The purpose of this study is to clarify the cause of the discoloration of gingiva by silver alloy powder. Sixty-four healthy rats were used in this study. With No. 1/2 round bur for the dental engine, standardized small cavity was prepared at the mesiolingual cervical portion of the upper molar. Silver alloy powder had been inserted into the small cavity of the maxillary left side of each rat, whereas the right side was used as control. Post operative changes in process of time in the gingival tissue were studied macroscopically, histopathologically and by means of analytical electron microscope (AEM).
The results were as follows;
1. Under the light microscope, many dark depositions (metal) were observed in the lamina propria of the attached gingiva. These dark depositions had been taken into the histocyte like cells and the multinucleate giant cells. Many small depositions were sporadically present around those histocyte like cells and the multinucleate giant cells.
2. Under the electron microscope, the dark depositions (metal) had been taken into the multinucleate giant cells. These cells had long cytoplasmic processes and they had pseudopodia in their membrane of opposite site of the dark depositions and many vacuoles in the cell. These had many lysosomes, vacuoles, endocytosed materials in vacuoles and Golgi's apparatus. The presence of dense concretions were shown to be the complexes of needle-like components and electron-dense materials. The needle-like components were usually organized into concentric lamellae, on which the dense materials deposited.
3. By AEM, it was determined that the elements Ag, Zn and Sn were present in the dark depositions (metal). The element of the concretions was Ag, which was considered to be the form of Ag₂S.
4. It was confirmed by this experimental study that the concretions were an essential factor in the discoloration of gingiva by the silver alloy powder, and the concretions were shown the form of the small dense granules as the result of the dissolution of the silver alloy powder.

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Neuraminidase assay method originally developed by Barrett and Heath was improved for the investigation of the activity in gingival crevicular fluid, and the activities from periodontally healthy subjects and diseased patients were measured. The relationships between the activities and clinical findings, such as DI-S, CI-S, GI and pocket depth, were studied.
The following results were obtained:
1. About 85% of the activity of purified Clostridium perfringens neuraminidase (type V, Sigma Co.) was destroyed after 15-min vibration, but the addition of 5% bovine serum albumin seemed to protect the enzyme fully from denaturation during both extraction and incubation procedures.
2. The characteristics of neuraminidase activity elucidated in gingival crevicular fluid were as follows;
1) 10mM CaCl₂ activated the enzyme miximally.
2) The optimal pH was determined to be 6.0.
3) 25 mM of phosphate buffer was the best ionic strength to give a maximal enzyme activity.
4) Detergents like Triton X-100 and deoxycholic acid did not affect the enzyme activity.
3. Centrifugation, ultrafiltration, thimerosal, and chloroform inhibited the degradation of sialic acid. However, the neuraminidase activity in gingival crevicular fluid was not affected by either thimerosal or chloroform.
4. After centrifugation, the neuraminidase activity in gingival crevicular fluid increased during the stor-age at -20°C for 4 days, but the activity did not change during the storage from 4 to 12 days.
5. The mean value of neuraminidase activity in gingival crevicular fluid from periodontally diseased patients was statistically higher than that from periodontally healthy subjects. The activity showed significant correlations (p<0.01) with all the clinical findings.

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There have been no biochemical studies on Veillonella, a gram-negative coccus found in the oral cavity, in relation to periodontal disease.
We isolated Veillonella alcalescens TF-1 from human saliva and cultured it under anaerobic conditions. After preparing a cytoplasmic extract of this bacterium, we measured in it some enzymatic activities related to periodontal disease, that is, protease, collagenase and fibrinolytic activities as well as vascular permeability factors.
The following results were obtained:
1) Protease activity was increased by the addition of thiol compounds and decreased by the addition of thiol inhibitors and heavy metals.
2) Strong collagenase and fibrinolytic activities and factors affecting vascular permeability were found in the extract.
From the above results, it is thought that V. alcalescens may possibly be involved in periodontal disease.

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In order to clarify the pathophysiological role of glycylprolyl dipeptidyaminopeptidase, partial purification and some properties of this enzyme in guinea pig peritoneal exudate fluids by injection of formalintreated Bacteroides gingivalis cells were studied. The supernatant fluids of guinea pig peritoneal exudates after injection of Bacteroides gingivalis 381 cells were collected by washing with phosphate-buffered saline (PBS). Glycylprolyl dipeptidylaminopeptidase was partial purified by ammoniumsulfate fractionation, DEAE sephadex column chromatography, and Sephadex G-200 gel filtration. Final enzyme sample was separated from collagenase-like peptidase, elastase-like peptidase, trypsin-like peptidase and leucine aminopeptidase, and the purification ratio was 31-fold as specific activity per protein.
The enzyme properities were as follows;
1) The optimum pH for the enzyme activity was 8.6 using Tris-maleate buffer.
2) The Km value was 0.1mM using glycylproline p-nitroanilide tosylate as a substrate.
3) The enzyme activity was not affected by EDTA, but strongly inhibited by HgCl₂.
4) The enzyme activity was slightly inhibited by PCMB but activated by dithiothreitol.
5) Protease inhibitors, diisopropylfluorophosphate and bestatin inhibited the enzyme activity.
In order to clarify the origin of glycylprolyl dipeptidylaminopeptidase in peritoneal exudates, lymphocytes and macrophages were isolated from peritoneal exudates using Percoll density gradient centrifugation. The homogenates of lymphocytes or macrophages were fractionated by linear sucrose density gradient centrifugation. The activity of glycylprolyl dipeptidylaminopeptidase was associated with acid phosphatase activity. These data suggest that the origin of glycylprolyl dipeptidylaminopeptidase is confined in lysosomes in lymphocytes and macrophages.

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Toothbrushing is the most fundamental to control periodontal disease. The purpose of this study was to evaluate the effect of toothbrushing alone on the composition of subgingival microbial flora by darkfield microscopy.
Fourteen subjects with periodontal disease were selected for this study. Clinical and microbiological monitoring was carried out before and about 1 month after oral hygiene instruction. With a clean curette, samples of subgingival bacteria were collected from 39 periodontal pockets which could be probed to 4mm or more, and were examined immediately by darkfield microscopy. On each slide, 200 bacteria were counted and classified on a percentage basis into one of the following categories; (1) coccoid cells, (2) spirochetes, (3) motile rods and (4) others. For each area sampled, the following clinical criteria were also recorded; (1) gingival index, (2) plaque index, (3) pocket depth and (4) bleeding index.
The results indicated that toothbrushing changes the proportions of certain bacterial forms (coccoid cells and spirochetes). By toothbrushing, the percentage of coccoid cells increased significantly from 14.8% to 34.9%, while spirochetes decreased significantly from 37.3% to 18.7%. No significant changes occurred in motile rods and others. Coccoid cells were negatively correlated with all clinical parameters recorded, while spirochetes were positively.

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A new method using slow release material for the access to subgingival plaque was developed. The advantages of this method are as follows:
1. The material itself which is inserted in the pocket has a capacity to be dissolved.
2. Any antibacterial or antiinflammatory drugs can be mixed in the material.
3. The material has enough viscosity to attach tooth surface and soft tissue.
4. It is possible to gain any form from this material.
5. This material has no side effects.
The purpose of this study was to introduce this method. The slow release material is made of Hydroxypropylcellulose (HPC). HPC is white powder. It is dissolved in water, methanol and ethanol, and changes into solid form in about 24 hours. Chlorhexidine gluconate (CH) and tetracycline (TC) were added to the HPC solution. The solid form of HPC is cut into strips (10mm length, 1mm width and about 0.3mm thickness) and inserted in periodontal pockets.
Release of drugs from the strips was measured both in vitro and in vivo. In vitro, both CH and TC were almost released from the strips into the water by 5 hours. Release of TC from the strips which was inserted in the pocket was measured. Even 24 hours after the insertion of the strips, the presence of TC in the pocket was ensured.
From these results, this method seems to be effective for the access to subgingival plaque.

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The plaque-removing effect of five different types of toothbrushes was tested in a single blind cross-over trial. All brushes were used by the scrub method. Ten dentists with a normal dentition and clinically healthy periodontal tissue volunteered for this experiment. Percentage of plaque removal on the upper central incisors and the Plaque Control Record (O'Leary et al., 1972) were used as measures of comparison.
There were no statistically significant differences between five toothbrushes on the basis of percentage of plaque removal. But on the average, the best cleaning effect was found for the Perio II (H) toothbrush and G. U. M. #411 toothbrush. The former brush had the hardest nylon filaments and the latter brush had the highest number of filaments of the five brushes examined. An analysis of the P. C. R. demonstrated that the Perio M toothbrush, the largest in the size of the head, exhibited the poorest cleaning effect, especially on the buccal surfaces of the lower jaw (p<0.05).
It is considered from these results that the small head toothbrush with high number of hard filaments is effective on the plaque removal, but further studies will be needed.

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“Occlusal Prescale” which allows immediate and direct observation of the occlusal tooth contact area and the pressure distribution between the upper and lower teeth was developed. This pressure detecting sheets is composed of two polyester sheets, and one of these sheets have a layer of microencapsulated color forming material.
In the clinical use of this “Occlusal Prescale”, it is suggested that it will be better to avoid both the possibility of the color forming material to be leaked out in the mouth and the contacts between saliva and “Occlusal Prescale”. The purpose of this study was to know the effect of wrapping the “Occlusal Prescale” with polyethylenetelephtalate on the measurring. The results obtained were as follows:
1. The material used for the wrapping was not torn in occlusion.
2. Any statistical differences could not be found between the Prescales with and without wrapping material regarding both occlusal tooth contact area and occlusal force.
3. It was not necessary to take account of the effects of saliva on the measuring.
From these results, “Occlusal Prescale” wrapped with polyethylenetelephtalate can be used in human mouth.

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The purpose of this study was undertaken to compare with factory workers and outpatients in our hospital, using epidemical indices.
The clinical survey was examined on the plaque index, the probing depth, the gingival bleeding index, the mobility, the furcation problem and the marginal overhanging.
The results were obtained as follow.
1. The average of the plaque indices were showed on 0.79 in the workers and 1.07 in the patients.
2. The average of the gingival bleeding indices were showed on 10% in the workers and 47% in the patients.
3. The average of the probing depth were showed on 1.87mm in the workers and 2.94mm in the patients. The latters were showed on the statistically superior to the formers (p<0.01).
4. The access of gingiva to the marginal restoration were showed on 58.6% in the workers and 56.7% in the patients.
1) Above all, Poor marginal restoration were showed on 97% in the workers and 90% in the patients.
2) Subgingival restoration were showed on 83.6% in the workers and 90% in the patients.

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