Bibliometric analysis of dental education journals , Web of Science , 2007-2013

In recent years, several bibliometric evaluations covering various clinical specialties in dentistry have been carried out. However, there are no recent reports in the area of education. The aim of this brief report is to describe the bibliometric profile of dental education journals included in the Web of Science databases (ISI). A bibliometric study of the two dental education journals included in the Science Citation Index expanded database from Web of Science was conducted. Analyze results and Citation Report tools were used to consider the following variables for the total of articles by journal: amount of papers, publication year, affiliated organizations and countries, keywords, number of citations and most cited articles. A total of 1,279 articles were analyzed: Journal of Dental Education (JDE) with 956 papers (74.75%) and European Journal of Dental Education (EJDE) with 323 paperss (25.25%). The United States had the largest number of articles (695), mainly in JDE, and England (110) in EJDE. Consistently, American institutions have the highest productivity in the area. The more used keywords were learning and curriculum. Given the influence that dental education has in all the areas of the profession, it is necessary to further investigate and focus on the quality of research in this area.


Introduction.
In recent years, there have been various bibliometric assessments in the dental field at international level [1][2][3] .This is a way of knowing quantitative and qualitative aspects of knowledge production in various scientific disciplines and generates data to design policies which promote scientific development 4 .
Currently, several databases are used as sources to carry out bibliometric assessments but two are most commonly used: Scopus and Web of Science (usually known as ISI); the latter being considered as the de facto standard 3 .The most commonly measures used in these evaluations are productivity (number of published articles) and the impact factor (number of citations an article attracts over a period of two years).Additionally, some indexes are trying to mix two variables into a single one, as the Hirsch or hindex which equals the amount of n articles with at least n citations 4 .
In dentistry, evaluations about specific clinical areas, such as oral and maxillofacial surgery 5 , implantology 6 , orthodontics 7 , periodontal regeneration 8 , endodontics 9 , among others, have also been recently conducted.In general, these studies have shown that research is of a low level of evidence and concentrated in a few developed countries [5][6][7][8][9] , although some developing countries have placed in better positions in the past few years [1][2][3] .
The area of dental education impacts all dental specialties, as they depend on the educational methodologies being used in the profession.However, no bibliometric assessments have been carried out in dental education recently 10 or they have only focused on specific publications from the United States [11][12] , The objective of this brief report is to describe the bibliometric profile of dental education journals included in the Web of Science databases (ISI).

Materials and methods.
A bibliometric study focused on publications about dental education was conducted.The analyzed database corresponded to the Science Citation Index Expanded Web of Science in the Web of Knowledge platform (Thomson-Reuters, New York, USA).All journals in the "Dentistry, Oral Surgery & Medicine" category were reviewed.The analysis included only those focused on the area of Dental Education regardless of publication year.The algorithm used in the advanced search system corresponded to: OS= (EUROPEAN JOURNAL OF DENTAL EDUCATION OR JOURNAL OF DENTAL EDUCATION) These results included documents in the Articles and Reviews categories, excluding proceedings, letters and editorial material.
By using Analyze Results from the Web of Knowledge platform, information on the following variables was obtained from all the articles and separated by journal: the amount of documents, publication year and affiliated organizations and countries.
With the Citation Report tool from the Web of Knowledge platform, information on the following variables was obtained: number of citations and most cited articles.
Based on keywords from the 500 most cited articles, a keyword cloud, including the 50 most commonly used ones, was generated by a web service, Wordle.net.The information was tabulated in a MS Excel 2003 worksheet (MS Corp., Redmond, USA).The data were presented using graphs and tables with frequency and percentages.

Results.
A total of 1,279 publications from two dental education journals: Journal of Dental Education (JDE) with 956 documents (74.75%) and European Journal of Dental Education (EJDE) with 323 documents (25.25%) were analyzed.Both journals were indexed in Web of Science in 2007.Distribution of articles according to year of publication is shown in Figure 1.
Table 1 shows distribution of the ten countries with the largest number of publications, at least thirty each, sorted by the total in both journals.
Table 2 shows distribution of the twenty institutions with the largest number of publications, at least twenty five each, sorted by the total in both journals.
Table 3 shows the twenty most cited articles in April 2014.Figure 2 shows the word cloud."Dental" and "education" were the most widely cited keywords.
In order to assess other terms, both words were excluded from the graphic analysis 110

Discussion.
The results of this study indicate that JDE triples the productivity of EJDE.The articles published in these journals are mostly from United States, in the case of JDE, and England, in the case of EJDE, with preponderance of American institutions.The subject with the highest impact in dental education relates to curriculum and learning.
It is difficult to explain why JDE triples the amount of published articles in EJDE.It might be due to specific factors regarding the editorial process of both journals, the age of JDE and older associated research networks.However, from 2007 to 2013, the number of published articles in EJDE has increased and tripled the one in JDE.Therefore, the gap between the two magazines would likely disappear in the medium term.In any case, these differences do not seem to have influenced the impact factor (IF) of both journals.According to the Journal Citation Report 2012 13 , EJDE has an IF of 1.012 and JDE presents 0.989.Neither does it seem to influence the most cited articles.In spite of the fact that the first three items on the list were published in EJDE, fourteen of the twenty most cited belong to JDE, which is close to the overall proportion of articles published by both journals.
By analyzing the origin of the articles, it can clearly be seen that there is an inbred tendency.In the case of JDE, nearly 70% of its articles have authors affiliated with an American institution and in the case of EJDE almost 40% are affiliated to an English one, matching previously reported data 10 .This scenario is not inherently undesirable, understanding that many scientific journals have rather geographically bounded audiences associated with national or continental agencies.Besides, the educational models in dentistry are different in Europe 14 and North America 15 , thus this tendency is expectable.
The increased presence of American institutions is mainly associated with the highest proportion of articles in JDE over EJDE.Besides, it relates to higher productivity in dental sciences by the United States, which widely leads the rankings at the level of publications in ISI journals 3 and Scopus [1][2] .
In relation to the keywords, education and dental were the most widely used with similar proportions, then, they were not considered to better appreciate the rest of them.Beyond generic words for the area, such as students, health and dentistry, it can observed that the most commonly used terms correspond to learning and curriculum.This is partially coincident with a prior study on content analysis of articles published between 2003 and 2008 in both journals 10 .In this report, the major topic was curriculum, but no studies on learning theories were counted.This difference may be due to the fact that, between 2007 and 2013, articles relating assessment of students' learning rather than theories on the area were published.Nevertheless, the evaluation of this fact exceeds the goal of this report and should be addressed in future studies.
Regarding curriculum, there is a strong interest in identifying the key aspects of the way in which future dentists are being educated and how to efficiently improve it [14][15] .Also, considering the differences between and within countries, it is likely that curriculum remains the main research topic in dental education.
Given the influence that dental education has in all areas of the profession, it is necessary to further investigate and focus on the quality of research in this area.
The results of this research support the conclusion that scientific productivity published in the two most important journals in dental education, as well as a greater development in curriculum and learning, is concentrated in few countries, led by The United States and its institutions.

Table 2 .
Distribution of articles in dental education journals according to institution of origin, 2007-2013.

Table 3 .
List of the 20 most cited articles published in dental education journals, 2007-2013.
Figure 1.Distribution of articles in dental education journals, 2007-2013.