Aborigines of Formosa are of a minority race living on highland from the central to eastern regions of Formosa and are said to number about 250 thousand accounting for about 1.8% of the Formosan population. These aborigines are classified into ten tribes but they all belong to the Mongoloid race. For this paper, the Ami, one of the tribes of the aborigines, were investigated physical-anthropologically. Plaster casts of all teeth of the upper and lower jaws of 245 men and women combined were used and observations of crown morphology were made and measurements were taken. The results of the investigation were compared with those of each tribe of the Formosan aborigines and with those of Japanese of various locations mainly around Kyushu. The results were as follows : 1. The crown width was slightly smaller than that of the other Formosan aborigines and quite smaller than that of Japanese and the difference was considerable for the lower teeth in particular. The crown thickness of the Ami showed no great difference as compared with that of the other Formosan aborigines and was slightly smaller for the lower teeth as compared with that of the residents of Goto and Tanegashima islands. 2. Frequency of occurrence of double shovel-shaped incisors on the labial side of the incisor was high for both the upper and lower jaws in comparison with that of the other Formosan aborigines and Japanese around Kyushu. The frequency of occurrence for the upper jaw was much higher than for the lower jaw. 3. Frequency of occurrence of shovel-shaped incisors on the lingual side of the incisor was quite high for the upper jaw as was for the other Formosan aborigines and was higher than that of Japanese around Kyushu. The frequency for the lower jaw was markedly lower than that for the upper jaw. 4. Morphology of the grooves in the occlusal surface of the upper premolars showed a tendency similar to that for Bunun tribe. As compared with the other Formosan aborigines and Japanese, the Ami tended to show slightly regressive morphology. 5. In development of cusps of premolars in the lower jaw, the lingual cusp of the first premolar was poorly developed. This finding applied to the other Formosan aborigines and Japanese. Many Kyushu people however appeared to show good development of the lingual cusp. For the second premolar, development of the lingual cusp was marked and another cusp appeared on the linguodistal side, resulting in three cusps in quite many instances. The same applied to the other Formosan aborigines and Japanese. 6. Regression of hypocone at the upper molars was hardly seen for the first molar. For the second molar, considerable regression was seen. For the Ami, the tendency toward regression was slight as compared with Japanese. 7. Frequency of occurrence of mesiodistally compressed crown type for the Ami was about the same as that for the other Formosan aborigines but was higher than that for Japanese. Frequency of occurrence of carabelli's cusp for the Ami was the highest among the Formosan aborigines and was higher than that for Japanese. 8. Frequency of occurrence of the dryopithecus pattern at the lower first molar for the Ami was slightly higher than that for the other Formosan aborigines, but the difference was not so great. The frequency for the Ami was lower than for Japanese. At the second molar, the frequency was considerably low and types like regressed +5, +4, ×5, and ×4 increased, and about the same tendency as for the other Formosan aborigines and Japanese was seen. 9. Frequency of occurrence of protostylid, 6th cusp, and 7th cusp at the lower first molar was lower than that for the other Formosan aborigines and Japanese. Frequency of occurrence of deflecting wrinkles was higher than that for the other Formosan aborigines and Japanese.

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The purpose of this study was to evaluate the efficiency in removing the smeared layer by the use of ultrasonic vibration and some irrigating solution. With use of extracted human maxillary anterior teeth with their root canal untreated, enlarging and preparation of the root canals were done with K-files after the root canals were filled with 10% NaOCl, and then the root canals were cleansed by one of the following methods : (1) the root canals were filled with 10% NaOCl and ultrasonic vibration was applied for 2 minutes ; (2) the root canals were treated by the same method as in "1" and then the root canals were filled with 15% EDTA and ultrasonic vibration was applied for 2 minutes. The results were as follows : 1. It was impossible to remove the smeared layer by enlarging and preparation of the root canals only with K-files after the root canals were filled with 10% NaOCl. 2. Ultrasonic vibration with 10% NaOCl was a little effective in dissolving the smeared layer in the middle areas of the root canals. However, it was not effective in the apical areas. 3. Ultrasonic vibration with 15% EDTA was very effective in dissolving the smeared layer in the middle areas of the root canals. However, it was not effective in the apical areas. 4. In order to increase cleaning effect in the apical areas of root canals, abundant use of EDTA and NaOCl appears to be necessary.

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Experiments were conducted on ten human maxillary anterior teeth, extracted for the purpose of assessing the cleansing effects of root canals, using a new style perforated standard needle. Another five teeth, which were reamed and filed after 10% NaOCl was instilled using a conventional syringe in the root canal, were examined as a control. Enlarging and cleansing of the root canal was conducted by the same procedures for both the control and experimental groups. Following this, two ml of 10% NaOCl was instilled using the new style needle and was left alone for three minutes, and two ml of 15% EDTA was also instilled into the root canal, in the experimental group. The materials obtained by these procedures were examined under scanning electron microscopy. The method, in which the root canal was filled with 10% NaOCl using a conventional syringe, and enlarged by a reamer and a K-type file, proved insufficient for cleansing the root canal. Pulp tissues, dentin chips and smeared layers were observed on the root canal walls. However, when two irrigating solutions were mutually instilled using this needle in the root canal, then left alone for three minutes, pulp remnants, dentin chips and smeared layers were effectively removed from the root canal walls. These findings indicate that the irrigating solutions are able to penetrate into the apical area of the root canal, when the new style perforated needle is added to the conventional procedures ; however, solutions were unable to reach this area by other methods. Thus, a large benefit can be gained when using this needle in endodontic therapy.

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An epidemiological survey of prevalence and treatment needs of periodontal diseases using CPITN was performed on 378 inpatients at a mental hospital in Kitakyushu city. All of the inpatients who had teeth had some sign of periodontal disease, and symptoms of diseases were revealed in most of the sextants which were assessed for all age groups. The percentage of inpatients having worse symptoms and having no or few teeth was higher than that of normal persons reported previously. This finding indicates that oral hygiene instruction and treatments of periodontal diseases is insufficient for inpatients of mental hospitals.

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The short-term buccal absorption of phenol and p-chlorophenol were examined using the rat. At the early stage before 30 minutes, they showed different absorption behaviors from those after 30 minutes. The logarithmic absorption after 30 minutes was well approximated by linear correlation with time in the same manner as in the other routine long-term absorption tests, as reported in the previous paper. However the early stage of absorption before 30 minutes appeared not to be governed by the first-order rate process and it could not be approximated by any linearity even on the semi-logarithmic paper. It should be noted that phenol and p-chlorophenol were much more rapidly absorbed by mucous membrane at the earlier period after they came in contact with the membrane.

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An epidemiological survey of periodontal diseases was performed using CPITN on 181 medical college students in Taiwan between 18 and 24 years old and 141 age-matched dental college and school of dental hygiene students in Japan. More than 96% of the students of both countries had gingival bleeding after gentle probing (Code 1) or worse symptoms (Code 2-4). The Taiwanese college students had a higher tendency of having pathologic pockets 4 or 5 mm deep (Code 3) than the Japanese students. The mean number of sextants where supra- or subgingival calculus or worse symptoms were extremely large was about 5 for the Taiwanese students, but was larger than 3.5 (females) and 4 (males) for the Japanese students. Although neither Taiwanese nor Japanese students required complex treatments of periodontal diseases, more than 94% of the students needed oral prophylaxis (scaling).

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Recently, polyethersulfone resin (PES), substituing for acrylic resin, has been introduced as a denture base material. PES excells in mechanical properties, thermal resistance, and abrasive resistance, and is stable chemically, and has no harmful effect on the oral mucosa. Thus, PES appears to have favorable properties for a denture base material. There are, however, some unclear aspects in its manageability and clinical applications. Therefore, an investigation was made of its plasticity, vertical dimensional change of artificial tooth at molding of the denture, bonding strength of artificial tooth to PES, deformation at molding. The results were as follows : 1. The test portion was selected under the clasp tang where considered to be the most difficult to mold and the feasibility of packing was examined. As a result, it was found that relief of 0.65mm and over would be required to pack under the clasp tang completely. 2. Examination of rising of artificial tooth at molding the denture, the eliminable area changing to 3, 6, and 10mm, showed that increase in the width of eliminable area tended to increase the extent of rise of artificial tooth. Making the width of the eliminable area 3mm, resulted in 0.17 ± 0.09mm rise and the effect on occlusal vertical dimension increase was made small. 3. The bonding material specified for PES did not produce satisfactory bonding strength of artificial tooth to PES. Only when undercut had been given on the base of the artificial tooth, the bonding strength of artificial tooth similared to that to heatcured polymerized resin. 4. A mold shrinkage rate of PES was rather large with 4.4 ± 0.3%.

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The combination of impression materials suitable for split impression taking was between polysulphide rubber impression material and sillicone rubber impression material. With the use of these materials, accuracy of split impression taking from a metal model of the upper edentulous jaw was examined. The results were as follows : 1. Type I trays, which have no interlocking device, showed considerably small percentages of displacement. Taking impression from a metal model was thought to have made it possible to maintain the right-half and left-half trays in position rather accurately, even without an interlocking device. 2. Type I trays, and Type II trays which are Type I trays with an interlocking device provided at the handle, on the whole, showed considerably small percetages of displacement. Type III trays with an overlapping zone at the joint showed large percentages of displacement. 3. The overlapping zone intended to reduce slack at the joint between the right-half and left-half trays did not serve its purpose and contrarily caused deformation to be greater. Type IV trays with magnets at the overlapping zone reduced deformation.

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Thermal analyses were carried out for four commercial pattern resins and three waxes, and fracturing aspects of the resin pattern-enveloping crystobalite investment mold at the heating process were observed. In the thermal analyses, the resin materials showed 4 to 15 times larger maximum expansion than the waxes at the temperature of 200 to 320℃ depending on the products. They maintained solid or rubbery state up to the temperature they showed maximum expansion. These characteristic thermal behaviors may probably be the cause of the mold fracture. The crack initiation in the mold was effectively reduced by increasing the investment thickness or strength, the sprue diameter, or the wax coating thickness on the resin pattern.

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A case is reported of eosinophilic granuloma arising in the mandible of an 11-year-old girl. The patient complained that she had been suffering from contact pain in the lingual gingiva of bilateral mandiblar molar regions. Resorption and redness of lingual gingiva with erosion were found in the first-visit examination. Under clinical diagnosis of a chronic periodontitis in the region of <654|456>^^^-, chemotherapy was carried using antibiotics. But her lesions were unchangeable, so a biopsy was performed. The biopsy revealed a formation of abnormal granuloma with infiltration of eosinophils and lymphocytes and proliferation of histocytes. Pathological diagnosis was an eosinophilc granuloma included in the category of Histocytosis X. The treatment of the eosinophilic granuloma has been a surgical curettment, radiotherapy and hemotherapy. For treatment of her disease, the hemotherapy using oxyphenbutasone (Tanderil) was selected. Selecting this drug brought about a satisfactory result.

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