2003 Volume 9 Issue 2 Pages 167-175
The purpose of this study was to make a standard of occlusal load center (OLC) from a standpoint of muscle activity when it was used for the evaluation of occlusal support in prosthodontic treatment. The experimental occlusal contact was set by using lower splint which was divided into 9 pieces of anterior block, right and left premolar and molar blocks. The bite force and EMG of right and left masseter and temporalis muscles were recorded from 8 normal subjects with complete dentition during maximal clenching. The occlusal stops were gradually increased by exchanging the premolar and molar pieces of splint so as to keep the shortened dental arch concept. The relations of the location of OLC, bite force and EMG among 15 kinds of occlusal conditions were investigated. Conclusions were as follows,
1. The location of OLC was significantly different among 15 kinds of occlusal conditions, and the difference of occlusal condition was clearly distinguished by the OLC. Thus OLC was supposed to be a useful parameter for the evaluation of occlusal contact.
2. The bite force and integrated EMG were gradually increased with the increase of occlusal stops. In the comparison with the occlusal conditon of full splint, the bite force of the other occlusal conditions had significant difference except for the occlusal condition without a unilateral second molar piece. The integrated EMG in the occlusal condition with the pieces of second premolar bilaterally had no significant difference. These findings suggested that muscle activity was more affected by the distribution than by the number of occlusal stops.
3. The standard area of OLC for the evaluation of occlusal support in prosthodontic treatment was elliptic in shape. Its antero-posterior center was almost the same as the center of the second premolar and its right-left center was almost the same as Palatine Raphe. The range of ellipse distributed antero-posteriorly from the mesial contact point of first premolar to the distal contact point of first molar, and transversely between the center of lateral incisor.
