Levels of evidence and journal impact factor in oral and maxillofacial surgery

The aim of this study was to identify the relationship between quality of research, in terms of levels of evidence, and journal impact factor (IF), and to describe the pattern of publications in oral and maxillofacial surgery. All four major journals in this subject area only, and with a published IF, were included in the study. Latest published IF dated 2004 was chosen, and all articles related to its calculation were accessed and classified into four levels of evidence. Correlation between levels of evidence and IF was investigated and the pattern of publications was described. All eligible 932 published articles were analysed. None (0%) were level I evidence, 20 (2%) were Level II, 70 (8%) level III and 337 (40%) level IV; 465 (50%) articles were classified as non-evidence. IF ranged from 0.689 to 1.154. There were statistically significant correlations between levels of evidence and IF (rho = 1.0, P < 0.01). Among the 465 non-evidence articles, there were 219 (47%) case reports, 91 (20%) animal studies, 52 (11%) laboratory studies, 35 (8%) technical notes, 24 (5%) tutorial articles, and 16 (3%) reviews articles.