Temporomandibular joint dysfunction in Parkinson ’ s Disease : an integrative literature review

Mailing address: Taysa Vannoska de Almeida Silva 2a Travessa PIO XII, 58 Cajueiro Seco Jaboatão dos Guararapes, Pernambuco, Brasil CEP: 54330-323 E-mail: taysavnk.fisio@gmail.com ABSTRACT Temporomandibular joint dysfunction is a set of disorders involving the masticatory muscles, temporomandibular joint and associated structures. It is known that the progression of motor symptoms in Parkinson’s disease is an indication that these people are more prone to the development of this dysfunction. Thus, this study aims to investigate the signs and symptoms of temporomandibular dysfunction in people with Parkinson’s disease. The search was performed in the databases: MEDLINE/ PubMed, LILACs, CINAHL, SCOPUS, Web of Science and PEDro, without timing or language restriction. Specific descriptors were used for each database and keywords, evaluated by the instruments: Critical Appraisal Skill Program and Agency for Health care and Research and Quality. A total of 4,209 articles were found but only 5 were included. After critical analysis of the methodology of the articles, one did not reach the minimum score required by the evaluation instruments, thus, it was excluded. The selected articles addressed, as signs and symptoms of temporomandibular joint dysfunction, the following: myofascial pain, bruxism, limitation of mouth opening, dislocation of the articular disc and asymmetry in the distribution of occlusal contacts. Further studies are needed in order to determine the relationship between cause and effect of the analyzed variables, so as to contribute to more specific and effective therapeutic interventions.


INTRODUCTION
Parkinson's disease (PD) is considered one of the most prevalent neurodegenerative disorders in the elderly, affecting 0.3% of the general population, affecting more men than women 1 .It is a progressive degenerative clinical syndrome of the central nervous system that causes movement disorders due to dopamine deficiency in the nigrostriatal pathway of the brain 2,3 .The diagnosis is based on clinical features through motor symptoms that include: bradykinesia, muscle stiffness, postural instability and resting tremors that extend down the neck and face.Non-motor symptoms such as olfactory, gustatory, sleep disturbance and cognition dysfunction are also present 2 .
Motor symptoms are related to the development of postural alterations, such as: cervical spine flexion, thoracic hyperkinesis, scoliosis, abduction of the shoulders and flexion of the arms 4 .It has been demonstrated that changes in neck posture can lead to changes in the biomechanics of the temporomandibular joint, affecting the function of the stomatognathic system and leading to the development of temporomandibular joint dysfunction (TMD) 5,6 .A recent study showed that the prevalence of TMD in the elderly population with PD is 23.08% reaching women more frequently 7 .
TMD is defined as a set of joint and muscular disorders of multifactorial and dynamic etiology 8 .The main clinical alterations are: headache, neck pain, temporomandibular joint pain, muscle pain, muscle fatigue, limitation of opening of the mouth, opening deviation and joint noises 9 .
Because it is a multifactorial pathology, there are different instruments for its evaluation, organized in anamnestic 10 and clinical 11 and diagnostic criteria 12 .Among the instruments used for assessment of the condition, the Diagnostic Criteria for TMD Research (RDC / TMD) has shown the most verified psychometric properties and accuracy, characterizing itself as one of the most appropriate instruments for the evaluation of TMD 12 .
The progression of motor symptoms in PD, such as deficiency in axial control and mandibular movements, indicates that these individuals are more likely to the development of this dysfunction 2,13,14 .In addition, these functional alterations contribute to generation of pain and poor perception of oral health 14,15 .Despite the importance of the subject, there are not published studies that gather scientific evidence on the subject yet.Therefore the purpose of this review is to gather studies that address the signs and symptoms of temporomandibular joint dysfunction in people with PD and its relation with oral health quality.

METHODS
It is an integrative review of the literature, which allows the search, critical evaluation and synthesis of the available evidence on a delimited theme or guiding question based on evidence, which contributes to the practice in health care.The study was performed according to the following steps: elaboration of guiding question, literature research, data collection, critical analysis of included studies, discussion of the results and presentation of the integrative review 16 .
The guiding question of the present study was: What published scientific evidence addresses the signs and symptoms of temporomandibular joint dysfunction in Parkinson's disease?
A bibliographic survey was carried out in the databases LILACS (Latin American and Caribbean Literature in Health Sciences), PEDro (Database on Evidence in Physiotherapy), MEDLINE / PubMed (US National Library of Medicine), Scopus Cinahl (Cumulative Index toNursing & Allied Health Literature) and Web of Science.For the research of articles were used specific descriptors for each database and keywords (Figure 1).For a better critical analysis of the methodology of the included articles, two instruments were applied that allowed the evaluation of the different study designs: 1-Critical Appraisal Skill Programme (CASP) (adapted) 17,18 e and 2-Agency for Healthcare and Research and Quality (AHRQ) 19,20 .

The inclusion criteria for
The original CASP 17 contemplates eight specific evaluation tools for different study designs such as reviews, cohorts, clinical trials, cross-sectional studies etc.In this review, an instrument adapted from CASP18 was used, which included 10 items to be scored, including: 1) objective; 2) adequacy of the method; 3) presentation of theoretical and methodological procedures; 4) sample selection criteria; 5) sample detailing; 6) relationship between researchers and respondents (randomization / blinding); 7) respect for ethical aspects; 8) accuracy in data analysis; 9) property to discuss results and 10) research contributions and limitations.For item 8, the appropriateness of data analysis, such as intention-to-treat analysis, was considered methodological analysis rigor.At the end, studies were classified in level A (score between 6 and 10 points), being considered as a good methodological quality and reduced bias, or level B (up to 5 points) meaning satisfactory methodological quality, but with risk of considerable bias 18 .
The AHRQ ranks studies at six levels according to the level of evidence: (1) systematic review or meta-analysis; (2) randomized controlled trials; (3) non-randomized clinical trials; (4) cohort and casecontrol studies; (5) systematic review of descriptive and qualitative studies and ( 6) only descriptive or qualitative study 20 .
The search by crossing the descriptors and keywords in the pre-established databases resulted in the identification and selection of four thousand two hundred and ten articles.After initial screening, the duplicated articles were excluded and the remaining articles were submitted to a title review for inclusion and exclusion criteria, seven articles were considered eligible.However, of those initially considered eligible, two published papers did not fit in the criteria established in this review.After the final evaluation only five articles were eligible for qualitative analysis, as shown in Figure 2. means satisfactory methodological quality, but with a considerable risk of bias 18 , this study was taken from the articles that will be discussed.

MEDLINE/PubMed "temporomandibular joint disorders"[MeSH] OR "temporomandibular joint disorders"[All Fields] OR ("temporomandibular"[All Fields] AND "joint"[All Fields] AND "disorder"[All Fields]) OR "temporomandibular disorder"[All Fields])) AND ("parkinson disease"[MeSH Terms] OR ("parkinson"[All Fields] AND "disease"[All Fields]) OR "parkinson disease"[All Fields] OR ("parkinson's"[All Fields] AND "disease"[All Fields]) OR "parkinson's disease"[All
The four studies included a total of 302 people of both sexes, with clinical diagnosis of Parkinson's disease and similar mean age (between 50 and 70 years).Only three of the analyzed articles showed the time of diagnosis (ranging from 2 to 18 years) and the classification of signs and symptoms of disease severity (mild to moderate) according to the Hoenhn & Yahr scale, as shown in Figure 3.
When analyzing the selected publications one of them scored three according to the instrument, CASP 18 .This is a case report 21 24 reached score 8 because it did not explain the selection criteria of the sample neither the ethical aspects of the research.The main information of the articles of this review is presented in Figure 4.
After a full reading and analyzing the methodological quality of the studies involved: (i) Two articles 7,22 reached score nine, because the researchers did not perform randomization/blinding; (Ii) The article of 2012 23  To investigate the prevalence of TMD in people with PD and to analyze the distribution of occlusal contacts.
RDC/TMD -assesses the signs and symptoms of TMD 12 ; T-Scan III Portable Occlusal Analysis System.
-Signs and symptoms of TMD; -occlusal asymmetry -Prevalence of 23.8% TMD signals in patients with PD; -The TMD affects more women; -People with PD showed high frequency of oclusal asymmetry.

Silva et al., 2015 7
To analyze the impact of TMD on oral health in people with PD according to the severity of the disease.

FIM -degree of functional
independence 29 ; RDC/TMD -assesses the signs and symptoms of TMD; OHIP-14 -assesses the impact of oral health 27 .
-Functional independence Degree; -Signs and symptoms of TMD; -Oral health.
-There was a significant difference between the groups with and without TMD domain with respect to psychological disability evaluated by OHIP-14.

Silva et al.,2012 23
Trace the presence of signs and symptoms indicative of TMD in a person with PD.
RDC/TMD -assesses the signs and symptoms of TMD.
-Signs and symptoms of TMD; -TMD, displacing the disk and limiting the amplitude of mouth opening had a negative impact ADL's related stomatognathic system.

Watts et al., 1999 24
To characterize the relationship between bruxism and Parkinson's disease.
Questionnaire structured by the authors.
-Bruxism -DTM -involuntary jaw movements / mouth -People with PD show 4.2 times higher risk (RR = 1.42 ; 95% CI 2.3 = 0.88) of developing bruxism; -25% less risk (RR = 0.75 ; 95% CI = 0.17 Regarding the evaluation by using the AHRQ 20 all the articles obtained six points fot the level of evidence because they are cross-sectional observational studies and case report.Both the description of the methodology used as well as the levels of evidence of the studies, classified by the adapted CASP 18 and AHRQ 20 are represented in Figure 5.

LITERATURE REVIEW
In the present review, four articles were found 7,[22][23][24] , those aimed to investigate the presence of signs and symptoms of temporomandibular dysfunction in people with Parkinson's disease (PD) and its relationship with oral health 7 .
Parafunctional activities can be diurnal or nocturnal (occurring during sleep).The diurnal ones include the clenching of teeth, lip biting, chewing or other objects, digital sucking, improper posture habits, as well as other habits that the individual performs, most of the times, unconsciously.Nocturnal parafunctional habit is very common and is called bruxism.This term consists of a rhythmic attrition of the teeth in non-masticatory movements of the mandible, especially during sleep 25 .
In the study conducted by Watts et al. 24 one hundred people with Parkinson's disease were compared to 100 healthy people, using a questionnaire structured by the authors that evaluated the signs and symptoms of TMD.The results indicated that people with Parkinson's disease present a 4,2 fold greater risk (RR = 1.42, 95% CI = 0.88, 2.3) for developing bruxism, this result corroborates the research carried out by Alencar et al. 26 who observed a correlation between bruxism and reduction in dopamine levels.As well as the group with Parkinson's disease presented a 25% lower risk (RR = 0.75, 95% CI = 0.17 3.26) for having TMD, this data, however, diverged evidences that show that the progression of motor symptoms in PD: cervical spine flexion, thoracic hyperkinesis, scoliosis, abduction of the shoulders and flexion of the arms4, lead to deficiency in axial control and mandibular movements, these characteristics are an indication that these people are more prone to the development of this dysfunction 2,13,14 .
In the case report 23 presented in this review, a woman with PD was diagnosed with TMD because of the dislocation of the disc of the temporomandibular joint and limitation of the opening amplitude.This condition has a clinical importance, since studies have shown that these aspects are one of the main factors involved in the development of TMD.
Silva et al. 7,22,23 used as instrument of assessment for TMD, gold standard; the questionnaire Diagnostic Criteria for Temporomandibular Disorders Research (RDC/TMD) 12 .The study aimed to evaluate the presence of signs and symptoms of this disorder.In the study published in 2015 7 , the authors described that there was no significant association between TMD and the severity of PD, and that the impact of oral health conditions on social aspects was weak.In the studied sample, the most observed characteristic of TMD was joint disc displacement with reduction.In addition, a negative correlation was observed between the severity of PD symptoms and the impact on oral health (r = -0.167,p = 0.207).However, comparing the impact of oral health between the groups with and without TMD, significant differences were observed in the sub-items of the OHIP-14 27 scale: functional limitation", "psychological discomfort", "physical incapacity" and " with TMD.A similar finding could be observed in the case report 23 , in which the authors reported that the clinical picture of the participant had a negative impact on the activities of daily living, especially in functions related to the stomatognathic system.Bakke et al. 14 , stated that the oral functions of individuals with PD are more compromised according to the severity of the motor symptoms, and this could influence the occurrence of TMD in this population, however, no significant associations were found between the impairment motor and TMD diagnosis in a study of 2015 7 .The authors explained this result because the sample was composed of individuals in the PD stage, and propose new studies evaluating other factors such as changes in posture and muscle tone to better evaluate the correlation.
Silva et al. 2015 7 observed in their study the impact of oral problems on the quality of life; and the questionnaire of choice by the researchers was OHIP-14 27,28 .In the study, the authors found no significant correlation between motor impairment and impact on oral health.This result is in disagreement with the data described by Bakke et al. 14 who evaluated the impact of oral health on subjects in the moderate to severe stages of PD.The authors explain this divergence by the fact that their sample is made up of individuals in less advanced stages of PD, are semi-dependent individuals with a good perception of their overall health and have no impact on the performance of daily living activities according to the high score of FIM 29 .
A comparison performed in the same study 7 of the impact of oral health among individuals with and without TMD, higher OHIP-14 scores were found among those with TMD, despite the poor impact indicated by the different sub-scales.The researchers explain this finding by the fact that only two individuals were classified with myofascial pain, which is reported in the literature as the main factor with the greatest negative impact on oral health.The difference was significant in the sub-item Psychological Inability.It has been demonstrated that all diagnoses resulting from RDC / TMD have a significant impact on oral health.
The authors 7 still address the fact that most evaluations and interventions performed in people with PD observe only motor and cognitive aspects which might lead them to ignore symptoms of equal importance to their health and quality of life, influencing the measurement of symptoms DTM and the perception of oral health, since those aspects are based on self-report.
Among the goals of the articles 7,22 is the investigation of the prevalence of temporomandibular dysfunction in people with Parkinson's disease, however both articles were produced by the same research group and therefore the prevalence used will be the highest value, 23.8% for a sample of 42 individuals.Silva et al. (2016)  22 highlighted the relationship between TMD and dental occlusion using the T-Scan III version 8.0 occlusal analysis system to determine the occlusal contact points.They observed that a large part of the total sample exhibited asymmetry in the distribution of contacts occlusal.Such asymmetry occurred in people with and without TMD, and according to the authors, this may have occurred due to the fact that individuals with PD have altered muscle and postural tonus that influence muscle activation and as a consequence of the position of the mandible 22 .Because constant contractions of the facial and neck muscles reflect on the number of occlusal contacts predominantly on the right side 30,31 .However, no significant difference was found in the distribution of right-to-left occlusal contacts in relation to the left between the groups with and without TMD (p = 0.883).
In the literature this correlation has divergent opinions [32][33][34] .In some researches, the authors says that this may be partially due to the different evaluation instruments used.Carbon paper has traditionally been used to determine occlusal contact points, however other studies have shown that this material can lead to false-positive results due to the influence of factors such as salivation and occlusal morphologyl 32 .And that the analysis with the T-Scan system has shown satisfactory reliability, since its readings are more precise and less subject to external interferences, besides the ability to analyze the symmetry on both sides 33,34 .
Previous studies have shown that changes in occlusal contacts may lead to functional disharmony between the masticatory muscles and the temporomandibular joint, resulting in excessive intra-articular pressure, a set of micro and macro traumas and subsequent joint degeneration, characteristic of TMD 35 .
In the scientific literature, there are a number of reasons for the lack of consensus about changes in dental occlusion being an etiological factor for TMD, one of the possible reasons is that the studies use different methods of analysis 36 .In the described study 22 there was no significant association between TMD and occlusal contact asymmetry (p=0.466).Silva et al. 22 explain this finding, by showing that the asymmetry occurs through the mechanism of compensation, in other words, the response of the periodontal ligament leads to a muscular activation to adjust the mandible and this occurs independent of TMD.Even though no significant difference in occlusal asymmetry between individuals with and without TMD was found, it was observed that this condition is more frequent among people with dysfunction 37 .Despite the characteristics present in Parkinson's disease, they raise the hypothesis about a higher presence of TMD in this population.The case report 23 was useful to stimulate new research and to present the importance of knowing new affections with the intention of designing therapeutic strategies claiming the maintenance of quality of life 38 .Two analyzed articles 7,22 , highlighted the scarcity in scientific production that addresses the presence of TMD and its correlation with oral health.In addition, three of the cited articles 7,22,24 presented limitation in the research, because they are a cross-sectional study that only allows the creation of associations and does not allow conclusions on causality.Therefore, new studies that address other factors associated with temporomandibular joint dysfunction, such as pain in the stomatognathic system and articular noise, should be performed.In addition longitudinal studies that determine the cause effect relationships of the analyzed variables.

CONCLUSION
The analyzed articles in this literature review indicated the main signs and symptoms of TMD in people with PD: myofascial pain, bruxism, limitation of the opening of the mouth, displacement of the articular disc with reduction and asymmetry in the distribution of occlusal contacts.
Regarding the impact on oral health, the studies shown a negative correlation between the moderate and severe stages of the disease and that psychological impairment influences on the activities of daily life of those people.
Such information may help guiding future studies that aims to investigate other factors associated with temporomandibular joint dysfunction, since there is not enough data regarding this topic.Consequently, it would be possible to provide valuable information for the application of therapeutic and prevention strategies for this population.
obtaining and selecting articles by means of searches performed between June and June 2017 were: (1) Articles that addressed the signs and symptoms of temporomandibular dysfunction in people with Parkinson's disease; (2) No restriction of language and year of publication; (3) Complete articles published in periodicals.The following were excluded: (1) Repeated studies in databases; (2) Monographs; (3) Review articles; (4) Publications not available in full or whose results have not yet been published.

Figure 1 .
Figure 1.Search strategy used for MEDLINE/Pubmed, PEDro, LILACS, Scopus, Cinahl, and Web of Science

Figure 2 .
Figure 2. Diagram of articles selection process
is a case report, it score seven points, because some of the aspects evaluated by the instrument were not suitable for the type of study, such as: to present General characteristics of the articles included in the review PD: Parkinson's disease; CG: Control Group; HY: Hoehn & Yahr Parkinson disease escalation scale; Gender: ♂= male and ♀= female; NR: Not reported.Figure 3.
Critical Appraisal Skill Programme 17 ; AHRQ: Agency for Healthcare and Research and Quality 20 CASP: