Hallmark of success: top 50 classics in oral and maxillofacial cone-beam computed tomography

Introduction

Cone-beam computed tomography (CBCT) is a relatively recent technology, which can provide three-dimensional volumetric information about oral and maxillofacial structures. It involves having an X-ray source and detector simultaneously rotate 360 degrees around the patient’s head, which is fixed and stabilised. This is then used to generate multi-planar three-dimensional volume data set to provide diagnostic images. Compared to conventional CT, CBCT has numerous benefits including reduced radiation dose, improved image accuracy, and superior image resolution [1]. For these reasons, it has been used for various applications including assessment of tooth root morphology [2,3], pathology and resorption of temporomandibular joint (TMJ) disorders [4], implant correlation to anatomical structures [5], periapical lesions [6], and endodontics [7]. Because of the varied clinical applications of oral and maxillofacial CBCT, it is important to survey the existing literature and study the trends of this progressive field.
Bibliometrics utilises statistical analysis to examine the effectiveness and efficiency of peer-reviewed research [8]. Citation analysis, a frequently used method, analyses publications by their citation counts and reflects the impact and quality of the top articles [9]. In spite of some limitations, citation analysis remains an important method to assess publications that have made a significant impact on a particular field [10]. The two most widely used bibliometric databases are Thomas Reuter’s Web of Science, which provides coverage of 12,000 journals, and Scopus, covering over 22,000 journals and proceeding volumes [11].
Although there are several bibliometric analyses published in the field of dentistry and radiology [12-20], no bibliometric studies have been published on the topic of oral and maxillofacial CBCT, which is the premise of our study.

Material and methods

A database of the most-influential publications on the topic of oral and maxillofacial CBCT was generated using Thomas Reuter’s Web of Science and Elsevier’s Scopus. All journals were included regardless of their field of specialty, language, country of origin, or electronic availability of the abstract.
We used key terms for 1) cone-beam computed tomography (CBCT), 2) oral and maxillofacial pathologies, and 3) oral and maxillofacial anatomical structures.
The terms were combined in the following format:
1. (Cone-beam CT OR CBCT OR Cone-beam Computed Tomography OR C-arm CT OR Flat Panel CT OR Digital Volume Tomography OR DVT OR Compact CT OR Compact Computed Tomography OR Volumetric CT OR Volumetric Computed Tomography OR Ortho cubic);
AND
2. (Osteonecrosis OR Osteoporosis OR Impacted Teeth OR Supernumerary Teeth OR Dental Fractures OR Maxillary Sinus OR Surgery OR Mandibular Canals OR Endodontic Lesions OR Jaw deformities OR Orthodontics OR Reconstructions OR Surgery OR Trauma OR Airway OR Apical Periodontitis);
AND
3. (Maxillofacial OR Craniofacial OR Dental OR Jaw OR Mandible OR Maxilla OR Oral OR Tooth OR Teeth OR Nasopalatine Canal OR Temporomandibular Joint OR TMJ).
A total of 4953 publications resulted from these search terms with publication dates ranging from 1975 to 2016. The publications were arranged by their total citation counts, in descending order. One board-certified radio­logist and one board-certified dentist screened the 321 top-cited manuscripts for inclusion of the publications that discussed the clinical applications of oral and maxillofacial CBCT. Publications that used reconstruction models, extracted teeth, phantom models, or human cadavers were excluded. Additionally, those that were not related to oral and maxillofacial CBCT, explored basic science research, or did not include human subjects were excluded. Meta-analyses, reviews, letters, editorial, and communication and case reports were also excluded.
From the 321 most cited articles, 50 publications were chosen based on the above inclusion and exclusion criteria and compiled into the database. This is a sufficient sample size, which allowed us to identify the common characteristics of the most cited articles.
Citation counts from Scopus, Web of Science, and Web of Science Core Collection were collected and crosschecked. Final citation counts reported in our manuscript were taken from Thomas Reuter’s Web of Science.
Using the method described by Lim et al. [21], we collected the following data: article title, WOS all database citations, WOS Core Collection citations, Scopus citations, year, journal of publication, authors, number of authors, number of institutions, country of primary institution, study design, sample size, and imaged structures.
We reported continuous variables using mean, median, and range. Categorical variables were analysed by frequency and percentage. SPSS 20 was used to summarise the data.

Results

The list of top 50 articles, their total citation counts, and citations per year were taken from Thomson Reuter’s Web of Science. This was cross-matched with the list generated by the same search terms using Elsevier’s Scopus. The top articles are listed in Table 1.

Citations (total and citations per year)

The top 50 publications were cited between 43 and 170 times, with a median of 55.5 citations. On an annual basis, they were cited between 2.6 and 17 times, with a median of 7.1 citations per year. The top three publications by total citations were: 1) “Limited cone-beam CT and intraoral radiography for the diagnosis of periapical pathology”, with 170 citations, 2) “Accuracy of cone beam computed tomography and panoramic and periapical radiography for detection of apical periodontitis”, with 144 citations, and 3) “A clinical study of changes in the volume of bone grafts in the atrophic maxilla”, with 120 citations. After adjustments were made for the number of citations per year, the top two articles remained in the same order, with 17.0 and 16.0 citations per year, respectively. How­ever, “Comparison of airway space with conventional lateral head films and 3-dimensional reconstruction from cone-beam computed tomography”, with 12.6 citations per year, became the third most-cited article on an annual basis.

Year of publication

The year of publication of top-cited publications ranged from 1989 to 2011. All, except for one paper, were published after the year 2000. Figure 1 shows a graphical distribution of the top-cited publications.

Number of authors

The articles had an average of five authors. The most prolific authors are Cevidanes, Lucia Helena S. and Miller, Arthur J., who each had five publications. Cevidanes, Lucia Helena S. had two first authorships and Miller, Arthur J. had three last authorships. The top authors in the field are summarised in Table 2.

Country of origin

The United States of America contributed 15 of the highly cited publications to the field of oral and maxillofacial CBCT. This was followed by Brazil, and Japan, which contributed six and five publications, respectively. The countries that contributed two or more publications are summarised in Table 3.

Journals of publication

The 50 most-cited articles were published across 17 different journals. The top journals were American Journal of Orthodontics and Dentofacial Orthopedics (n = 12), Journal of Endodontics (n = 8), and Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology (n = 8). Table 4 shows the journals with two or more publications and their impact factors.

Additional descriptors

We also analysed the manuscripts based on their study designs (prospective or retrospective), number of affiliated institutions, sample sizes, and primary imaged structures. This information is summarised in Table 5.

Discussion

We identified the top 50 cited articles in the field of oral and maxillofacial CBCT. Out of the 50 articles, the only article published before 2000 was “Craniosynostosis: diagnostic value of three-dimensional CT reconstruction”. This article, by Vannier et al., was published in Radiology in 1989. This shows that CBCT is a rapidly expanding field of imaging that has only recently been utilised for clinical practice. The top three articles identified by citation per year compared the utility between oral and maxillofacial CBCT to radiographs in the diagnosis of periapical lesions, apical periodontitis, and nasopharyngeal airway restriction, respectively [22-24]. The third most cited article by total citation counts, “A clinical study of changes in the volume of bone grafts in the atrophic maxilla”, by Johansson et al., published in Dentomaxillofacial Radiology in 2001, examined volumetric changes associated with bone grafts.
The articles were affiliated with an average of 5.24 authors and 3.7 institutions, and most of the articles (n = 30) had three or more affiliated institutions. This shows that there is much collaboration in the field. Most of the articles (n = 38) had a patient sample size of less than 100, indicating that larger sample size is not necessarily correlated with success. Most of the studies (n = 42) were prospective. Although the majority of the studies (n = 27) imaged primary tooth pathologies, there were also a significant number of articles that discussed imaging of bone grafts or dental implants (n = 7), upper airways (n = 5), the skull (n = 4), and other maxillofacial structures (n = 7). Thus, it can be seen that oral and maxillofacial CBCT has a wide array of clinical applications.
The top three journals were American Journal of Ortho­dontics and Dentofacial Orthopedics (n = 12), Journal of Endodontics (n = 8), and Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics (n = 8). There is healthy competition amongst the different countries in this research field. The United States of America (n = 15) was the most productive country, followed by Brazil (n = 6) and Japan (n = 5). Importantly, Sweden (n = 2) contributed two of the three most cited articles.
Identification of top articles by their citation counts is a relatively good measure of academic success but this approach also has its limitations. The first is the “obliteration by incorporation” phenomenon, which occurs when the information becomes common knowledge so that the landmark articles are rarely cited [25]. Because CBCT is a relatively new technology, we suppose that this phenomenon did not significantly affect our study. The second limitation is that publications from earlier years were more likely to appear in our database because they have had more time since publication and were thus more likely to be cited. For example, the third most cited article in our database, “A clinical study of changes in the volume of bone grafts in the atrophic maxilla”, published in 2001, had a total citation count of 120 (7.5 citations per year), while the fifth most cited article, “Comparison of airway space with conventional lateral head films and 3-dimensional reconstruction from cone-beam computed tomography”, published in 2009, had 12.6 citations per year with a total citation count of 101. In addition, our database did not include articles published after 2011 because these articles did not have enough time to accumulate an adequate number of citations. Because the research field is still in its infancy, it would be valuable to re-examine the literature after a few years to identify the top-cited publications.
Self-citation is another limitation of citation analysis. Previous research indicates that self-citations do not significantly influence research [26]. However, it may play a role in our bibliometric analysis because each article had five authors on average. Furthermore, open-access articles may be able to acquire more citations because they are available without subscription [27]. However, in our bibliometric analysis, open-access articles did not play a major role because only five of the top 50 articles were available via open access. This is probably because most academic researchers would likely have access to institution-based journal subscription services and be able to access information found in these articles. Lastly, we only considered articles that were published in peer-reviewed academic research journals in our study. Thus, we did not include “grey literature” such as opinion or positional papers, government documents, or conference proceedings.
Furthermore, Scopus, Web of Science, and Google Scholar generated different citation counts. Web of Science was used for this study because it was the most consistent with our search criteria. Lastly, we found many irrelevant publications in our initial search – these were filtered out after discussion with a team of three independent reviewers.

Conclusions

The use of CBCT for oral and maxillofacial applications is a relatively novel concept that only emerged in the beginning of the 21st century. Since then, it has been studied in a variety of applications including imaging of primary tooth pathologies, upper airways, the skull, and other maxillofacial structures. Currently, most of the original clinical research in this area is conducted in a prospective multi-institutional approach involving small sample sizes (fewer than 100 patients). However, given the rapid growth in this area, it would be valuable to reassess the trends in a few years. Our study identifies the characteristics of successful literature in the field of cone-beam oral and maxillofacial computed tomography. This information is important for academic dentists to gain valuable insights regarding the trends that are steering the field of oral and maxillofacial CBCT and thus publish effectively in the future.

Conflict of interest and sources of funding statement

Dr. Khosa is the recipient of the Canadian Association of Radiologists/Canadian Radiological Foundation Leadership Scholarship (2017). The authors have no relevant disclosures and no conflicts of interest. There was no commercial funding for this study.

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