Levels of evidence and journal impact factor in oral and maxillofacial surgery: a 15-year follow-up

This study was performed to assess changes over time in the quality of research in oral and maxillofacial surgery (OMS) by examining the level of evidence of published articles. A secondary aim was to determine the relationship of the journal impact factor to these levels of evidence. The four major OMS journals with an impact factor were assessed. Articles published in 2017 and 2018 were categorized based on their level of evidence, and their correlation with the 2019 journal impact factor was investigated using Spearman's rank correlation coefficient (rho). The total number of published articles increased by a factor of 2.4 over a 15-year period, from 932 in 2002-2003 to 2253 in 2017-2018. The percentage of articles increased by 1.0% for level I evidence, 3.4% for level II, 8.2% for level III, and 4.1% for level IV. Non-evidence articles reduced by 16.7%. All journals showed an increase in impact factor, and a significant correlation was noted between the proportion of published higher-level evidence articles and the impact factor over time (rho=0.811, P=0.001). It is concluded that OMS journals currently display a higher proportion of good quality articles leading to a better impact factor than 15 years ago.