## 1 Introduction  
Temporomandibular joint disorders (TMD) can involve the masticatory musculature, the temporomandibular joint (TMJ), or both [1].  
TMDs can be classified as an intra-articular or extra-articular disease: (a) Intra-articular TMDs include (1) congenital or developmental disorders, (2) degenerative joint disorders, or (3) any condition involving the articular disc, the condyle, and the glenoid fossa.  
(b) Extra-articular TMDs include all masticatory muscle disorders: (1) myofasical pain disorder, (2) local myalgia, (3) myositis, and (4) myospasm [1].  
The causes of TMD include micro- and macrotrauma and systemic, iatrogenic, occlusal, and mental health disorders [2]. Unconscious teeth clenching induces constant trauma to the muscles and joints and represents, therefore, one of the major causes of myofasical pain [3].  
Myofasical pain syndrome represents one of the most common TMDs and chronic problems in the maxillofacial region. Myofasical pain is classified as a dysfunction of the stomatognathic system that belongs to Axis I pain-related TMDs.  
In the new DC/TMD, the term myofasical pain describes two new DC/TMD conditions: (1) myofasical pain, defined as pain spreading beyond the site of palpation but within the boundary of the muscle being palpated, and (2) myofasical pain with referral, defined as pain in a specific site that creates pain in another area beyond the boundary of the muscle being palpated [4].  
It is a painful condition characterised by trigger points, which can create local and referred pain, tenderness, autonomic phenomena, anxiety, and depression [5]. A myofasical trigger point (MTrp) is a hyperiritable spot which provokes pain when compressed and can lead to a characteristic referred pain and motor dysfunction. The painful symptoms radiate pain to distant sites [4; 6].  
Studies report various treatments for MPS, such as exercises, Trp injections, medications, and other alternative therapies [7]. Most symptoms get better with a combination of non-invasive treatments and occlusal devices. Other means are recommended for chronic or refractory cases, such as nonsteroidal anti-inflammatory drugs, muscle relaxants, benzodiazepepines, or antidepressants [1].  
Tension-type headache (TTH) is the most prevalent primary headache disorder and affects 80% of the population; therefore, the socio-economic consequences are significant. Studies show that the pain elicited by active MTrPs reproduces the headache pattern in TTH patients [8].  
This prospective study reports on 10 patients with headaches and orofacial pain from myofasical pain syndrome, caused by unconscious clenching [9], treated with pathological therapy: passive aligners and biofeedback exercise.  
This study aimed to evaluate the repeatability of the variation in functional connectivity at rest after treatment, the actual stretch/lengthening of the masseaters (taken as a reference for masticatory muscles) after treatment, and their correlation with the development of symptoms (VAS and palpation).  
Therefore, we wanted to see if the results obtained with therapy were repeatable using functional magnetic resonance imaging. This enables us to correlate a subjective datum (pain) to an objective one (variation in the functional connectivity of the networks correlated with pain perception).