[A clinical and physiological evaluation of the unilateral occlusal deficit and its RPD treatment--a four-year follow-up study].

The aim of this study was to evaluate the longitudinal clinical and physiological changes in masticatory function for unilateral shortened arch, partially edentate patients by treatment with removable partial denture prostheses from the denture insertion over approximately four years of observation. The present follow-up study was conducted using objective findings and standpoints of unilateral occlusal deficit case, especially the clinical and physiological relation between musculature activity and changes of load center location periodically. The changes in masticatory functions by the muscle activity observed in EMG, and the occlusal loads and distributions throughout the arc, were surveyed by the modified Prescale system. The findings were statistically analyzed by using a sophisticated computer system that was developed by our research institute. The results were as follows: i) The functional musculature of unilateral shortened arc patients was clearly activated by using the unilateral RPD, and the improvements continued for four years after initial denture insertion. ii) The activation of masticatory muscle by denture-wearing over time, was in edentate side masseter, although the amplification of anterior temporal muscle was distinct in mandibular cases. iii) The muscle activity during rhythmical motion, such as tapping with denture-wearing, increased about two times than that of two and three years from the starting edentate value similarly to the clenching values within the measured period. iv) The masticatory efficacy of unilateral free end saddle prosthodontics was estimated using the changes in I-EMG values during peanut mastication. These findings suggested that the use of RPD accomplished an arc form and improved masticatory function for agglomeration of foods and masticatory efficiency over time.