# Use of Tens in the Diagnosis of Functional Mandibular Lateral Deviation
###### Abstract
In general terms, it could be suggested that orthodontic therapy should achieve an occlusion that does not require neuromuscular adaptation and that the therapy itself should adapt to the neuromuscular system. Several years ago, some authors stressed the importance of the mandibular rest position and its reproducibility as a diagnostic reference [13; 14]. According to this idea, the mandibular rest position is largely determined by the spatial position in which the occlusal contact occurs. Therefore, the mandibular rest position is usually \"adapted\" by the neuromuscular system, which will keep the mandible in a position appropriate for stomatognathic functions. A recent literature review indicates that there is strong clinical evidence that Rest Mandible Position (RMP), Rest Vertical Dimension (RVD), and the Interoclusal Dimension (IOD) are to be found within a three-dimensional spatial \"range\" largely determined by the active adaptation of the neuromuscular system [15]. This adaptation is extensive, but in specific cases, probably associated with other not necessarily occlusal components, dimensional variations may go beyond the limits of muscular compensation and induce occlusal instability and/or acute and chronic suffering [16; 17]. The basic idea of these observations is that starting from a relaxed neuromuscular resting position of the mandible, it is possible, by comparing it with the habitual occlusion, to assess the three-dimensional occlusal space in which the contact between the jaws should take place without an adaptation effort of the stomatognathic musculature. The use of dental ULFTENS is among the techniques used to achieve muscle relaxation and a resting position of the jaw. Dental ULFTENS belongs to the category of TENS that involves, in a general sense, the cutaneous stimulation of nerve branches located more proximally to the electrode application site. The mechanism of action of such stimulation has been extensively studied and demonstrated and involves, depending on the frequency of delivery, the intervention of different response modulation centers. Stimulation with frequencies below 20 Hz is referred to as low-frequency TENS, and below 4 Hz is referred to as ultra-low-frequency TENS, also called \"acupuncture-like\" in some cases [18; 19]. In the case of low and ultra-low-frequency TENS, a central mechanism of action mediated by the prefrontal cortex and the ventrolateral PAG has been suggested. This action involves, among others, an endorphinic activity at the PAG level, a peripheral response characterized by modulation of central pain pathways, and a reduction in muscle tone together with a lowering of sympathetic tone [20]. Transcutaneous electrical nerve stimulation and conditioned pain modulation influence the perception of pain in humans [21]. Dental ULFTENS consists of transcutaneous electrical stimulation with an electrosttimulation of the V and VII pairs of cranial nerves. It is performed through the application of electrodes bilaterally at the level of the area anterior to the tragus. The stimulation frequency is of the order of 0.66, which is why it belongs to the ultra-low category, and the amplitude of this stimulation is such that it evokes a minimal passive upward movement of the jaw. This is determined by the direct action of the impulse that reaches deep into the mandibular branch of the trigeminal, through the coronoid incisura, exciting its motor fibers and causing peripherally in a formic way a contraction of the elevator muscles of the mandible. In this way, it would act according to a central mechanism as mentioned above and associate an automatic peripheral muscular upward movement of the mandible. Dental ULFTENS has been shown to be able to reduce the myoelectric activity of the master and anterior temporalis muscles in a resting position [22].