Although textbooks are often the first sources to be consulted on a given subject, they are often dated. When the material is delivered to the publisher it may already be several years old, and the publication process often takes several additional years. Textbooks are particularly problematic in that the sources of information are often absent and incorrect information is sometimes propagated from one textbook to another. Increasingly popular electronic textbooks have the potential to be more current than in the past. For these reasons, journals represent the most current source of information in any discipline. The quality of research in the scientific journals, such as the Journal of Dental Research and the Journal of Periodontal Research is consistently high.
Schemes have been developed by Journal Citation Reports (JCR, Thomson Reuters, Philadelphia) and others to rate the relative impact of journals, i.e., a ratio of citations to articles published. In 2016, the impact factor (IF) for the New England Journal of Medicine was 72.4, but it ranged from 2.8 and 4.2 for the top ten dental journals (out of 82 journals). Higher ratings are to be expected for journals that serve much larger audiences than oral health care professionals. IFs are most appropriately compared to those within the field of dentistry. Ratings below 1.0 are considered low impact. These rating are helpful but not the end-all in characterizing the quality of journals and are readily available through some university libraries. More about IF calculation by JCR is available on YouTube.2
The most critical indicator of quality is whether or not a journal is peer reviewed. Peer review means that several experts in an appropriate field critically evaluate the manuscript and provide recommendations to the editor. Ideally, the editor will maintain complete anonymity between authors and reviewers. Most journal papers that are eventually published are returned to the authors at least once for revisions and many are rejected. According to Brian Burt1, the top dental journals publish fewer than half of the manuscripts they receive. You can determine if a journal has a peer review process by looking for the listing of an editorial review board at the front of the issue or by reading the journal's guide to authors. This is usually published once a year, and the explanation of the submission process will probably indicate if peer review is involved. Examples of peer reviewed journals include the research journals listed in the preceding paragraph as well as the Journal of Dental Hygiene, the International Journal of the American Dental Association, and the Journal of Dental Education.