Idiopathic dental conditions and the potential involvement of trigger points

Transcription

1 Idiopathic dental conditions and the potential involvement of trigger points Dr James Tang, CES, MBA, BDS, LDS RCS GDP, NASM Corrective Exercise Specialist, Level 3 Personal Trainer (REP registration no R ), Sports Nutritionist & Level 3 Sports Massage Therapist, with special interest in postural dysfunction and lower back problems Introduction Chronic myofascial pain is a condition that affects the fascia, the connective tissue that covers the muscles, hence the term myofascial. It is characterised by trigger points in the musculature and is the most common cause of musculoskeletal lower back and neck pain. Myofascial pain syndrome typically occurs after a muscle has been contracted repetitively or because of stressrelated muscle tension. In dentistry, trigger points in the masticatory and certain neck muscles can manifest as dental pain, temporomandibular joint (TMJ) dysfunction and sinus problems. These trigger point-induced conditions can be incredibly debilitating because their origins are difficult to identify. They can be responsible for chronic pain that seems to have no means of relief, which can ultimately result in depression. Here, the author will attempt to explore the interrelationships between myofascial pain and dentistry and give practical advice so that dentists can manage the intriguing symptoms of myofascial origin more effectively. So, what are trigger points? The term trigger point was coined by Dr Janet Travell in 1942 to describe painful nodules felt within tight bands of muscle. They are so ubiquitous that they can occur in any of the 700+ muscles in our bodies even babies have them. Unlike acupuncture points, trigger points are micro contraction knots within a muscle fibre that can be physically felt with the fingers. They should, however, not be confused with muscle spasms which affect the entire muscle, and they are not the same as tender points in patients with fibromyalgia who suffer from widespread diffuse musculoskeletal pain. 1

2 The effect of trigger points in the host muscles They are hyperirritable spots located within skeletal muscle and feel like nodules on palpation; when compressed, they cause a significant amount of pain. Essentially, part of the muscle fibre is contracted into a small thickened area and the rest of the fibre is stretched. The muscle fibres affected are not available for contraction as they are already contracted, making the host muscle weak. As a result, muscles containing trigger points are fatigued more easily and do not return to a relaxed state as quickly when muscle contraction ceases. The contracted tissues restrict blood and lymphatic circulation in their immediate vicinity, resulting in accumulation of metabolic by-products and deprivation of oxygen and nutrients. This crisis of energy produces sensitising substances that can cause pain, e.g. bradykinin, which is known to activate the muscle s nociceptors. Trigger points will not disappear without intervention; they accumulate over a lifetime and can exist indefinitely in a latent state. Although the actual pain may subside within a week or so, active trigger points simply turn latent and can be reactivated easily. Latent trigger points are the main cause of stiff joints and the restriction of a range of movements due to muscle tightness and weakness of the host muscle. They can also keep muscles out of balance, causing joints to click during function, and can potentially lead to osteoarthritis. Active trigger points usually refer pain locally and/or to distant areas of the body, and common patterns have been identified, but these referral patterns do not necessarily conform to the nerve pathways. As the majority of trigger points are not located where you feel symptoms, treating the painful area will not provide 2

3 relief. To complicate the situation further, they can also manifest in secondary muscles or as satellite trigger points in and around the vicinity of the primary site. Trigger points have been implicated in a range of conditions and they can often mimic the symptoms of others. They can cause diverse symptoms that are not normally associated with muscular problems. Many types of joint pain are mistakenly diagnosed as arthritis or tendonitis. Physiology of trigger points Muscle contraction begins with the two contractile proteins, myosin and actin, arranged in a series of compartments called sarcomeres that run the length of the myofibril. The actin is anchored to the end and the myosin sits within the middle of the sarcomere, pulling the actin from either end towards the middle to generate tension (sliding filament theory of muscle contraction). During muscular contraction, the myosin heads attach themselves to the actin filament and rotate, pulling on these filaments. Muscles with trigger points manifest in the region where sarcomeres and motor endplates become overactive. The actin and myosin myofilaments sitting within a taught band stop sliding over one another. The current hypothesis about the formation of trigger points involves the energy crisis component. When the nerve impulse arrives at the motor endplate, neurotransmitter acetylcholine is released causing calcium to be released from the sarcoplasmic reticulum (SR) and the muscle fibre involved to contract. Normally, when contraction of the muscle fibre ceases, the motor endplate stops releasing acetylcholine and the calcium pump in the SR recycle calcium back into the SR. Where there is an excessive motor endplate release of acetylcholine, surplus calcium can be released by the SR causing a maximal contracture of a segment of muscle, leading to maximal energy demand and impairment of local circulation. As a result of this deprivation of fuel and oxygen, the calcium pump is unable to return calcium back into the SR, and the muscle fibre continues to contract, creating trigger points. This vicious circle is self-perpetuating unless there is some form of intervention. Furthermore, the attachment sites of these tight muscle fibres can also become tender as they are stressed by the contraction in the centre of the fibre. 3

4 Why do we get trigger points? Active trigger points are often caused by an injury, prolonged poor posture or repetitive use. It is believed that trigger points are part of our protective mechanism. Any change in muscle biomechanics over time can manifest as areas of tight muscles, and because trigger points make the host muscles weak, they are a useful mechanism for rapidly switching off muscle power around an injury. This is essential if, for example, there is a fracture. Myofascial muscle pain is therefore a key part of our protective mechanism because pain is a valuable alarm bell that warns of a problem. 4

5 The relevance of trigger points in dentistry Head and neck symptoms caused by trigger points include, but are not limited to, toothache, hypersensitivity, malocclusion, TMJ dysfunction, trismus and sinus pain. Trigger points can cause diverse symptoms such as blurred vision, dizziness, vertigo, dry eyes and balance problems. They can also cause numb lips, painful tongue and drooping eyelid (Travell and Simons, 1999, ). Temporomandibular joint (TMJ) dysfunction The TMJ is a synovial joint between the articulation of the temporal bone of the cranium and the mandible. The symptoms of TMJ dysfunction can vary from mild occasional discomfort to frequent and extreme misery. Although trigger points are often involved in TMJ disorders, they are not always the primary cause because they can develop secondary to conditions such as TMJ synovitis and arthritis. Whatever the cause, the presence of trigger points can exacerbate the condition, worsen the prognosis and interfere with primary interventions. The various muscles that control jaw function have to work in synchrony for optimal masticatory performance. Trigger points in the masticatory muscles of the jaw and anterior neck, such as the sternocleidomastoid, are typically involved with the symptoms associated with TMJ disorders, including jaw clicking, dislocation, trismus and malocclusion (Travell and Simons, 1999, ). Furthermore, if the lateral pterygoid is tight or shortened by trigger points, this can easily lead to misalignment of the jaw, causing malocclusion and associated problems. Amazingly, trigger points that cause TMJ problems may also cause other diverse symptoms such as vertigo, vision disorders, tinnitus, itchiness deep in the ear, sinus issues, toothache and more! The involvement of trigger points in these muscles should not be ruled out if a patient is suffering from TMJ symptoms. Practical advice on the management of myofascial TMJ conditions Principles of management are based on an accurate diagnosis and should be non-invasive and reversible. The objective is to control pain, relax muscles and eradicate the causative trigger points. Although a combination of treatment is often required, it is possible to eradicate the symptoms simply by using 5

6 myofascial release techniques to remove the culprit trigger points in the involved muscle(s). A thorough clinical examination, history-taking and radiography should be used to exclude any pathology in the TMJ because structural changes are usually absent in myofascial pain. It may be necessary to refer your patients for behavioural or psychological assistance because there is often a strong correlation between TMJ problems and various types of emotional stress. Bruxism is common and many patients exhibit nocturnal teeth grinding. To avoid additional anxiety, it is important to reassure them that their condition is often self-limiting. General advice should also recommend the avoidance of repetitive jaw movement (constant chewing overtaxes the masticatory muscles) and prolonged jaw opening, as well as a soft diet. External application of heat can be recommended as this increases blood and lymphatic circulation to muscles that have been affected by trigger points. Although trigger points in masticatory muscles can result in malocclusion, poor occlusal balance can predispose to muscle imbalances and therefore rectification of the precipitating occlusal problems may help to prevent recurrence of problems. Soft splint therapy can be used to dampen the impact of jaw clenching and reduce muscle activity. Nevertheless, all these measures offer only symptomatic relief and will not eradicate the trigger points involved. Myofascial therapy is the only way to get rid of the trigger points. 6

7 Practical advice on the management of dental-related myofascial trigger points Trigger points in the pterygoid muscles These trigger points are a frequent cause of pain in the TMJ but unfortunately they are well hidden by the mandible, making it difficult to access for treatment. The medial pterygoid Anatomy this muscle originates from the medial surface of the lateral pterygoid plate of the sphenoid bone, the pyramidal process of the palatine bone and the maxillary tuberosity. It inserts to the medial surface of the ramus and the angle of the mandible. Action elevates and protrudes the lower jaw. Trigger points in the medial pterygoid restrict jaw opening and can cause pain in the TMJ. Pain can be referred to the hard palate and tongue, making swallowing painful. Treatment it is possible to massage the medial pterygoid extra-orally by pressing up with your thumb inside the inner edge towards the back of the mandible. The lateral pterygoid Anatomy the superior head originates from the lateral surface of the greater wing of the sphenoid and inserts to the capsule and articular disc of the TMJ. The inferior head originates from the lateral surface of the lateral pterygoid plate of the sphenoid and inserts to the neck of the mandible. Action protrudes the mandible, opens the mouth and moves the mandible from side to side. Trigger points in this muscle are the prime source of myofascial pain and TMJ dysfunction. Constant trigger point-generated tension here tends to pull the mandible forward, making the TMJ click and possibly even dislocating the joint. Trigger points can develop in this muscle as a result of repetitive biting, teeth grinding, prolonged jaw opening due to dental 7

8 work or breathing difficulties, emotional stress, thumb sucking, nail biting or occlusal malalignment. Pain can also be referred to the cheek and can mimic sinus pain (as with the masseter). Trigger points in the masseter and temporalis can predispose to satellite trigger points developing in the lateral pterygoid by making them work harder to open the mouth. Treatment massage the lateral pterygoid intra-orally with the index finger. The fingertip should seek the deep pocket posterior to the upper molars then push both inward and upward using tiny, short strokes. If trigger points are present, this can be excruciatingly painful. Sternocleidomastoid (SCM) trigger points Trigger points in this muscle can cause an incredible amount of pain (but it is all referred elsewhere and the muscles themselves rarely hurt) and a bewilderingly diverse set of symptoms, including headache, dry cough, sore throat, sinus pain, excessive eye tearing, visual disturbances and dizziness. Anatomy the SCM originates from the mastoid process with the sternal division runs diagonally downwards to attach to the sternum. The clavicular division attaches onto the medial aspect of the clavicle. Action unilateral contraction turns the head towards the opposite side whilst bilateral contraction flexes the neck and translates the head forward. Characteristics trigger points in the sternal division refer pain deep in the orbit, TMJ, back and top of the head. The clavicular division refers pain to the forehead, ear and ipsilateral molar teeth. It is unusual for trigger points on one side to refer pain to the contralateral side, but frontal headaches caused by clavicular trigger points can be cross-referred to the opposite side of the forehead. Trigger points in the SCM are frequently sponsored by trigger point activities in the upper trapezius typically induced by a forward head posture when these neck extensors have to remain constantly contracted to support the weight of the head. 8

9 Management trigger points in the sternocleidomastoid can be so tender to pressure that they can be mistaken for tender lymph nodes. To massage the sternocleidomastoid, grip the muscles between your fingers and knead firmly. Search for trigger points in each of the two branches, starting up behind the earlobe, all the way down to the clavicle. Please beware the carotid arteries and avoid massaging where you can feel a pulse, high up under the chin alongside the trachea. Masseter trigger points Anatomy the masseter is a powerful muscle of mastication consisting of a superficial and deep head, both originating from the zygomatic arch. The superficial part inserts on the masseter tuberosity at the outer surface of the mandibular angle whereas the deep part runs further dorsally to the outer surface of the ramus of the mandible. Characteristics those in the deep layer anterior to the ear can cause pain in the TMJ. Masseter trigger points can increase muscle tension so much that it can result in trismus. Trigger points in the superficial masseter in the middle of the muscle belly cause toothache that resembles dental abscess pain. Patients can usually pinpoint their toothache in their lower molars. Trigger points in the superficial masseter just below the zygomatic arch give patients a feeling of toothache that extends up into the roots, with sensitivity in their upper premolars and first upper molar. Pain is typically worse in the early morning or early evening. Like many of the trigger points in the TMJ musculatures, this one is activated by uneven and repetitive chewing or biting on hard objects (such as regular nail biting). These unpleasant symptoms can be avoided by giving up these habits. Misinterpretation of these symptoms can result in unnecessary and irreversible dental procedures, such as extraction. The secondary effect of masseter trigger points is that they may cause patients to neglect brushing due to hypersensitivity, leading to deterioration of their oral health. Trigger points in the masseter can also cause pain in the front of the face, under the eyes or over the eyebrows, symptoms often mistaken for sinusitis. 9

10 Practical advice on eradicating trigger points in the masseter: the trigger points are in the belly of the masseter just behind the roots of the teeth. Pressing on this knotted muscle can usually reproduce the symptoms in the teeth. Massage the masseter with two fingers, one inside and one outside, with your thumb inside the mouth, and knead the muscle between your thumb and fingers. Seek out each exquisitely tender knot, from the maxilla to the bottom of the mandible, and massage it as strongly as is bearable. Alternatively, apply firm but constant pressure on the trigger point until the pain subsides. Repeated treatment may be required for stubborn trigger points to completely release. Temporalis trigger points Anatomy the temporalis is a large, thin, fan-shaped masticatory muscle located in the side of the skull above and in front of the ear. It originates from the temporal and infratemporal crest, passing beneath the zygomatic arch and inserting into the coronoid process and the anterior ramus of the mandible. It elevates and retracts the mandible. Causes of temporalis trigger points masticatory muscles are easily overloaded, especially when we clench or grind our teeth (bruxism) which can activate trigger points in the muscle, or trigger points in the muscle can cause bruxism. In both cases, the temporalis becomes overworked and strained. Trigger points can result from prolonged jaw opening due to dental treatment: extensive dental work leads to trigger points in the temporalis muscle, adding to the facial pain and post-operative toothache, leading to the mistaken assumption that further dental work is required, which of course only worsens the problem. Other causes include chronic mouth breathing, excessive gum chewing, a cold draft of air on the side of the face and poor occlusion. Characteristics trigger points in the masseter and sternocleidomastoid sponsor satellite trigger points in the temporalis and can easily be reactivated shortly after attempts to subdue them. Furthermore, a hyperkyphotic posture, typically related to a forward head posture, can also lead to formation of trigger points in the temporalis. Unfortunately, muscles have this type of effect on one another. It is therefore important to track down and treat all the muscles that are interrelated by proximity or function. 10

11 Temporalis trigger points are associated with head pain. They refer pain to the ipsilateral head, sometimes to the front of the head over the eyebrow, and to the face and upper teeth. Sometimes, pain can be felt in the side of the face as a diffuse jaw pain extending all the way down to the neck region. Temporalis trigger points can also cause pain and hypersensitivity in the maxillary teeth. Diffuse pain in the upper teeth during mastication is likely to be coming from the temporalis. Trigger points in the front create sensitivity in the front teeth and those in the back create sensitivity in the back teeth. Temporalis trigger points are a feature of TMJ problems and chronic trigger points in the temporalis and masseter muscles can cause permanent structural damage to the synovial joint of the TMJ. Advice on treatment of temporalis trigger points find the trigger points at the front of the muscle first and build up gentle pressure. This often reproduces the deep pain that radiates to the teeth. Similar to the treatment of the masseter trigger points, maintain a firm and constant pressure until the pain alleviates. Then, massage the area gently and repeat with the next trigger point. To prevent these trigger points from recurring, advise your patients to eradicate causative factors such as gum chewing or chewing hard substances (e.g. finger nails). False sinus symptoms Trigger points in the jaw muscles can mimic the symptoms of sinusitis. When conventional sinus medication does not relieve a patient s sinus discomfort, it is pertinent to consider the involvement of trigger points as a differential diagnosis. Trigger points in the facial muscles, jaws and front of the neck can cause the production of excess mucus in the sinuses, nasal cavities and throat, which can lead to continuing sinus drainage, constant clearing of the throat, chronic cough, allergic rhinitis (runny nose), and persistent hay fever or cold symptoms. Naturally, all these widely varying symptoms can have causes other than myofascial trigger points. Nevertheless, any examination should consider the involvement of trigger points for abnormal and unexplained symptoms in the face, ears and jaws. Unfortunately, many dentists and patients are still illinformed about trigger points. 11

12 Management when trigger points are the cause of symptoms in the jaws, face, eyes, ears or teeth, significant relief can be obtained by applying myofascial release techniques. 12

13 Practical advice on the general principle of managing trigger points Combined with some simple lifestyle changes, myofascial release of trigger points can yield dramatic, immediate and sustainable results. The objectives of such therapies are: To identify the correct trigger point(s). To deactivate the point(s) using myofascial release. To prevent recurrence. Identify the correct trigger point(s) It is important to have good knowledge of the anatomy of the muscles to be treated because alleviating myofascial pain depends on locating the trigger points. The good news is that they always originate at the midpoint of a muscle s fibres where the motor nerve enters, transmitting the nerve impulse which initiates muscle contraction. The problem occurs when the fibres do not always run from one end of a muscle to the other. The orientation of the fibres in muscles varies, depending on their designated function. In a muscle made for speed, the fibres are parallel, running straight from end to end, and its trigger points are easily found halfway along. However, muscles that are made for power, like the masticatory muscles, have their fibres running diagonally at some angle to its length. Since trigger points may be found in the centre of each individual fibre, they may be situated anywhere along the muscle. That said, trigger points (active/latent) are relatively easy to locate because they are always very painful on palpation. Another problem with treating trigger points is that they typically refer pain to another site and working on the area where the pain is felt will not offer pain relief. Fortunately, the referral pattern is reproducible and well documented. The pattern of referral can be easily reproduced when the trigger point is pressed. To complicate the matter further, trigger points in the sternocleidomastoid and upper trapezius can sponsor satellite trigger points in the masticatory muscles and unless these primary trigger points are also dealt with, simply eradicating those in the satellite sites may not produce the desired long-lasting effects. It is therefore important to track down and treat all the muscles that are interrelated by proximity or function. Muscles do not operate in isolation this explains why 13

14 development of primary, central trigger points in one area of the body may lead to secondary or satellite trigger points distally. Using appropriate techniques to deactivate the point(s) Eradicating these trigger points completely usually requires multiple treatment sessions, depending on the muscle in question and the irritability of the trigger points involved up to five times a day for a week or so may be required. Persistence pays off. Clearly it is impractical for dentists to be always involved so it is advisable to instruct patients to carry out self-myofascial release so that they can mange their own trigger points in the comfort of their home. However, before attempting to treat patients, you should familiarise yourself with the effect of self-myofascial release. The best place to start is to run your fingers along your quadriceps you will almost certainly be able to feel numerous nodules that are painful to firm pressure. Applying a thin layer of cream or oil will help your finger to glide along the skin. You should use the thumb of one hand supported by the thumb of the other. Once you can feel the knot, press on it firmly (ischemic compression) until you can feel the pain (intensity 7/10; if you apply too much pressure and cause too much pain, your muscles will contract unnecessarily). Maintain the same pressure until the pain dissipates (this usually takes seconds). Unlike the trigger points in the masticatory muscles which can be easily manipulated with the fingers, finger pressure may not be adequate on the thick muscles of the legs and you may require tools such as foam rollers. Myofascial release with deep stroke massages can also be used. They work by breaking into the chemical and neurological feedback loop that maintains the micro muscular contraction. They also increase the circulation that has been restricted by the contracted tissue. Massage should be deep and in one direction only (do not attempt to rub the trigger points to and fro) and the pace should be slow because the aim is to deactivate overactive tissue and nothing should be done to make the tissue more excited. You may be tempted to discontinue working on the trigger point the moment it stops actively referring pain. However, if the trigger point still hurts when you press on it, you have only soothed it into a latent state which can be easily reactivated with the slightest overload, such as biting heavily or repetitive chewing. 14

15 The science behind this involves autogenic inhibition by activating the Golgi tendon organs located in the musculotendinous junctions. Skeletal muscle contains muscle spindles and the Golgi tendon organs, two neural receptors. Muscle spindles are sensitive to a change and rate of muscle being stretched. When stimulated, they will generate a stretch reflex that causes the muscle to contract. The Golgi tendon organs are stimulated by a change and rate of tension; this stimulation causes the muscle to relax. When a change in tension is sustained at an adequate intensity and duration, muscle spindle activity is inhibited causing a decrease in trigger point activity, allowing the muscle fibres to stretch, unknot and realign. Note, there are certain medical contraindications for trigger point therapy, such as, but not limited to, infectious skin conditions in the area involved, heart failure, or any other organ failure, and cancer. Prevention strategies Although aches and pains from trigger points are common, there can often be an underlying pathology. It is equally important to identify the causative factors of these trigger points as they rarely develop in isolation and may return if the underlying cause is not identified and addressed, whether it be a forward head posture, repetitive chewing actions, bruxism or faulty occlusion etc. If these are not rectified, symptoms can simply recur. Summary This article highlights the diversity of symptoms that can be caused by trigger points. As a consequence, it is possible to consider their involvement as a differential diagnosis for a patient s dental conditions. Presenting symptoms Bruxism Trismus TMJ dysfunction syndrome Sinus symptoms Likely location of trigger point(s) Temporalis Masseter Zygomaticus major Pterygoid muscles Masseter Sternocleidomastoid Lateral pterygoid 15

16 Toothache and hypersensitivity Clavicular branch of sternocleidomastoid Upper trapezius Masseter Temporalis Longus capitis (one of the neck flexors) 16