By Dr. Andrea Gizdulich
Introduction
The increasingly frequent occurrence of habitual and persistent headaches in patients with anatomical and / or functional problems affecting the Stomatognathic apparatus explains the need to include secondary tension headaches among dental pathologies. Furthermore, it must not be underestimated that the awareness of a link between these two pathologies has spread even among the mass media, influencing public opinion. Understanding the causal relationships between the masticatory apparatus and secondary headaches requires a deep knowledge of the pathophysiology of the stomatognathic system, the initial tract of the digestive system but also part of the Locomotor System. Equipped with a bone skeleton, joints and a complex and varied musculature, it has a rich innervation and proprioception largely dependent on the second and third branches of the Trigeminal nerve, as well as specific organs such as the teeth, located in the maxillary and mandibular arches. Some peculiarities give this apparatus unique anatomical-functional characteristics in the human body: the mandible, unique and unequal bone, has two specular joints that bind it to temporal bones (ATM), complex in form and function, owe their ability to ensure movements of rotation and translation in the presence of inter-articular discs (on which the upper ends of the external pterygoid muscles are inserted). This ensures that the jaw is able to move in different planes of space and in practically infinite directions, albeit for modest traits. The rich masticatory musculature, inserted on both sides of the jaw, is equally obliged to simultaneously participate in any position or mandibular movement. Muscle function is basically carried out by strong lifting muscles, by less powerful lowering muscles, because they are assisted by the force of gravity and by other muscles that cause protrusion-retrusion movements. Many cervical muscles cooperate with the masticatory muscles, especially the trapezius and sternocleidomastoid muscles to which the movement of the head on the neck is entrusted, which consequently determine the position of the maxilla.
Of all the movements that the jaw can make, it is worth considering carefully what causes the maximum possible contact between the two dental arches. The position of maximum dental intercuspidation, defined as "occlusion" is essential for masticatory function. It is carried out at the end of each chewing cycle and generally at the beginning of each swallowing act, ie up to about 2000 times in 24 hours. Every single component of the stomatognathic apparatus, muscles, joints, mucous membranes and especially the alveolar-dental ligaments that surround each individual root are richly innervated by mechanoreceptors. Consequently every contact between the dental arches in maximum intercuspidation provokes an influential proprioceptive imput on the tone and the muscular posture, which for number and concentration of receptors, perhaps does not have the equal in any other territory of the organism. Dental occlusion, conditioned by the number, shape and position of the teeth, is therefore implicated in the posture of the head for cervical muscular involvement. Modernly the physiological position of occlusion is considered to be achieved thanks to an isotonic and balanced contraction of the competent muscles. Whenever this balance cannot be achieved due to different causes, but mostly related to the situation of the dental arches, an "adapted" occlusion will have to be considered pathological.
Physiopathology of Musculoskeletal Pain
The progress of the clinical knowledge of muscular pain, with its complex syndromic manifestations, over the last twenty years, has been acquired thanks to many scholars, among whom has exalted the personality of Janet Travell, whose studies have opened a new fundamental chapter diagnostics of one of the most widespread suffering.
Pain, defined as myofascial because it involves the skeletal musculature and its bands and aponeuroses, is preferably established in the muscles with greater postural commitment, both for causes that are chronically active (such as the commitment to a forced postural adaptation), and for acute traumatic causes ( as, for example, the "whiplash"). The pathogenesis of my fascial pain is correlated to a microtraumatic lesion of the fine muscular structures, sarcolemma and endoplasmic reticulum, which would determine an increase in endocellular free calcium, inducing a stable shortening of the sarcomeres with consequent establishment of a crisis condition of the muscular energy balance and an inability to reuptake calcium. It has been ascertained that, when the contracture takes place in areas of a muscle where the plates are located, there is a condition of dysfunction of some plaques which, producing in excess acetylcholine compared to the hydrolysis capacity of cholinesterase, would lead to a series of circles vicious with increased contracture, capillary spasms, reduction of the metabolic intake, and also the release of substances with a sensitizing effect both on sensitive and vegetative nerve endings in the area. The vicious cycle now described would determine the origin of the so-called Myofascial Trigger Points (TrP). A TrP (Fig. 2) is a hyperexcitable nodule placed in a band of tense and therefore palpable muscle tissue, which when stimulated gives rise to intense local painful response, sometimes accompanied by other phenomena such as a local shock provoked (local twitch response ), pain referred to a well defined and constant area for each TrP and altered neurovegetative and proprioceptive responses. The most characteristic symptom is referred to pain; the pathogenesis of this particular allodynia is not entirely clear; instead, it is known that it always occurs in a specific location typical of the TrP that generated it. Since the TrP site is constant in the muscular bodies, due to their interdependence with the seat of the motor plates ("central" TrP) or with the muscle-tendon insertions (TrP of "attack"), it was possible to create a map of the zones reference of pain, taking into account that also TrP coming from different muscles may have in common the site of referred pain.
Etiopathogenesis and Clinic of Cranio-Mandibular Disorders
The mandibular movement that determines the meeting of the dental arches in occlusion, given its continuous iteration, requires a prompt and direct muscular action. Therefore the starting position of the mandible, commonly known as the resting position, must be in conditions such as to perform this movement instantaneously. The ideal resting position is one in which the musculature is equally in a state of rest, retaining only the basic tone as the only contractile activity. From the physiological rest position the physiological occlusion can be realized which totally depends on the efficiency conditions of the teeth. When these conditions do not exist, the masticatory and cervical musculature must intervene to create a preventive accommodation of the mandibular resting position in order to make the movement direct and ready. The accommodation takes place through a series of muscular contractions which in reality cancel out the situation of muscular rest, instead establishing a hypertonus of various muscular heads, as can be verified by electromyography.
The noxae that can alter occlusion are multiple and can act in every age of life; they are linked to disorders of the development of the maxillary bones, to eruption disorders and subsequent alignment of the teeth, to dental diseases that determine the organic damage or even the loss of the sick tooth and finally to causes connected to dental therapies, when they are not able to restore satisfactory morphological and functional conditions of the dental arches. The inevitable consequence of such noxae is occlusion accommodated in a forced postural position and today rightly considered pathological. The occlusal alteration generates a condition called "Cranio-mandibular Disorder" which can be characterized by different clinical pictures. The clinical picture, in most cases, is devoid of symptoms but rich instead of only objective signs that express a condition of precarious balance. When and if this equilibrium should break, headaches and neck pains arise, expression in the territory of the head and neck of Myofascial Painful Syndrome. Finally, there are clinical pictures complicated by concomitant pathological phenomena affecting the TMJ, forced by the forced dislocation of the jaw, which generate articular noises and impediments of various nature and degree with or without painful manifestations. To better understand the possible myogenic pathogenesis of these headaches it is useful to consult the map of the reference areas of pain caused by the main TrP, inspired by the text by Travell and Simons (Fig. 3).
| HEADACHE | PROOF OF DOLOREMIOFASCIALE |
| Migraine (with or without aura) | High |
| Episodic or chronic tension headache | Very high |
| chronic or paroxysmal cluster headache | Low |
| Mixed headaches not associated with structural lesions | Low |
| Acute or chronic headache and neck pain associated with head trauma | Moderate-High |
| Headache and facial pain associated with circulatory disorders | Low |
| Headache and facial pain associated with non-vascular cranial lesions | Low |
| Headache associated with intake - substance suppression (alcohol, caffeine, nitrates, analgesics, etc.) | Low |
| Headache associated with infections | Low |
| Headache associated with metabolic disorders | Low |
| Associated headache Cranio-cervico-mandibular disorders | High |
| Cranial nerve neuralgia | Low-Moderate |
| Cervicogenic headache | High |
Table 1 - Correlation between headaches and myofascial TrP, according to the criteria of the Classification of Headaches, Cranial Neuralgias and Facial Pain of the International Headache Society.
Diagnostic procedures
The diagnostic procedures are divided into two distinct phases. The first, entrusted to the criteria of the clicnic semiotics, aims to investigate the existence of problems affecting the stomatognathic apparatus that justify the diagnostic direction towards the condition of Cranio-mandibular disorder and towards the possible interdependence between this and the headache, resorting to the anamnesis, to the examination of the radiograms (generally the orthopantomography of the dental arches is sufficient, accompanied, if necessary, by radiograms of the temporo-mandibular joints), then to the objective examination. This in turn requires a careful inspection of the posture of the head on the neck in antero-posterior and lateral vision and of the shape of the face, with the patient standing; a thorough inspection of the oral cavity in the various components, single teeth and dental arches mucous labial and of the cheeks, tongue vaulted palate etc. The movements of the jaw in opening, closure, protrusion and laterality will then be examined; any vibrations and articular noises associated with the movements and also the possible existence of joint palpatory pain must be detected. The complex of specific signs and symptoms collected with these maneuvers is generally sufficient to direct towards a diagnosis of pathological occlusion and associated myofascial pathology. In this case it is necessary to search for the ideal occlusion, which is essential for programming the treatment. For this it is necessary to resort to the second diagnostic phase which is computerized instrumental:
- Surface electromyography;
- Kinesiography (scan of mandibular movements);
- Sonography to record vibrations and noises produced by the joints of the moving jaw;
- Low frequency TENS;
The diagnostic test begins with the resting electromyographic recording of thunderstorms, masseters, digastrics and sternocleidomastoids detected at the mastoid insertion. Other muscle pairs can also be recorded, such as trapezoids.
The test is repeated after the application of TENS for about an hour. The comparison between the tracks before and after the relaxation induction provides data of great interest. In summary, a generalized decrease in values means the existence of a hypertonic state, with a return to a temporary situation of normality induced by the effect of TENS on the masticatory muscles, which in turn allows a relaxed spatial position of the jaw, defined "position physiological rest "
ideal for recording the physiological movement towards the best occlusal contact. It is possible, using the mandibular scan, to observe the movement in the three planes of the space documenting the trajectories of the path covered. In the case of pathological occlusion, quantitative and qualitative alterations of this path will be observed and it will be possible, by introducing a particular recording material between the teeth, to find the position of physiological occlusion represented by an ideal path in an equilibrium situation of the electromyographic values.
Therapeutic Addresses
The treatment of pathological occlusion and related symptoms is orthopedic. It consists of the application of an intraoral resin device, preferably applied to the lower arch and built according to the findings obtained with the instrumental examination (Fig. 4).
Table 1
