1996 Volume 2 Issue 2 Pages 101-109
Recently, a bite force measurement using a pressure sensitive sheet which enables us to measure the bite force quantitatively at multiple bite points on the dental arch was developed. Clarifying bite force distribution in normal subjects would provide a useful guidance for occlusal examination and diagnosis. In this study, we investigated bite force distribution on intercuspal clenching in normal subjects and relationships among the clenching level, bite force distribution and masticatory muscle activities.
Four healthy subjects with normal dentition were used in this study. Bite forces on each mandibular tooth and masticatory muscles' EMGs were recorded simultaneously on intercuspal clenchings with various levels of magnitude. The bite force was measured by using the pressure sensitive sheet“Dental Prescale 50H, type R” (Fuji Photo Film, Co., Japan) and the specially designed image scaner“Occluzer FPD-703” (Fuji Photo Film, Co., Japan) . Bite force distribution was defined as the proportion of bite force on each mandibular tooth to the total bite force. EMGs were recorded from bilateral masseter, anterior and posterior temporal muscles. These were then integrated and provided for analysis.
As the results, the proportion of bite force on each tooth was almost constant irrespective of the magnitude of total bite force, when the clenching level was moderate and more of voluntary clencning in each subject. The proportion of bite force was higher on the tooth located more posteriorly in the dental arch. The highest proportion was found on the second molar in all subjects. However, the bite force proportion of the same named tooth was different among the subjects. The bite forces showed symmetrical distribution bilaterally on the dental arches.
Relationship between the total bite force and integrated EMG activity of each muscle was different among the muscles, and also among the subjects.
These results indicate that the bite force distribution on the dental arch was constant irrespective of the clenching magnitude and masticatory muscle activities, and that there were common characteristics in the bite force distribution in normal subjects. The bite force distribution by this measurement would contribute to evaluate the occlusion as a objective parameter.
