Number of authors

A total of 7,745 authors participated in the 2,291 articles in this period. A proportion of 46% of authors appear in a single publication (n = 3586/7745), 23.2% (n = 1799/7745) in two publications; between three and five publications or more are credited with 19.8% of authors (n = 1534/7745), and 3.3% of authors with more than 10 publications (n = 258/7745). These values are consistent with claims that a small group of authors make a greater number of contributions on specific topics.^29,31 In a classification based on number of publications per author (Table 1), ten authors have significant productivity on the subject, including Paiva, from Brazil, with 33 publications, followed by Schwendicke from Germany and Twetman from Denmark with 29 articles each. The average citations by number of articles range from 3 to 10, with Schwendicke as the lead author in this respect. Three of the authors do not appear in publications as main authors, while the remainder vary between 2 and 4 articles heading the list of authors. It becomes difficult to analyze the contributions of each author within each publication, as information in this regard is not available. On the other hand, it may be possible to find lead authors not heading the list of contributors, although this may be changing along with the journals’ policies for publication.³²

The average number of authors per publication was 3.38. Publications with a single author accounted for 3.45% (n = 79/2,291); two authors for 7.6% (n = 173/2,291); three authors for 13.0% (n = 298/2,291); four authors for 10.8% (n = 413/2,291); five authors for 19.2% (n = 439/2,291); 6 authors for 16.4% (n = 376/2,291) and articles with 7 authors accounted for 8.6% (n = 198/2,291).

More than 7 authors were found in 31.3% of articles (n = 716/2,291) and the maximum number of authors was 25. These results are consistent with the current trend, showing that more and more research is being published in collaboration by multiple authors, while unique authorship is becoming less frequent.^32,33

Cooperation among authors

The network resulting from this analysis is shown in Figure 2. It shows relationships among authors, represented by the proximity of the nodes and the connection edges; the size of nodes represents number of publications, and lines indicate collaborative publications. Colors represent collaboration groups (clusters)²⁷ showing the formation of communities by relative frequency in their links in specific fields within the topic of dental caries in this case.³⁴ The network shows 35 collaboration groups of 851 authors who met the inclusion criteria. The main authors in this collaborative network are Paiva, Mendes, Twetman, Levy, Lingstrom, Lo, and Schwendicke. These maps are a good representation of the situation in terms of cooperation; however, there are some limitations regarding possible biases that are usually controlled using disambiguation thesauruses and by the use of author identification, such as ORCID.^29,35

Source: by the authors

Figure 2 Network of author cooperation on dental caries, 2014-2018 

Journals with publications on dental caries

The 2,291 articles were published by 177 different scientific journals; this corresponds to a relatively small number of titles, meaning that information on dental caries is probably concentrated. Table 2 groups the 10 scientific journals with the most publications on dental caries. 44.4% (n = 1017/2,291) of total production was published in these 10 journals. The impact factor (Journal Citation Reports) ranges from 1,383 to 5,380. Caries Research is the journal with the largest number of publications on dental caries (n = 176 articles) and is the only one specialized in the subject, while the others include articles on various disciplines of dentistry (endodontics, periodontics, orthodontics, social and community dentistry), and only two share topics with other disciplines such as medicine.

Geographical distribution

With the total number of publications, an analysis was made by country of origin and associated institution according to the information included for main authors. The documents on dental caries originated in 110 countries, 38 of which are in Europe, 32 in Asia, 23 in Africa, 15 in America and 2 in Oceania. 16.4% (n = 18/110) of countries produced more than 50 articles. The countries with the most production on dental caries are the United States (n = 488), Brazil (n = 424) and England (n = 187). The other seven countries and their production are shown in Figure 3. As for production in America, in addition to the U.S. and Brazil, the production concentrates, in order, in: Canada in 13th place with 61 articles, Chile in 23rd place with 29 articles, and Colombia in 37th place with 15 articles.

Source: by the authors

Figure 3 Distribution of publications on dental caries by country, 2014-2018 

Distribution of institutions and cooperation

A study on the institutions associated with authors was carried out (it should be noted that an author may be associated with several institutions), with 2,070 institutions found for the 2,291 articles. 67.3% of institutions contributed one publication; 13.2% two publications; 5.3% three publications, and 2% contributed more than twenty publications. Table 3 lists the top 10 institutions producing caries-related articles. This classification shows two universities in Brazil, the University of São Paulo with 91 publications, and Universidade Federal Rio Grande do Sul with 47 publications; these were followed by the University of Copenhagen in Denmark with 56 publications. Three U.S. institutions are listed within the top 10 most productive. In Colombia, the top institution regarding the amount of publications on this topic is Universidad del Bosque, with 6 publications and 21 citations.

The cooperation network among nations was analyzed for countries with at least 10 publications on the subject; all countries that had no connections with others were excluded. The two largest groups are around the United States and Brazil, with the most collaborations with China, England, Sweden, Australia, India, Germany, and Japan among the most important. In this context, several productive Latin American networks appear among the most cooperative. Chile appears with the most connections (with Brazil, USA, Australia, England, Finland, Germany, Israel, Denmark, Egypt, Spain, Switzerland), followed by Colombia (with Brazil, USA, Germany, England and Denmark) and Mexico (with USA, Brazil, France and Canada).

A qualitative review of this list shows that university institutions are dominant, but there are also some hospitals and government institutions, indicating that this topic is both of academic and governmental public interest.

Citation analysis

A citation is described as an article mentioning or referring to another article, which is known as article of origin.³⁶ The 2,291 articles contain a total of 45,889 references; in addition, they have been cited by other authors 9,410 times at the time of the analysis. The author with the most citations is Kassebaum with 191; 32.56% of the articles do not have citations (n = 746/2,291), representing a significant number of articles with no citations. 67.43% (n = 1545/2,291) have more than one citation and 3% (n = 69/2,291) have more than 20. It should be noted that articles are cited for various reasons, including quality, valuable content or because of their popularity with or without regard to quality, among other factors.³⁷ The average number of citations per article is 4.1. Table 4 shows the 10 most cited authors and their articles, excluding those who, having a significant number of citations, had no connection with other authors.

Citations reflect the visibility of publications. It is generally considered that open access publications38 are increasingly cited and this may be a limitation for the analysis; on the other hand, the fact that an article is more visible is not related to it being of a better quality, in fact, some publications may have a low citation indicator as they are new in the scientific field.39 The most cited article in the list is “Global Burden of Untreated Caries. A Systematic Review and Metaregression” by Kassebaum et al, with 191 citations, corresponding to 64 per year. The journal most frequently related to these high scores is Journal of Dental Research, which has an impact factor of 5,380 with seven of the ten publications. Some analyses state that the journals with the most impact factor are often more cited because more libraries want their access and therefore are available to a greater number of researchers.⁴⁰ Of the 10 publications in the list, the most cited are associated with authors from the United Kingdom, followed by the United States. Brazil is the only Latin American country among the first. As for the topics in this list of articles related to dental caries, there are four studies related to public health and epidemiology, three related to sugar intake and three to biological and biochemical aspects. The citations, therefore, allow to establish basic and influential documents in the academic community.³⁶ On the other hand, this analysis may be limited by the parameters established, as well as the fact that the analysis only covers five years, which may limit the influence of important articles that were left out due to the period of analysis. But it can also be an opportunity for other researchers to expand the information on this same topic.

Co-citations analysis

Co-citation is understood as the relation created when an article cites two others, suggesting a relation among them because of content.⁴¹ The VOSviewer 1.6.9 software was used for this analysis, including the 2,291 articles but especially those containing one citation that has been used at least 20 times. Under these conditions, of the 45,889 references in the articles, 180 references reached the analysis threshold. In Figure 4, the size of nodes indicates the number of citations. The larger the node the more times it has been cited. In this representation, smaller distances indicate stronger relations, and colors separate groups by similar topics. Six thematic groups appear in this analysis. Four groups (dark blue, violet, red and yellow) show a nucleus with closer thematic relationships. An analysis by titles associated with each color yields the following groups: red includes articles on dental caries and general health aspects of interest to government institutions such as the World Health Organization; yellow is related to detection and diagnosis; dark blue to biology, microbiology and basic sciences; lilac articles are related to disease impact; the green group is related to techniques and treatment, and the light blue group is related to genetics and molecular biology topics. This indicator also shows the proximity relation that appears when an author belongs to a particular subfield within the topic, as it is understood that articles are cited together when the relations among them are closer.⁴²

Source: by the authors

Figure 4 Co-citation analysis among highly referenced articles on dental caries, 2014-2018 

Co-occurrence analysis

Co-occurrence identifies the most common keywords in abstracts and titles, as well as the keywords that most frequently appear in articles and the corresponding proximity between two or more terms.^43,44 The analysis included all the keywords of the 2,291 articles that had 10 occurrences minimum; of the 6,979 keywords, 405 were included on the threshold. The distance among terms provides information about the relationship among terms and is established by counting the number of times a word appears in titles and abstracts.^26,45 In this way, the more proximity between two terms, the stronger their relation. Colors represent the possible groupings by theme.

The most common keywords and their occurrence values were dental caries with 1980, oral health with 549, children with 526, and prevalence with 356. The 20 most common terms and their values can be seen in Figure 5. Analyzed by year in Overlay Visualization by VOSviewer, it shows that since 2016 there have been higher frequencies in the following words: association, global burden, periodontitis, and caries detection. The association of the keywords periodontitis and caries detection may be explained because the number of publications related to prevention programs for both diseases have increased.

Source: by the authors

Figure 5 List of the 20 most common keywords and their occurrence values in dental caries 2014-2018 

Study limitations

It should be noted that there is no scientific literature database containing all the world’s production regarding a single topic. This suggests that the results obtained and analyzed in this article contain only the scientific production of a set period of time to analyze this type of data; therefore, some relevant publications may be outside the analysis and others, which are very recent, could have a high impact on the discipline and subject matter, but at the time of the study may have had a low specific weight in the analysis. On the other hand, some authors suggest that indicators such as the H index may contain biases, and therefore suggest to apply other metric types; however, the databases of scientific production analysis keep using such indicators.