Temporomandibular disorders (TMDs) are common in the general population. Patients who suffer with sleep disordered breathing (SDB) may have existing signs and/or symptoms of TMDs or develop these disorders during treatment with mandibular advancement type oral devices (MADs). When treating SDB patients with MAD therapy, it is critical to properly evaluate the temporomandibular structures to asses a baseline status as well as give the patient adequate informed consent prior to therapy. The aim of this paper is to provide a brief overview of TMDs and suggest a cursory examination protocol that the clinician can easily incorporate into their examination and consultation protocol.
Temporomandibular disorders (TMDs) are prevalent conditions in the general population.1-4 TMDs are defined as a collection of symptoms and signs involving masticatory muscles, the temporomandibular joints (TMJs) or both.5 The pain reported by TMD patients is typically located in the muscles of mastication, in the preauricular area, or in the TMJs.6 Other symptoms of TMD may include restricted mandibular range of motion and a functional alteration or deviation of the jaw opening or protruding motions. Screening questions for TMDs may include
- Do you have difficulty, pain, or both when opening your mouth, for instance when yawning?
- Does your jaw “get stuck,” “locked,” or “go out”?
- Do you have difficulty, Pain or both when chewing, talking, or using your jaws?
- Are you aware of noises in your jaw joints?
- Do your jaws regularly feel stiff, tight, or tired?
- Do you have pain in or near the ears, temples, or cheeks?
- Do you have frequent headaches, neck aches, or toothaches?
- Have you had a recent injury to your head, neck or jaw?
- Have you been aware of any recent changes in your bite?
- Have you previously been treated for unexplained facial pain or jaw joint problems?
Population studies have reported the prevalence of TMDs to be from 8% to 15% for women and from 3% to 10% for men2, suggesting that TMDs are significant causes of pain in the head and face region. While the etiology of TMDs is still not well described in the literature, it is generally thought that they are conditions comprising both psychosocial and neurophysiologic entities.8 Inflammatory mechanisms have been shown to be involved in temporomandibular joint pain and dysfunction.9 Milam proposed a possible etiology for inflammatory mechanism of the temporomandibular joint structures by what was described as a hypoxic-reperfusion injury.10 This process occurs when the capsular pressure of the temporomandibular joint exceeds the end-capillary perfusion blood pressure of the feeding vasculature. The area then undergoes reperfusion via mouth opening or relaxation of the elevator muscles. Capsular nociceptive fibers triggered by pathologic loading of the highly innervated synovial tissues may also stimulate the release of calcitonin gene-related peptide and substance P, leading to further inflammatory processes. Albeit a sometimes controversial suggestion, pathologic loading of the joint structures is often attributed to sleep parafunctional behaviors such as sleep bruxism.11 Sleep bruxism has also been suggested to be at least partially responsible for stomatognathic muscle pain.12, 13 Christensen reported that muscle pain was noted in subjects who voluntarily clenched for 20-30 seconds.14 Kydd and Daly reported that nocturnal clenching events can last as long as 20-40 seconds.15 Clark demonstrated that the average bruxing event was up to 60% of the force generated during voluntary maximum clenching prior to sleep.16 It may be inferred, then, that these parafunctional events could lead to tissue injury and subsequent nociceptive signaling from both the myogenous and arthrogenous components of the temporomandibular joint complex.
As part of a comprehensive workup, a systematic approach to patient evaluation is key to an accurate diagnosis and ultimately, therapeutic success. The examination should include an assessment of the stomatognathic musculature, the condition of the TMJs and the measurement of the mandibular movements. The most widely used and accepted method for evaluating the condition of the stomatognathic musculature is by digital palpation.17-19 Application of about 4-5 pounds of pressure (the pressure necessary to blanch the finger nail bed) applied with the palmer surface of the index, middle and ring fingers across the muscle fibers can be diagnostic of muscular abnormalities.20 The examination should identify tender areas as well as potential trigger points, which are thought to arise from abnormal motor end-plate activity releasing excessive amounts of acetylcholine.21 Trigger points are focally tender spots in taut bands of skeletal muscle that refer deep, aching pain to distant sites, often including non-muscular structures. A cursory stomatognathic muscle examination would include the following muscle groups; temporalis, masseter, sternocleidomastoid, splenius capitis, semispinalis capitis and the anterior portion of the trapezius muscle. The lateral pterygoid muscle, involved in opening and protruding the mandible, must be functionally assessed as it is not possible to manually palpate this muscle.22,23 The parafunctioning patient may not necessarily present with painful masticatory symptoms. Examination of the oral structures may reveal worn dentition as well as scalloping of the oral tongue lateral borders and ridging of the buccal mucosa.24-27
The temporomandibular joint can also be assessed by digital palpation. The location of the mandibular condyle can be identified in the area anterior to the tragus of the ear by having the patient open and close several times and feeling for the movement of the lateral aspect. It is important to have the patient then clench their teeth in order to ensure proper positioning of the finger tips. If muscle contraction is felt, it is probable that the fingers are resting on the area of the deep portion of the masseter muscle and not the lateral aspect of the condyle. Joint popping or crepitation can also be assessed by light digital palpation or by using the bell end of a standard stethoscope.
Measurement of the mandibular range of motion can be easily accomplished utilizing a millimeter ruler. It is important to first measure the over jet and over bite when calculating the range of mobility. Normal range of motion for mouth opening in men and women is 42 mm and 38 mm respectively.28, 29 When analyzing lateral movements, the midlines should be noted. Normal lateral movements are approximately 8-9 mm while protrusive movements are considered normal in the range of 6-7 mm.30 It should be noted if there are deviations with opening and protrusive movements. It should also be noted if lateral movement ranges are not symmetrical.
Temporomandibular disorders include a variety of musculoskeletal disorders that may affect mandibular function. MAD therapy may cause transient TMD symptoms when the device is first worn, but usually these symptoms resolve within a few days. If the problem persist, it is important for the clinician to discern whether the problem was caused by the MAD, the problem occurred coincidentally with use of the MAD or if is the expression of a problem that was there previously. Incorporating a systematic approach to assessment of the stomatognathic structures as part of the evaluation protocol will help the practice to identify patients who may be at risk for development of signs or symptoms. Ultimately, the practice will be better prepared to provide the patient with a thorough informed consent and better manage problems should they arise.
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