Clin Oral Invest (2014) 18:683–684 DOI 10.1007/s00784-013-1171-4

LETTER TO THE EDITOR

The 100 most cited articles in dentistry—some discussions Poramate Pitak-Arnnop

Received: 18 November 2013 / Accepted: 13 December 2013 / Published online: 8 January 2014 # Springer-Verlag Berlin Heidelberg 2014

Sir, I was very interested to read the article by Feijoo et al. [1] outlining the 100 most cited articles in dentistry. Although this report reveals useful information, there are some areas for discussion on which I would like to expand. First, the investigators analysed citations of articles in the field of “Dentistry, Oral Surgery, and Medicine” published from 1945 through June 2012. As the authors reminded us, a small number of publications after 2000 were included probably because of insufficient time to be cited. A bibliometric analysis by Loonen et al. [2] showed that a published article had the critical citable period of 16 years. The number of citations increased more steadily without any strong fluctuation after the second year of publication. The average number of citations in the first 2 years after publication was only 2.5 % of the number of citations during the 16-year critical citable period. This can be implied that a scientific report published in June 2012 will exponentially gather citations after 2014 and its critical citable period will last until May 2028. The group of highly cited articles can be dominated by some of older publications in older journals [3–5]. Hence, citation analysis disregarding the critical citable period seems to skew the study results by Feijoo et al. [1]. Second, the authors found that the most common types of cited articles were case series (22 %) and narrative reviews/ P. Pitak-Arnnop Department of Oral and Maxillofacial Surgery, Research Group for Clinical and Psychosocial Research, Evidence-based Surgery and Ethics in Oral and Maxillofacial Surgery, UKGM GmbH, University Hospital of Marburg, Faculty of Medicine, Philipps University, Marburg, Germany P. Pitak-Arnnop (*) Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie, UKGM GmbH, Universitätsklinikum Marburg, Baldingerstraße, 35033 Marburg, Germany e-mail: [email protected]

expert opinions (19 %). The topics of interest that received high citations were periodontology (43 %), dental implantology (11 %), and adhesive restorations (8 %). These results are likely to be difficult to be interpreted because there may be the vast differences of total publications in each article type/research area. A retrospective cohort study by Sandhu [6] reported that only one meta-analysis was published in two oral-maxillofacial surgery journals during 1999–2009. In contrast, case series (33.4 % or 1,099/3,294) and technical notes (14.2 % or 469/3,294) ranked first and second in order of total publication numbers, respectively. Dental publications may not differ from other specialities in a lack of high-level articles and a prominence of articles in levels 4–5, and the amount of periodontology/implantology/adhesive dentistry articles may be much higher than those in other fields. If so, there is no surprise that case series/narrative reviews/expert opinions and periodontology/implantology/adhesive dentistry papers may have more chance to get the place in the “top-100 cited dental articles” list. Let’s see an example. Had 2,200 case series and two systematic reviews/meta-analyses in the field of dentistry been published between 1945—June 2012, most cited case series would have been only 1 % (or 22/2,200) while all systematic reviews/meta-analyses (2/2 or 100 %) would have accumulated top citations (P=0.0007). As a result of this, systematic reviews/meta-analysis might be considered more influential than case series in terms of percentages in the “100 top cited dental articles” list. In other words, two systematic reviews/ meta-analyses (if there had been only two) could not get more numbers in the “top 100 cited dental articles” list than 2,200 case series (in any case, 2 are less than 2,200). This means that there could be only 0 to 2 systematic reviews/meta-analyses in the list, while case series in the list could range from 0 to 2,200 papers. Contrary to the findings by Feijoo et al. [1], an analysis of “early” citations of oral-maxillofacial surgery articles showed

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that full-length (research) articles got the first place in the “50 most cited articles” list, while short communications (case reports) and reviews were in the following ranks [7]. Hence, to ensure that the low-level publications (case series and narrative reviews/expert opinions) and some research areas of dentistry (i.e., periodontology, dental implantology and adhesive restorations) attracted a big bulk of citations, the investigators (Feijoo et al. [1]) should demonstrate the total number of each article type/research area. Univariate analysis will be useful before concluding the relationship between citations and article types/research areas. Third, the authors stated in the “Abstract” and “Results” sections that 22 case series were in the “50-top cited articles” list. However, in “Table 3 of Feijoo et al. [1],” they quote that 23 % of the most cited articles in dentistry were case series. This discrepancy requires further explanation. Fourth, it is also important to note that case series and narrative reviews, despite low-level evidence, may be the “best available” evidence in clinical practice, such as reports on rare diseases, the determination of aetiology of some disorders or unexpected evolution/complications of a disease and its management. In these circumstances, it may be difficult to conduct a randomised or cohort study. Moreover, case reports may also help to introduce a new hypothesis for future research [8]. For details on pitfalls and limitations of evidence-based medicine, I refer the interested readers to my previous publication [9]. Taken together, Feijoo et al. [1] presented an excellent analysis and interesting information on the 100 most cited articles in dentistry, but their study results need to be interpreted with caution.

Clin Oral Invest (2014) 18:683–684 Ethical approval Not required Disclosure of potential conflicts of interest The author indicates full freedom of manuscript preparation and no potential conflicts of interest. Financial disclosure There was no grant support for this letter.

References 1. Feijoo JF, Limeres J, Fernández-Varela M, Ramos I, Diz P (2013) The 100 most cited articles in dentistry. Clin Oral Investig. doi:10.1007/ s00784-013-1017-0 2. Loonen MP, Hage JJ, Kon M (2007) Value of citation numbers and impact factors for analysis of plastic surgery research. Plast Reconstr Surg 120:2082–2091 3. Fardi A, Kodonas K, Gogos C, Economides N (2011) Top-cited articles in endodontic journals. J Endod 37:1183–1190 4. Hui J, Han Z, Geng G, Yan W, Shao P (2013) The 100 top-cited articles in orthodontics from 1975 to 2011. Angle Orthod 83:491–499 5. Zhang WJ, Li YF, Zhang JL, Xu M, Yan RL, Jiang H (2013) Classic citations in main plastic and reconstructive surgery journals. Ann Plast Surg 71:103–108 6. Sandhu A (2012) The evidence base for oral and maxillofacial surgery: 10-year analysis of two journals. Br J Oral Maxillofac Surg 50:45–48 7. Brennan PA, Habib A (2011) What are we reading? A study of downloaded and cited articles from the British Journal of Oral and Maxillofacial Surgery in 2010. Br J Oral Maxillofac Surg 49:527–531 8. Nabil S, Samman N (2012) The impact of case reports in oral and maxillofacial surgery. Int J Oral Maxillofac Surg 41:789–796 9. Pitak-Arnnop P, Hemprich A, Pausch NC (2011) Evidence-based oral and maxillofacial surgery: some pitfalls and limitations. J Oral Maxillofac Surg 69:252–257

The 100 most cited articles in dentistry--some discussions.

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