Employing the T-Scan/BioEMG III Synchronized Technologies to Diagnose and Treat Chronic Occluso-Muscle Disorder

Employing the T-Scan/BioEMG III Synchronized Technologies to Diagnose and Treat Chronic Occluso-Muscle Disorder

Robert B. Kerstein, DMD (Tufts University School of Dental Medicine, USA & Private Dental Practice Limited to Prosthodontics, USA)
DOI: 10.4018/978-1-5225-9254-9.ch007


This chapter discusses chronic occluso-muscle disorder, which is a myogenous subset of temporomandibular disorder (TMD) symptoms resultant from occlusally activated muscle hyperactivity. It also describes the computer-guided occluso-muscle disorder treatment known as disclusion time reduction (DTR), that studies repeatedly show reduces many common muscular temporomandibular disorder symptoms. T-Scan-based research since 1991 has determined that a significant etiologic component of occluso-muscle disorder is prolonged (in time) occlusal surface friction shared between opposing posterior teeth during mandibular excursions, that occurs in both normal chewing function and during parafunction. This friction results in prolonged compressions of the periodontal ligament (PDL) fibers of the involved teeth, which when in excursive opposing occlusal contact, also experience pulpal flexure that leads to pulpal neural activation, which together with the periodontal ligament compressions, trigger excess muscle contractions within the masticatory muscles. It is this unique neuroanatomy that incites and perpetuates many chronic muscular TMD symptomatology, that can be readily resolved in patients that meet the diagnostic criteria for DTR candidacy, using the ICAGD coronoplasty that is performed in the maximum intercuspal position (MIP), without employing treatment splints, deprogrammers, appliances, orthotics, or mandibular repositioning. Additionally, this chapter will highlight the newest disclusion time reduction therapy (DTR) studies that support the clinical implementation of this highly effective measured occlusal treatment for occluso-muscle disorder.
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Chronic Occluso-muscle Disorder (Dawson, 1989a) is a myogenous subset of Temporomandibular Disorder symptoms that afflicts the masticatory musculature with chronic pain, headaches and dysfunction. The associated muscle hyperactivity is a primary source of the frequently observed and highly similar group of symptoms that suffering patients commonly describe (Glickman, 1979a; Dawson, 1989a):

  • Chronic facial pain, chronic temporal headaches, frequent clenching and grinding of the teeth, morning jaw pain, eye strain, earaches, chewing fatigue, chewing muscle and tooth pain, temperature sensitive teeth, and mild clicking and popping of the Temporomandibular Joints.

Muscle hyperactivity etiologies previously cited within the literature are Bruxism (Clayton, Kotowicz, & Zahler, 1971; Dawson, 1989b), clenching habits (Bertram, Rudisch, Bodner, & Emshoff, 2002), malocclusion (Mohlin, et. al., 2004), Trigeminal Neuralgia (Zakrzewska & McMillan, 2011), and occlusal interferences (Glickman, 1979b; Baba, Yugami, Yaka, & Ai, 2001).

Longstanding advocated treatments for chronic masticatory muscle hyperactivity have attempted to treat the symptomotology (Herman, Schiffman, Look, & Rindal, 2002) without addressing an underlying non-physiologic occlusal surface friction problem, that has been shown to be etiologic for the hyperactivity (Williamson and Lundquist 1983; Kerstein & Wight, 1991; Kerstein, 1995; Kerstein, Chapman, & Klein, 1997; Kerstein & Radke 2006; Kerstein & Radke, 2012). Despite the number of studies that have demonstrated an occlusal surface friction/masticatory muscle hyperactivity relationship to symptom appearance and frequency, an occlusal etiology as being causative for chronic Occluso-muscle Disorder symptoms, has not yet been widely accepted within the differing disciplines of Dental Medicine. In the traditional approaches to treating Occluso-muscle Disorder symptoms, the occlusion has been considered a limited component of the etiology, in favor of emotional and psychological factors, where it has been suggested that treatments be reversible and non-invasive to the teeth and oral structures.

Appliance therapy (Bertram, Rudisch, Bodner, & Emshoff, 2002) is the most frequently employed treatment. The main effects an intraoral appliance creates that can improve Occluso-muscle Disorder symptomotology are:

  • The appliance interferes with the function of the teeth by limiting frequent tooth interdigitation and fictional occlusal surface excursive contact that occurs during parafunction and swallowing. This buffers the physiologic occlusal friction problem that is etiologic for the hyperactivity, by not letting teeth frictionally engage when the appliance is in place

  • The appliance opens the vertical dimension, repositions the mandible in a chosen new anteroposterior and mediolateral position, and unloads the Temporomandibular Joint structures by moving the condyle vertically down and slightly out of the glenoid fossa.

Appliance therapy is often combined with muscle relaxant, pain, and anti-inflammatory medications, physical therapy to the jaw musculature (McNeely, Armijo, Olivo, & Magee, 2006), trans-cutaneous electronic nerve stimulation (TENS) (Alvarez-Arenal, Junquera, Fernandez, Gonzalez, & Olay, 2002), and soft food diets. All of these treatment approaches have been reported to be somewhat helpful to the chronic Occluso-muscle Disorder patient, and are considered viable, reversible Occluso-muscle Disorder treatments. Occlusal adjustment procedures, if employed at all in the conventional treatment protocol, follow the Appliance Therapy treatment phase, because the appliance has been considered to be a reversible therapy (Okeson, 1985a; Solow, 2011).

Key Terms in this Chapter

ICAGD Coronoplasty: ICAGD is a measurement driven, computer-guided, occlusal adjustment procedure that shortens prolonged excursive movement occlusal surface contact frictional durations. It is an excursively focused occlusal adjustment procedure that is performed from MIP. It is commenced with excursive movement occlusal adjustments, which differs from all other advocated occlusal adjustment and Equilibration procedures that commence with closure movement occlusal corrections. The main objective of ICAGD is to shorten the posterior disclusion time to < 0.5 seconds in all three excursions, to compress the excursively engaged teeth and their respective Periodontal Ligament fibers, for far less time than in the pretreatment condition. Shortening the disclusion time equally shortens the excursive masticatory muscle contraction durations and lessens the volume of excursive muscle contractions, by markedly lessening the time periodontal ligament mechanoreceptors are compressed during excursive movements. A post treatment disclusion time per excursion of < 0.5 seconds establishes a statistically significant, hyperactive muscular relaxation effect from within the patient’s own neurophysiology.

Disclusion Time Reduction (DTR): Reducing the time-duration that posterior occlusal surfaces frictionally engage during right, left, and protrusive excursive movements to be less than 0.5 seconds per excursion. It is routinely accomplished by reshaping the opposing occlusal surfaces that frictionally engage using the ICAGD coronoplasty, with or without adding in steeper anterior guidance contacts that will more rapidly lift apart the posterior teeth.

Time-to-Muscle Shutdown: This muscular physiologic assessment measures the time required for the masticatory muscles to reach their baseline contraction level, after a patient commences an excursion from the maximum intercuspal position (MIP), through to complete posterior disclusion. The muscle shut down timing values should fall within the disclusion time durations. Short disclusion time induces a very short duration of a muscle’s return to its’ functional baseline.

Unmeasured Occlusal Adjustments: Unmeasured occlusal adjustments involve subjectively interpreting the size, color, and shape characteristics of articulating paper markings to determine occlusal contact force content. Current research indicates that clinicians guess (< 14% accuracy) at which contacts they believe are forceful contacts, whereby this method does not guide a clinician to select correct contacts for treatment. Unmeasured occlusal adjustments have yielded mixed results in the treatment of occluso-muscle disorder. This random, subjective contact selection that is based upon paper mark appearance characteristics, has led to unpredictable therapeutic effects that have been reported in unmeasured occlusal adjustment studies.

Lingual-to-Lingual Working Excursive Contacts: Masticatory muscular hypercontraction is a PDL mechanoreceptor compression mediated process. Lingual-to-lingual excursive interfering contacts compress the PDL mechanoreceptors similarly to how buccal-to-buccal working side interfering contacts do, but the lingual-to-lingual contacts cannot be visualized intraorally. Tooth compressions and PDL compressions occur in all directions such that lingual-to-lingual contacts are often a significant component of a prolonged working side group function that creates hyperactivity in the masticatory musculature. Lingual-to-lingual working side contacts can be clearly observed in T-Scan data when they exist in an excursive movement.

Excursive Occlusal Surface Friction: Opposing posterior tooth occlusal surface “milling” engagement that occurs early in an excursive movement, in and around the central fossa prior to when the anterior guidance lifts the posterior teeth apart. The duration of the excursive frictional engagement is equal to the time duration that the involved teeth compress their respective periodontal ligament mechanoreceptors. The PDL mechanoreceptor compressions in turn, hyperactivate the masticatory musculature.

Maximum Intercuspal Position (MIP): MIP is the patient’s maxillomandibular relationship where the teeth are in maximum occlusal contact irrespective of the position of the condyle-disk assemblies. MIP is where the patient’s teeth habitually fit when they self-close into complete tooth intercuspation. ICAGD is performed in the MIP, which simplifies treatment for the patient by maintaining the habitual occlusal contact pattern. Since the patient is not moved to a different occlusal position there is no need for them to adapt to an appliance, a new vertical dimension, or a newly established closure occlusal contact pattern. Additionally, treating an occluso-muscle disorder patient in MIP is easier for the clinician because the patient stays in their stable base occlusal contact pattern during treatment.

Average Chewing Pattern (ACP): A method for studying human mastication in the sagittal, coronal, and frontal planes that uses magnet-based mandibular incisor point electrognathography, which records chewing movements with a magnet anchored to the mandibular incisors while subjects unilaterally chew gum. The average chewing pattern (ACP) is computed from 10 to 20 cycles of gum chewing recorded by how the magnet is tracked in three planes of motion.

Unique Molar Pulpal and Periodontal Ligament Mechanoreceptor Neuroanatomy: The molar and premolar pulp fibers and periodontal ligament mechanoreceptors are part of the peripheral nervous system (PNS). Peripheral nerves lie outside of the brain and spinal column, such that they usually make their initial synapse outside of the central nervous system (CNS). However, the molar pulpal fibers and the periodontal ligament (PDL) mechanoreceptors are unique in that despite being peripheral nerve afferents, they are the sole human peripheral nerves that enter the CNS directly (into the mesencephalic nucleus) and travel further within the CNS to the trigeminal motor nucleus, where they make their first synapse with the efferent motor fibers to the four muscles of mastication, the tensor tympani, the tensor veli palatini, the mylohyoid, and the anterior belly of the digastric muscles (the swallow mechanism muscles). These same fibers also travel within the brain directly to the reticular formation (without any intervening synapses), which is a major neural center that controls functions like swallowing, sleep, posture, and breathing.

T-Scan 10/BioEMG III: The T-Scan 10/BioEMG synchronization records simultaneously, both occlusal contact force and timing data, and its corresponding muscle activity levels. The two integrated systems capture real-time occlusal contact data and masticatory muscle electrical potentials that during playback, are analyzed by the clinician in a dynamic “Movie”, where both technologies play side-by-side on the computer desktop. In this way, transitory occlusal contact force and timing variances can be time-correlated to specific changes in masticatory muscle activity levels. Both the T-Scan data and the EMG data can be played together forwards and backwards continuously, in 0.003 second frames, or in stop-action, to be able to view small time-increments that relate occlusal function to muscle function. Clinically implementing the T-Scan 10/BioEMG III synchronization module is practicing “state of the art” occlusion.

Beck Depression Inventory (BDI-II): An emotional depression index questionnaire comprised of 21 multiple choice questions. The BDI-II estimates a subject’s level of depression scored on a 4-point scale, where for each question asked the subject circles a numerical choice that reflects their current feeling.

Factors that Promote Long Disclusion Time: Prolonged disclusion time and occlusal surface excursive friction are present within an occlusal scheme resultant from many contributory factors. These eight factors predispose the occlusion to excursive movement friction: The Angle’s Classification, an anterior Open Occlusion, the presence of occluding third molars, poor vertical tooth orientation, a lack of canine contact in MIP, shallow anterior guidance surfaces, an exaggerated Curve of Spee, tipped-up mesiodistal molar orientation, and lingual-to-lingual working side excursive contacts.

Open Canine Contact: When a space exists between opposing maxillary and mandibular canines in the maximum intercuspal position. A lack of canine contact predisposes the occlusal function to prolonged posterior disclusion time and prolonged occlusal surface excursive friction, which can lead to the development of hyperactive masticatory musculature. Open canine contact is such an important factor in creating excursive masticatory muscle hyperactivity, that when treating occluso-muscle disorder patients who present with open canine contact, it must be addressed before any other clinical step can be successfully undertaken.

Working Side Group Function: Working side group function describes an occlusal scheme where the first molar, both premolar teeth, and the canine, all together share the lateral excursive guidance on the side toward which an excursion is made. The posterior teeth stay in contact initially, and then progressively disengage as the anterior guidance lifts the posterior teeth apart. Since the 1980s working side group has been advocated as an acceptable occlusal scheme. However, modern research has shown that working side group function with molar and premolar shared guidance contact is problematic neurophysiologically, because it activates the most muscle masticatory muscle contractions during working excursive movements.

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