The salivary expulsion reflex in the human parotid was studied upon gustatory stimulation with 5% citric acid. The volume of released saliva was measured with a device employing a pressure transducer and was demonstrated as an expulsion curve. Simultaneously, the output of the transducer was electrically processed by a “sample and hold” circuit and displayed on an ink recorder as a graph indicating expulsion velocity. With this method, it was possible to obtain measurement of a small volume of saliva which had been transiently expelled from the parotid duct in a short period of real time (below 0.1 sec). In the expulsion curve, small fluctuations were observed which were the result of small amounts of saliva expelled transiently from a parotid duct. Volume of outflow due to the transient expulsion varied but the time process of them was identical. Small amounts of continuous steady saliva were observed, although transient expulsions usually indicated intermittent patterns which had started during a regular period. We were then able to consider that the shape of the expulsion curve depended on the frequency and the amplitude of each transient expulsion. We suggested that because of several factors, the origins of the transient expulsion and intermittent expulsion pattern are related to the myoepithelial activity of the parotid gland.
In the present study, the authors examined the junctional strength of visible light-curing denture base resin and resin teeth in comparison with that of conventional heat-curing resin. The results obtained were as follows : 1) When visible light-curing resin was used as the resin block on which resin teeth were implanted, the fracture strength for resin teeth having retention holes in the basal planes, was approximately 1.5 times as large as that for teeth with no retention holes. Also, samples in which the resin tooth surface was treated with dichloromethane had a value approximately twice as large. 2) When heat-curing resin was used as the resin block on which resin teeth were implanted, employing visible light-curing resin for repair, the fracture strength was small in comparison with the values obtained for specimens described in 1).
The purpose of this study was to verify histologically the biocompatibility of a resilient resin (Softic 49, Kerr Sybron) when placed into surgical osseous cavities and into subcutaneous spaces, in rats. Fibrous connective tissue was subsequently observed in close association with the subcutaneous and intra-osseous resin implants. Near the material, and in contact with the fibrous capsule, newly formed osseous trabeculae were seen. In both sites, there was a mild inflammatory reaction. It was therefore concluded that the material has slightly irritant properties.
In the previous studies, using Pearson's product moment correlation coefficient, we found that in most cases of cancers, statistically significant positive correlations were observed between natural background radiation exposure rate and crude cancer mortality rate over the period 1950-1978. Furthermore, we found that the statistical significance of correlation between natural background radiation exposure rate and the age-adjusted cancer mortality rate in the same period mostly disappeared. We studied the cause of this apparent correlation and found that the prefecture with a higher natural background radiation exposure rate had a greater component ratio of older people. In Japan, a number of prefectures with a higher natural background exposure rate are located in relatively thinly populated districts which have been experiencing an outflow of the younger generation to more highly industrialized and urbanized areas. Therefore, statistically significant positive correlations were observed for almost all cancers between natural background radiation exposure rate and crude cancer mortality rate. In the present investigation, we statistically tested the frequency distributions of natural background radiation exposure rate and age-adjusted cancer mortality rate, and calculated Spearman's rank correlation coefficient between natural background radiation exposure rate and the age-adjusted cancer mortality rate. The frequency distribution of the natural background radiation exposure rate and that of the age-adjusted mortality rate appeared normal in most cases of cancer, and the statistical significance of correlation between natural background exposure rate and the age-adjusted cancer mortality rate did not differ much on the whole, even though we used Spearman's rank correlation coefficient between them.