on fluoride varnishes. You see that some of the articles use the word varnish and some use the plural varnishes. You also check the MeSH Terms on several of these articles and do not see a MeSH term applied that is specifically related to varnish. The search fluoride AND caries AND prevention AND (varnishes OR varnish) finds over 330 results. Don't forget the parentheses or the search will process incorrectly and you will retrieve over 5700!
You can focus your search further using the options available under the Limts tab.
The Systematic Reviews limit is found by scrolling down on the Limits page to the Subsets box, and then scrolling down in that box to Topics. Selecting the Systematic Review subset in PubMed focuses search results on potentially high quality clinical evidence. You will still need to decide if the retrieved articles are actually systematic reviews, that is reviews that follow a structured and defined method to identify and evaluate pertinent research.
Limiting the search fluoride AND caries AND prevention AND (varnishes OR varnish) to Systematic Reviews retrieves more than 25 results that include several recent systematic reviews worth reading and evaluating.
Notice that there is also Dental Journals subset. Generally, you do not want to limit your search to just articles in dental journals. However, this limit can be a useful tool when you are exploring the dental implications for a broad topic such as a disease. Once words for specific dental implications have been found it is best to run another search using those words without the Dental Journals limit. Remember, many important dentistry articles are published outside standard dental journals.
Searches about therapy or interventions can be focused on potentially high quality clinical research using the article type limits Meta-Analysis, Clinical Trial or Randomized Control Trial.
Meta-Analysis: "Works consisting of studies using a quantitative method of combining
the results of independent studies (usually drawn from the published
literature) and synthesizing summaries and conclusions which may be
used to evaluate therapeutic effectiveness, plan new studies, etc. It
is often an overview of clinical trials." (PubMed definition)
Clinical Trial: "Work that is the report of a pre-planned clinical study of the safety, efficacy, or optimum dosage schedule of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques in humans." (PubMed definition)
Randomized Control Trial: "Work consisting of a clinical trial that involves at least one test treatment and one control treatment, concurrent enrollment and
follow-up of the test- and control-treated groups, and in which the
treatments to be administered are selected by a random process, such as
the use of a random-numbers table." (PubMed definition)
If your question specifically relates to a particular age group make sure to add that information to your search. The Ages box on the Limits page lists the age groupings that are applied by PubMed indexers. You can make more than one selection.
- All Infant: birth-23 months
- All Child: 0-18 years
- All Adult:19+ years
- Newborn: birth-1 month
- Infant: 1-23 months
- Preschool Child: 2-5 years
- Child: 6-12 years
- Adolescent: 13-18 years
- Adult: 19-44 years
- Middle Aged: 45-64 years
- Middle Aged + Aged: 45+ years
- Aged: 65+ years
- 80 and over: 80+ years
PubMed covers journals published in many languages, although the majority are published in English. Many non-English articles will have English language abstracts. Non-English articles are indicated by [brackets] around the article title and text naming another language, such as Chinese in the example below.
Search results can be limited to specific languages using options found on the Limits page.
PubMed presents results with the most recently added article records listed first. The database contains information about articles dating back to 1950. Select Specify Date Range from the drop down list to focus your search on a particular time period.
Click on the check mark in the Limits tab to turn off previously selected limits.
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