Aim: Research on temporomandibular disorders (TMD) has increased rapidly over the past two decades. Studies have evolved from a biomechanical framework to an understanding centered on psychosocial factors. However, the global research map of the literature has not been evaluated using bibliometric methods. The primary objective of this study is to map the bibliometric landscape of the literature addressing psychological status in TMD between 2004 and 2024, and to identify research trends, the most influential publications, authors, countries.
Materials and Methods: The study’s dataset was obtained from the WOS Core Collection database. After applying the specified exclusion criteria, 1272 articles and review articles published between 2004 and 2024 were included in the analysis. The bibliometric analysis was carried out using the VOSviewer software. Annual output, country productivity, co-authorship, citation patterns, and keyword co-occurrence were assessed.
Results: A significant increase in the number of publications was observed, particularly accelerating after 2014 and peaking in recent years. Ohrbach R., Lobbezoo F., and Svensson P. were at the center of research networks, while the most cited study was conducted by Schiffman E. and colleagues, who introduced the diagnostic criteria for TMD. While the USA held a quantitative lead in scientific output, a dynamic and multi-centered collaboration network also emerged, involving Italy, Brazil, and several European countries. Studies focusing on “diagnostic criteria” in the early stages have gradually given way to psychosocial and patient-centered themes such as “depression”, “anxiety”, “chronic pain” and “quality of life”.
Conclusion: This study presents evidence-based findings through bibliometric analysis, highlighting an increase in scientific literature addressing the psychological status in TMD over the past 20 years. It identifies the most influential authors, publications, countries, international collaborations, and research trends. Recent TMD research trends suggest a shift towards a comprehensive biopsychosocial model emphasizing the prevention of disability.
Keywords: Anxiety, bibliometric analysis, depression, psychological stress, temporomandibular disorders
INTRODUCTION
Temporomandibular disorders (TMD) are an umbrella term that encompasses a group of musculoskeletal and neuromuscular disorders characterized by clinical symptoms affecting the masticatory muscles, temporomandibular joint, and associated anatomical structures [1]. Although the etiology of TMD has long been attributed primarily to occlusal and mechanical factors, current scientific evidence strongly suggests that these approaches alone are insufficient, and the field is evolving towards a psychosocial model [2]. With its high prevalence in the general population, TMD presents not only as an individual health issue but also as a significant public health problem. This condition can significantly reduce patients’ quality of life and result in substantial socioeconomic costs [3].
Psychological factors, general joint and muscle disorders, and various chronic diseases can be underlying causes of TMD [4]. It is increasingly recognized that psychological conditions such as stress, anxiety, and depression can be both a trigger and a result of TMD symptoms [5]. For example, psychological stress can lead to an increase in parafunctional habits, such as bruxism, which causes excessive fatigue in the masticatory muscles and places abnormal loads on the joint. It can also affect pain perception and modulation pathways in the central nervous system, thereby lowering the patient’s pain threshold [6]. A systematic review by Santos and colleagues suggests a significant association between anxiety and TMD [7]. Similarly, depression is more common and severe in patients with TMD, particularly those with the myofascial pain, and it contributes to both chronic nature of the pain experience and a reduction in the patient’s quality of life [8]. Determinants of high pain-related disability are linked to psychosocial factors such as severe depression, somatization, chronic pain, and treatment-seeking behavior [9]. TMD severity has been shown to have significant relationships with jaw pain, neck disability, headache, anxiety, and sleep quality [10].
Findings of OPPERA (Orofacial Pain: Prospective Evaluation and Risk Assessment) studies suggest that psychological factors play a significant role in the development and severity of TMD [11-13]. The risk of developing first-onset TMD is significantly higher in individuals with high levels of psychological stress, anxiety, depression, and somatization. Psychological factors are a strong predictor of TMD onset [13]. Somatic and psychological symptoms emerged as a robust risk factor for TMD. Several psychological variables predicted increased risk of TMD, including reported somatic symptoms, psychosocial stress, and affective distress [11]. This situation demonstrates that the pain experience is shaped not only by peripheral factors but also by psychosocial processes. Findings from OPPERA’s genetic studies have defined various disrupted biological pathways related to inflammation, pain processing and psychological function, suggesting that TMD should be regarded as a multisystem disorder rather than an isolated jaw or dental disorder [4,13].
There are time-dependent changes in the biopsychosocial characteristics associated with TMD [12]. A bibliometric study on TMD has highlighted focus areas, including anatomical factors, symptoms, biopsychosocial factors, and epidemiology in TMD. Psychological factors such as depression, anxiety, and stress are among the prominent keywords [14]. However, the general trends of publications, influential authors, collaboration networks, and research trends in this field have not yet been comprehensively evaluated with bibliometric techniques. Bibliometric analyses are a powerful methodological tool for revealing the structural characteristics, global distribution, and development trends of studies on a specific topic [15,16]. In this context, understanding the development of scientific interaction between TMD and psychological status on a global scale is crucial for future research. Therefore, the present study aims to analyze the scientific literature on psychological state in TMD over the past 20 years using bibliometric methods, mapping global research trends, the most influential publications, authors, countries, and collaboration networks in this field.
MATERIAL AND METHOD
The Web of Science Core Collection database, considered the gold standard for mapping scientific research due to its comprehensive and interdisciplinary nature, was used for data collection. The search strategy was created by combining two sets of keywords with the Boolean operator “AND.” The first set contained terms describing temporomandibular disorders [TS=(“temporomandibular disorders” OR “temporomandibular disorder” OR “temporomandibular joint (TMJ) disorders” OR “temporomandibular joint (TMJ) disorder” OR “temporomandibular joint disorder” OR “temporomandibular joint disorders” OR “temporomandibular joints disorders” OR “craniomandibular disorders” OR “craniomandibular disorder” OR “myogenous TMDs” OR “myogenous TMD” OR “temporomandibular dysfunction” OR “temporomandibular joint disease” OR “temporomandibular joint diseases” OR “temporo-mandibular joint disorders” OR “temporomandibular joint dysfunction” OR “temporal mandibular disorder” OR “temporomandibular diseases” OR “temporomandibular dysfunctions” OR “TMJ disorders” OR “TMJ dysfunction” OR “TMJ syndrome”), while the second cluster included terms expressing psychological status [TS=(“psychological stress” OR “anxiety” OR “depression” OR “psychological distress” OR “psychological health” OR “mood disorders” OR “psychological disorder” OR “psychological status” OR “psychological symptoms” OR “psychological assessment” OR “psychological well-being” OR “psychological profile” OR “psychological comorbidity”)]
As a result of the comprehensive search, 1522 records were initially identified. These records underwent a systematic screening process based on exclusion criteria. First, publications outside the 2004–2024 time frame, which was the focus of the study, were excluded, resulting in a reduced number of publications to 1312. After selecting the document types “Article” and “Review Article” the number further reduced to 1298. After applying the language criterion of including only English publications, this number reduced to 1272 (Figure 1).
VOSviewer (version 1.6.20), a widely accepted software in the field, was used for data visualization and network analysis [17]. VOSviewer provides advanced capabilities for creating and visualizing bibliometric networks, enabling the mapping of complex relationships between bibliometric data, including authors, countries, institutions, and keywords. Using this software, annual output, country productivity, co-authorship, citation patterns, and author keyword co-occurrence were assessed. For all networks, node size denotes production (publications or occurrences), edge thickness represents relational strength (links or total link strength), and color encodes cluster membership. For the overlay map, color instead reflects the average publication year, thereby visualizing temporal shifts in topic prominence.
The bibliometric analysis utilized in our study was derived from publicly accessible the open-access Web of Science database. As such, ethical committee approval was not required.
RESULTS
A total of 1272 studies examining the psychological status in TMD were identified. The annual publication count graph presented in Figure 2 reflects the psychological status in TMD and the increasing interest in this area between 2004 and 2024. Interest in the topic developed gradually during the first half of the twenty-year period analyzed (2004-2012). A clear turning point emerged in 2014, with the research area gaining acceleration. It was determined that the number of publications fluctuated over the last 10 years, peaking in the last two years. When evaluating the distribution of publications by country (Figure 3), the United States ranked first with 256 publications. The United States was followed by Brazil with 186 studies, Italy with 116 studies, and China with 99 studies.
Co-authorship of Authors
The analysis of author collaboration networks reveals the structure of scientific communities in a research field and the connections between key authors. The analysis performed with VOSviewer identifies the authors with the most collaboration and the highest total link strength, showing the authors at the center of research communities who direct the flow of information.
The analysis revealed that 4907 authors contributed to the psychological state in TMD. Among these authors, 112 authors were identified who had conducted at least five studies and whose studies had been cited at least 5 times. Upon examining the dataset, it was observed that names such as Ohrbach R. (40 links, 168 total link strength), Lobbezoo F. (33 links, 124 total link strength), and Svensson P. (36 links, 107 total link strength) were at the center of the network in terms of both the links number and the link strength. These authors stood out as the most productive and collaborative researchers in the field. Following them, others such as List T., Maixner W., and Michelotti A. also established a significant number of collaborative networks (Table 1).
Upon visual examination of the collaboration map, the identified authors were divided into 10 distinct clusters (Figure 4). Distinct clusters, represented by different colors and concentrated around authors, were observed. The green cluster was seen to gather around Ohrbach R. and Maixner W. Similarly, the blue cluster gathered around authors such as Lobbezoo F., the orange cluster around Svensson P. and Visscher C., and the pink cluster around Michelotti A. The authors in the red cluster formed the largest cluster visible on the map, despite being unable to establish sufficient connections on their own. The co-author analysis revealed that the field has a highly linked structure, but it is clustered around several major clusters.
Citations of Documents
Citation analysis of documents identifies the most influential and fundamental studies in a scientific field. This analysis highlights the documents with the highest number of citations, mapping important publications that form the theoretical basis of the field.
When examining these highly influential publications listed in Table 2, the most cited study in the field is the article “Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD)” published by Schiffman E. and colleagues in 2014 (2783 citations). Second on the list is the review titled “Bruxism physiology and pathology: an overview for clinicians” by Lavigne G. et al., published in 2008 (536 citations), and third is the publication titled “Painful Temporomandibular Disorder: Decade of Discovery from OPPERA Studies” (441 citations). These studies were followed by Turner J.’s “Mediators, moderators, and predictors of therapeutic change in cognitive-behavioral therapy for chronic pain” (389 citations) and Maixner W.’s publication titled “Overlapping Chronic Pain Conditions: Implications for Diagnosis and Classification” (377 citations).
Citations of Authors
Author citation analysis aims to identify the most influential authors in a research field, those frequently referenced in the literature. This analysis identifies authors with the highest number of citations and publications, highlighting the pioneers in the field and the magnitude of their contributions to the literature.
Among authors, 110 were identified who had published at least five papers and had had their papers cited at least five times. Upon examination of the dataset, the 110 authors who contributed the most were Ohrbach R. (with a total link strength of 1443), Lobbezoo F. (1404 total link strength), and Maixner W. (1052 total link strength). Following them were Yap U. (993 total link strength), Michelotti A. (976 total link strength), Visscher C. (968 total link strength), List T. (946 total link strength), Svensson P. (873 total link strength), Manfredini D. (796 total link strength), and Fillingim R. (675 total link strength) were also among the top 10 most influential authors in the field (Table 3).
Upon examining the citation map, it was observed that these authors were positioned at the center of the network as large nodes, forming a dense citation network around them (Figure 5). In particular, the blue cluster, formed by Ohrbach R. and Maixner W., and the red cluster, including Lobbezoo F. and Michelotti A., emerged as the two main scientific centers in the field. Additionally, Yap A.U. (yellow cluster) and Manfredini D. (green cluster) also contributed to the field, although not as much as the other authors.
Citations of Countries
The citation analysis of countries visualizes the global distribution of scientific production and the impact of countries in their respective research fields. This method identifies the countries with the most citations, revealing the centers of global knowledge production, the leading countries, and their respective contributions to the literature.
In the analysis of countries, 76 countries contributed to the field on psychological state in TMD. 42 countries conducted at least five studies in the field, and these countries received more than five citations. According to the analysis results, the US was found to be the leader in this field with 14077 citations. It was followed by Italy (6224 citations) and Brazil (3899 citations). Countries such as Canada, Sweden, and the Netherlands ranked after these three countries (Table 4).
When examining the citation network map (Figure 6), it was observed that the US (blue cluster) was located at the center of the network and had strong connections with many other countries. Different countries, such as Italy, the Netherlands (red cluster), Canada (turquoise cluster), the UK, and Germany (green cluster), were seen to be clustered. This figure showed that the global flow of information in psychological state research in TMD is predominantly US-centered, but some European countries (Denmark, Sweden, Netherlands) also have strong connections in the networks.
Co-occurrence of Author Keywords
The analysis of author keyword co-occurrence determines the conceptual map of a research field and its fundamental research themes. Based on the frequency with which keywords appear together in the same documents, this analysis visualizes the main topics in the field, emerging trends, and intersections between different research areas, revealing the thematic structure of the information.
The analysis identified 2102 keywords. Forty of these keywords were used at least 15 times in the studies. According to the analysis, terms such as temporomandibular disorders (1415 total link strength), depression (543 total link strength), anxiety (502 total link strength), orofacial pain (292 total link strength), and stress (263 total link strength) emerged as the most frequently used keywords. The average years in which these keywords were most prominent were identified (Table 5).
Cluster analysis of the keyword network revealed that the field consists of distinct color clusters representing related but different areas of expertise (Figure 7). The yellow cluster consisted of terms such as bruxism, myofascial pain, and masticatory muscles. The green cluster consisted of keywords such as chronic pain, orofacial pain, and headache, demonstrating the link between TMD and other chronic pain syndromes. Keywords such as anxiety, depression, quality of life, and stress formed the blue cluster. The red cluster consisted of keywords such as temporomandibular disorders, research diagnostic criteria, and epidemiology.
The overlay visualization map (Figure 8) visualized keywords using color codes. The cooler colors, closer to blue on the map, represented older research trends, while the warmer colors, closer to yellow, represented more recent research trends. Upon examining the map, it was observed that the pioneering concepts forming the foundation of the field were keywords in blue and purple tones, such as DC/TMD, somatization, and epidemiology. It was found that keywords in green tones, representing the field’s maturation period, such as chronic pain, headache, sleep, bruxism, and especially anxiety and depression, were located at the center. Keywords in yellow on the map, such as stress, COVID-19, and comorbidity, showed that the focus of studies changed over time.
DISCUSSION
This bibliometric analysis presented the scientific map of the psychological state in TMD and its transformation between 2004 and 2024. Findings of our study revealed that this field has not only grown in volume but has also undergone a significant conceptual transformation. The field has shifted from traditional biomechanical and occlusal-focused approaches to a more holistic model that treats TMD as a complex psychological condition. Indeed, the fact that names such as Ohrbach R., Lobbezoo F., and Svensson P. were among the most productive and network-central authors in the field revealed that this transformation had been driven by specific authors. When examining the most cited publications that form the scientific backbone of the field, Schiffman et al.’s study ranked at the top [18], followed by Lavigne et al.’s review on bruxism [19] and Slade et al.’s OPPERA studies [4]. According to the author citation analysis results, the authors with the highest number of citations were Ohrbach, R., Lobbezoo, F., and Maixner, W., confirming the established structure of authors in the field. The quantitative leadership of the United States in the geographical distribution, closely followed by Italy and Brazil, demonstrated the global nature of this field. Keyword analysis revealed that the most frequently used keywords after the term”temporomandibular disorders” were depression, anxiety, orofacial pain and stress.
The consistent increase in the number of publications suggests that TMD is increasingly recognized as a significant public health concern and the increasing attention devoted to its psychological dimension. When examining the studies conducted by countries, the quantitative leadership of the USA in this field is consistent with other bibliometric analyses [14,20]. Italy, Brazil, and China follow the USA. However, when examining the citation network map of countries, the US leads in terms of productivity and citations, while European countries such as Italy, Canada, and Sweden have high citation rates despite producing fewer publications. On the other hand, Brazil has a relatively low impact despite its high production, and the same low impact applies to China. This multipolar structure indicates that knowledge is being researched on a global scale.
One of the most concrete and effective reflections of the conceptual transformation in the field is the change in diagnostic criteria. The Research Diagnostic Criteria for Temporomandibular Disorders, presented by Dworkin and LeResche in 1992, represented a significant first step toward an etiology-based classification system [21] However, over time, some limitations and inadequacies of this pioneering system, particularly in terms of validity and diagnostic accuracy in clinical practice, became apparent. At this point, the work of Schiffman, E., and Ohrbach, R., highlighted the weaknesses of the RDC/TMD and led to the development of a new evidence-based system. The study established international standards for the diagnosis and classification of TMD, resulting in the RDC/TMD system, which is suitable for both clinical and research purposes and has higher validity and reliability [18]. It has thus become the fundamental reference point in the field. Lavigne’s article, “Bruxism physiology and pathology” provides clinicians with a comprehensive framework for understanding the pathophysiology of bruxism. Most subsequent studies have focused on pain mechanisms, psychosocial factors, and neurophysiological processes related to chronic pain. This demonstrates that the field is approached not only from a dental or temporomandibular joint perspective, but also through a multidisciplinary approach involving neurology, psychology, and pain science. From a bibliometric perspective, the most influential themes in the field revolve around the standardization of diagnostic criteria, understanding the mechanisms of bruxism and chronic pain, and examining psychosocial factors.
The fact that the most frequently used keywords after “temporomandibular disorders” in keyword analysis are “depression” and “anxiety” shows that psychological status is now part of TMD research. The prevalence of psychological disorders such as anxiety and depression in TMD patients is significantly higher than in the general population. This raises a frequently debated question in the field: Does psychological stress cause TMD, or do chronic pain and dysfunction cause these psychological conditions [22,23] Current evidence suggests that this relationship is not unidirectional but rather involves a reciprocal and cyclical interaction. Anxiety and depression can exacerbate existing TMD symptoms by lowering the pain threshold and disrupting pain modulation mechanisms, while the chronic pain, social isolation, and decline in quality of life associated with TMD also negatively affect an individual’s mental health [7,8]. Therefore, the centralization of the keywords “depression” and “anxiety” in the keyword network serves as evidence for this bidirectional and complex relationship. Psychological and pain-related keywords such as depression, anxiety, orofacial pain, and stress indicate that psychosocial factors play an important role in the etiology and management of TMD and related pain disorders. Furthermore, the frequent repetition of concepts such as bruxism, chronic pain, and temporomandibular joint reflects that the studies encompass both biomechanical and neuropsychological dimensions.
Examining the change of keywords over time allows for an understanding of the distance the field has covered and the conceptual transformation it has undergone between 2004 and 2024. The overlay visualization map shows that in the early stages of the field, the focus was on fundamental and definitional concepts such as “myofascial pain”, “diagnostic criteria TMD” and “epidemiology”. However, over time, the shift in the map’s colors toward warm tones, such as green and yellow, indicates a change in the research agenda. The centralization of concepts such as “chronic pain”, “headache”, “sleep” and “bruxism” indicates a phase in which the psychosocial model has taken hold, recognizing that TMD is not just a local problem but a complex syndrome intertwined with chronic pain, sleep disorders, and parafunctional habits [24,25]. Current concepts, such as “COVID-19”, “quality of life” and “oral health” which are visible in the hottest yellow areas of the map, indicate the field’s newest research areas and future potential. The emergence of the term “COVID-19” demonstrates the field’s sensitivity to global health crises and that the effects of pandemic-related stress on TMD are being investigated. Similarly, the prominence of concepts such as oral health, quality of life, and stress indicates that the focus of research is shifting from symptom management to a more holistic approach centered on the patient’s well-being and quality of life. This time-dependent change highlights the need for researchers and clinicians to shift their attention from the mechanical dimension of pain to the patient’s emotional and psychological world, thereby shaping treatment approaches according to this holistic perspective [26,27].
CONCLUSION
In conclusion, this bibliometric study reveals that the literature addressing psychological status in TMD between 2004 and 2024 has undergone not only quantitative growth but also conceptual evolution. Findings suggest that TMD is shifting away from biomechanical and occlusal-based approaches and is being addressed within a multidisciplinary framework that also encompasses psychological processes. In particular, the centralization of the concepts of depression and anxiety in the keyword network shows that TMD is not just a local pathology but is closely related to the individual’s psychological state, functionality, and quality of life. Approaches that center the biopsychosocial model in TMD research, which are holistic, patient-centered, and aimed at preventing pain-related disability, will shape future directions.
Mehmet Dogan
