H. TSCHERNITSCHEK *, J. STREMPEL, M. EISENBURGER, A. ROSSBACH (Medizinische Hochschule Hannover, Poliklinik f. Zahnärztliche Prothetik, D-30623 Hannover)
The functioning of the masticatory system depends on neuromuscular regulation. This regulation is affected to a different degree by the loss of teeth and the incorporation of dentures. Without sufficient compensation by the neuromuscular system mastication may degrade. In previous studies we could show that the kind of denture influences the myoelectric activity of the m. masseter. The purpose of this study was to determine the EMG analysis method which is best suited to analyze the interference pattern of the masseteric EMG recorded with surface electrodes during maximal voluntary contraction. This should be done by comparing WILLISON analysis, spectral analysis and integrated EMG.
126 patients were examined, 57 with complete dentures and 69 with natural teeth serving as control group. The masseter EMG was recorded bilaterally, amplified with an EMG amplifier, digitized and stored on a PC. A PC program was developed performing an enhanced WILLISON analysis, a frequency analysis based on the calculation of the EMG power spectrum by means of a FFT, and the calculation of integrated EMG. The statistical analysis of the resulting EMG parameters was done using the SPSS statistical package.
Performing a discriminant analysis using WILLISON parameters only, 77% of cases were classified correctly. Corresponding results yielded 69% for frequency parameters only and 68% for integrated EMG only. The combination of WILLISON parameters and frequency parameters increased the correct classification rate to 81% , whereas inclusion of integrated EMG did not result in any amelioration. Similar results were obtained in studies on implant based dentures and on TM J disorders.
We conclude that the combination of WILLISON analysis and spectral analysis is best suited for the evaluation of the surface EMG signal from m. masseter. whereas integrated EMG analysis yields no further enhancements.