NEUROMUSCULAR DENTISTRY :
PHYSIOLOGY OF OCCLUSION –
TEMPEROMANDIBULAR JOINT DISORDERS (TMD) AND
OBSTRUCTIVE SLEEP APNOEA (OSA)
The definition of occlusion has been evolving down the years. Occlusion can be centric, physiologic or myocentric. In epigenetic terms, occlusion can be defined as that end point of the body with respect to the plantar surfaces of the feet, and within these two boundaries, all functional spaces for physiological processes must be accommodated. This definition summarizes the need for us dentists to think of more than just the teeth and the whole body as a single concept.
Myocentric occlusion is the occlusal relationship between mandible and maxilla that minimizes the need for muscles accommodation and posturing, and allows normal decompression of neural and vascular intra capsular tissue and associated connective tissue. It provides the optimal condylar position that we strive to achieve in a gnathic system that may have become pathologic due to previous condylar positional discrepancies leading to TMD (Tempero-mandibular dysfunctions).
This can be explained only with the help of an actual knowledge in the science of Neuromuscular Dentistry (NMD). The science of NMD is well chronicled in hundreds of scientific articles and textbooks including past anthologies.
The term temporomandibular joint disorder (TMD) is defined as a group of abnormal conditions involving the masticatory muscles, the temporomandibular joints, and the associated neurological and musculoskeletal structures. There are many theories that proposed to find out the cause for TMD. The role of occlusion in the etiology of TMD has been widely documented in the dental literature. One theory proposed as the basis of TMD is that it is mainly the result of a dysfunctional masticatory system that is characterized by complex interactions between various muscles, two temporomandibular joints, and mandible. Occlusal disharmony can result in hyperactivity and a disturbed pattern of muscle contractions leading to muscular pain and joint overload.3 This would bring TMD study and treatment in line in the muscle physiology that is, muscles functioning under less than ideal conditions commonly result in compensating muscle activity, if not corrected can progress into a chronic condition of pain and dysfunction.
DENTAL OCCLUSION IS THE FOCAL POINT OF OUR POSTURE
Centric occlusion (CO) and centric relation (CR) are terms that have always ended up pushing the mandible upward and backward. But for a TMD patient, isn’t it that very same CO that has led to the problem? What all we do, to try and coerce that patient into CO….the Dawson’s technique, the forced swallow technique, the hand in mouth technique! Have you ever given it a thought that while forcing the patient to bite into that CO, you may be actually pushing the mandible, and hence the condyles, backward and upward into the retrodiscal pad of the glenoid fossa? That CO may only be his habitual occlusion, which his body may have self repaired to compensate for that small occlusal discrepancy, which we always tend to overlook. The muscles of mastication that act upon the mandible have been trained by our CNS to keep the condyles and hence the mandible in that erroneous position to avoid that high point! AND THAT’S HOW WE CREATE TMD!
In simple words, bite registration decides the fate of the patient. If taken correctly, he’s going to be the happiest patient. The smallest occlusal discrepancy would transform the perfectly normal TMJ complex into a TMD, hence leading the patient to headaches, neck aches, migraine, etc. These patients then visit the ENT specialist, the neurosurgeon, the orthopedician, etc., for treatment of these aches but to no avail. Almost 80% of patients end up with TMD as a result of that discrepancy and suffer the agony and would need to depend on medicines all their life.
WHAT IS NEUROMUSCULAR DENTISTRY?
Neuromuscular Dentistry is the science of dentistry that embodies adopted accepted scientific principles of patho-physiology, anatomy, form and function. NMD objectively evaluates the complex relationship between teeth, temperomandibular joints (TMJ) and the masticator muscles in order to achieve an occlusion that is based on the optimal relationship between the mandible and the skull – Neuromuscular Occlusion (Myocentric) (Fig.1). This is achieved by relaxing the muscles controlling the jaw position to establish a true physiological rest position upon which treatment considerations are based.
In summary, NMD is the science of occlusion encompassing not only the teeth but the objective evaluation of the status and function of the jaw muscles and joints – before, during and after treatment – to achieve the optimal result.
So, by deprogramming those muscles of mastication by relaxing them with a TENS device and then scanning with a highly sophisticated mandibular tracking device (fig 1), we create the actual occlusion by finding the myocentric occlusion. The TENS unit is connected to trigger points on the patient’s head and neck and sends rhythmic pulses to each of those points in a measured rate controlled by the practitioner. This increases blood flow, the release of endorphins, and the movement of waste products in order to relax the jaw and place the TMJ in its proper position. Using this technique, we are able to find the patient’s optimal physiological bite position and register this information with the assistance of the K7 evaluation computer system. The difference is that, when the muscles relax, the mandible, more often than not, drops. This exposes the actual physiological Freeway Space at rest, which has been the real culprit all the while, trapping the oral tissues and the condyle. The TENS helps free the mandible from this grip. When the mandible gets free, it has the freedom to move forward. How much forward, is decided by the tracking device. That position is then maintained with an orthotic (fig 2) or jigs or even crown build-ups (fig 3) and orthodontic treatments (fig 4).
TMD is common in deep bites, midline discrepancies, narrow arches, tongue thrusts, etc. These patients invariably suffer from headaches, neck aches, shoulder aches, tinnitus, pain around eyes, migraines, facial asymmetry, etc. 60% of all those uncured headache patients queueing up at the ENT’s clinic are TMD patients. Identify these problems and solve it even without the equipments. For example: correct the deep bites by giving crown build ups on either side of the posterior arches after bringing the mandible downward and forward to an inter incisal position with an overbite of 1.5mm and overjet of 1mm. Another case would be clearing the midline discrepancy by manually shifting the mandible laterally so that the lower labial frenulum is aligned with the upper labial frenulum and train the mandible into that occlusion with the help of an inclined plane. Although, kinesology would be advised for precision.
Neuromuscular occlusion is defined as a stable maxillomandibular position at occlusion arrived at by isotonic contraction of relaxed masticatory muscles. This is achieved by stimulation of muscles on a trajectory from a resting mandibular position. The instrumentation developed has enabled (1) measurement by surface electromyography (EMG) (Fig 5) of masticatory muscle activity at rest and under a range of activations, such as clenching of the teeth; (2) tracking of the mandible to precisely record and analyze where its movements and the electrical activity of associated muscles can be followed during jaw opening and closing, and during movement of the mandible forwards, backwards, and laterally as during eating; and (3) .Electrosonography(ESG) enables the dental practitioner to listen to joint sounds during movements of the mandible. An ideal temporomandibular joint (TMJ) is one that is silent during such movements, whereas one where sounds are present suggests abnormalities within the joint complex.
The problem in India is that, Occlusion is only defined in our curriculum; it is not taught as a subject. Articulated with its opposing tooth, each tooth can be considered a separate occluding skeletal joint. This relates to the position of the condyle in the glenoid fossa which in turn affects the occiput and the cervical spine. Therefore occlusal dysfunctions are orthopedic in nature, representing the terminal end point of the postural chain. Hence, when the TMD disappears, you can see a marked improvement in his posture and facial symmetry, hence conforming to the golden proportion of that patient. The person becomes attractive and pain-free.
Lifestyle diseases are on the rise in the world especially in India where the proportion of the middle class is increasing manifold. Hypertension, cardiovascular diseases, diabetes, increased lipids are just to name a few. We hear about sudden cardiac arrests and related deaths, irrespective of age and sex, very regularly nowadays; especially during sleep. It is also common to hear that these deaths are labeled as myocardial infarctions and that it was unfortunate! But, do you know that 75% of these “unfortunate” deaths could have been avoided if only he/she was diagnosed for a killer disease known as “OBSTRUCTIVE SLEEP APNOEA (OSA)”. It is very commonly treated by sleep medicine specialists in the west by both physicians and dentists. But here, in India, even the sleep physicians are finding it tough to get through to the patient due to the lack of awareness.
Now, what is OSA? It is a self-explanatory term which describes the condition wherein the person is not able to breathe normally at sleep due to an obstruction in the airway. The upper airway occlusions comprises of the naso-pharyngeal blockages like polyps, adenoids or deviated septums; oro-pharyngeal occlusions like macroglossia or posterior mandibular positioning; velo-epiglotto-pharyngeal occlusions like tonsillitis or a long uvula; or even a large neck circumference (increased BMI). All these press upon the airway, leaving the person gasping for air to breathe. The tongue (the genioglossus attached to the mandible) (fig 6) is almost always the biggest troublemaker. During sleep, when our whole body is at rest, the mandible falls backward pulling the tongue along with it, thus obstructing the airway space. This results in lesser oxygen entering the body during sleep. Hence, the heart would need to pump out oxygen-rich blood at a higher pressure. Since, the oxygen intake is at a lower level, the resultant hypercapnia (increase in blood-CO2 level) sends signals to the brain to ask the person to wake up and breathe, saving him/her. Long term apnoea leads to a weak heart killing the person, eventually, during sleep.
First, we need to diagnose the patient. All prospective OSA patients need to undergo a sleep study at night, where they need to sleep one night in a hospital with an ambulatory sleep study machine. The most important reading from this sleep report would be the AHI (apnoea-hypopnea index). The normal level is 3. Currently, all diagnosed OSA patients are treated with a large C-PAP machine which is expensive and has compatibility problems. Patients with AHI of 3 to 70 can be treated with oral appliances and if more than 70 with C-PAP’S (or both) (fig 7& 8).
The treatment is basically getting rid of these airway occlusions. The patient, at first needs to be cleared by the ENT, for any nasal/throat obstructions. We now need to keep the tongue forward during sleep with adjustable custom made oral appliances. These are constructed by recording the correct bite-registration; which is normally 30% of maximum opening and 70% of maximum mandibular protrusion also checking for adequate muscle facilitation. This helps in keeping the mandible and the attached tongue in a forward position opening up the airway. The C-PAP also works in an almost similar manner by passing positive air pressure through the nostrils, thus opening the airway. However, due to its cumbersome nature, more and more patients are now opting for oral appliances (fig 7).
Common sleep problems like snoring, night clenching, sleep bruxism, sleep restlessness, restless leg syndrome, sleep talking, somnambulism, disturbed sleep and excessive daytime sleepiness need to be identified. These are things that are seen in almost everyone but need to be tackled seriously.
So, think neuromuscular…broaden the horizon of your thinking…STOP CONSIDERING YOURSELF AS JUST A ‘TOOTH DOCTOR’!
Dr. Rajesh Raveendranathan BDS, MICCMO
Dr. Meera Mathai MDS
I used to have constant headaches for nearly 20 years. I've met lots of ENT surgeons and neurologists and have been consuming their medicines until I heard about Dr. Raj's NMD therapy from a friend of mine who got cured by him. I am really thankful to him for freeing me from my aches. I never realized my tiredness during any physical activity could in any way be related to my snoring.