[Human mandibular movements during swallowing saliva. 1. Tooth contacts and rest position]

We investigated the swallowing of saliva on 11 adults with a normal tooth alignment and a normal occlusion. The envelope of sagittal incisal point movements of the mandible was analyzed by means of the infrared sensor system. Frankfurt horizontal plane was used as a reference plane. The following conclusions were obtained based on the experimental results. 1. The mean linear distance between retruded tooth contact position (RCP) and intercuspal position (ICP) was 1.35 mm. 2. The mean linear distance between most retruded tooth contact position during swallowing saliva (SRCP) and ICP was 0.13 mm. The ratio of SRCP to RCP was about 10 percent. 3. The rest position of the mandible induced by swallowing saliva (RP) was 1.05 mm apart from ICP. 4. The maximum interocclusal distance during a cycle of swallowing saliva (MOP) was 1.70 mm in the average of 11 subjects. RP and MOP were significantly different from each other in the average of 11 subjects. However, individuals whose RP and MOP were significantly different were 6 subjects of 11.