INTRODUCTION

Language involves exchanging information effectively. Language disorders may interfere with social integration and affect personal development in several domains ¹ . Chronologically, language acquisition in normotypical children follows an unwavering order, though its pace varies considerably ² . According to the American Speech, Language, and Hearing Association ³ , alterations of speech, language and hearing are regarded as language disorders, and they cause negative impact on children’s lives and may be considered a public health problem ⁴ .

The different health professionals who monitor child development should be properly trained to identify the landmarks expected at each age. In addition to speech-language pathologists, who can diagnose and treat language disorders, other health professionals such as pediatricians, pediatric dentists, psychologists and education professionals are part of the supporting network for children’s language development ⁵ . These professionals should pay special attention to children’s global development and resort to a multidisciplinary approach when any speech delay or disorder is suspected.

Some studies report that language disorders are the most prevalent conditions among children ^{4 , 6} . Dentistry plays a crucial role in identifying children with speech disorders, and its integration with speech therapy is of the utmost importance. Disharmonies in dental arches, malpositioned teeth, or missing teeth can cause articulatory speech disorders, because the balance of the stomatognathic system, which involves the teeth, lips, and tongue, plays an important role in the articulation of consonants through obstruction and modification of airflow ⁷ . Language development disorders may interfere in health promotion as a whole. A multidisciplinary approach can help improve quality of life, especially of children and adolescents, and contribute to providing more precise guidelines and public health promotion ⁸ .

The use of bibliometric studies has been suggested to help the academic community identify the history and tendencies in a given area or topic, by analyzing the quantitative aspects of the science and scientific production that provides critical input to research on the subject ^9-11 . The number of times a publication is cited in other articles is a potential marker that represents its influence ¹² . Widely cited articles are expected to have high quality and data that significantly contribute to knowledge ¹³ . Although numerous bibliometric studies have been conducted in areas or topics related to dentistry ^{10 , 14 , 15} , analyses of children’s speech have not been performed to date.

The aim of this study was to assess the 100 most frequently cited articles on language disorders in children and adolescents by means of a bibliometric analysis. Given that a multidisciplinary approach is crucial for a comprehensive and effective treatment, the present study also aimed to ascertain which of these articles reported some interaction with dentistry during their production. Based on the analysis, this report intends to provide an overview of existing research on this topic, identifying areas of interest as well as poorly researched areas, and encouraging future research in the field.

MATERIALS AND METHOD

RESULTS

The searches on the WoS-CC retrieved 88,804 articles. The 100 most frequently cited articles were organized in decreasing order according to the number of citations and are listed in Table 2 . Altogether, the articles were cited 41,108 times (mean of 411.09 citations per article), and only 224 (0.54%) were self-citations. The most widely cited article (1,431 citations) was “Specific reading disability (dyslexia): What have we learned in the past four decades?” by Frank R. Vellutino, published in 2004 ²¹ . The articles were published between 1986 and 2017 and most of them were published in the first decade of the 21st century.

Authorship metrics

Bishop DVN and Tomblin JB were the authors with the largest number of publications. The co-authorship map shows four major clusters, highlighting authors such as Bishop DVN, Tomblin JB, Catts HW, Zhang XY, and Tall P. Collaborations among authors occurred at national and international levels ( Fig. 1 ).

Fig. 1 Co-authorship map. 

Area of expertise

Speech-language pathology was the most frequent area of expertise (32%), followed by psychology (27%) and neurosciences (9%). Some articles covered two or more areas, such as neuropsychology and linguistics (3%). No article on dentistry was found ( Fig. 2 ).

Fig. 2 Area of expertise. 

DISCUSSION

Both speech-language pathologists and dentists deal with the functions of the stomatognathic system, so their interdisciplinary work is of the utmost importance to providing successful treatment ¹⁷ . Interaction between them has increased substantially. The number of citations of scientific articles depends on the year in which the study was submitted for publication, given the profusion of articles over time. Scientific papers are not usually cited until 1-2 years after publication, generally reaching a peak after 3-10 years, after which they continue to be cited at a lower rate. In general, a widely cited article is regarded as a milestone and may therefore have considerable influence on research and practice ¹⁸ . To become a classic, an article must be cited at least 400 times ¹⁹ . In the present bibliometric study, 30 articles were cited 400 or more times and four were cited more than 1,000 times.

Self-citations, albeit in a low number, were observed in this study. They can affect bibliometric data because they may be considered inappropriate ²⁰ . Nevertheless, they are sometimes necessary, as most authors have been researching a topic for a very long time and can provide deeper insights into it. In such cases, self-citations are useful and contribute to the body of knowledge ^{10 , 20} .

The most frequently cited article had 1,431 citations. Its main goal was to provide an updated review of the previous four decades, drawing upon historically influential and contemporary concepts regarding the etiologies of “specific reading disorder” or “dyslexia” ²¹ . This large number of citations over the years shows that this article has had considerable impact on the understanding of dyslexia, a language disorder that mainly affects the ability to read and write. The fact that it was so often cited was probably because of the influence it can have on people, especially during the literacy development phase ²¹ .

Europe and North America were the continents with the largest number of articles in the list of the top 100 citations. The United States had the largest number of articles. Some of the world’s leading research centers are in the USA, where large-scale funding is made available to the scientific community ²² . No publications were retrieved from South America, Africa, or the Middle East. Other bibliometric studies have shown that these continents have linguistic and financial barriers, as well as few partnerships with other institutions and researchers ^{23 , 24} . This scenario shows the need for and importance of collaborative networks among authors from different countries for scientific construction in developing countries, as well as in those with striking differences in culture, history, capacity, and productivity.

The Journal of Speech Language and Hearing Research and the Journal of Child Psychology and Psychiatry were the journals with the largest number of published articles. The former was founded in 1936 and addresses normal and disordered speech, language, and hearing processes and related areas such as cognition, oral motor function, and swallowing, with significant contributions to the advancement of knowledge (https://pubs.asha.org/journal/jslhr). The latter was founded in 1960, with the main objective of selecting research articles on children in different areas of expertise such as psychiatry, psychology, pediatrics, psychoanalysis, social case work, and sociology. It is concerned with developmental psychopathology and child development and has gained additional importance for research and clinical practice, having made numerous contributions, especially to emotional factors with an impact on language disorders (https:// acamh.onlinelibrary.wiley.com/journal/14697610). Bishop DVN and Tomblin JB were the authors with the largest number of publications in the field. The studies by Dorothy Bishop, a psychologist from the University of Oxford in the UK, have had an extremely relevant impact on neuropsychology, speech-language pathology, and developmental psychology. Around 1990, she presented numerous findings on topics such as autism spectrum disorder, dyslexia, and specific language impairment, which had been poorly investigated until then. She devised many methods for evaluating children’s language, including the test for reception of grammar and the children’s communication checklist. Psychology has increasingly contributed to scientific breakthroughs, providing broader understanding of human relationships, and enabling us to rethink and analyze some issues ^{25 , 26} . The second most frequently cited author, James Bruce Tomblin, a psychologist from the University of Iowa, USA, has made remarkable contributions to the epidemiology, etiology, assessment, and treatment of childhood language disorders. He and his colleagues developed a valid and reliable system for diagnosing specific language impairment.

In the bibliometric analysis, the prevalence of observational studies was higher than that of intervention studies. Observational studies are less expensive, more convenient, and easier to perform, especially on children and adolescents ²⁷ . Most observational studies dealt with etiology and risk or prevalence and incidence, which is expected, given that the investigator in these studies does not interact with the participants, but examines the natural relationships between factors and outcomes ²⁸ . Etiology and prevalence are still highly investigated, considering that the etiopathogenesis of language disorders is not yet fully understood and that it may involve organic, intellectual/cognitive, and emotional factors (family context), and in most cases, all possible factors are related ²⁹ .

Autism spectrum disorder (ASD) was the most frequently addressed clinical condition. It is characterized by various alterations in language development (alterations of speech, echolalia, and mutism, among others) ^{1 , 30} . The fact that this was the most frequently addressed topic in this bibliometric study shows how concerned global research is with its elucidation. Studies have reported high worldwide prevalence of ASD, which affects 62 out of every 10,000 individuals, with higher prevalence among male children ³¹ . Autism is still heatedly debated worldwide and has come under the spotlight because of its different clinical manifestations, high incidence, and the concern regarding its impact on child development ¹ . The multidisciplinary approach is of the utmost importance in cases of ASD ¹ . Speech-language pathology (32%) and psychology (27%) were the areas under which most studies were published. Both fields seek to understand the behavior of language. Human behavior, emotional factors, stress, anxiety, and depression interfere with language development, and here, the role of both psychologists and speech-language pathologists is important ^{25 , 31} . Clinical manifestations of behavior and human development in different age groups were the target of these two main fields in this bibliometric analysis. Psychology seeks to understand human behavior and its complexities, whereas speech-language pathology seeks to prevent and treat disorders that affect human communication _skills ^{25 , 31 , 32} _.

The current bibliometric study did not retrieve any publications in the field of dentistry. A child’s first contact with healthcare professionals often involves pediatricians and pediatric dentists ³³ . Pediatric dentists address different clinical conditions and should endeavor to understand the patients’ language development in addition to their initial complaint. The need for a multidisciplinary approach to healthcare means that the roles of all professionals are crucial to providing comprehensive, humane care ³⁴ . This is especially true regarding children and adolescents with language disorders, because they do not easily understand instructions, which could compromise their general health. Although language disorders have been widely studied in the past few decades, and despite the large number pediatric dentistry articles published on oral health comorbidities ^{33 , 35 , 36} , the paucity of studies on language disorders shows the need for further research.

The present bibliometric study has some limitations such as the fact that it included only research papers, case reports, case series, and review articles, leaving out a sizable number of important books or book chapters and conference proceedings. As this was a bibliometric analysis rather than a systematic review, it did not evaluate the methodology, quality, or risk of bias of the studies. The fact that the 100 most frequently cited articles on language disorders did not address dental problems does not indicate a lack of integration between the areas, but only that they were not among the most frequently cited articles. Nevertheless, it is essential to encourage dental researchers to investigate language disorders.

CONCLUSION

To conclude, the analysis of the 100 most widely cited articles on language disorders provides better understanding of children’s language development and shows the major characteristics of important articles published in this field. Most of the studies were performed in North America. Bishop DVN (UK) and Tomblin JB (USA) were the most frequently cited authors, and the Journal of Speech Language and Hearing Research presented the highest number of publications. Most studies on ASD had an observational design. Speech-language pathology was the most prevalent area of expertise, and there was no collaboration with the dental field that involved children and adolescents. Therefore, our findings demonstrate that dental researchers should be encouraged to investigate language disorders, and the interplay between speech-language pathology and dentistry should be strengthened and worked on further.