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INTRODUCTION
Jens C. Türp
Craniomandibular Dysfunction
Terminology
Technical terms must be clarified to avoid misconceptions and misunderstandings, especially when describing the factors relating to function. In particular, a distinction must be made between “dysfunction of the masticatory system,” “craniomandibular dysfunction,” and “myoarthropathy of the masticatory system”; these terms should not be considered synonymous. In 2016, the German Society for Functional Diagnostics and Therapy published proposed definitions for these and other important terms for the first time.1
Dysfunction of the masticatory system
Dysfunction of the masticatory system refers to a “short- or long-term disturbance of the homeostasis or economy of the masticatory system caused by any structurally or functionally substantiated deviation from normal function, such as functional deficits due to trauma, injury to the structural integrity, and functional/parafunctional stress, including deviations that justify prosthodontic, orthodontic, or surgical measures.”1
Craniomandibular dysfunction
Craniomandibular dysfunction (CMD) is classified as “a specific functional disorder that affects the muscles of mastication, the temporomandibular joints (TMJs), and/or the occlusion.”1 Clinically, CMD encompasses the areas of pain and/or dysfunction.
Pain is manifest as:
- Masticatory muscle pain
- TMJ pain
- Toothache of (para)functional origin
Dysfunction can appear in the form of:
- Painful or nonpainful limitation of movement of the mandible (aspect aimed at mandibular movements)
- Hypermobility or incoordination of the mandible (aspect aimed at mandibular movements)
- Painful or nonpainful intra-articular dysfunction (aspect aimed at the TMJ)
- Premature contacts interfering with function and gliding obstacles (aspect aimed at the occlusion)
CMD is a collective term that encompasses symptoms not in need of treatment and symptoms that do need treatment. In principle, there is always a need for treatment when pain is present; in the case of dysfunction, the need for treatment is dependent on the severity of the dysfunction.
Myoarthropathy of the masticatory system
Myoarthropathy of the masticatory system (MAP), a term introduced in 1970 by Tübingen dentist Willi Schulte,2 denotes a subgroup of craniomandibular dysfunction. It refers to symptoms and findings affecting the muscles of mastication, the TMJs, or associated tissue structures; it does not take into consideration the occlusion. This term equates to the term “temporomandibular disorder (TMD).” If pain is involved, these symptoms can be summarized under the heading “myoarthropathic pain.”
Etiology
Numerous mechanisms have previously been held responsible for the etiology of myofascial pains of the muscles of mastication and pains in the TMJs. Nociceptive pain is currently the underlying basis of models for these musculoskeletal symptoms. This nociceptive pain can be triggered by overloading of the tissue and promoted by a number of disposing factors. Microtrauma and local ischemia3—together with their structural and functional counterparts, such as activated osteoarthritis,4 the myofascial trigger point,5 local muscle fatigue, and aching muscles6—essentially serve as overarching pathophysiologic explanatory models. Common to these hypotheses is the assumption that, at the end of the causal chain, afferent nerve fibers and tissue cells release protons7 and other endogenous algesic substances (eg, glutamate, substance P, bradykinin, histamine, prostaglandin E, serotonin, potassiu