Exploring publications in 3 major orthodontic journals: A comparative bibliometric analysis of two 10-year periods (2002-2011 and 2012-2021)

Introduction

This study aimed to perform a bibliometric analysis examining contributing countries and collaborative networks, authors and collaborative relationships, the performance of the institutions, and cocited journals and references in 3 major orthodontic journals ( American Journal of Orthodontics and Dentofacial Orthopedics , European Journal of Orthodontics , and Angle Orthodontist ) over two 10-year periods (2002-2011 and 2012-2021).

Methods

In this study, 4432 publications in the first decade and 4012 publications in the second decade were quantitatively analyzed and visualized using visualization software such as VOSviewer (Leiden University, Leiden, Netherlands), CiteSpace (Drexel University, Philadelphia, Pa), and Scimago Graphica (SCImago Lab, Spain).

Results

Institutions in the United States had the highest number of publications through the 2 decades, whereas Brazil, South Korea, and China achieved significant improvements in performance in the second decade compared with the first. Closer collaborative networks among scholars were revealed in the second decade. The cocitation analysis of the journals showed that highly cited journals included more professional orthodontic journals in the second decade than in the first decade.

Conclusions

Bibliometric analysis of publications in 3 major orthodontic journals over two 10-year periods revealed a trend of diversification in countries and institutions participating in publishing, international collaborations, and collaboration networks among authors in the field of orthodontics during the 2 decades.

Highlights

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We analyzed publications in 3 major orthodontic journals in 2002-2011 and 2012-2021.
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Institutions in the United States were the most productive country in the 2 decades.
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Academic orthodontic departments at universities contributed more publications.
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Professional journals on orthodontics were cited more frequently from 2012 to 2021.

Orthodontics, presently known as orthodontics and dentofacial orthopedics, is defined as the specialty area of dentistry concerned with the diagnosis, supervision, guidance, and correction of malocclusions. Pierre-Joachim Lefoulon first coined the term “orthodontosie” in 1841, which symbolized orthodontics as an academic field and a specialty. The International Journal of Orthodontia (firstly renamed the American Journal of Orthodontics and later renamed the American Journal of Orthodontics and Dentofacial Orthopedics [ AJO-DO ] in 1986) was created in 1915 with Martin Dewey as the editor and was the first scientific journal focused entirely on research progress in the field of orthodontics. In recent years, the scientific production of orthodontics has progressively shown an upward trend with the ever-growing demand for programs and tool knowledge. At the same time, the number of orthodontic journals listed in the category of “Dentistry, Oral Surgery and Medicine” in Journal Citation Reports (property of Clarivate Analytics, Philadelphia, Pa) has also increased. Only 3 orthodontic journals were included in Journal Citation Reports in 2008, compared with 17 in 2022. More researchers and institutions have become involved in the academic orthodontics field, and publications in the field of orthodontics have also increased significantly. Therefore, conducting bibliometric analysis of published publications is highly needed.

By taking the bibliometric system and bibliometric characteristics as research objects, bibliometrics aims to study the distribution structure, quantity relationships, change rules, and quantitative management of bibliographic information by means of mathematics and statistics. Bibliometrics first emerged in the early 20th century and evolved into an independent discipline in 1969. Originally applied to library and information science, bibliometrics has now been extensively adopted in multiple fields, including chemistry, food, and medicine. It is a method to quantitatively review and investigate existing literature in one field. A systematic understanding of the developmental changes and trends in this field can be achieved by collecting and analyzing detailed information, such as authors, keywords, journals, countries, institutions, and references. In addition to being widely used in studies of stomatology, bibliometrics has been applied to studies of periodontics, endodontic microbiology, and oral pathology. Numerous bibliometric analysis articles on both general ^, and specific orthodontic topics have been published. Therefore, bibliometrics was selected in this study to analyze orthodontic publications in 3 major orthodontic journals.

In 1996, a retrospective observational study of publications in the British and European Journal of Orthodontics from 1989 to 1993 was conducted. A bibliometric study in 2006 analyzed publications in 3 major orthodontic journals over two 5-year periods (1993-1998 and 1998-2002). The characteristics of publications from 1998-2003 and 2004-2008 in 3 major orthodontic journals and Journal of Orthodontics were investigated in a 2011 bibliometric analysis using the random sampling method. In 2014, another bibliometric study analyzed publications from 3 major orthodontic journals over two 5-year periods, 1998-2002 and 2008-2012, which raised the attention of the authors. These 2 studies included 10 years. Therefore, through extending the period to 20 years, the evolutionary process of the publications in 3 major orthodontic journals— AJO-DO , European Journal of Orthodontics ( EJO ), and Angle Orthodontist ( AO ) over the past 2 decades (2002-2011 and 2012-2021) was analyzed, which was reasonable and logical, leading to reliable conclusions. In addition to the 3 major orthodontic journals, the characteristics of orthodontic publications published in other orthodontic and nonorthodontic journals with impact factors, such as authorship characteristics and publication trends, are also worthy of analysis.

Herein, this study aimed to comprehensively analyze and visually present the characteristics of publications published in 3 major orthodontic journals over the past 2 decades, including contributing countries and collaborations, authors and collaborative networks, the performance of the institutions, cocited journals and references, and to review the differences and developments over the 2 decades.

Material and methods

In this study, bibliometrics was adopted for characteristic analysis, including countries, institutions, authors, and cocitation of publications in 3 major orthodontic journals ( AJO-DO , AO , and EJO ) over 2 decades (2002-2011 and 2012-2021). Journals were selected by referring to studies by Kanavakis et al and Baumgartner et al, and the same 3 journals ( AJO-DO , EJO , and AO ) were included in this study, all of which had impact factors in the time covered by this study (2002-2021).

In the data acquisition process, documents were retrieved using the retrieval formulas: “(SO=(“American Journal of Orthodontics and Dentofacial Orthopedics” OR “Angle Orthodontist” OR “European Journal of Orthodontics”)) AND PY=(2002-2011)” and “(SO=(“American Journal of Orthodontics and Dentofacial Orthopedics” OR “Angle Orthodontist” OR “European Journal of Orthodontics”)) AND PY=(2012-2021)” in the Web of Science core collection. We screened the documents according to type and information integrity. Documents that did not meet the requirements below were excluded. Only journal articles and review articles were included, excluding other publications, such as editorial materials, letters, news, bibliographic items, conference proceedings, recensions, and reprints. Articles with incomplete information were also excluded. Information about authors, institutions, and countries was checked. Publications missing any piece of information were excluded from the investigation. Twenty publications published in AJO-DO in the first decade were excluded according to the above criteria. The articles included were exported as plain text files for subsequent analysis and information extraction, including the authors, institutions, sources, countries, and references ( Fig 1 ).

Bibliometric software such as CiteSpace (Drexel University, Philadelphia, Pa), VOSviewer (Leiden University, Leiden, Netherlands), and Scimago Graphica (SCImago Lab, Spain) was used during the visualization process. In this investigation, network visualization using VOSviewer and Scimago Graphica were combined to analyze geographic distribution, international collaborations, and cocited journals. Citespace was used to analyze authors’ contributions and collaborations, as well as cocited references.

Results

After performing the data extraction step 1 ( Fig 1 ), 5892 publications (3266 from AJO-DO , 1688 from AO , and 938 from EJO ) were extracted in 2002-2011, and 5548 publications (3072 from AJO-DO , 1433 from AO , and 1043 from EJO ) in 2012-2021. After data extraction steps 2 and 3 ( Fig 1 ), 4432 articles (2116 from AJO-DO , 1411 from AO , and 905 from EJO ) in 2002-2011, and 4012 articles (1815 from AJO-DO , 1250 from AO , and 947 from EJO ) in 2012-2021 were finally included in total in the bibliometric analysis. During the 2-decade observation period, the number of annual publications of the 3 journals included in the study was generally stable. A slight peak in AJO-DO publications was observed during 2007-2011 ( Fig 2 ).

The 2 regional maps in Figure 3 illustrate the geographic distribution of countries contributing more than 4 articles in 3 major orthodontic journals (48 countries in the first decade and 56 countries in the second decade). If the reference standard is extended to publishing at least 1 article, 67 countries could be counted in the first decade and 82 countries in the second decade. Table I summarizes the top 10 countries with the most publications in the first and second intervals, the sources of these publications ( AJO-DO , AO , and EJO ), and the proportion that each part accounts for the total number of documents issued by the journal. Specifically, United States (U.S.) institutions contributed the largest number of publications, with 1101 papers issued in the first interval, accounting for 24.8% of the total publications in this stage, and 1007 papers issued in the second stage, accounting for 25.1%. The number of articles published in Brazil, South Korea, and China increased significantly from the first to the second interval, from rank 4 (360 publications), rank 6 (279 publications), and rank 9 (217 publications) to rank 2 (548 publications), rank 3 (352 publications), and rank 4 (341 publications), respectively. In the first interval, the sum of the publications in the top 10 contributing countries accounted for 91.2% and 91.8% of the total publications in AJO-DO and AO , respectively, and the proportion increased to 98.3% and 96.9% in the second interval. However, the proportion was relatively low in EJO , with 67.1% and 75.6% in the first and second intervals, respectively ( Table I ).

Table I

Top 10 countries with the most publications

2002-2011					2012-2021
Country	Publications	AJO-DO	AO	EJO	Country	Publications	AJO-DO	AO	EJO
U.S.	1101	730 (34.5)	327 (23.2)	44 (4.9)	U.S.	1007	569 (31.3)	339 (27.1)	99 (10.5)
Turkey	476	146 (6.9)	217 (15.4)	113 (12.5)	Brazil	548	308 (17.0)	182 (14.6)	58 (6.1)
Japan	415	162 (7.7)	173 (12.3)	80 (8.8)	South Korea	352	184 (10.1)	146 (11.7)	22 (2.3)
Brazil	360	223 (10.5)	104 (7.4)	33 (3.6)	China	341	194 (10.7)	107 (8.6)	40 (4.2)
United Kingdom	299	113 (5.3)	46 (3.3)	140 (15.5)	Turkey	295	110 (6.1)	135 (10.8)	50 (5.3)
South Korea	279	158 (7.5)	102 (7.2)	19 (2.1)	United Kingdom	264	92 (5.1)	39 (3.1)	133 (14.0)
Italy	272	119 (5.6)	103 (7.3)	50 (5.5)	Italy	253	71 (3.9)	89 (7.1)	93 (9.8)
Germany	264	98 (4.6)	88 (6.2)	78 (8.6)	Japan	247	120 (6.6)	77 (6.1)	50 (5.3)
China	217	87 (4.1)	87 (6.2)	43 (4.8)	Switzerland	225	64 (3.5)	28 (2.2)	133 (14.0)
Canada	148	93 (4.4)	48 (3.4)	7 (0.8)	Canada	180	73 (4.0)	69 (5.5)	38 (4.0)
No. of publications (top 10 countries)	3831	1929	1295	607	No. of publications (top 10 countries)	3712	1785	1211	716
Total no. of publications	4432	2116	1411	905	Total no. of publications	4012	1815	1250	947
Total percentage	86.4	91.2	91.8	67.1	Total percentage	92.5	98.3	96.9	75.6

Note. Values are presented as n (%) unless otherwise specified.

Figure 3 shows the intensity of the collaborations among countries in the 2 intervals. More continual participation in cooperative networks and increased collaboration intensity between countries were seen in the second interval compared with the first interval. U.S. institutions maintained the most frequent and stable cooperation with other countries, including Italy, South Korea, Brazil, and Japan ( Fig 3 ).

The number of institutions that contributed at least 1 publication was higher in 2012-2021 than in 2002-2011. Table II presents 18 institutions with the most publications in the 2 decades. Among these 18 institutions with the most publications in the first interval, 6 institutions were in the U.S. institutions, followed by Turkey (3 institutions). University of Florence (Italy) and the University of São Paulo (Brazil) ranked first in the number of publications. In the second interval, U.S. institutions continued to have the most contributing institutions (6 institutions), followed by South Korea (3 institutions), Brazil (2 institutions), Switzerland (2 institutions), and China (2 institutions). University of São Paulo in Brazil contributed the most publications ( Table II ).

Table II

Top 18 institutions with the most publications

2002-2011						2012-2021
Institution	Country	Publications	AJO-DO	AO	EJO	Institution	Country	Publications	AJO-DO	AO	EJO
University of Florence	Italy	125	61	53	11	University of São Paulo	Brazil	151	96	37	18
University of São Paulo	Brazil	125	91	23	11	University of Bern	Switzerland	116	38	9	69
University of Michigan	U.S.	98	53	41	4	KyungHee University	South Korea	111	73	33	5
Texas A&M University	U.S.	97	54	32	11	University of Alberta	Canada	111	38	47	26
Seoul National University	South Korea	94	50	36	8	Seoul National University	South Korea	105	39	56	10
Selcuk University	Turkey	78	24	40	14	University of Zurich	Switzerland	101	22	14	65
University of North Carolina	U.S.	78	57	19	2	University of Michigan	U.S.	88	48	19	21
University of Athens	Greece	73	40	18	15	Yonsei University	South Korea	79	43	33	3
University of Alberta	Canada	69	39	29	1	Sichuan University	China	77	38	31	8
University of Iowa	U.S.	67	38	28	1	Federal University of Rio de Janeiro	Brazil	72	27	28	17
Aristotle University of Thessaloniki	Greece	66	35	17	14	University of Athens	Greece	69	20	11	38
University of Hong Kong	China	63	20	22	21	University of Connecticut	U.S.	69	29	20	20
Erciyes University	Turkey	60	16	27	17	University of Florence	Italy	67	16	21	30
University of California	U.S.	58	44	14	0	A.T. Still University	U.S.	64	52	11	1
University of Washington	U.S.	56	54	0	2	Saint Louis University	U.S.	63	44	15	4
Tokyo Medical and Dental University	Japan	55	17	33	5	University of California	U.S.	63	45	16	2
Yonsei University	South Korea	55	28	21	6	Peking University	China	59	31	21	7
Ankara University	Turkey	53	17	23	13	University of North Carolina	U.S.	59	34	21	4