Abstract
The purpose of this experiment was to clarify the effect of the occlusal contact condition of the lateral excursion on the masticatory path patterns. For the 60 healthy subjects, the masticatory movement and the occlusal contact of moving laterally for 1 mm (L1), 2 mm (L2) and 3 mm (L3) were recorded respectively. After classifying the masticatory path patterns of chewing chewing gum, the occlusal contact condition of the lateral excursion were related quantitatively with the masticatory path patterns and the following results were obtained.
1. The frequency of the path patterns from pattern I to VIII were 40.8%, 10.8%, 28.3%, 5%, 4.2%, 4.2%, 5%, and 1.7%, respectively (pattern I: opened towards the working side and closed in a convex manner, II: similar to pattern I but closed in a concave manner, III: opened first towards non-working side then towards working side and closed in a convex manner, IV: similar to pattern III but closed in a concave manner, V: opening and closing paths were convex, VI: a reverse pattern of the regular pattern, VII: opening and closing paths crossed each other, VIII: opening and closing paths were a straight line) . Since pattern VIII had only 1.7%, it was discarded from the following comparisons.
2. For all pattern groups (I-VII) at both working and non-working sides, the number of tooth contact at each lateral position decreased significantly as the excursion moved laterally from L1-L3.
3. The appearance rate of the number of tooth contact: For the working side of L1, group I and II had fewer tooth distribution. For the balancing side of L1, all groups had occluding contacts. For the working side of L2, groups I, II, VI, and VII had fewer tooth distribution. For the balancing side of L2, only group I showed no tooth contact. For the working side of L3, all groups showed fewer tooth distribution. For the balancing side of L3 all groups had a tendency to disappear. Significant differences were found for 4 pairs at L1, for 16 pairs at L2, and for 12 pairs at L3.
4. It was concluded that the occlusal contact condition at the lateral excursion changed according to the distance from centric occlusion. Also the difference in the masticatory path pattern was most evident at 2 mm lateral excursion. And this difference in the occluding condition of the lateral excursion was related to the difference in the masticatory path pattern.
