Muscle type temporomandibular disorders and orthodontics

With painful temporomandibular disorders, the physiotherapist treatment makes it possible to treat the pains and dysfunctions of the masticatory apparatus. When these are diagnosed before orthodontic treatment, it is necessary to treat them so that they do not interfere with the dentofacial orthopaedics treatment. In this perspective, lingual rehabilitation according to the method «Fournier» is associated with Schultz Autogenic Training.


INTRODUCTION
Article available at https://www.jdao-journal.org or https://doi.org/10.1051/odfen/2018062 TMD are multifactorial and complex pathologies. They can cause disorders characterized by pain and impaired manibular mobility. Depending on the evolution of etiological concepts, the management of TMDs has fluctuated.
In 1934, the first clinical signs were described 4 . During the golden age of the articulators and up to the 1980s, occlusion was perceived as the primary etiology of TMDs. The recommended treatment was to restore a "perfect" occlusion. This view continues to this day in the minds of some practitioners and patients, thus complicating therapeutic management. However, despite restoring their occlusal balance, some patients still experienced pain, mandibular functional discomfort, and/or decreased chewing strength. Since then, the concept of "occlusal whole" gave way to "neuromuscular theory 27,24 . " Thus, there was doubt over exclusively occlusal etiology and the introduction of the notion of muscular disharmony and stress in the onset of pain; the muscles that hold the mandibular position that is supposed to be "at rest" are overstretched. In 1992, psychosocial factors were incorporated into research diagnostic criteria for TMD (RDC/TMD).
Today, it is recognized that multifactorial etiopathy of TMD can combine occlusal, parafunction, postural imbalances, orofacial dyspraxia, and stress. Faced with this etiological heterogeneity, treatment cannot therefore be only local and mechanical, but must also be overall and behavioral. Treatment will aim to establish a balance by acquiring new masticatory and swallowing behavior consistent nasal breathing, realignment of spinal curvatures, stress management, and elimination of harmful habits.
The clinic highlights one common point for all patients with this pathology-i.e., a dysfunctional tongue and at least one parafunction such as centered, eccentric bruxism; sucking or biting of the lips, cheeks, tongue, fingers, objects; onychophagy; significant gum chewing; and nonphysiological mandibular movements. A uncoordinated tongue does not always lead to TMD, but they often go hand in hand with a tongue in a bad position.
The temporomandibular joint (TMJ) has the capacity of being highly adaptable. Patients with oromotor dyspraxia will not develop symptoms as long as balance is compensated by the physiological adaptation of the body. The precarious balance is threatened when the capacity for accommodation is exceeded. It can then be an expression of a malfunction of the masticatory apparatus. It should be noted that not all dyspraxic tongues need to be reeducated, but it should be done in a patient with TMD. A tongue that is not on the palate can create imbalances in the mouth, which can worsen existing negative bad habits and tics. They reflect a certain state of stress and deep tensions. 3 MuSCLE TYPE TEMPOROMANDIBuLAR DISORDERS AND ORTHODONTICS Therapeutic management of TMD will combine lingual training with Schultz's autogenic training. The former makes it possible to achieve a biomechanical balance of oral function, and the latter is used to stop parafunctions.

Diagnostic categories
The diagnostic criterias for TMD (DC/ TMD) were redefined in 2014. These entities, some of which may be combined, include 8 : -Masticator myalgia (three subgroups: local myalgia, diffuse myofascial pain, and myofascial pain with referal); -TMJ arthralgia; -TMJ disc displacement (with reduction, with reduction with intermittent locking, without reduction with limited opening, without reduction without limited opening); -TMJ degenerative disease; subluxation; secondary headaches attributed to TMD.
Regardless of diagnosis, the most common reason for consultation is pain, dysfunction (limiting mouth opening, difficulty chewing), and, incidentally, joint noises.
Based on the prevalence of TMD 21 , we can note that muscle pain is the most common diagnostic feature (45.3% of the population represented), with other causes being disc luxations (36.2%), arthralgia/arthritis/arthrosis (18.4%), and asssociated symptoms (Table I). Fifty years ago, a new area of expertise was developed in physiotherapy: maxillofacial functional rehabilitation, which was more commonly attributed to speech therapists. Two physiotherapists were interested in the question. The same subject, the masticatory apparatus, but two different approaches and two different schools. The first 19 aims at treating the consequence, above all by restoring correct mandibular kinetics. This work is based on the reprogramming of mandibular movements. The second school 9 , on the other hand, focuses its treatment on correcting the cause before treating the consequences. Thus, lingual training was born. This oromyofunctional education helps to establish a myofunctional balance and abolish harmful habits. Before starting lingual training, it is possible to offer the patient initial counseling and muscular relaxation exercises.
In all of the exercises recommended below, it is essential to adhere to the painless and fatigability rule. No exercise is beneficial if it causes the slightest pain or discomfort, at the risk of provoking a nociceptive reaction that can result in reflex contracture. The patient must learn how to do the exercises for themselves, in order to control the intensity of their actions, and have a faster amelioration of their pain. The patient will be able to use these techniques as often as possible.

Thermotherapy
This is the first method to offer the patient in a lot of pain.
INDICATION: muscle pain and contractures (people with arthralgic pain are more tolerant of cryotherapy) TECHNICAL: local application of heat to painful masseters DuRATION: approximately 20 min; several times a day when necessary PRINCIPLES: use of self-heating compresses or small packs of gels to be heated at proper temperature Endobuccal massage ( Fig. 1) In most cases, the pain is of muscular origin and primarily involves deep masseters.
There are many physiological benefits of massage: -On the vascular system, by allowing local hyperemia by vasodilation of the superficial blood vessels, which results in redness and warmth of the skin on the massaged site. This phenomenon allows an increase in blood flow, thus increasing the supply of oxygen and nutrients, with the consequent acceleration of the elimination of toxins.

EXERCISES TO BE PROPOSED AS FIRST INTENTION IN CASE OF MUSCLE PAIN
-On the lymphatic and immune system, by stimulating it. Indeed, lymph and lymphatic organs contribute to the protection of the body by filtering pathogens, abnormal cells, and foreign particles. These will then be released into the bloodstream. -On the autonomic nervous system, by activating the the parasympathetic nervous system, with the subsequent decrease in heart rate, respiratory rate, improvement in digestive function, and increased muscle relaxation. In conjunction with this, there will be a decrease in the secretion of stress hormones (cortisol and adrenaline). Massage affects the secretion of endorphins in the brain. These hormones have an analgesic effect and provide a state of well-being. -On the muscular system, by the analgesic action of massage; this is often recognized by patients but rarely yet proven in scientific and clinical studies.
The "Gate control" theory 16 has been mentioned many times. It states that massage would trigger stimuli through low-threshold, fast-conduction myelinated fibers. This results in presynaptic inhibition. The presynaptic gate closes, preventing the target cell from being reached and transmitting the painful message to the cortex.
This theory has been widely criticized 22 and the initial model has been modified, involving not one but two families of interneurons: one inhibiting and the other activating transmission neurons (T neurons) 28 .
INDICATION: muscle pain and contractures TECHNICAL: The impact and analgesic effect are much greater when massaged is delivered tranversely through exobuccal and endobuccal routes. This involves placing the thumb (inside oral mucosa) and the index finger (outside of the cheek) on both sides of the masseter and sliding the fingers toward the labial commissure.
DuRATION: approximately 5 min; to be repeated several times per day PRINCIPLES: This maneuver, like all physiotherapy exercises, it must be painless. Massage is the most effective when it can be repeated several times a day. That is why we should teach it to our patients. First, so that they can control their painful areas. Indeed, the physiotherapist can sometimes massage too hard and provoke a nociceptive reaction; the painful muscle will contract even more reflexively.
Second, the patient will be autonomous and able to use self-massage when they need it. This will help the masseters relax more quickly and efficiently.
The "contracture release" The massage of the pterygoid muscles is frightfully excruciating and we are never certain we are truly on the muscle. The "contracture release" technique is more effective in relaxing them.
The contracture release technique is based on Sherrington's reciprocal inhibition principle 26 , which allows two motor responses. The first states that excitation of a motor neuron of a muscle (agonist) results in inhibition of the motor neuron of the antagonistic muscle (via an inhibitory interneuron located in the gray matter of the spinal cord, therefore, in the central nervous system). That is, it is not the antagonist muscle that is inhibited but its motor neuron (a muscle is either silent or excited but never inhibited). Secondly, this isometric muscle contraction will facilitate the activity of its agonists. Contracture release also optimizes immediate muscle relaxation after intense contraction. Indeed, we are witnessing a change in the viscous muscle stiffness after imposing a prior contraction effort 12 .
INDICATION: Muscle contractures, trismus resulting in amplitude limitations of mandibular kinematics. This exercise is contraindicated for joint pain.
TECHNICAL: There are five types of movement: oral closure, oral opening, mandibular propulsion, right and left side lateral movements.    PRINCIPLES: This is a purely isometric movement, without displacement against significant resistance. All movements must be made exclusively without occlusal contact. The goal is the release of muscle tension and joint stiffness. This exercise is mostly effective on trismus and oral opening limitations.
If the pain is too severe, it is then more appropriate to suspend this exercise for a while, and use heat application and massage instead. At the point when the patient is less painful, the contracture release can be repeated for 1 second and in a very small range of oral opening. Progression will be achieved by increasing the contraction time and the amplitude of oral opening.
This therapy consists of fixing incorrect linguistic postures and praxis according to tryptic 3 : at rest, swallowing, and phonation. At the same time, it is necessary to achieve a balance between the agonist and antagonist muscles and nasal ventilation during wakefulness, sleep, rest, and exertion. Posture disorders are managed while parafunctions can be eliminated through the practice of Schultz relaxation.
Interest TMD can be perpetuated by lingual malposition and the presence of bad habits and tics. It is essential to correct the poor lingual posture, to restore the functions that integrate a tongue into the palate and, above all, to intervene on the behavioral factors through "stress management. " The Fournier method incorporates the fact that the patient must acquire the tools that will enable them to manage their deep tensions. The patient must be able to identify them on their own before they become permanent and thus avoid chronic transformation of the pain. This is the only way to achieve sustainable results.

LINGUISTIC TRAINING ACCORDING TO THE METHOD PROVIDED
The patient is the main actor in their treatment. With this in mind, all exercises must be learned and practiced daily, until the pain is gone and the correct motor pattern is acquired at the orofacial sphere. As long as the ingrained corrections are not obtained, it is necessary to continue with the same sessions.
The uniqueness and difficulty of this method lies in the fact that the physiotherapist is essentially there to teach exercises and to support the patient in their care process. The patient needs to understand that if they want to get better and feel good over time, they need to change their behavior patterns and accept the "letting go" of their parafunctions.

Reminders (Chateau's Tryptic)
Lingual posture at rest (Fig. 7) The apex, the tip of the tongue, is in contact with the retroincisive papillae on the palate. "Contact" implies touching, even facing, but especially not in force. The edges of the tongue have no indentations and are at the level of alveolar processes. The tongue should have a dome form.

Swallowing
Normal swallowing is accomplished by the apex pressing hard on the retroincisive papillae, unlike the resting position where the tongue barely touches, with interdental contact and without any involvement of the labiojugal muscle band, starting at 3 years.

Phonation
In normal phonation, LNDT palatals should be apex on retroincisive papillae. When the patient suffers from oromotor dyspraxia, palatal sounds can become dental sounds. As their name indicates, the tongue will then project onto the teeth.

Linguistic rehabilitation
The first-line exercises described above can provide quick relief, but are often insufficient to permanently resolve TMD. Therefore, it is advisable to explain to the patient that a lingual dyspraxia appears to be a maintenance factor for TMD. When symptoms persist, tongue movement training should be provided. This will only be effective if it is accompanied by Schultz's relaxation.
It should be noted that scientific evidence of the effectiveness of different physical therapies is weak, limited, and has little long-term impact 17 . On the other hand, they seem to bring genuine relief in the short term. To who should the patient be referred to?
In order to be able to intervene on TMD on a long-term basis, it is preferable to refer the patient to a therapist capable of managing lingual dyspraxia while working on the behavioral aspect. It should be noted that not all physiotherapists trained in the Fournier method are trained in Schultz relaxation. If this is not the case, patients may be referred to a sophrologist or hypnotherapist in addition to tongue training.

The "lingual trilogy"
The concept of stress in TMD is no longer discussed 25,14 . This has made it possible to take a psychophysiological approach to TMD and no longer just mechanical and occlusal.
A model 18 is representative of what we tell our patients. Orthlieb evokes a triad: Predisposing factors/Triggering factors/Maintenance factors. According to this author, in taking a medical history we find: -Predisposing factors (maximum interscuspal position disorder, postural abnormalities, tension, stress, depression, parafunctions, which would deccrease the resistance threshold of the mandibular system); -Triggering factors (alteration of occlusal relationships following implant installation, wisdom tooth extraction, uncompensated tooth extraction, long-term dental care, poorly balanced bridge, orthodontic treatment or masticatory apparatus trauma, and psychological shock that can lead to increased stress); -Maintenance factors (lingual dyspraxia, tension, stress).
In view of this, it would be inconceivable not to deal with the deep tension and stress, which are not only predisposing factors but also triggering factors and especially all factors that contribute to the maintenance these disorders.

Behavioral approach
Generally, patients expect "classic" training combining massages, mandibular mobility exercises, etc. They often have great difficulty perceiving the relationship between the behavioral aspect and the onset of their symptoms. To change the behavioral character, and thus to act on the stress and tension factors, it is preferable to minimize the occlusal aspect and introduce the notion of "demystification of the disease" 6 .
The link between TMD and occlusion has not been proven. An imperfect occlusion does not automatically result in TMD, despite the presence of triggering factors. Because the adaptative capacity of the masticatory apparatus

MANAGING TENSIONS IN TMDs
is not the same in all individuals and differs according to the periods of life 10 , some patients will develop TMD at some point in their lives, and others will not. Likewise, there may be perfect occlusions with TMD. However, there is no doubt that those who combine lingual dyspraxia, fluctuating psychological state, tension, and stress will be more likely to develop TMD at some point than others.

Bad habits and tics
Bad habits are acts that a subject undertakes on their body, whose deep origin is instinctive; but this aspect is masked by a character of irresistibility and insatiability 1 . Tics are unconscious acts represented by repetitive movements from time to time, beyond the control of the will. This could be likened to a reaction that persists even after the original excitement that gave rise to it has disappeared, such as the remaining linguistic impulse (called the "tongue stage"), that may be caused by an overly peremptory or too early stoppage of the thumb sucking. It seems that the tic is accomplished by itself, apart from the participation of the conscience, often even against the patient's will.
Despite their different origins and characteristic mode of expression, one thing that combines the bad habits and tics, the tense state they convey, the pleasure, and the relaxation they provide when they are performed. The study of cognitive and affective neurosciences provides a better understanding of the origin of parafunctions and the difficulty stopping them 15 . Indeed, these archaic tics appear to be the responsibility of the reptilian brain, which is responsible for basic needs (thirst, hunger, sleep, sexual impulses), defensive reflexes (flight, aggression) and not the neocortex, the seat of cognition. Asking a patient to stop licking or biting their lips is very difficult. The tic surpressed by an external constraint can cause anxiety, as can the repressed bad habit.

Changing behavior
Several authors 9,17 refer to the "self-management" of dysfunction. Breaking the vicious circle of pain and contracture cannot be done without eliminating parafunctions, easing muscle tension, decompressing the joint, and relieving pain. Patients must act according to their symptoms 13 . Pain and dysfunction must no longer be suffereed, but accepted and dealt with. Chronic pain and psychosocial stress are intimately related 17 . Psychological difficulties would act as a "catalyst" for TMD 10 . The masticatory apparatus would be a preferred area for somatization of psychological disorders.
Strictly reeducating TMD mechanically is not enough and does not protect against the risk of reoccurence. A more psychological approach to TMD is essential, in the sense that the patient must learn to let go if they wants to deal with their stress and tensions, and therefore their dysfunction.
In summary, effective long-term maxillofacial training involves technical exercises for the mechanical aspects, but above all, stress management. In order to manage these patients, often described as "difficult, " it is necessary to be able to hear their pain, their suffering, to lead them to change their way of doing things, and perhaps in some way, to change their way of being.
It is the most effective technique for dealing with deep tensions. It is a method of relaxation, which involves putting oneself in a modified state of consciousness, close to deep sleep. The patient must acquire the skill in order to practice this alone. This autonomy is essential in order to obtain deep relaxation and thus a therapeutic effect. The patient will develop a genuine "conditioning" that will allow them to relax their tensions when and where they want. Schultz's relaxation acts on neurovegetative hyperactivity, and therefore on stress, tension, and fatigue.
In TMD management, it is essential to make the patient be aware of the need to change their behavior pattern. Their mouth pain and discomfort is not just a reductive or nonreductive disc luxation, or an occlusal balance that has been altered. They are mainly caused or perpetuated by lingual dyspraxia and by the presence of bad habits and tics that will have to be corrected.
Combining TMD treatment with relaxation is the first therapeutic approach to avoid the risk of reappearance of pain and dysfunction.
Only this combination gives the patient the means to manage their deep tension.