Therapeutic exercises for the control of temporomandibular disorders

Contact address: Monique Lalue Sanches Rua Pereira da Nóbrega, 324 – Apto 43 – São Paulo/SP – Brazil CEP: 01.549-020 – E-mail: moniquelsanches@uol.com.br 1 Specialist in TMD and Orofacial pain, UNIFESP. 2 PhD in Anatomy and Associate Professor at the Morphology and Genetics Department, UNIFESP. 3 PhD in Morphology, UNIFESP. Introduction: Temporomandibular disorder (TMD) is a multifactorial disease. For this reason, it is difficult to obtain an accurate and correct diagnosis. In this context, conservative treatments, including therapeutic exercises classified as stretching, relaxation, coordination, strengthening and endurance, are oftentimes prescribed. Objective: Thus, the aim of the present article was to conduct a literature review concerning the types of exercises available and the efficacy for the treatment of muscular TMD. Methods: The review included researches carried out between 2000 and 2010, indexed on Web of Science, PubMed, LILACS and BBO. Moreover, the following keywords were used: Exercise, physical therapy, facial pain, myofascial pain syndrome, and temporomandibular joint dysfunction syndrome. Studies that did not consider the subject “TMD and exercises”, used post-surgery exercises and did not use validated criteria for the diagnosis of TMD (RDC/TMD) were not included. Results: The results comprised seven articles which proved therapeutic exercises to be effective for the treatment of muscular TMD. However, these studies are seen as limited, since therapeutic exercises were not applied alone, but in association with other conservative procedures. In addition, they present some drawbacks such as: Small samples, lack of control group and no detailed exercise description which should have included intensity, repetition, frequency and duration. Conclusion: Although therapeutic exercises are considered effective in the management of muscular TMD, the development of randomized clinical trials is necessary, since many existing studies are still based on the clinical experience of professionals.


INTRODUCTION
Temporomandibular disorder (TMD) is a collective term that covers a broad spectrum of clinical problems of the temporomandibular joint (TMJ), masticatory muscles and associated structures.It is mainly characterized by pain, joint sounds and irregular or limited mandibular function. 1,2It is most prevalent in females aged between 20 and 45 years old 3 and it is subdivided by the American Academy of Orofacial Pain (AAOP) into muscular TMD and articular TMD; with the muscular type being much more prevalent, although it is possible for both to occur concomitantly. 1 TMD classification is based on different forms and methods.The classification developed by Dworkin et al, named as Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD) 4 is one of the most used.
TMD has no specific etiological factor, however risk factors that affect the dynamic balance of the masticatory system have been identified.These risk factors are divided into traumatic, anatomical, physiopathological and psychosocial. 1,3For this reason, and for having a benign course, 5 it often becomes difficult to obtain definite, accurate and correct diagnosis.][8][9][10] Treatment includes heat or cold therapy, cognitive-behavioral therapy, use of intraoral appliances and different types of physical exercises.However, current evidence of the effectiveness of physical exercises is poor due to a limited number of appropriate randomized clinical trials. 11.6,7,9,10,12,13,14 Exercise is the first treatment choice for patients with muscular TMD, since it presents low cost and good effectiveness, 9,15 in addition to having the same prognosis of treatment performed with oral stabilization appliances. 12,14n order to analyze the effectiveness as well as the different types of exercises available for the treatment of muscular TMD, a literature review was carried out.The review included researches conducted between 2000 and 2010, indexed on Web of Science, PubMed, LILACS and BBO.Additionally, the following keywords were used: Exercise, physical therapy, facial pain, myofascial pain syndrome, and temporomandibular joint dysfunction syndrome.In selecting the sample, the following inclusion criteria were applied: Articles addressing not only diagnosis of muscular TMD by means of validated criteria (RDC/TMD), but also the use of therapeutic exercises for its treatment.Studies that did not consider the subject "exercises and TMD", used postsurgery exercises and were in a language other than Portuguese or English were excluded.Based on this information, the goal of this study was to present, through a review, the modalities of exercises available for the treatment of muscular TMD.The effectiveness of such exercises was assessed as well.
Therapeutic exercises are intended to perform muscle contractions and body movements in order to improve the overall function of individuals.Additionally, they aim at helping patients to find out the real necessity of exercises in their daily routine.This includes exercise positive and progressive performance as well as adjustment in terms of the type and amount of appropriate forces applied to the body system, aiming at treating the deficiency by improving musculoskeletal function and maintaining well-being. 9[18][19][20]

TYPES OF EXERCISES Stretching and relaxation
This type of exercise aims to decrease tension of the muscle fibers. 10It can be performed passively, when there is help for achieving the desired movement, or in an active way, when the movement is performed without any assistance. 18These exercises are recommended when motion range is limited and pain is present. 1,18,19,21The elevator jaw muscles are stretched when the jaw moves downwards (opening the mouth). 8,9This is considered an isotonic exercise because it presents dynamic muscle work, with rhythmic alternation between contraction and relaxation. 22uscles can also be stretched by means of the reciprocal inhibition technique in which opposing mus-Therapeutic exercises for the control of temporomandibular disorders original article cles are contracted isometrically (counter-resistance force), actively assisting the movement of stretching and consequent relaxation of the muscle. 12,23he contraction-relaxation technique, also used to stretch shortened muscle fibers, is the contraction of a strained muscle followed by its relaxation, which allows passive stretching of this muscle. 16,23ne of the exercises frequently used to promote relaxation and stretching of the elevator jaw muscles involves opening and closing the mouth slowly, with the apex of the tongue positioned on the lingual surface of the maxillary incisors (pronunciation of the letter "N"). 10Pronouncing the letter "N" several times a day and keeping the tongue in this position, with lips closed, also promotes muscular relaxation. 9,19his technique must be performed several times a day in order to assure its effectiveness. 10

Coordination exercises
Elevation and depression movements of the jaw are performed bilaterally, symmetrically and with equal intensity.When this does not occur, it results in movement incoordination.Many times, besides causing limited range of motion and pain, TMD also causes incoordination of jaw movements, thus causing joint sounds. 21he therapy that promotes coordination of the muscles involved in the movements cited above includes exercises of opening and closing the mouth slowly in front of a mirror with a straight vertical line drawn, with the patient trying to keep the midline of the lower dental arch parallel to the mirror during the execution of movements. 8,17,24This same exercise is also performed by placing right and left index fingers in the lateral pole region of the mandibular condyle, with the purpose of assisting movement coordination. 3,9Twenty repetitions of this exercise, three times a day, are recommended.
Another way to promote coordination of masticatory muscles is to exercise a resisted isometric contraction of low intensity in the opposite direction of the movement performed. 25

Strengthening and endurance exercises
Muscular strength is mainly achieved by isometric exercises, although it can also be obtained by isotonic (concentric and eccentric) 24 and isokinetic 22 exercises.Isometric exercises promote muscular contraction without the occurrence of adjacent joint movement, thus, it is considered a static muscle exercise. 22sometric exercises for the masticatory muscles are performed by applying a counter-resistant force to the movement being performed. 16Forcefully placing the chin on a closed hand during depression jaw movement (mouth opening), and hindering its elevation (closing) by pressing the inferior incisors with the index and middle fingers are considered muscular strengthening exercises that depress and elevate the jaw, respectively.In lateral jaw movements, the counter-resistance force is applied by means of pressing the lateral area of the mandibular body with the index and middle fingers, exerting a force opposite to the movement performed.These exercises should be repeated several times a day.An excessive counter-resistance force should not be applied, in which case reciprocal inhibition would occur, 25 causing loss of exercise function; that is, it would cease to be an exercise for strengthening and become an exercise for relaxation.

RESULTS
Results are shown in Table 1.

DISCUSSION
The model of chronic pain used to give insight into the etiology, maintenance, and management of TMD comprises a mixture of biological factors embedded in a matrix of psychological and psychosocial factors that produce a sensation of pain which is unique and specific to each individual.Therefore, no isolated factor contributes to the understanding of how clinicians decide on treatment options or how patients respond to long-term treatment, 7 which results in a variety of studies with very different outcomes. 10,13,18,19Individuals who report pain and functional limitation, oral parafunctional habits, pain in other regions of the body and disease summarization present TMD of greater severity and longer duration. 26rescription of exercises as the treatment of choice requires not only knowledge of the anatomy of the muscles with regard to their shape, type, function and location (fixed attachment and mobile attachment), original article Moraes AR, sanches ML, Ribeiro EC, Guimarães As motion. 1,18,19,21Coordination exercises improve joint muscle function, mobility and biomechanics, reestablishing synchronism of jaw movements.Such exercises comprise mouth-opening and mouth-closing isotonic exercises. 8,17,24On the other hand, strengthening and endurance exercises hinder relapse of TMD and are performed through isometric exercises along with the application of a light counter-resistant force.
but also knowledge of the biomechanics of the affected joint.With that in mind, it is possible to develop and prescribe an unlimited number of exercises.
Exercises for stretching and relaxation are prescribed as a first-choice therapy when painful symptomatology is present.Basically, they are aimed to decrease pain by means of increasing local circulation.They also work to improve flexibility and range of It should be noted that therapeutic exercises have been classiied into diferent types for didactic purposes, only.Additionally, exercises are designed for groups of muscles, not for single muscles or isolated situations.For example, the contraction of a muscle group automatically causes its antagonists to stretch and vice versa.
Patient's awareness is also of great importance to achieve treatment success.Training the patient on how to do the exercises and checking if they have been performed correctly are measures that should be taken in order to reduce patient's errors and increase the likelihood of managing the TMD. 9 Patients with breathing problems frequently report depression, fatigue and sleep disorders.As a consequence, they present alterations in pain sensitivity. 15Primary and accessory respiratory muscles usually contribute to craniofacial pain and associated symptoms in the cervical region.Therefore, they influence head posture. 27ome authors have considered body posture to be important in the diagnosis and prognosis of TMD, 19,24 since postural exercises are also recommended to restore or optimize alignment of the craniomandibular system. 18esearches addressing the use of exercises to manage muscular DTM present some limitations which must be highlighted.Terms such as manual therapy, mobilization, manipulation and therapeutic exercises are too generic and may involve diferent forms of movement.Therefore, a detailed description of the techniques used is very important not only to allow study reproducibility, but also to conirm its results. 18,28ch description should include frequency, number of repetitions, intensity of performance, treatment period and manner of conducting the exercises.Moreover, the prescribed exercises are usually performed in conjunction with other therapies, making it difficult to verify the real effectiveness of the proposed exercise.Additionally, most studies do not have a control group, which leads one to question whether the exercise was really effective or if there was clinical relapse due to the natural course of the disease. 8Furthermore, several studies present a major flaw in terms of defining which subgroup of TMD was treated, thus, raising doubts about the effectiveness of the treatment prescribed. 17Likewise, the limited number of samples studied is not enough to yield significant conclusions regarding the recommended treatment, besides being usually based on empirical findings. 3However, since the majority of the exercise techniques used is based on clinical experience, one of the major limitations is the lack of randomized clinical trials based on standardized research criteria. 29he results of the present study demonstrate that the success of therapies that recommend the use of exercises in the treatment of muscular TMD is directly related to a correct diagnosis.
Additionally, although therapeutic exercises present a promising future in the control of TMD, further randomized studies should be carried out in order to provide more knowledge on how to prescribe such exercises (duration, frequency, etc.) and to access their actual eicacy in the diferent subtypes of TMD.

Table 1 -
Studies concerning the achievement of therapeutic exercise in the treatment of muscular TMD classified by diagnostic criteria of RDC/TMD, combined with other therapeutic techniques or alone.* It was assessed the effectiveness regarding the decrease of pain and increase of mandibular movement amplitude.trial assessing the eicacy of adding 6x6 exercises to selfcare for the treatment of masticatory myofascial pain 45 G1 -counseling, relaxation and stretching G2 -G1 + 6X6 exercise from Rocabado Results: Similar and efective G1 = G2 Therapeutic exercises for the control of temporomandibular disorders original article