and/or functional alterations of the masticatory apparatus, fundamentally in the Temporomandibular Joints (TMJ) and the associated cranio-cervical musculature. The most frequent causes of this disease are situations of instability in dental occlusion (the way in which the upper teeth fit together with the lower teeth), craniofacial trauma, certain psychological disorders (anxiety, stress or depression) that lead to bruxism (grinding and/or clenching of the teeth), or the presence of generalized diseases such as rheumatoid arthritis or fibromyalgia, which can affect the TMJs and the masticatory musculature, respectively.