Haemodynamic changes induced by submaximal isometric contraction in painful and non-painful human masseter using near-infra-red spectroscopy.

Although mechanisms underlying chronic muscle pain are poorly understood, one prevalent theory is that it is due, in part, to localized hypoxia. The purpose of this study was to evaluate this theory using non-invasive near-infra-red spectroscopy that monitors relative changes in intramuscular haemoglobin (Hb) concentration and oxygen saturation levels. Data were collected for the human masseter muscle during and following three isometric 30-s trials at 50% maximum voluntary contraction. Ten females, with a history of chronic muscle pain in the jaw, and eight matched healthy females without muscle pain (controls) participated. Results showed that, upon initiation of masseter muscle contraction, there was a rapid reduction in the intramuscular Hb concentration concomitant with a reduction in oxygen saturation levels. After cessation of the contraction, the Hb concentration increased rapidly and then fell toward the baseline. Significant differences in the recovery profile for oxygen saturation were found between the first trial and the following two trials for both the muscle pain- and control group. Looking at the first trial only, and adjusting for covariates of height, weight and bite-force in the analysis, revealed a marginally significant postcontraction difference between the two groups with a lower level of oxygen saturation during recovery in the group with chronic muscle pain. Significant group differences were found in Hb concentrations without any significant trial effect. It is likely that the well-known changes in intramuscular blood flow that occur during and after contraction in human muscles are reflected in these altered relative Hb concentrations. The group with chronic muscle pain showed a clearly reduced magnitude of the Hb concentration change in the postcontraction recovery period. The results support the concept that patients with chronic muscle pain have a slower intramuscular reperfusion during the recovery phase after sustained isometric contractions.

Neuropathic implications of prosthodontic treatment.

Associated with prosthodontic procedures, there may be the development of a chronic pain state caused by injury to peripheral branches of the trigeminal nerve. Neuropathic pains have not been discussed in the prosthodontic literature and yet are becoming increasingly common, especially in relation to the placement of implant prostheses. This article reviews the pathophysiologic and clinical features associated with neuropathic pain after dental procedures (traumatic neuralgia). The prosthodontist should become aware of neuropathic pain as a possible complication of treatment and informed consent should be obtained before procedures are started that might damage nervous tissue.

Masticatory muscle pain: a review of clinical features, research findings and possible mechanisms.

A review of chronic muscle pain is presented. The clinical features of various chronic muscle pain problems in the jaw region are discussed. Additionally, some of the objective findings of experimental studies which have utilized an acute experimental pain model (isometric contraction) in the jaw system are discussed. Some theories elucidated to explain chronic muscle pain are reviewed with emphasis on the possible role of the sympathetic nervous system which controls intramuscular blood flow. Blood flow studies are one way to evaluate post-contraction recovery of muscle to see if differences exist in subjects with or without chronic muscle pain. Methods to evaluate intramuscular blood flow during muscle contractions and some recent work looking at this issue are discussed. At present, a satisfactory model for evaluating chronic muscle pain has not been developed.

The utility and validity of current diagnostic procedures for defining temporomandibular disorder patients.

This paper describes the evolution of different concepts of classifying and defining Temporomandibular Disorders (TMD) for both clinical and research settings. The literature is reviewed with respect to the utility and validity of the different questionnaire and examination procedures that have been used to assess TMD patients. The presented view is that many of these procedures have not been validated, that there is a lack of standardization in the use of the procedures themselves, and that an ideal method of classifying this broad group of patients into better-defined subgroups has not yet been developed. More standardized and better-defined research by trained and calibrated researchers is needed worldwide to elucidate these subgroups so that a better and widely agreed upon research classification system can be developed for widespread use. It also seems clear that as research requirements for defining TMD patient subgroups become more stringent over time, it may not be practical for the clinician to implement them on a day-to-day basis in his or her practice. As such, a practical utilitarian definition of the common subtype of TMD patients is also needed which parallels any research grouping, so that data from research are valuable and generalizable to the practicing clinician.

Chronic paroxysmal hemicrania presenting as toothache.

Chronic paroxysmal hemicrania is an intermittent head-pain problem that is characterized by pain paroxysms lasting about 15 minutes. The attacks usually produce pain in the frontotemporal region and are responsive to indomethacin. A set of symptoms that defines chronic paroxysmal hemicrania is presented, and two cases in which the presenting symptom was toothache are reported. It is emphasized that clinicians should consider chronic paroxysmal hemicrania in the differential diagnosis of orofacial pain.