Studies on Masticating and Biting Forces in Upper Second Premolars of Complete Dentures

As the analysis of the masticating movement, the studies on the masticating forces and the electromyographic investication have been mainly reported. But, as for the masticating function on the complete denture, there are something yet to study its analysis on the masticating forces, the biting forces and the EMG in only upper first molars. Then, the author uses the semi-conductor apparatus developed by Moriya and Fukamizu, and leaves on the records of these forces and the EMG of the masseter and temporalis on the upper second premolar of complete denture wearers (10 males) from 50 to 60 in age at variuos occlusal positions. As the results of these efforts, the following conclusions are obtained. 1. The biting forces in upper second premolars are 7.3-7.9 kg at the intercuspal position, 6.3-7.6 kg at the working side of the lateral position, 3.1-3.5 kg at the ballancing side and 3.0-3.2 kg at the protrusive position. 2. The masseter and temporalis of both side at the intercuspal position, its muscles of woking side at the lateral position and the masseters of both side at the protrusive positionare marked active. And the muscle activities begin earlier than the biting forces. 3. The masticating forces in upper second premorals are 2.4-4.9 kg by peanut, 2.0-5.3 kg by ham and 2.2-4.8 kg by pickled radish. Its forces are largest values in the fourth and fifth period, and are smallest value in the first period. The duration is largest value (0.33-0.53 sec) in the first period and smallest value (0.25-0.34 sec) in the second period. The interval (I) and term (T) are largest values (I: 0.79-0.90 sec, T:1.17-1.36 sec) in the fifth period and smallest values (I: 0.48-0.66 sec, T: 0.76-1.02 sec) in the third period. The forces in the swallowing period have a tendency to be smallest value every foods. 4. When the masticating movement of peanut, ham and pickled radish are obtained by means of the masticatory rhythm, the following finding are obtained. As for the duration, the first period in all foods is largest (0.42-0.67 sec) and the second period is smallest (0.35-0.52 sec). Among foods, the ham is largest, in order next comes peanut and pickled radish. Regarding the interval, the fifth period in all is largest (0.70-0.92 sec) and the second period is smallest (0.31-0.62 sec). Among them the peanut is largest, then ham and pickled radish is smallest. As for the term, the fifth period in all is largest (1.10-144 sec) and the second period is smallest(0.68-1.04 sec).