J Orofac Pain
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This study examined masseter and temporalis pain-pressure thresholds in 29 patients with chronic bilateral myogenous temporomandibular disorder and in 11 controls. Patients with evidence of temporomandibular joint pathosis were omitted. The influence of time, facial side, muscle site, and side of greatest spontaneous pain on pain-pressure thresholds was measured. ⋯ Mean pain-pressure thresholds in patients differed over the four sessions, which is consistent with recent reports of fluctuating levels of pain in patients with temporomandibular disorders. Additional findings included significant pain-pressure threshold differences among muscle sites in patients and controls, and lower patient pain-pressure thresholds relative to controls. Within- and between-session reliability was adequate for patients (r = .85 and r = .75, respectively) and controls (r = .90 and r = .75, respectively).
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To assess the knowledge and beliefs of practicing dentists regarding temporomandibular disorders and chronic pain, a random sample of dentists in the Kansas City metropolitan area was surveyed. A survey instrument examining knowledge and beliefs in four domains (psychophysiological, psychiatric disorders, chronic pain, and pathophysiology) was used. The responses of the practicing dentists were compared to the responses of panels of experts. ⋯ The findings partially replicate an earlier, similar survey of dentists in the Seattle, Washington, area. The findings suggest that the role of psychiatric disorders and psychophysiologic factors in the etiology of temporomandibular disorders is widely acknowledged by practicing dentists. However, there is considerable discrepancy between practicing dentists and temporomandibular disorder experts on the pathophysiology of temporomandibular disorders and how best to diagnose and treat these chronic conditions.
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Pain and tenderness at trigger points and referral sites may be modified in subjects with myofascial pain in the head and neck region by injecting local anesthetic into active trigger points, but the effect of injection on jaw muscle pain-pressure thresholds has not been measured. The mechanism by which trigger-point injection affects muscle tenderness is also unclear and may be related to the "hyper-stimulation analgesia" induced by stimulation of an acupuncture point. A pressure algometer was used before and after an active trigger point injection in the masseter to measure the pain-pressure threshold in the masseter and temporal muscles of 10 subjects with jaw muscle pain of myogenous origin. ⋯ In the control group, the pain-pressure threshold increased significantly at all recording sites in the masseter after acupuncture-point injection. Although local anesthetic injection acts peripherally at the painful site and centrally where pain is sustained, pain-pressure thresholds were not dramatically increased in myofascial pain subjects, in contrast to controls. This suggests that in subjects with myofascial pain, there was continued excitability in peripheral tissues and/or central neural areas which may have contributed to the persistence of jaw muscle tenderness.
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Comparative Study
Comparison of pain and quality of life in bruxers and patients with myofascial pain of the masticatory muscles.
Although it has been suggested that bruxism is a cause or a risk factor in myofascial pain of the masticatory muscles, the prevalence of pain in bruxers and its characteristics have not been assessed or compared to those of myofascial pain patients in general. In this study, self-reports of pain and quality of life were recorded on 100-mm visual analogue and five-point category scales from two research populations: (1) 19 nocturnal bruxers who participated in a polysomnographic study and (2) 61 patients with myofascial pain of the masticatory muscles with no evidence of bruxism who participated in a controlled clinical trial on the efficacy of oral splints. ⋯ The fact that pain from bruxism was worst in the morning suggests that it is possibly a form of postexercise muscle soreness. Myofascial pain, which was worst late in the day, is likely to have a different etiology.
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The measurement of the pain-pressure threshold in the human jaw muscles may be affected by variables such as the size of the pressure-transducer recording surface and the rate of applied pressure. The jaw muscles have a complex architecture that results in changes in muscle stiffness and compliance when different motor tasks are performed. Such changes in the jaw muscles are likely to affect the pain-pressure threshold. ⋯ There were no apparent regional differences in pain-pressure thresholds in the masseter or temporalis muscles at different amounts of tooth clenching or jaw gapes. Pain-pressure thresholds were consistently higher in the temporalis muscle. When quantitative measures of jaw muscle pain-pressure thresholds are planned, the nature of the motor task should be controlled.