Reported concepts for the treatment modalities and pain management of temporomandibular disorders

The most important stage of a treatment protocol is education with cognitive awareness training and relaxation therapy as well as self-observation that should be completed by patients with masseter hypertrophy, tension-type headaches or bruxomania (the grinding of teeth occurring as a neurotic habit during the waking state). It is important to explain to the patient the background of the disorders (especially the role of one’s emotional stress) and warn about habitual parafunctional activities (e.g., nonfunctional tooth contacts or oral mucosa biting). The patient should be aware of what he or she does with their teeth, and when they fall into bad habits, try to eliminate that habit [28].

Muscular training is the primary mode to achieve muscle restoration, especially after traumas and injuries. It is thought to be the most conservative treatment as well as the simplest and most non-invasive method of TMD treatment. In patients with severely expressed asymmetries and symptoms, exercises to restore the muscular equilibrium seem to be the only proper route of treatment [3, 29]. Muscular therapy must be restrictive; it should be carried out moderately, and the intensity should be increased with time to avoid aches and patient discouragement from the suggested treatment. In this situation, muscular therapy is effective in 70 % of suffering patients. In some cases, such as patients with muscular or joint (muscular or arthritis pain) pain, the mouth opening is limited, and therefore, therapy is less effective [3, 27]. The exercises can require stretching, relaxation and isometric movements that should be performed routinely to eventually lead to a shortening of the excessively expanded muscles or to a restoration of the full length of the shortened muscles. Additionally, the natural tension and symmetric jaw movement can be restored [3].

The training is underdone to correct the mobility of the mandible. To strengthen the muscles and to acquire balance between the left and right sides, opening the mouth along a straight line in front of the mirror is recommended. The resistance is acquired from the gentle pressure of the patient’s fingers to the mandible. The exercises are repeated in sets of 15 to 20 repetitions, 2 to 3 times a day. The improvement should be observed after 6 weeks [3].

Research from Bae and Park [30] showed that active and relaxation exercises could improve the limited range of motion, deviation and pain in masticatory muscles. For muscle relaxation, they recommend putting the front one-third of the tongue on the anterior part of palate and applying a light force to the tip of the tongue so it does not touch the teeth, having the patient maintain this position as long as he/she can withstand (3 times over a period of 4 weeks, 10 min each time).

In case of too wide of a mouth opening, or excessive mobility of the jaw and mandible deviation during opening (with excluded suspicion of subluxation), the exercises are limited, and straightening of the opening pathway are recommended. The exercise involves opening the mouth with the tip of the tongue touching the palate (usually near the A-H line) in front of a mirror, along the straight line. It is recommended to maintain the contraction of the tongue muscles for two seconds during mouth opening. The exercises should be repeated 2 to 3 times a day, 15 to 20 repetitions each [3].

To achieve the proper relation of the jaw, centric relation (CR) should be restored. It is easily performed by occlusal splints. An occlusal appliance is any removable artificial occlusal surface used for diagnosis or therapy affecting the relationship of the mandible to the maxillae. Occlusal appliances may be used for occlusal stabilization, for the treatment of temporomandibular disorders, or for the prevention of dentition wear [31]. Occlusal splints are used in a vast majority of patients with TMDs to restore the static and dynamic symmetry of the stomatognathic system. Most commonly, they are used in cases with disc displacement [3, 32, 33]. The splints are fabricated individually by an experienced team consisting of a dentist and technician.

One of the most popular occlusal splints is the Michigan-type bite splint, precisely described by Ramfjord and Ash Jr [34]. This splint could be used in both dental arches, but preferably in the maxilla. The mandibular splint is used when the posterior area is missing teeth in the mandible and unwanted tooth movement must be avoided. The main purpose of this device is to disengage the occlusion, place the condyle in the centric position, relax the masticatory muscles and prevent further tooth wear due to nocturnal parafunctional activity. The main features of this splint are freedom in centric and canine guidance.

It is important to note that the relation of the maxillary and mandibular arches may differ after the treatment when compared to the initial state, especially when partial coverage splints are used [32, 35]. After the replacement of the mandible, the condyles are replaced, and consequently, the mandible is positioned properly and the pain is reduced [32].

Walczynska-Dragon and Baron [10] have proven that occlusal splint therapy using the SVED (Sagittal Vertical Extrusion Device) appliance decreases not only aches in the head and all parts of the spine but also disc displacements within 3 weeks of treatment. The next decrease in frequency of unwanted, unfavorable symptoms was observed after 3 months of treatment with splints. When properly performed, these splints also unblock a limited mouth opening.

Research performed by Lee et al. [36] in a group of 59 patients with somatic TMJ dysfunction showed that intraoral appliance could improve cervical spine alignment and alleviate symptom severity.

The occlusal splints are also used in the initial phase of treatment in patients with mouth overclosure caused by a pathologic deep bite. Before the prosthetic rehabilitation of the severe tooth wear, one should remember that initially, splint therapy should be applied to adapt the stomatognathic system to the new occlusion [37]. A classification of the occlusal appliances with activities and recommendations is presented in Table 2.

Beside occlusal splint therapy subsequently selective grinding of the teeth to restore physiological and/ or proper and /or balanced occlusal support is required in some cases [27].

Myofascial pain is a common symptom of TMD – it is often associated with the clenching of teeth, grinding and stress. TMD myofascial pain occurs in 31 to 76 % of the population [38‐41]; it can be relieved by massage therapy, which leads to re-establishing the proper flexibility and muscular length and relieves pain. The massage therapy for TMD might be divided into effleurage, kneading, friction, stretching and petrissage, leading to the permanent adaptation of the muscles. The types of massage and their influence to the surrounding tissues are presented in Table 3 [26, 42]. Massage reduces tissue swelling as well as pain in TMD patients [21, 41, 43]. The pressure used during massage must not be too intense and should increase over time at each therapeutic session because therapy performed too strongly may lead to increased muscular tonus [44]. Massages should be performed twice a week, with a minimum of 30 min for each session. It takes at least 8 therapeutic sessions to receive true relief [23]. In addition to the local influence, massage leads to the relaxation of the entire body and reduces stress, thus improving the patient’s mood [45, 46]; it reduces tension headaches and muscle aches, restores equilibrium between the masseter tension, and improves mastication [26]. The physiotherapist may also recommend heating or cooling of the affected muscles [28].

To restore the accurate function of the TMJ, changes in daily habits is important. The change of food consistency (eating softer foods), applying cold or heat, and avoiding extreme movements of the mandible (chewing gum, wide yawning or loud singing) might be enough to decrease TMD symptoms [47]. In this situation, counselling, behavioral therapy and stress management should also be applied to decrease muscle hypertension and bad habits [25].

Manual therapy is similar to massage therapy, but the procedure performed by the physiotherapist is different; it refers to stimulation of the so-called “trigger points”. There are two main methods of treatment by applying manual therapy: mobilization and the muscle energy technique.

The mobilization technique is most commonly used in disc displacements; it involves repeated traction or sliding movements at a slow speed and with increasing amplitude. The desirable effect is to increase the limited range of motion within the joint and reduce pain. The movements are carried out perpendicularly or parallel to the plane of the treated joint, oscillating, and typically repeated 8 to 10 times in 3 sets. The procedure is performed in a seated position with the patient’s head stabilized on the chest of the physiotherapist who holds the patient’s head and mobilizes the mandible with one hand. Traction consists of 3 stages: relaxation (abolition of forces acting on joint), tension (remotion of the articular area) and stretch (increase in remotion of articular area) [48, 49].

The muscle energy technique (MET) is used when limited movements of the mandible are observed and caused by soft tissue (muscles and connective tissue) damage. The treatment involves repeating 3 phases: the first phase is making a movement that is possible due to limited tissue elasticity; in the second phase, the patient slightly tightens the muscles trying to make a move in the opposite direction of the force created by the physiotherapist and should last approximately 10 s; in the last phase, the patient relaxes the muscles. The technique can be performed both in a seated or lying position [50, 51].

Physiotherapy involves many techniques of treatment. The most common massage and manual therapies were previously described, but for TMD treatment, also other techniques are used. Among them, biofeedback, lamp exposure, iontophoresis, ultrasound and transcutaneous electrical nerve stimulation (TENS) are used.

The purpose of biofeedback is to stimulate the muscles to work properly and achieve maximal relaxation of the muscles in a short period of time. The therapy involves electromyography to train the adequate neuromuscular tension of the patient and develops the ability to alter a physiological response. The surface electrodes are placed on the muscles (typically masseter) uni- or bilaterally; other muscles (e.g., anterior temporalis) may also be included. SEMG biofeedback may include muscle tension discrimination. The treatment protocol involves teaching the patient how to open their mouth properly to strengthen the tension of the tongue and protrude the mandible. Only after this are the electrodes applied in line with the muscle fibers (usually upon the midsubstance of the masseter muscle belly). The measurements of the minimal muscular tension are performed when the patient rests with all their muscles relaxed; this is used as a reference in the follow-up. Observing the movements and muscular tonus the patient exercises help to restore the appropriate muscular activity [52‐54].

Transcutaneous Electrical Nerve Stimulation (TENS) is another well-known method of pain relief for TMDs. The method is based on electrical stimulation of pain areas via surface electrodes and is considered safe and non-invasive. TENS helps to relieve chronic and acute pain in joint and/or muscle disorders. Unfortunately, due to the small number of studies (especially randomized trials), TENS cannot yet be considered a standard treatment for TMDs, as its effectiveness is still uncertain [55]. In addition to the therapeutic value of electric potential, a tool called electromyography (EMG) is used for establishing muscular function and is the most reliable and objective technique [56].

For pain release, especially in subacute arthropathies and inflammatory rheumatic diseases, heat treatment is applied; it alleviates strong pain, although the result is typically short-therm. Heat is supplied either by means of Solux lamps (ca. 15 min from 20 cm distance) or through a thermophor filled with water at a temperature of 158 to 176 °F (70 to 80 °C) and wrapped with a towel. Other recommendations to decrease pain are sulfur and iodide baths. Cryotherapy is another form of temperature related therapy but applies cold instead of heat. Cold packs, cold spray or air, and ice compresses are used as analgesic agents. The application of cold is used immediately prior to kinesiotherapy and helps fight muscle hypertension and tendinopathies as well as rheumatic diseases. One should remember that there is a high risk of frostbite (skin damage due to low temperature) with this form of therapy. The cold compresses should be applied for 10–15 min. Cryotherapy leads to the attenuation of pain, reduces stiffness in the TMJ and increases mandibular mobility [57].

A new method of rehabilitation with the aim of TMJ stabilization and increased jaw stability is taping, or Kinesio Taping (KT). KT also decreases drooling and provides mouth closure. To increase jaw stability, one piece of tape in a “Y”-shape cut should be prepared and placed proximal to the joint; the superior tail is shorter than the inferior tail. The superior tail should be applied diagonally along the upper jaw and directed towards the lower cheek with “paper-off” tension. The tape width should be 1.5 to 2 inches (3.8 to 5 cm). The mandible cannot subluxate at the movement. To decrease the hypermobility of the joint and release TMJ pain, two tape pieces (1 inch wide and 2 inches long each) should be placed diagonally to each other over the joint, forming an “X”. To improve jaw stability, tape is usually applied to both sides. The balance in head position and body posture usually leads to a decrease in hypertension of not only the masticatory muscles but also the neck, arms and spine [58, 59]. The method is quite new but has become increasingly popular [60, 61]. The special therapeutic tape adheres to the skin with adequate flexibility and consists of a polymer elastic strand wrapped by 100 % cotton fibers. The tape allows for a normalization of muscle tone and increases the process of self-healing. KT stimulates an endogenous analgesic system and changes the subjective feelings of the patient. Alignment of muscular tone is possible by improving proprioception. KT could be applied for myofascial pain therapy in a range of masticatory muscles, especially the masseters. The clinical technique has been described by Kase et al. [62].

Ultrasound therapy is one of the efficacious methods for pain reduction, decrease in muscular tonus and improving the function of the muscles. It consists of three types of signals: constant waves, sound impulses and ultrasound combined with stimulation current, which is found to be most effective. The procedure is performed 6–12 times, every 1–2 days, 6–8 min each. The impulses should be applied at 0.5–0.7 W/cm in the case of devices with constant waves, and 0.6–0.9 W/m in the case when sound impulses (50 or 100 Hz) are emitted [57].

There are few rarely used methods of TMD management. Among them are iontophoresis with different medications (e.g., nonsteroidal anti-inflammatory drugs, steroids and analgesics), especially in patients with concurrent temporomandibular joint disc displacement without reduction and capsulitis [63]. As the data show, pain release is not observed, but patients present with a wider opening of the mouth than when analgesics alone are used [63]. Inflammatory processes may be healed with a laser light that is used at a wavelength of 904 nm and a frequency of 700 Hz at 30 mm depth into the skin. This method had gained popularity [57].

Pharmacotherapy for TMD is not commonly used. It is only used when other somatic symptoms, such as sleep disorders, chronic pain, arthralgias, inflammatory diseases, myalgias or neuropathies are associated with TMD [28]. As TMD may manifest from different systemic diseases (e.g., arthritis, inflammatory bowel diseases, Parkinson disease), it is important to diagnose the patient properly and implement treatment for the underlying disease, especially when depression is a suspected diagnosis [47, 64]. One has to remember that pharmacotherapy has its goal in decreasing pain and inflammation within the joint and/or muscles. This therapy improves function and inhibits the progression of the disease [65]. Pharmacotherapy can be considered as a complementary therapy rather than a treatment itself. The exceptions are systemic diseases with TMJ involvement [57].

For TMD release, the most commonly used medications are myorelaxants, nonsteroidal anti-inflammatory drugs (NSAIDs), analgesics, tricyclic antidepressants, benzodiazepines and corticosteroids [28]. The first medication of choice for moderate pain relief is acetaminophen (average daily dose of 325–1000 mg). NSAIDs and analgesics help to relieve pain (including radiating pain) in the head, jaw muscles, face, neck or shoulders. A high efficiency of TMD pain relief is shown with ibuprofen* and meloxicam** (average daily dose of 400–800 mg* and 7.5–15 mg**). In this particular situation, pharmacotherapy is considered a supportive therapy that supplements other therapies. Used by itself, pharmacotherapy is considered for palliative therapy [48]. NSAIDs decrease pain and stop the inflammatory process [64].

Muscle relaxants (baclofen, tizanidin, cyclobenzaprine), opiates (morphine), anticonvulsants (e.g., gabapentin), ketamine, and TCA (e.g., amitriptyline) have also been used clinically for TMJ management, but there is no evidence for their efficacy [65, 66]. To achieve the myorelaxation effect with low CNS impact, metaxolone is recommended (average daily dose of 800 mg).

In specific cases, medications should be used admittedly. During acute spasms (sudden muscular contraction and painful shortening that is maintained over time), anesthetics are advised to block the pain and allow therapeutic stretching. Usually, the analgesic blockage with an infiltration of 1 ml of 2 % lidocaine (without vasoconstrictor) in the involved muscle is applied. A complementary therapy may include dypirone 500 mg (also in association with a myorelaxant, such as orfendrine, if necessary) 3 times a day, for 2 days [46]. In this situation, 90 % of cases require analgesic therapy [65].

In myositis and other inflammatory disorders, the most appropriate strategy is the administration of one dose of corticosteroid intramuscularly. Another approach is the injection of an analgesic or anti-inflammatory agent. The most common injections contain corticosteroids (with anti-inflammatory action) or hyaluronic acid [67]. In animal models, the use of an inhibitor selective for the inducible COX-2 enzyme may attenuate the neurogenic component of inflammation [47]. COX enzymes are blocked by NSAIDs. Unfortunately, those medications have a high risk of adverse side effects, which may include exacerbation of hypertension or gastrointestinal upset that may lead to ulcerations. COX-2-selective NSAIDs (eg. Celecoxib, Meloxicam) which have less side effects, are not found to be better for the treatment of TMD. There is a hope that lotions containing NSAIDs will not have as many side effects and will have a positive impact on relieving pain [65].

In chronic facial pain, aside from pain relievers, antidepressants should be used as a supplementary treatment [47]. Antidepressants may be used for chronic pain as a primary analgesic. These medications manage headaches and neuropathic pain, reducing the feeling of depression caused by pain and improving sleep quality [65].

It had been proven that NSAIDs relieve pain in patients who suffer from arthritis. In this situation, diclofenac at a maximum dose of 50 mg orally 3 times daily or naproxen sodium 500 mg twice a day are recommended, as they improve pain in more than half of the patients [65]. It had been shown that the use of antibiotics, such as doxycycline or other tetracyclines, could help prevent condylar resorption. Regardless of their antibiotic activity, antibiotics inhibit matrix metalloproteinases (MMPs), whose levels are elevated in inflammatory processes involving TMJ [67]. Doxycycline is also a medication of choice in patients who undergo orthognathic surgery to avoid the resorption process [68].

For anxiety treatment and stress relieve, benzodiazepine (eg. Diazepam 5 mg, Lorazepam 1 mg or Alprazolam 0.5 mg) for 5–10 days should be prescribed [46].

Clinical investigations by Bakke et al. [69] and Emara et al. [70] confirm the possibility of applying botulinum toxin type A (BTX-A) for the treatment of disc displacements using injections in the lateral pterygoid muscles. BTX-A decreases myofascial pain and symptoms in the bruxers by reducing muscle tension [71].

Botulin is a biologic neuromuscular blocking agent that works as a muscle relaxant and therefore relieves pain in the head and neck; it also decreases neuromuscular tonus and bruxing at night. Hypertrophic masseter muscles activity is also reduced. Due to the large scope of BTX-A, it can be used in various temporomandibular disorders, such as bruxism, oromandibular dystonia, myofascial pain (also including TMJ involvement), trismus, hypermobility, masseter or temporalis hypertrophy, headaches and neck pain [72, 73].

A common method frequently used in Asian countries is a needle puncture, also known as acupuncture. This method is also gaining popularity in western countries. Acupuncture originated in China over 3,000 years ago. A skilled acupuncturist restores whole body balance and the flow of energy within it (called Qi) to relieve a patient’s pain and to improve the inflammatory process within the joint and decrease hypertension. The method is more successful in patients who change their dietary habits (soft food, avoidance of chewing gum, less saturated fats, coffee and fried foods in the diet). Interestingly, acupuncture is very successful in long-term follow-ups (18–20 years). There are several recommended acupuncture points (e.g., SI-18, GV-20, GB-20, ST-6, ST-7, BL-10 and LI-4) that should be “triggered” weekly, 30 min per session. Needles are inserted within the pain area and around the ear and jaw. In some cases, needles near elbows, knees and the big toe are inserted to relieve pain and inflammatory process within the TMJ. It is recommended to complete 6 sessions of acupuncture treatment, but chronic disorders may require more. Often, acupuncture should be associated with pharmacotherapy [66, 74‐76].

A modern approach of needle puncture is based on the findings of trigger points in painful muscles [77]. Dry needles are inserted at the trigger points, or taut bands, which are not related to the meridian or Chi points, are placed according to traditional Chinese acupuncture practices [78, 79]. Biochemical differences have been found between healthy muscle fibers, and active and latent trigger points [80]. Therefore, needle puncture at trigger points actually change the biochemical environment of the painful muscles of TMD patients.

In rheumatoid disorders, the TMJ is usually only one of the joints (or only one of the organs) involved in the disease process. The pharmacologic treatment in this case plays a crucial role and is not only an adjuvant therapy. In those cases, pharmacologic treatment refers to the whole systemic disease and not only to the TMD.

Among patients with juvenile idiopathic arthritis (JIA), joint involvement may be accompanied by periodontal disorders and gingivitis; it usually shows no relation in higher incidences of the caries process. TMD in this disorder are confirmed by the Ai Helkimo and Di Helkimo indexes, which show that disorders within this joint are reported both objectively and subjectively [81]. Patients with JIA or RA (rheumatoid arthritis) are believed to suffer from TMD in 1 to 25 % of cases, but up to 75 % prevalence might be observed. Arthritis may be asymptomatic but might be associated with TMJ pain, especially during movement. The disorders may include condylary damage and synovitis. The untreated process may lead to mandibular growth disturbances, leading to laterogenia, malocclusions and micrognathia. The joint involvement would, in this case, impact the treatment decisions. In pharmacotherapy, systemic methotrexate and/or TNF inhibitors are used. Additionally, corticosteroids might be successful for modifying the course of the disease. Splint therapies and functional orthodontic appliances might still be used but are adjuvant to the pharmacologic treatment. The medications themselves may reduce the inflammatory process within the joint [82‐85].

The arthrocentesis that involves draining the joint with a therapeutic substance reduces the inflammatory process, evacuates inflammatory exudate, releases the disc, breaks up adhesions, eliminates pain, and improves joint mobility; this should be performed with the mouth wide open and a protruded mandible [80, 85]. Two needles are used to puncture the joint space to restore normal maximal mouth opening and functioning. This technique has limitations due to low tolerability and difficulties in performing the procedure; therefore, single needle arthrocentesis has become more popular [86]. Randomized controlled trial carried out by Vos et al. [87] tried to determine the effectiveness of arthrocentesis compared to conservative treatment as initial treatment with regard to temporomandibular joint pain and mandibular movement. They showed that arthrocentesis reduces pain and functional impairment more rapidly compared to conservative treatment but in long term observations the effectivnes of both treatment modalities achieved comparable outcomes.

The method of intra-articular injections of platelet-rich plasma (PRP) to patients with persistent pain related to severe temporomandibular joint dysfunction described by Pihut et al. [88] seems to be a valid procedure for decreasing TMD pain.

In the most severe cases in who TMJ is too severely damaged by the inflammatory process to be cured in a conservative way, implants are used to replace the TMJ. Examples include the Christensen system, the TMJ Concepts system and the Lorenz (BMF) system. Ciocca et al. [89] showed the regenerative properties of mesenchymal stem cells and CAD-CAM-customized pure and porous hydroxyapatite scaffolds to replace the temporomandibular joint condyle. Previously mentioned articles and other papers have confirmed that tissue engineering and stem cells therapy seem to be a promising alternative to the traditional procedures for the management of pain associated with degenerative TMJ disease [90, 91].

The main indication for TMJ replacement is pain relief and functional improvement in arthritis (osteoarthritis, psoriatic, rheumatoid arthritis and ankylosing spondylitis). The other situations where the TMJ needs replacement are ankylosis, damage by trauma and complications after earlier joint replacement [92, 93]. In a a case of severe malocclusion, dentofacial anomalies and unilateral condylar hyperplasia or hypoplasia complicated by TMJ dysfunction the surgical procedures combined with orthodontic treatment should be considered [94, 95].