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TMJ/TMD Historically

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Introduction – the genesis of Neuromuscular Dentistry

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Dr. Bernard Jankelson introduced the term Neuromuscular Dentistry to the dental profession in 1967. The masticatory system is a three dimensional system composed of Teeth, Temporomandibular Joints and Muscle. Without muscles the masticatory system is static and non-functional. Neuromuscular dentistry is a comprehensive concept of a dynamic masticatory apparatus that follows universal anatomic and physiologic laws.

However, dentists did not have the technology or protocols to objectively evaluate and diagnose masticatory muscle function/dysfunction or predictably restore masticatory muscles to optimum function. Yet, there is universal consensus that 90% of temporomandibular dysfunction is myogenous in origin. The dental profession operated in a two dimensional field of teeth and temporomandibular joints. Qualitative or quantitative evaluation of the important muscle component could not be possible until development of appropriate measurement technologies. Neuromuscular dentistry operates in a dynamic three dimensional field of teeth, joints and muscle.

The seed of neuromuscular dentistry begins with a little told story of how Dr. J., as he was known to friends and colleagues, became involved in neuromuscular medical research at the University of Washington and University of Oregon Schools of Medicine. In the early 1940’s his beloved wife, Cherub, developed symptoms of neuromuscular disorder characterized by muscle weakness, vertigo, visual disturbance and other non-specific neuromuscular symptoms. He traveled the world looking for answers and a diagnosis. One of the leading experts on what is now called multiple sclerosis was a physician, Dr. Jonez, at nearby Tacoma St. Joseph Hospital. The diagnosis was made. In the early 1940s there was no known treatment. Dr. Jonez and Dr. Jankelson began a friendship and collaborative search for answers.

Drs. Jonez and Jankelson theorized that the problem was related to degenerative changes in the conductive myelin sheath of the nerves that prevented proper electric conduction. The next hypothesis was based upon the fact that myelin is a prodigious consumer of oxygen. Their early collaboration focused on ways to get more oxygen to the myelin sheath in order to prevent nerve degeneration. Dr. J continued to work with physicians and physiologists at the University of Washington and Oregon Bioengineering Departments following the hypothesis of possible beneficial therapeutic effects from increasing oxygen availability to thwart the continuing nerve degeneration. Something must have worked because his beloved Cherub lived a productive and happy 86 years.

With this early background, the genesis of neuromuscular dentistry began with the collaboration of Dr. Bernard Jankelson and Dr. H.H. Dixon, a renowned muscle physiologist, working together at the University of Oregon School of Medicine in the early 1960’s. The technology to change muscle metabolism and muscle resting states with low frequency TENS was the breakthrough that brought dentistry into a 20th Century paradigm consistent with the rapid technology associated with modern medicine. The electrical parameters established by Dixon and the insight of Jankelson to deliver the stimulus via the coronoid notch to proximate Trigeminal (V) and Facial (VII) cranial nerves exiting the cranium provided, for the first time, the technology whereby the dentist could directly alter the metabolic state of masticatory muscle to facilitate diagnostic and treatment outcome.

Dr. Jankelson assembled a R&D group of former Boeing engineers and biomedical engineers in 1970 to develop biomedical instrumentation to track jaw movement in three dimensions. Four years later, in 1974, the first clinical jaw tracking device was introduced. The system sensed the location of a small magnet attached to the labial of the lower incisor teeth helping the clinician diagnose and treat occlusal mandibular dysfunction with objective physiologic measurement data.

Technology to monitor masticatory muscle activity at rest and in function in a clinical environment was necessary to elevate diagnosis and treatment of occlusion from art to science. Surface electromyography (sEMG) is the technique by which the action potentials from muscle fibers are recorded and displayed. This technology became available to the dental clinician in 1979. Real time sEMG was integrated into the three dimensional computerized jaw tracking system in 1987, allowing clinicians to objectively correlate muscle activity and jaw position.

What is Neuromuscular Dentistry?

Forty years of research and clinical application of the neuromuscular instrumentation and clinical paradigms can be summarized to answer “What is Neuromuscular Dentistry?”

1. Neuromuscular dentistry utilizes advanced, scientifically recognized biomedical instrumentation to objectively measure known physiologic parameters of mandibular masticatory function.

2. Neuromuscular dentistry paradigm states that generic universal cellular, histo-chemical, musculoskeletal anatomic and physiologic principles are the key to understanding masticatory function/dysfunction. Neuromuscular principles are consistent with known scientific axioms of other scientific disciplines.

3. Neuromuscular paradigm is based upon the principle that the biomechanics of occlusion follows known neurophysiologic (not necessarily mechanical) principles involving the temporomandibular joints, the teeth and the masticatory musculature.

4. Neuromuscular paradigm proposes that occlusal proprioceptive sensory information can affect many other musculoskeletal system of the body.

5. Neuromuscular dentistry clinical paradigm defines the objective of optimizing joint and muscle function BEFORE altering and/or restoring the dental intercuspation.

6. Neuromuscular clinical objective is to restore the dental occlusion to a position that minimizes the need muscle for muscle accommodation and facilitates muscle relaxation.

7. Neuromuscular paradigm considers the TEETH to be the dominant component of the masticatory triad because muscles and the TMJs will follow the dictates of intercuspal closure to HABITUAL (CENTRIC) OCCLUSION during deglutition. The MUSCLES and TMJs will try to accommodate to the habitual (centric) intercuspal position. When the need for accommodation exceeds the adaptive capacity of the muscles and joints it often results in pain and dysfunction of these structures.

8. Neuromuscular clinical protocols require reversible occlusal therapy until measurable physiologic parameters and patient response suggest a stable physiologic occlusal position has been established. The patient must be asymptomatic and stable for at least three months before phase II final occlusal restoration.

9. Neuromuscular dentistry is based upon restoration of the dental occlusion to a position (Myocentric Occlusal Position) defined by minimal muscle electrical activity of the posturing mandibular muscles along an isotonic path of mandibular closure (REST).

10. Neuromuscular data suggest that deficiency of posterior occlusal support (Posterior Hypo-occlusion) is the most common occlusal finding in TMD patients. Restoration of the posterior deficiency is initially accomplished with reversible appliance therapy (Phase I Therapy), followed by Phase II irreversible therapy only when indicated and desired by the patient.

Neuromuscular occlusal objectives

1. Provide occlusal relationship of the mandible to maxilla that minimizes need for muscle accommodation and posturing.

2. Provide an occlusal relationship that allows for optimal decompression of nerve, muscle and vascular structures of the facial and masticatory system. Decompress the retro-discal tissues of the temporomandibular joint.

3. Reduction or elimination of nerve entrapment by restoring muscles to their optimal resting length. Hypertonic muscle spasm shortens muscle which can entrap nerves intra-muscularly or as the nerve passes between muscles or other anatomic structures.

4. Decompression of the temporomandibular joint is facilitated by a stable and measurable neuromuscular intercuspal position. The temporomandibular joint is the only joint in the body where anatomic relationships within the joint are dictated by an external terminal contact end point i.e. habitual (centric) occlusion.

5. Restoration of optimal posture of the head and neck with minimal muscle activity at rest of all related muscle groups.

Neuromuscular protocols

1. Relax the muscles

2. Measure the muscle relaxation

3. Decompress the TMJ

4. Record the relaxed jaw position.

5. Initiate appropriate neuromuscular occlusal therapy using the myocentric recording which is a position along the isotonic path of mandibular closure.

Conclusion

Neuromuscular principles and techniques combine state of the art technology with universal anatomic and physiologic principles to help trained clinicians treat patients with temporomandibular disorders, complex restorative problems, restoration of edentulous patients and orthodontic treatment. The management of occlusion as a dynamic three dimensional biologic system, rather than a static two dimensional system, allows the trained neuromuscular dental clinician to diagnose and manage difficult occlusal problems with predictable outcome never before attainable. Join the ICCMO to learn more about, and become trained in Neuromuscular Dentistry to help patients suffering from TMD.


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