Duplicate publications and related problems in published papers on oral and maxillofacial surgery.

As duplicate publication is unethical, our aim was to find out how common it is among published papers on oral and maxillofacial surgery. We used PubMed to identify index articles published in 2010 in the Journal of Oral and Maxillofacial Surgery, the British Journal of Oral and Maxillofacial Surgery, and the European Journal of Cranio-Maxillo-Facial Surgery, and searched for possible duplicate publications from 2008 to 2012 using the first or second and last authors' names. Suspected duplicates were categorised into "non-duplicate" (no overlap), "duplicate" (identical results and conclusions), or "salami-sliced" publications (part of the index article repeated or continued). Of the 589 index articles, 17 (3%) had some form of duplication, but specifically, we found 3 duplicate, and 15 salami-sliced publications. Most redundant articles originated from China (n=4), followed by Italy, Japan, and Germany (3 from each) and the United States and Denmark (2 each). Of the 18 redundant publications, 9 did not reference the related index article. Duplicate material is still being published, and salami-slicing is relatively common among publications on oral and maxillofacial surgery. Further research is required into the extent and impact of this finding.