Passive depression of the lower jaw reflexively evokes the extrinsic tongue muscle EMG activity. This reflex is called the jaw-tongue reflex (JTR) and was reported to be evoked by the afferents from the temporal muscle (TM) . The present study was carried out to determine which types of proprioceptors in the TM could evoke the JTR in the chloralose-anesthetized cats, with the following results: (1) Isometric contraction of the tonically stretched TM slightly in-hibited the tonic extrinsic tongue muscle EME activity (JTR) which was induced by the tonic stretch of the TM. (2) Stimulation of the TM nerve evoked EPSPs or IPSPs in the hypoglossal motoneurons (XII MNs) . These two types of synaptic potentials were recorded from the XII MNs sending their axons to the medial branch as well as those sending their axons to the lateral branch of the hypoglossal nerve. (3) The threshold of these synaptic potentials of the XII MNs was about twice the TM nerve threshold, and their amplitude increased with the elevation of the stimulus intensity up to five times the TM nerve threshold. (4) There were XII MNs which were excited by the gentle pressure applied to the belly of the TM. It was concluded that JTR can be evoked by the Group II afferents from the muscle spindle secondary endings in the TM.
Denture bases are mainly classified into resin denture base and metal denture base according to the denture base material used. In this paper the influence of these material on the mechanical properties of the upper complete dentures was studied. The test denture bases were acrylic resin denture base, carbon fiber (CF) -cloth reinforced acrylic resin denture base, stainless steel swaged metal base using 4-META adhesive resin and Co-Cr alloy cast metal base. The mechanical properties of these denture bases were evaluated by the uniform-moment bending method, considering the loading in the occlusal situation. The findings are as follows: Co-Cr alloy cast metal and stainless steel swaged metal have high Young's modulous and strength in comparison with those of acrylic resin and CF-cloth reinforced acrylic resin. But, the denture base as a construction had not large difference of the mechanical properties between these four denture base material. Therefore, it would be suggested that the denture base material used for palate had not more influence on the mechanical properties of the upper complete denture.
Presently, dental office contamination is a very important problem during the dental treatment of patients who have human immunodeficiency virus (HIV) or hepatitis B virus. So, we examined how many oral bacteria were splashed around a dental chair when we used the air turbine for five minutes. By the results of this study, it was recognized that a considerable number of bacteria was splashed around the dental chair, particularly on the breast of the patient. And the goggles of the dentist were also contaminated by the oral bacteria. Accordingly, when a dentist treats patients who carry the HIV or the hepatitis B virus, he will be contaminated by these pathogenic factors. It is well-known that the dentist is contaminated by hepatitis B virus more frequently than the other people are. Consequently, we considered that dental treatment might bring about hospital infections, such as by the HIV and hepatitis B virus.
Serum and gingival crevicular fluid (GCF) from the patients with periodontitis were examined for local immune responses against 4 periodontopathic bacteria. Immunoglobulin G antibody titers to the bacterial antigens were measured by the enzyme-linked immunosorbent assay (ELISA) . As bacterial antigens, Bacteroides gingivalis, Capnocytophaga Ochracea, Actinobacillus actinomycetemcomitans and Fusobacterium nucleatum were used. They were ultrasonicated and the soluble supernates were obtained as antigens. The GCF was collected from the maxillary and mandibular anterior regions of 10 patients. Some were allowed to collect the GCF from different regions. The ratio of the antibody titer of the GCF to the serum was calculated. The IgG titers against B. gingivalis and F. nucleatum showed statistically a significant correlation between the values of the serum and the GCF. The highest ratio was found in the IgG titer against B. gingivalis, showing an average value of 0.80. However, the GCF IgG titers against B. gingivalis and A. actinomycetemcomitans showed sometimes different values in different regions of the same mouth. A positive correlations was not found between the GCF IgG titers and the various clinical parameters.
The efficacy of subgingival plaque control by the direct irrigation technique was studied. Twelve adult patients with periodontal pockets of 4mm or more received an initial treatment, followed by irrigation using the device called Pocket Irrigator PT-01 with distilled water or 1/30 diluted iodine complex solution. The clinical and microbiological parameters were recorded prior to the irrigation and immediately after, at 1 hour, 1 day and 1 week after the irrigation. The plaque index (P1. I.), gingival index (G. I.), gingival crevicular fluid (G. C. F.) and probing depth were used as clinical parameters. Samples of the bacteria were collected with paper points from the periodontal pockets. The samples were examined by dark field microscopy with the Petroff-Hauser counting chamber. The total number of bacteria and the microbial composition of each of the 12 pockets were examined. The clinical data showed no significant changes before and after the irrigation. The total number of bacteria decreased immediately after the irrigation and then increased gradually. The number of bacteria, however, maintained a lower level than those of the baseline during the whole experimental period. A significant change in the microbial composition also appeared. The proportion of motile rods and spirochetes decreased until 1 day and then increased gradually near to that of the baseline. The results indicate that pocket irrigation by distilled water or 1/30 diluted iodine complex solution is effective to eliminate the subgingival plaque until 7 days.