Articles: pain-threshold.
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Sensibility and pain thresholds were measured in 27 patients with myofascial pain and craniomandibular disorders and in 19 controls. A monopolar electric stimulator with increasing direct current values was used to record pain and sensibility thresholds in the lower incisors. Patients with myofascial pain had a tendency towards lower sensibility and lower pain thresholds than the controls, although the differences were not statistically significant.
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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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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.
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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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The optimal treatment of pain requires an understanding of the mechanisms involved. Pain is a sensory end-point that can be generated by a number of dissimilar processes. Consequently, the concept of treating pain as a unitary symptom is obsolete. ⋯ Clinical pain is more than a reflection of sustained peripheral input and it is, to a large extent, the expression of changes produced in the CNS, including the phenomenon of central sensitization. We need to treat both the disease/injury process in the periphery and the changes it induces or triggers in the CNS. Prevention of central sensitization will substantially eliminate the hyperalgesia and allodynia that patients find so distressing, and it offers new possibilities for the development of novel analgesics or antihypersensitivity drugs.