Previous longitudinal cephalometric studies of patients wearing complete dentures have shown that resorption of the residual ridges will cause marked changes in jaw and occlusal relationships. These changes have been found to effect also the EMG clenching activity of jaw closing muscles. Since there are about 45 millions edentulous complete denture wearers alone in the U.S., it is extremely important from the standpoint of complete denture treatment and maintenance of the jaw and occlusal relationships to get further information whether and how changes in these relationships will affect the jaw and facial muscles in the vital oral functions of chewing and swallowing. No studies, so far, seem to have been reported on this subject. The longitudinal electromyographic and cephalometric material for the present study was collected by the P.I. during 1975-78 at the University of Michigan School of Dentistry. Previous analyses of other parts of the comprehensive material has been published in 6 articles.
The Specific aims of the present research are: I. (a) To quantify the EMG activity of the ant. temporalis, masseter and digastric muscles during swallowing and chewing in a sample of 18 subjects provided with immediate complete dentures and followed up to the 6 month stage of denture wear. Fifteen of them were followed to the 1-year stage and 11 to the 2-year stage. (b) to correlate the changes in EMG swallowing and chewing activity between stages with cephalometric data on changes in jaw and occlusal relationships. II. In a pilot study of 6 complete denture wearers followed during 5 observation stages up to 1 year the aims are: (a) to quantify the EMG activity of the upper and lower lips to clench, tapping, swallowing and chewing at the different stages, and (b) to compare changes in lip activity with changes in lip contours and occlusal vertical dimension, as measured from lateral head films from the different stages. The EMG muscle activity in swallowing and chewing will be quantified from measurements of amplitude and timing according to Moller, and the EMG activity in biting activities by use of existing programs. The measurements on the cephalograms will be made electronically as previously reported. The correlation analyses between electromyographic and cephalometric variables will be performed according to the design and method previously described.
