Section 3-1. Good bites stimulate secretion of saliva with favorable quality

The vivid elderly persons are divided into two groups by the two axes such as chewing ability and occlusion strength into one group with adequate chewing ability and another group with inadequate chewing ability (Figure 7). Subsequently, these two groups are compared in terms of secretion function of saliva including amount (secretion amount) and quality (protein concentration). Incidentally, the former group with adequate chewing ability had 21.4 teeth as an average of remaining teeth number while the latter group with inadequate chewing ability had 6.8 teeth as an average. It would appear likely that their own teeth instead of implanted teeth are responsible for good chewing. However, judging from their systemic functions, it seems that not only the quantitative factors but also the quality of the residual patterns of their teeth are influential to their abilities. As stated in the previous section, this assumption seems correct because the saliva secretion function was not correlated with the currently remaining number of teeth and but instead, with the qualitative chewing ability.
To prove this hypothesis, shall we investigate the obtained results? The results showed that the group with adequate chewing ability exerted superior secretion of saliva and more favorable protein concentration compared with those of the group with inadequate chewing ability (Figure 8).
To our surprise, the former group with adequate chewing ability demonstrated about 2-fold higher secretion amount of saliva. Saliva is produced in salivary gland cells located around oral cavity as the outcomes of activities of these cells, followed by secretion from salivary gland to the mouth. In other words, the elderly persons exhibiting better chewing ability have superior activities of these salivary gland cells qualitatively and quantitatively whereas the elderly persons with inadequate chewing ability have deteriorated activities of these cells. To be careful about this is the fact that the cellular activities of salivary gland are not affected only by dental factors, if teeth are involved therein, but various neurotransmitters or trace amount of substances in blood might be largely implicated as the background factors. Accordingly, despite of correlation being observed between teeth and salivary secretion as the result of simple comparison, these statistic outcomes must be understood as “probably correlated” and further scientific investigations are required to definitely conclude “surely correlated”.For example, you might have heard “With advancing age, secretion amount of saliva is decreased” somewhere. This fact is really described in the text book of Nutritional Science. Which do you think about this opinion, correct or incorrect? Frankly speaking, this is completely incorrect, and a superstition. Advanced age is not responsible for less secretion amount of saliva but few original teeth causes less secretion of saliva. This was discussed at a special session about sputum in the general congress of IADR, International Dental Society, which was held in Cincinnati, USA. As is obvious from the data issued by the Ministry of Health, Labor and Welfare, the elderly persons have usually few original teeth because of extraction of lots of teeth during their lives. Therefore, if salivary secretion amount is compared between the younger generations and the elderly persons with disregarding the lost teeth, it is quite natural to observe that the younger persons showed much larger amount of salivary secretion relative to those of the elderly groups. Only these outcomes led us to wrongly conclude that aging is associated with less amount of salivary secretion. In actuality, loss of their own teeth resulted in less secretion of saliva and the comparison between the elderly persons with their own teeth and the younger persons demonstrated no difference in the salivary amount. On the contrary, the quite opposite findings were noted in some cases.Significance of saliva amount shall be described in the following chapters in details. However, the above-stated misunderstanding stemmed from shortsighted conclusion from the results obtained by simple comparison without any adequate investigations of background factors. It seems to us that such a mistake would frequently occur while studying the themes concerning problems related to teeth and aging. Physiological aging under healthy conditions of teeth is quite different from the pathological aging under abnormal occlusion or implantation of incompatible artificial materials in jaw. If the contents of my “Hazo” theory are generally understood and subsequent correction of the blind spot associated with the modern medicine and the health science is achieved, it is anticipated that incorrect common sense about the previously prevailing common sense on aging must be utterly reviewed. In other words, EBM (Evidence-based medicine) should be implemented. Now coming back to aging problems, survey and analysis of the obtained data on mixed subjects could not provide us with any meaningful information about real aging phenomena unless attention is paid to dental disorders and functional abnormalities existing as the background factors. For example, if we perform investigations on aging phenomena with enrollment of the elderly persons already affected with renal disorders and cardiac dysfunctions, the obtained results only reflect aging of pathological elderly patients; accordingly, these findings cannot be employed as the evidence representing physiological aging phenomena of human beings. Some persons insist that loss of teeth might be one aspect of duration of life and aging. However, they should recognize the fact that loss of teeth is mostly induced by bacteriological infections such as decayed teeth or periodontal infection (alveolar pyorrhea) (Please refer to Figure 8) but it is not due to gene-related duration of life. As shown in Figure IX, some elderly persons without any loss of their own teeth are really observed in the vivid elderly persons and are found within my patients who visit my clinic. Accordingly, I have decided to pursue actual influences of teeth on secretion of saliva by excluding individual differences in the subjects and influences of systemic background factors associated with salivary secretion.

■Figure 7
Tow-dimensional dispersion diagram by maximum occlusion strength and chewing ability
The vivid elderly persons are divided into two groups by the two axis such as chewing ability and occlusion strength into one group with adequate chewing ability and another group with inadequate chewing ability.

■Figure 8
Adequate chewing ability exerted superior secretion of saliva
The group with adequate chewing ability demonstrated about 2-fold higher secretion amount of saliva, with favorable quality (protein concentration)

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