Lip Sensation related to Stomatognathic Function in Man

—Effects of Surface Anesthesia of Lips on Jaw Movement in Chewing—

Abstract

In order to verify whether touch or pressure lip sensation between upper and lower lips plays a role in the regulation of mastication, we investigated the jaw movement of eight adult male subjects pre- and post- surface anesthesia of the lips. We used chewing gum and requested the subjects to masticate thirty strokes, first on the left side and then on the right. We recorded the jaw movement with the MKG (Model K-5) and devided each stage into the following classes: Stage 1 was pre-anesthesia, stage 2 was just after anesthesia, stage 3, 4, 5 and 6 were ten, twenty, thirty and forty minutes post-anesthesia respectively. Maximum opening distance, maximum lateral moved distance, and cycle time of each stroke were measured. The mean value of each stage was calculated and the changes were then compared and examined. A trend appeared with the change of maximum opening distance and the stages was observed in eight subjects showing a tendency to decrease to the minimum in stage 2 or 3 post-anesthesia, in both left and right gum mastication, and gradually increase to the pre-anesthesia value. There is a strong possibility that touch or pressure lip sensation between upper and lower lips takes parts in the regulation of the mandibular opening size during human mastication.