Changes in EMG activity during clenching in chronic pain patients with unilateral temporomandibular disorders.

The study assessed the differences in electromyographic (EMG) activity recorded during clenching in women with chronic unilateral temporomandibular disorders (TMDs) as compared to control subjects. Seventy-five full dentate, normo-occlusion, right-handed, similarly aged female subjects were recruited. Twenty five subjects presented with right side TMD, 25 presented with left side TMD and 25 pain-free control subjects participated. Using integrated surface EMG over a 1 s contraction, the anterior temporalis and masseter muscles were evaluated bilaterally while subjects performed maximum voluntary clenching. Lower EMG activation was observed in patients with TMD as compared to control subjects (temporalis: 195.74+/-18.57 vs. 275.74+/-22.11, P=0.011; masseters: 151.09+/-17.37 vs. 283.29+/-31.87, P<0.001). An asymmetry index (SAI) was calculated to determine ratios of right to left sided activation. Patients with right-sided TMD demonstrated preferential use of their left-sided muscles (SAI -5.35+/-4.02) whereas patients with left-sided TMD demonstrated preferential use of their right-sided muscles (SAI 6.95+/-2.82), (P=0.016). This unilateral reduction in temporalis and masseter activity could be considered as a specific protective functional adaptation of the neuromuscular system due to nociceptive input. The asymmetry index (SAI) may be a useful measure in discriminating patients with right vs. left-sided TMD.

Analysis of the area and length of masticatory cycles in male and female subjects.

It is difficult to determine the existence of a normal or physiological masticatory cycle, because there exists great individual diversity. This study presents some data about two parameters of masticatory cycles according to the frontal plane, i.e. the area and length of right-sided and left-sided cycles in a group of 30 young people, 18 women and 12 men. For our study the Myotronics K6-1 kinesiograph was used. It registers the magnetic field and allows us to obtain graphic recordings of the jaw movement in the three space planes. Other authors have analysed these parameters, but none of those reviewed provides information about the distribution to each side or according to the gender of sampling subjects selected for the analysis. We have tried to describe the normal morphology of the masticatory cycles and, also, establish a reference so as to provide help in the diagnosis of the functional pathology of the masticatory system.

Case report: impression and maxillo-mandibular relationship recording for construction of obturator prostheses.

The present case report describes a procedure for obtaining the master impression and the maxillo-mandibular relationship for the definitive prosthesis in a maxillectomy patient. After casting the metal framework, a visible-light-cured tray resin was spread over the resin retention grid and gradually cured. Modelling compound was extended over the resin with functional movements, and finally the margins of the defect were sealed with a dental impression wax. A column of light-cured resin was constructed from the lower face of the resin/compound/wax structure to the opposing dental arch. This column permitted recording of the maxillo-mandibular relationship.

A secure method for making removable dies.

Removable dies greatly facilitate fixed prosthesis fabrication and accurate marginal fit. The major difficulty when using removable dies is the correct positioning of the dowel pin in the stone base. This article describes a method for preparing removable dies that ensures accurate positioning of the dowel pin and provides external landmarks for precise location of the cuts to be made with the die saw. The method described is accurate, simple, inexpensive and can be performed in the dental laboratory.