Masticatory muscle hyperactivity has been considered a significant factor in promoting and perpetuating dysfunctional symptoms observed in Temporomandibular Disorder patients. Many therapeutic modalities have evolved within Dental Medicine that attempt to lessen or resolve the varying symptoms frequently reported by dysfunctional patients. One such method, known as Ultra Low Frequency (ULF) Transcutaneous Electrical Neural Stimulation (TENS), has been used to relax the masticatory musculature by applying an electrical stimulus to the efferent motor fibers of the Vth and VIIth cranial nerves, such that TENS can result in pain analgesia and patient sedation, restore compromised muscle physiology, and increase muscle resting length. TENS also aids in establishing a neuromuscular maxillomandibular relationship by inducing a muscularly contracted involuntary arc of closure. This chapter discusses TENS as a treatment modality for Temporomandibular Disorders, explains how to employ TENS to obtain a neuromuscular maxillomandibular relationship, and illustrates in a Clinical Case Report the use of TENS in combination with the T-Scan Computerized Occlusal Analysis System to measurably and physiologically balance a removable overlay anatomical acetyl resin orthotic prosthesis.
Masticatory muscle hyperactivity has been considered a significant factor in promoting and perpetuating dysfunctional symptoms observed in Temporomandibular Disorder patients. Muscle hyperactivity leads to facial pain, clenching and grinding habits, temporal headaches, and mandibular fatigue. Suggested muscle relaxation treatments include muscle relaxant medications (Dionne, 1997), biofeedback (Dalen, Ellertsen, Espelid, & Gronningsaeter, 1986), stress reduction counseling (Schumann, Zwiener, & Nebrich, 1988), intraoral orthosis (Carr, Christensen, Donegan, & Ziebert, 1991), and therapeutic massage (Wright & Schiffman, 1995).
Ultra Low Frequency (ULF) Transcutaneous Electrical Neural Stimulation (TENS) has been shown in to cause direct stimulation of motor nerves (Gomez & Christensen, 1991). This stimulatory effect can be used to relax hyperactive masticatory musculature, by applying a once-per-second electrical stimulus to the efferent motor fibers of the Vth and VIIth cranial nerves (Kamyszek, Ketcham, Garcia, & Radke, 2001). After electrodes are properly placed on the patient’s head (Figure 1), brief rhythmic twitch contractions are induced within the musculature, resulting in an increase in circulation and a reduction in posturing electrical activity (Kamyszek, Ketcham, Garcia, & Radke, 2001). Afferent nerve fibers are also stimulated during the pulsing, such that TENS has been used to provide analgesia for patients suffering from facial pain (Holt, Finney, & Wall, 1995), to control the pain response to cavity preparation (Horiuchi, Suda, Hanada, & Suzuki, 1978), and as a method of patient sedation (Shane & Kessler, 1967).
One set of three TENS electrodes are placed over the Left and Right Coronoid notches, with the third electrode placed on the center of the neck below the Nuccal Line. The second set of three TENS electrodes are placed over the Left and Right Scalene muscle groups, between the sternocleidomastoid and Levator Scapulae. A third electrode is centered on the neck beneath the one first placed below the Nuccal Line. Here, the patient is being pulsed into articulating paper to mark the occlusal contacts present on an orthotic
Studies involving ULF-TENS have determined that TENS reduces muscle activity levels on the resting EMG levels of both hyperactive and relaxed muscles (Kamyszek, Ketcham, Garcia, & Radke, 2001). Additionally, TENS has been shown to establish a nonendorphinergic analgesic effect that follows prolonged and continuous muscle pulsing (Pertovaara, Kemppainen, Johansson, & Karonen, 1982; Olausson, Eriksson, Ellmarker, Rydenhag, Shyu, & Andersson, 1986). However, one study revealed that although TENS reduced both pain and EMG activity of the anterior portion of the temporal muscle, it increased the activity of the masseter muscles during Maximum Voluntary Clench (MVC). The study showed that a single TENS application was an effective pain reducer, but it did not act homogeneously on the electrical activity levels of the muscles evaluated (Rodrigues, Siriani, & Bérzin, 2004).
Key Terms in this Chapter
Myocentric Occlusion: A maxillomandibular relationship established with a TENS-induced involuntary arc of closure that differs from a patient’s habitual closure arc into Maximum Intercuspation (MIP), and from a Bimanually Manipulated arc into Centric Relation (CR).
Myobite: Making an intraoral registration that captures the neuromuscular position, which was guided by electromyographic readings made while observing the mandibular tracking of the TENS-pulsed mandibular arc of closure. The Myobite registers the zone of improved function, which lies individually per patient, between the mandible and the maxilla.
Neuromuscular Physiologic Position: The maxillomandibular relationship determined with a TENS-induced involuntary arc of closure. The neuromuscular physiologic position is similar to Myocentric Occlusion.
Removable Overlay Anatomical Acetyl Resin Orthotic Prosthesis: A removable neuromuscular orthotic that covers all the mandibular teeth with anatomic tooth forms that maintains the physiologic neuromuscular position, and makes interocclusal contact with the opposing maxillary dentition.
Patient Self-Closure: A non - TENS induced arc of closure that a patient makes into their opposing dentition when wearing a neuromuscular orthotic. Patient self-closure is also a mandibular closure movement a patient makes into their habitual maximum intercuspal position (MIP) without TENS.
Subjective Interpretation of Articulating Paper Markings: A longstanding and unscientific method of selecting contacts for occlusal force reduction based upon the appearance of articulating paper markings. Subjective Interpretation principles suggest that large dark articulating paper markings are forceful contacts; lighter paper markings are low-force contacts; and many equal-sized paper markings spread around the arch indicate occlusal force balance and bilateral time simultaneity. These principles have always been widely believed to be a reliable despite having never been tested in any scientific study. Recent published studies have shown that the principles of Subjective Interpretation are unsubstantiated, and that dentists do not accurately perform the technique.
TENS/T-Scan: A combination approach to obtain on an involuntary arc of closure, TENS pulse-induced, relative occlusal force and real-time contact sequence data that records and describes the occlusal force distribution. The patient is repeatedly TENS-pulsed into an orthotic with the T-Scan recording sensor interposed between the orthotic and the opposing teeth, to measurably record in Turbo Mode, the orthotic’s occlusal contact forces. Subsequent corrective occlusal adjustments are guided by the T-Scan data, eliminating the clinician’s Subjective Interpretation.
Involuntary Arc of Closure: A TENS pulse-induced muscular closure movement that significantly differs from a patients’ habitual closure arc. Usually, the involuntary arc of closure brings the mandible forward and down out of the glenoid fossa to establish more of an edge-to-edge maxillomandibular relationship.
ULF – TENS: Ultra low frequency transcutaneous nerve stimulation. Electrodes placed on the patient’s head muscles induce brief, rhythmic, twitch contractions within the musculature, increasing circulation and reducing posturing electrical activity. ULF- TENS has been used to provide pain relief, and as a patient sedative.
Myo-Monitor: The Myo-monitor technology provides the clinician the ability to select pulse rate and pulse amplitude when TENS pulsing a patient to establish a neuromuscular position. The Myo-monitor has been used in published studies to measure human muscle function levels without TENS, and to repeatedly induce an involuntary arc of closure with TENS.