We are pleased to learn that Dr. Cooper agrees with the concept that surface electromyography (SEMG) is not useful for the diagnosis of temporomandibular disorders (TMDs). The information we acquired from other clinicians suggested that there is a strong belief that SEMG is diagnostic and, therefore, we wanted to discuss this aspect in our review article.
Dr. Cooper feels that the benefit of SEMG is as a measurement device for treatment. Dr. Cooper suggests that SEMG can monitor the muscle and be used to measure the success of treatment. Perhaps there is some truth to this premise, but at this time we feel the data are not convincing, as was reflected in our review of the literature.
In order for SEMG to be useful in monitoring treatment effects, we must overcome many of the variables encountered when collecting the data. Certainly, when one reevaluates the same patient over time, the variables of age, sex, skeletal morphology and skin thickness are relatively controlled. However, when a single patient is evaluated over time, the variables of electrode placement, cross talk, the presence of existing pain, psychological factors and facial expression are all potential sources of error. Future studies need to be directed toward determining how these variables can be controlled so that collected data are reliable and consistent.
Even if one assumes that subsequent recordings of the same patient are accurate, the real question is how do the data help us with treatment? If increased pain is related directly to increased SEMG activity, then, as the patient experiences less pain, the SEMG will decrease. We believe this is the point that Dr. Cooper is making. However, any source of pain (ear, tooth, neck) has been shown to influence SEMG. Therefore, the decrease in SEMG may not be related to the TMD symptoms.
This inherent problem in the use of SEMG may then lead to unnecessary or inappropriate treatment, to the physical and economic detriment of the patient. Should we then use SEMG to determine the success of an endodontic procedure as the pain is resolved?
Still, let us remember that many studies have demonstrated that muscle pain complaints are not necessarily related to increased SEMG recordings. In these patients, SEMG would not be a valuable measuring tool of treatment success. In fact, if the pain was resolving without change in the SEMG, would that suggest treatment failure?
The fact that this review article reports some of the same conclusions as previous reviews is not the fault of the authors; it is a reflection of the additional data collected since the previous reviews. Our review article is a cry for more evidence-based studies that will help us determine the usefulness of SEMG.
This review is not aimed at any clinician. Its purpose is only to reveal the present evidence so that clinicians can better understand the advantages and disadvantages of SEMG. The ultimate goal of a review article is to establish the parameters that will lead to better care for our patients.
