Section 3-4. Preclinical evidence obtained in animal experiments

I would like to introduce some important facts which were noted in other publications. The author of this report observed rats divided into two groups kept under different conditions. One group was given water-soluble food indicative of needing no chewing. Another group was fed with the same food which contained the same components but was a solid food, indicating that rats needed to chew this food. Under these different conditions, these rats were raised while time-course changes of parotid gland’s functions representing major three salivary glands were monitored. The results revealed significant differences. In the rats chewing solid food, appropriate sizes of parotid gland and favorable secretion of saliva were maintained; in sharp contrast, however, the rats given no chewing stimulation gradually showed atrophic changes. To our further surprise, internal changes occurred in the receptors for autonomic nerve systems in their teeth. In more details, the number of relevant receptors expressing on cellular membrane of salivary gland was extremely decreased. In addition, the composition of secreted protein was also changed.
Thus, I have obtained new clues. Namely, based on the findings that in the rats given no chewing stimulation, relevant changes were noted on the autonomic nervous system receptors existing on cellular membrane of salivary gland, it would appear likely that information from teeth in parallel with chewing stimulation was continuously transmitted to brain resulting in affecting autonomic nervous systems. In other words, during the course of repeated transmission of the continuous information which was generated as the chewing stimulation every meal to somatosensory area of cervical cortex, it is anticipated that its signals were transformed into autonomic nerve stimulation, evolving into providing definitive influences on both structures of salivary gland under control of autonomic nerve, and secretion systems. This indicates that superior salivary secretion functions in the vivid elderly persons with favorable chewing ability could be attributed to the interesting procedures that continuous stimulation from teeth plays a role as the continuous transmission of important information to brain to keep both the autonomic nerve functions and the subsequent secretion systems of saliva healthy. In response to continuous stimulation patterns of autonomic nerve from individual residual types of teeth, structure and functions of salivary gland are maintained and accordingly, it is anticipated that instinct qualitative and quantitative secretion of saliva to reflect the residual types of teeth could be obtained to respond to the same stimulation for secretion.