Bibliometric analysis of cerebral palsy and oral health in PubMed (1956-2021)

Cerebral palsy (CP) is the most common motor disability in childhood, and as far as we know, there are no biometric studies that have evaluated CP and oral health (OH) on a global level. The aim of this study was to present the worldwide research trends in studies of OH in persons with CP, using bibliometric analysis. Through bibliographic information on publications about OH and CP was obtained in the PubMed database, from 1956 to 2021. The extracted data included periodical, title, year of publication, authors, citations, impact factor, key words, country, most cited publications, and study design. A total of 567 articles were published and indexed in PubMed up until 6/28/2021. The data showed a constant growth and an exponential increase in the number of publications. The articles were written in 17 different languages, and 232 (90.63%) articles were in English. Among the 111 Periodicals, Special Care in Dentistry contributed the most to scientific research with 30 articles (17.3%). Brazil (25%) and the United States (17.24%) were the countries with the highest number of publications. Observational studies were the most frequent types of articles (76.29%), followed by case reports (13.36%). It was concluded that this current network analysis indicates that although there is a significant growth in the number of publications about OH in persons with CP, it is important to increase the number of interventional randomized clinical trial studies, to include this population in high-impact oral health investigations around the world.


Introduction
Dentistry is a vast area within the health sciences, with a large number of subareas, and among them, dental care for the disabled. Among the various types of persons with disabilities, cerebral palsy is the most common cause of physical disability in childhood. Persons with cerebral palsy often present permanent disorders in development, movement and posture, causing limitation in daily activity, and is attributed to nonprogressive disturbances which occur in the developing fetal or infant brain (Rosenbaum et al. 2007).
A bibliographic review evaluated 11 articles about oral health of children with cerebral palsy and Down Syndrome in order to define possible differences between those and the general population. The results demonstrated that children with cerebral palsy present higher prevalence of dental caries and periodontal disease and worse health, compared to control groups (Diéguez-Pérez et al. 2016).
Only one systematic review and meta-analysis was found, including 15 articles, which investigated the health of children with cerebral palsy compared to healthy children. A correlation was observed between cerebral palsy and dental caries in primary dentition, gingival status, Angle's Class II malocclusion and anterior open bite (Bensi et al. 2020).
In addition to dental caries and periodontal disease, other studies of salivary composition (Santos et al. 2016;, malocclusion (Yogi et al. 2018;Miamoto et al. 2010), temporomandibular disorder (Ortega et al. 2008), dental trauma (Cardoso et al. 2015), and a case report of Oral myiasis treated with ivermectin, (Shinohara et al. 2004) were found in the literature involving children and adolescents with cerebral palsy.
Bibliometric analysis can be applied to track development trends, access the influences of publications and compare academic performance between different countries in a given research area (Yao et al. 2018). Bibliometrics is an important tool for the quantitative analysis of the productivity of scientific research, helping to monitor and analyze the structure and growth of science (Cooper 2015).
The number of articles published in the field of dentistry has steadily increased over the past decade. This growth was mainly in research articles (Jayaratne and Zwahlen 2015). Bibliometric studies have shown that there are differences between dental subjects, study categories, and thematic areas. In the last bibliometric reviews of dentistry journals, some specific areas stand out, such as dental materials (Moraes et al. 2020), oral pathology (Bhalla and Chockattu 2020), and endodontics (Estrela et al. 2020) but the area of special patients is not even mentioned. However, in some bibliometric reviews with a specific theme in pediatric dentistry, there was a very low percentage of articles published with a specific theme of patients with special needs (6.5%) (Adobes Martin et al. 2021).
It can be observed that the amount of publications on cerebral palsy has increased in the last 3 years in the medical field.
There has been a very large increase in studies on Cerebral Palsy AND Comorbidities, comparing two different periods of time (Klawonn et al. 2020). However, until now no bibliometric study has assessed cerebral palsy and oral health globally.
Bibliometric methods have been used in several fields of dentistry (Patil et al. 2020;Ahmad et al. 2020;Liu et al. 2020) and specific dentistry journals (Valderrama et al. 2020;Bhalla and Chockattu, 2020). The aim of this study was to assess bibliometric characteristics and the worldwide tendency of all articles on cerebral palsy and oral health.

Search Strategy
Bibliometric data can be acquired through various search platforms. In this study, the PubMed database was chosen because of its broad coverage, international visibility, and the controlled vocabulary thesaurus for indexing and retrieving documents (Liu et al. 2020).
To further limit bias, a systematic literature search using a single database (PubMed) and focus on key areas of oral health in the field of cerebral palsy was performed.
Two independent authors evaluated the title and abstract of all articles selected. The following data was extracted: journal, title, year of publication, authors, citations, impact factor, keywords, country, most cited publications and study design.
When an abstract failed to provide the necessary information, the full texts were analyzed. Any disagreement about the studies was solved by consensus after a third review author was consulted. The inclusion criteria for article selection were articles in English and fully accessible text. Letters to the editor, duplicated articles, and articles without complete accessibility were excluded. The search strategy is shown in Figure 1. Data extraction was divided into two parts, the manual handling was transported to Microsoft Excel to perform statistical procedures. The main journals, countries, authors, institutions and most cited articles were classified according to the standard classification of the competition (SCR). Data visualization was performed using the VOSviewer technique to create scientific landscapes and networks based on citation frequency, countries, journals, authors and other information (van Eck and Waltman 2010). GunnMap 2 (http://lert.co.nz/map/) was used to generate the world map to show the publication distribution.
Study designs were classified as follows: observational, case report, literature review, systematic review (with metaanalysis or not), in vitro and interventional study.

Results
After applying the keywords cerebral palsy, oral health, dental caries, periodontal disease, malocclusion, tooth injuries, mouth neoplasm, oral medicine, and oral manifestations, the first article to be retrieved was from the year 1956 (Lyons 1956).
Thus, there was no year restriction regarding the inclusion of studies (1956 -2021). The applied strategy yielded a total of 567 articles.
After the preliminary screening, 335 publications were excluded. Among the total 567 documents there were multiple source types written in 17 different languages. Two hundred and thirty-two English language papers were included for the subsequent analyses, after applying the exclusion criteria: non-English articles, irrelevant articles on cerebral palsy and oral health, letters to editors, editorials, and articles that were unavailable in full-text were excluded. Source: Research data.

Country and Publication
The geographical distribution of publications included 35 countries/regions over six continents, as displayed in the density world map in Figure 3. There were 16 countries that published only one article each, and 10 countries that published at least five articles each. The top 10 most productive countries are shown in figure 3A. Brazil was the most productive country (25%, 58/232), followed by the US (40 publications), India (22 publications), Spain (13 publications), and Turkey (12 publications). Among these countries, five were developed countries (according to the definition of the United Nationswww.un.org) while five were developing countries. Research, Society and Development, v. 10, n. 13, e299101321279, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org /10.33448/rsd-v10i13.21279 6 Source: Research data.

Authors contribution
A total of 796 authors contributed to the publication of all the 232 papers included. The number of authors for a single document, also known as the transience index, is 149, accounting for 18.7% of all the authors. Only two authors published more than nine articles in this field. Santos, MTBR was the most productive author in this field with 22 publications, followed by de Oliveira Guaré, R (10 publications) both from Brazil. The top five productive authors in the field of cerebral palsy and oral health are shown in Table 1. There are thirteen authors in the top five lists because eleven authors published an equal number of articles.
Among the top 10 most cited authors, Santos, MTBR had the greatest citation numbers per publication (43.14), followed by de Oliveira Guaré R and Ramos-Jorge ML all from Brazil.

Institutions Involved
Institutions that are prolific in publishing papers on oral health and cerebral palsy are presented in Table 2  Legends: SCR, standard competition ranking. Source: Research data.

Keywords
There were 703 keywords in the 232 articles. The visualization of keywords is shown in Figure 5. This analysis was performed based on the terms extracted from the title and abstract fields of retrieved publications; a number of 35 terms met the threshold with a minimum number of 3 occurrences. The term with the highest frequency was cerebral palsy (107), followed by oral health (32), and dental caries (21). Source: Research data.
All documents collected were published in 111 different periodicals. Table 3 shows the most productive journals. The top 5 journals published 46.12% (107/232) of the articles. Eleven journals were published in developed countries, while two were published in a developing country. The most productive journals in this field were Special Care in Dentistry, Dental Traumatology, and Journal of Clinical Pediatric Dentistry.  Santos et al. 2003, Loo et al. 2008, Shinohara et al. 2004, Nelson et al. 2011, Mitsea et al. 2001, Benfer et al. 2013, Loo et al. 2009, dos Santos et al. 2005, Francis et al. 1987 Research, Society andDevelopment, v. 10, n. 13, e299101321279, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i13.21279 A comparison of three delivery methods of chlorhexidine in handicapped children. I. Effects on plaque, gingivitis, and toothstaining 1987 J Periodontol 127 Legends: SCR, standard competition ranking. Source: Research data.

Discussion
As far as we can tell, this is the first bibliometric study that analyzed the distribution of worldwide research on cerebral palsy and oral health through the database available, published and indexed in PubMed (https://pubmed.ncbi.nlm.nih.gov). It is important to emphasize that there was no restriction of periodicals in the surveys carried out in this study. Our assessment of cerebral palsy and oral health publishing trends covered a 65-year period (1956-2021).
Bhalla and Chockattu (2020)  In order to identify "What is the trend in pediatric dentistry?" Adobes Martin et al. (2020) selected and analyzed 200 articles with the highest Altmetric Attention Score (AAS), of which 13 (6.5%) were about patients with special care needs.
Garcovich and Adobes Martin (2019) performed a bibliometric study in the four journals related to Pediatric Dentistry listed in the JCR from 2014 to 2017. The highest AAS were found in those referring to preventive protocols or procedures, OHRQOL (quality of life related to oral health), and patients with special care needs. In some dental journals, there is a specific section for the diagnosis and treatment of dental problems related to patients with disabilities or special needs (Bhalla and Chockattu 2020).
There was a marked growth in the number of publications over the 65 years of evaluation of articles on cerebral palsy and oral health. In 2018, there was a greater number of productions (17 articles) (Figure 2), one being a Randomized Controlled Clinical Trial entitled "Evaluation of the effectiveness of a custom-made toothbrush in maintaining oral hygiene and gingival health in patients with cerebral palsy," published in Special Care in Dentistry from a total of 7 studies with this study design.
There are thirteen journals among the top five categories for most publications, including Developmental Medicine & Child Neurology and Research in Developmental Disabilities. These two medical and multidisciplinary journals focused on the topic of pediatric neurology and neurodisability in early childhood; and problems associated with developmental disabilities, respectively (Table 3). The only dental journal focused on the area of special patients is the Special Care in Dentistry.
Currently, cerebral palsy has been considered more than a motor disorder, and must be understood holistically. It should be seen as a developmental condition, with a high probability of affecting the children's (and family's) trajectory and development, therefore, it is necessary to think about interventions in the context of support and services that promote the development and well-being of the family. It must be considered a long-term condition, and that must be seen as a life perspective (Rosenbaum et al. 2019).
Despite the physical disability and comorbidities present in children and adolescents with cerebral palsy, many clinical studies have been carried out in this population (Rodrigues dos Santos et al. 2003, Santos et al. 2016, Yoshida et al.2019, Ferreira et al., 2021. The design of a study is an important factor that links research to clinical practice. Regarding the results found in this study, the observational cross-sectional study was the most frequent among all types of studies (n = 78, 44.06%), similar to the results found by Adobes Martin et al. (2021) who assessed trends in pediatric dentistry in an altmetric study (n = 53, 26.5%). It is important to emphasize that cross-sectional studies are the best way to determine the prevalence of a condition and are useful in identifying associations (Mann 2003) that can be studied more rigorously through a cohort study or randomized clinical trial.
Since this is the first study that evaluated Bibliographic information of publications about oral health and cerebral palsy, no other study was found to compare to the 31 Case-report found in this study. Liu et al (2020) evaluated traumatic dental injuries in a bibliometric analysis over two decades (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018), and found that most articles were case reports. However, it should be noted that the conclusions of case-reports could not be applied directly in clinical practice (Hurd 2014 In the list of the 100 most cited articles in the Journal of Dental Research (JDR), the majority of articles are from the US (52%) and the 7th country that most contributed was Brazil (Ahmad et al. 2020 Spain represents 48.68%, followed by Brazil (15.55%) and Turkey (7.38%) (Valderrama et al., 2020). It is possible to notice that Brazil stands out in the publications of dentistry nationally and internationally. This study, shows that almost 1/4 of the publications on cerebral palsy and oral health originated in Brazil.
The four authors that most published on cerebral palsy and oral health were Brazilian women, Santos, MTBR with the greatest number of publications, followed by de Oliveira Guaré R, Ferreira ACFM and Ramos-Jorge ML. Santos, MTBR who published 2.1 times more than Oliveira Guaré R and 3.5 times more than Ferreira ACFM and Ramos-Jorge ML. Santos, MTBR, Oliveira Guaré R and Ferreira ACFM, whereas three main affiliations were all from Cruzeiro do Sul University in the state of São Paulo, Brazil.
The main limitation of our study was to include only articles in English and only one database for resources (PubMed).
The results of this first study that addressed this issue demonstrated that there is a lack of high quality and well-designed clinical studies such as cohort studies and randomized controlled trial contributing to the future of cerebral palsy and health research.
A bibliometric characteristic of all articles published in the Brazilian Dental Journal (BDJ) in its 30 years of existence , is that the 3 authors with the most publications in the BDJ were Brazilians connected to University of São Paulo

Conclusion
This current network analysis indicates that while there is expressive growth in the number of publications about health in persons with cerebral palsy, in regards to caries and disease-specific research, there is a lack of mechanistic and comprehensive trial research. Therefore, because there is a lack of interventional studies, including cohort studies and randomized controlled trials, it is necessary to include the cerebral palsy population in high impact oral health investigations globally.