下顎中切歯の近心舌側捻転(winged teeth : WT)はモンゴロイド集団に特徴的に認められる形質と考えられている.一方, 遠心舌側捻転(counter-winged teeth : CT)はコーカソイド集団に比較的高い頻度で認められる.今回は上記のような上顎中切歯の特徴的な配列について, ネパール国住民70名から得られた歯牙石膏模型をもちいて検索した.上顎中切歯が示す捻転状態はDahlberg(1959)の分類に基づいて判定し, 以下のような結果を得た.両側性遠心舌側捻転はモンゴロイドや太平洋集団に比べ, ネパール人では比較的高頻度に見られ, コーカソイド集団にやや類似していた.一方, 近心舌側捻転の頻度はネパール人ではモンゴロイドや太平洋集団より低かった.これらの結果からは, ネパール人における上顎中切歯捻転の様式はコーカソイド集団に比較的類似しておりモンゴロイドや太平洋集団とはやや異なると考えられた.ネパール人における上顎切歯部の歯列異常については, 叢生が70例中わずかに4例見られたにすぎない.一方, 側方および正中歯間離開は各々7.14%および4.29%に認められた.また, 上顎中切歯における捻転と配列異常の頻度には有意な相関は認められなかった.このことから, 上顎中切歯の捻転様式は歯間の離開や狭窄によるものでなく, 歯根の形態など, 他の要因によるものと考えられた.

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After inducing bone debility in three-week-old male Wistar rats by providing calcium-deficient food, a treatment method combining standard food containing calcium and ECT (0.2 u/kg ; intramuscular injection), synthetic eel CT inducer, was used for five weeks, and the effect of the treatment was investigated. The results were as follows : I. Histopathological findings In the calcium-deficient food group, as compared with the control group, bone quantity decreased sharply ; fasciculated bone was resorbed over the whole area ; bone marrow enlarged markedly in spongy bone ; and low-calcified layers intermingled with connective tissues were seen. In the osteoid tissue, bone lacunae of irregular shapes were seen sporadically. In the calcium-deficient food plus standard food group, as compared with the calcium-deficient food group, bone remodeling was actively in progress and cementing lines were markedly seen in the transition area from bone resorption to bone formation. In the combined treatment groups, as compared with the calcium-deficient food plus standard food group, bone lacunae around the Haversian canals increased in spongy bone and so called the Haversian system was seen. Bone formation exceeded bone resorption and marked bone reconstruction was observed. The buccal and central alveolar bones adjacent to enamel organs showed active remodeling. As compared with the control group, however, many connective tissues were found in the spaces between trabeculae, and bone construction was decrased. II. In the calcium-deficient group as compared with the control group, the matrix formation surface in the whole of the alveolar bone was faveolate, and fasciculated bone, spongy bone, and cortical bone showed extensive resorption findings in the whole area. In the calcium-deficient food plus standard food group as compared with the calcium-deficient food group, the osseous layer in the whole of the alveolar bone showed active conversion of bone and the bone surface showed an increase in smooth planes. In the calcium-deficient food plus standard food plus ECT group as compared with the calcium-deficient food plus standard food group, bone construction in the whole of the osseous layer was expedited but the layer was formed thin as compared with the control group. Furthermore, bundles of collagen fibers running in a given direction were found and in the surface layer, collagen fibrils were found. On the basis of the foregoing findings, the combination therapy of Ca and CT for debilitated mandibles showed marked conversion of bone due to an increase in bone quantity and also showed clear reconstruction of bone.

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The TMJ dysfunction syndrome has been defined as the presence of one or more of the following symptoms : (a) pain and tenderness in the region of the muscles of mastication and the temporomandibular joint (TMJ) ; (b) sounds during condylar movements ; (c) limitation of mandibular movement, etc. In addition, the absence of organic changes in the TMJ is evident. This report is an epidemiological study, the purpose of which is to better understand the prevalence of the symptoms of the TMJ dysfunction syndrome and to aim at systematizing dental care for Nepali people. The subjects were 220 children aged 5-18 years (109 boys and 111 girls). The results obtained were as follows : 1. The incidence of TMJ sounds occurred in 13 children (5.9%)-5 boys (4.6%) and 8 girls (7.2%)-no significant difference was found between boys and girls. 2. The incidence of pain in the region of TMJ occurred in 5 children (2.3%)-1 boy (0.9%) and 4 girls (3.6%)-no significant difference was found between boys and girls. 3. The incidence of the limitation of mandibular movement occurred in 2 children (0.9%)-1 boy (1.8%) and 1 girl (0.9%)-no significant difference was found between boys and girls. 4. The incidence of the TMJ dysfunctin syndrome occurred in 17 children (7.7%)-6 boys (5.5%) and 11 girls (9.9%)-no significant difference was found between boys and girls. 5. The most frequently occurring symptom of this syndrome was the singular one of TMJ sounds.

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Hydroxyapatite coated blade-vent implant was implanted in the mandible of adult dogs and the superstructure of the implant was mounted on it. Lateral, vertical, and nonfunctional loading were made in the mesial direction through occlusal contact and a histological examination was made of changes in the mesio-distal bone structure around the implant. The findings suggest as follows : 1. In the cases of non-functional pressure loading, the reconstructive phenomenon of the bone around the implant scarcely occurred. 2. In the cases of vertical pressure loading, the osseous developmental hyperplasty was formed with time parallel to the implant. As in the cases which had insufficient support of bone causing cortical bone resorption, however, the bone remodeling for compensation was noted widely in the area around the body of implant. 3. In the cases of lateral pressure loading as compared with the cases of vertical pressure loading, the diffuse osteogenesis was observed with remarkable bone reconstruction at thick trabeculae just around the implant body. However the condition of the surrounding bone was still stable in the case with sufficient support of cortical bone. For the long-term case, the alveolar apical area presented the apposition of bone with time, with the difference being noted between mesial and distal bone levels. 4. The grade of osteogenesis was different according to compressive or tensile stress put upon the area, and the earlier osteogenesis was noted in the areas under the compressive stress. The findings that osteogenesis occurs differently according to the kind and size of the functional pressure transmitted to the bone through the implant suggests that bone reconstruction corresponds to the functional pressure.

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Effect of tooth movement on the dental pulp is unclear in many respects and reports on changes in pulpal nerve fibers due to changes in orthodontic force, in particular, have been very few. In the present study as a part of a fundamental research, mesial movement of the first maxillary molar of the rats was made with use of two different initial loads and changes in pulpal nerve fibers resulting from the tooth movement were observed. The orthodontic appliance consisted of a closed coil spring connecting the first maxillary molar to the central incisors. The initial loads applied with the coil was 15 g as optimum force or 150 g as excessive force, and it dissipated with time. After 1, 3, 7 and 14 days, the animals were perfused after an overdose of anesthetic. Serial sections of the experimental and control jaws were ordinary prepared, given silver impregnation and Hematoxyline・Eosin stain, and observed under the light microscope. The results were as follows : 1. The experimental tooth was tipped mesially involving intrusion of mesial root and extrusion of distal root. The degree of intrusion and extrusion depended on the magnitude of the orthodontic force. 2. The two groups showed a common finding of slight reversible inflammation of the pulpal tissues. However, no significant difference in pulpal damage corresponding to the difference in the initial loads was found between the two groups. 3. The pulpal nerve fibers showed greater degeneration by root intrusion than by extrusion. The degree of degeneration depended significantly on compression caused by the initial load. Since the nerve fibers can fairy bear stretching, degeneration of pulpal nerve fibers showed low dependency on the stretching caused by the initial load. So intrusion caused more damage to the pulpal nerve fibers than extrusion. 4. Degeneration of pulpal nerve fibers differed due to the difference in susceptibility to compression and stretching, and due to the load on root apex. With interruption of axonal continuity at the root apex, however, degeneration can be classified into slight degeneration and axonotmsis. Slightly degenerated nerve fibers without axonotmsis showed morphological recovery with dissipation of the load. Nerve fibers with axonotmsis, on the other hand, showed Wallerian degeneration on the distal side. With dissipation of the load thereafter, regenerated nerve fibers appeared. It was suggested from the foregoing results that the use of excessive force in the daily clinical practice would be considered undesirable on the basis of changes in the pulpal nerve fibers.

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This study was carried out to further understand the panoramic radiographic findings of postperative maxillary cysts. Of the radiographs kept in the Department of Dental Radiology at Kyushu Dental College Hospital, 160 cases of panoramic radiographs of postoperative maxillary cysts were analyzed. One hundred and sixty cases consisted of 100 males and 60 females. The results obtained by this study were as follows : 1. Of the 160 cases of postoperative maxillary cysts, 79 cases (49%) were located througout the anterior, posterior walls of the maxillary sinus and the alveolar bone. Sixty-two cases (39%) were located within the area from the anterior wall of the maxillary sinus to the alveolar bone. Two cases (1%) were located from the anterior wall to the posterior wall of the maxillary sinus. 2. Of the 160 cases of postoperative maxillary cysts, 144 cases (90%) were mono-locular. Sixteen cases (10%) were multi-locular ; 11 cases were di-locular and 5 cases were trilocular. 3. The average vertical dimension of postoperative maxillary cysts was 2.96±0.88 cm in males and 2.70±1.03 cm in females. The average horizontal dimension was 3.00±0.82 cm in males and 2.74±1.02 cm in females. There was no statistical significance in the difference between males and females in either dimension of postoperative maxillary cysts. 4. Of the 160 cases of postoperative maxillary cysts, 106 cases (66%) had a well-defined margin, while 54 cases (34%) did not. There was no significant relationship found between definitions of cyst margins and the clinical symptom of pain. 5. Of the 160 cases of postoperative maxillary cysts, 81 cases (51%) had a marginal sclerosis, while 79 cases (49%) did not. There was no significant relationship found between the marginal sclerosis of the cysts and the clinical symptoms of pain. 6. Of the 640 teeth in affected sides, 428 teeth (67%) were vital. One hundred and fifty-two teeth (24%) were missing. Sixty teeth (9%) were non-vital. 7. Of the 160 cases of postoperative maxillary cysts, 72 cases (45%) revealed an ill-defined appearance of the panoramic innominate line in affected sides, while 73 cases (46%) of an ill-defined appearance were in non-affected sides. Forty-five cases (28%) showed a thickened panoramic innominate line in affected sides, while 50 cases (31%) were seen in non-affected sides. In 11 cases (7%) the panoramic innominate line disappeared in affected sides, while in 3 cases (2%) of non-affected sides disappeared. 8. Of the 160 cases of the maxillary sinus in non-affected sides, 84 cases (53%) revealed a tri-angular shape. Forty-three cases (27%) revealed a tri-angular shape accompanied by a cyst-like radiolucency. Twenty-three cases (14%) revealed a normal shape.

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A computerized planimetric method (P%I) for measuring plaque adhesion area has been developed. The purpose of the present study is to evaluate intra- and inter-examiner reliability in assessing dental plaque by this method and the efficacy of the method itself. Correlation coefficient between intra-examiner and between 2 examiners were 0.99 and 0.92, respectively, which indicated significantly (p<0.001) high reproducibility. When plaque area was also measured by the Debris index (DI), Podshadley's patient hygiene performance index (PHP), Turesky modified Quigley-Hein plaque index (QHI), the Navy plaque index (NPI) on 221 tooth-surfaces in 18 volunteer students, significantly high correlation (r=0.80 to 0.84) was found between the P%I and these 4 indices. The P%I showed highest plaque reduction rate (40%), when plaque area in the same subjects was compared between before toothbrushing instruction and after instruction, although mean number of scores showed significant differences in all indices. These findings suggest that plaque adhesion assessment by a computerized planimetric method is highly effective in clinical investigations, especially in relatively small samples.

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Since the importance of the rigid connection between abutment teeth and retainer was advocated for supporting removable partial denture, the conical crown (Konuskrone) - retained dentures have stood high in the clinical evaluation. However, not a few problems involving falling down of inner crown, increase in abutment tooth mobility and breakage of denture have been reported. The present study was scheduled to experimentally investigate the characteristic behaviors of the abutment teeth for Konuskrone retainers when they were altered in number and location in the mandibular unilateral distal extension removable partial denture. Six types of unilateral distal extension partial dentures were constructed ; three of them were of unilateral designs having one, two and three abutment teeth on the same side of the denture base, respectively, and the other three of bilateral designs having additional one abutment tooth on the opposite side in each of the above unilateral designs. The tooth movement was measured in horizontal, frontal and sagittal planes by means of mandibular kinesiography (MKG) and laser displacement sensors on a Kennedy class II simulation model. The results obtained were as follows : 1. It was found that the abutment teeth movements involved not only simple tipping but also horizontal displacement and gyration of their tooth axes. 2. It was the most difficult to take countermeasures in Konuskrone to deal with the movement against the force from lingual side. 3. In the unilateral design, the primary abutment tooth movement could not be restrained by addition of one mesial abutment while one more mesial addition showed significant reduction in the movement. 4. In the case of the bilateral designs, application of only primary abutment tooth caused large displacement. Addition of one mesial abutment tooth on the denture side was effective for reducing the displacement ; however, one more mesial abutment had a tendency to rather increase the displacement. 5. In comparison of the designs having a given number of the abutment teeth, the bilateral design showed more favorable behavior than the unilateral with two abutment teeth while there was little difference in efficiency between them with three abutment teeth, against all the forces except from lingual side. No effects were found in both the two designs having two or three abutment teeth against the force from lingual side.

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Porous hydroxyapatite has been known to be effective basically and clinically for restoration and reconstruction of mandibular bone defect. Few studies however have been made on the nerve distribution into the pores of porous hydroxyapatite block implantation. An investigation therefore was made on the effect of porous hydroxyapatite block implantation on the restoration process of nerve tissues. For the experiment, 36 rabbits were used and the inferior alveolar nerve in the bone defect of 5×5 mm was ligated and excised. Two types of porous hydroxyapatite blocks (pore size : 90μm and 200μm) were implanted in the bone defect. These cases were compared with non-implantation control cases. These specimens were examined histopathologically and neurohistologically from the 3 rd to the 180 th day postoperatively. The following results were obtained : 1. Wound healing of the bone defect was delayed by porous hydroxyapatite block implantation. 2. New bone formation in the pores was comparatively speedier in 200μm hydroxyapatite block cases than in 90μm hydroxyapatite block cases. 3. The new bone formation in two types of hydroxyapatite block cases and in control cases was continuous from the host bone. 4. Porous hydroxyapatite block did not affect the the nerves of anterograde and posterograde degenerations. 5. In both implanted cases and control cases of the anterograde degenaration, resorption and disappearance of the nerve component were observed at the same time, but complete resorption of the nerve component was found earlier in control cases than in implanted cases. 6. Appearance of the growth of nerve fibers into the pore was later than in control cases. 7. Most of the nerve fibers growing from the cut-end of the nerve in the bone defect detoured hydroxyapatite block and grew. The nerve fibers growing into the pores were found only in part. 8. The nerve fibers ran about in the center of pores in the porous hydroxyapatite blocks. Pore-diameter had little effect on the nerve distribution. On the basis of the above-described results, wound healing with the hydroxyapatite block implantation appeared to have considerable effect on the nerve distribution. (restoration process of nerve tissues)

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The activator of Kyushu Dental College type allows molars without the occlusal surface grounded to participate in occlusion with the resin floor interposed ; whereas the conventional activator or biteplane has the occlusal surface of molars grounded and the molar regions are separated. Applications of these two types of activators result in differences in the mandibular position after operation. With the assumption that this difference is caused by whether molars are separated, the present experiment was conducted. Two kinds of biteplanes, those for anterior teeth and those for anterior teeth and molars, were mounted with adult dogs as the subjects, and the differences in the effect of those biteplanes on the mandibular condyle were examined histologically. The results were as follows : 1. As to width of the articular cavity, the central constricted region of the joint cavity in the ground with the biteplane for anterior teeth mounted showed severe constriction up to the 60 th day as compared with normal width. In the group with the biteplane for anterior teeth and molars mounted, slight enlargement was seen to the 20 th day and then normalcy was about restored by the 60 th day. 2. Bone addition in the mandibular condyle was marked from the middle to posterior regions in the group with the biteplane for anterior teeth mounted. In the group with the biteplane for anterior teeth and molars, bone addition was seen in the whole mandibular condyle. 3. Occurrence of bone addition was seen from the 20 th day and thereafter in the anterior teeth biteplane group. In the group with the biteplane for anterior teeth and molars mounted, on the other hand, bone addition was seen in the whole mandibular condyle from as early as the 10 th day. On the basis of the foregoing findings, it is suggested that the difference in the mechanism of action of these two devices is reflected in the positional relations of the mandibular condyle and mandibular fossa, and also affects treatment effect.

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The epithelia of rabbit fungiform papillae and filiform papillae were studied by electron microscopy. Further, filiform changes observed in the dorsal epithelium of fungiform papillae after chorda-lingual neurectomy were studied by scanning electron microscopy ; the state of keratinization of the epithelium was observed by transmission electron microscopy ; and the findings were compared with those in the epithelium of normal filiform papillae. The surface of fungiform papillae was relatively smooth, and the dorsal epithelium was covered by a thin keratin layer with no keratohyalin granules. In filiform papillae, the nature of keratinization was quite different between the epithelial cell layers on the anterior and posterior aspects of the papillae. On the anterior aspect, epithelial cells contained many keratohyalin granules, were nucleated to the topmost layer, and formed a soft keratin layer, showing a strong tendency toward parakeratosis. On the posterior aspect, in contrast, the cytoplasm of epithelial cells was rich in ribosomes and tonofibrils, but few keratohyalin granules were noted. The superficial cells had no nuclei or cell organelles and showed true keratinization, forming a hard keratin layer. After chorda-lingual neurectomy, taste buds in fungiform papillae degenerated, and marked progression of keratinization was observed in the dorsal epithelium of many fungiform papillae 1 week after denervation. The keratin layer on the dorsal aspect of these papillae was thickened, and the papillae were characteristically pointed as in filiform papillae and curved toward the pharynx. These changes became more notable with time, and the fungiform papillae were difficult to distinguish from surrounding filiform papillae by scanning electron microscopy 6 months after denervation. In the dorsal epithelium of fungiform papillae showing marked changes, transmission electron microscopy showed a pseudokeratotic layer occasionally containing condensed nuclei in the anterior aspect of the papillae but a keratin layer without nuclei or cell organelles in the posterior aspect. The ultrastructural examination of markedly degenerated fungiform papillae revealed a dual keratinization pattern similar to that in the epithelium of filiform papillae. Keratohyalin granules were observed in fungiform papillae showing marked keratinization. The appearance of keratohyalin granules not observed in normal fungiform papillae showing only mild keratinization suggests that they play a role in keratinization of fungiform papillary epithelium.

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Restoration of tooth with composite resin filling may cause pulpal damage. Recently, some causes are mentioned in reports : (1) chemical irritation by composite resin, (2) bacterial infection, (3) interaction between bacterial and chemical irritation, and (4) microleakage of margin, etc. Real cause however has not yet been established. With a view to clarifying the cause of pulp damage induced by composite resin filling, maxillary 1 st molars of Wistar SPF rats were used for histological examination in this study. This experiment is divided into five groups and performed under the condition of maximum prevention of bacteria and marginal leakage : (1) EZ group : mesial surface of the tooth was filled with zinc oxide eugenol cement and sacrificed after two weeks, (2) CR group : mesial surface of the tooth was filled with composite resin and sacrificed after two weeks, (3) CR-P group : mesial surface of the tooth was filled with composite resin. At two weeks when the pulp was thought to be healing, calcium hydroxide pulpotomy was performed, (4) NO-P group (control group) : calcium hydroxide pulpotomy only, and (5) EZ-P group (control group) : calcium hydroxide pulpotomy followed by zinc oxide eugenol cement filling (mesial surface) two weeks later. The rats of (3), (4) and (5) were sacrificed at 1-week, 2-week and 4-week postoperatively. The results demonstrated that the dentin bridge formation in the teeth filled with composite resin was poor as compared with the controls. Thus, it is suggested that the composite resin restoration may reduce the pulp potential of dentin bridge formation.

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The purpose of this research was to study the influence of the difference in dietary physical consistency, which is the representive factor of local environmental factors, on the morphology, the bone mineral levels and the physical strength of the mandibular bone in the growth stage. Three-week-old rats of Wistar strain were used. Thirty rats were randomly divided into three groups : the hard diet group (control group), the kneaded diet group and the powdered diet group. All of the rats were fed for six weeks. After six weeks, the rats were sacrificed. Roentgenographic lateral cephalograms were taken to investigate the morphological changes of the mandible, and the mineral content of the mandibular bone by the microdensitometry method and mandibular physical strength by compressive test were examined. The results were as follows, 1. The average compressive strength of each diet was 64.8 kg/cm^2 for the control group and 1.9 kg/cm^2 for the kneaded diet group. 2. There were no significant difference in body weight between the control group, the kneaded diet group and the powdered diet group throughout the experimental period. 3. The lateral cephalometric analysis showed the morphological changes at the mandibular ramus, including angular process. Morphologic reduction was found significantly in coronoid process of kneaded diet group and in coronoid process, condyle and angular process of powdered diet group. 4. The bone mineral content of alveolar bone and mentum was significantly lower in both the kneaded and the powdered diet group. Meanwhile at the region of the mandibular lower margin and angular process, the content was significantly lower in powdered diet group. 5. Compressive strength of mandible was significantly lower in kneaded diet group and powdered diet group. The strength declined with decreasing of physical strength of diet. From these results, it is suggested that the difference of dietary physical consistency influences not only morphological chages but also alteration in internal characteristic of mandibular bone in the growth stage.

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This study was application of the computer and the video digitizer to colorimetry of the teeth of children. However, the chromatical values are not assured, because this equipment was developed for computergraphics. So in the region of crown color, the guaranteed degree and the way of mathematical conversion were researched. After establishing the way for conversion, VITA LUMIN shade guide, upper primary central incisors, and upper permanent central incisors were chromatically examined in CIE 1976 (L^*a^*b^*) Color Space by this system. 1. The guarantee of the chromatic values measured by this system in the region of crown color. The three color charts whose hue is 10YR, chromaticness is 3, and lightness is 6, 8, 9, were chosen as the three standard colors. When measured values were converted with each XYZ value, the value of color differrence between converted values and published values was 1.62 on the average. 2. The chromatic values of VITA LUMIN shade guide. The distribution range in the center was as follows. (L^*value : 60-80, H^*value : 80-112, C^*value : 11-25). The less the number of the shade guide was named, the lighter and the more yellowish. In comparison with A system, B system showed yellowish, C system became darker, and D system were low chromaticness. 3. The chromatic values of upper primary central incisors (upper A), and upper permanent central incisors (upper 1). The distribution range in which 95% cases were included was as follows. upper A……L^* : 62.2-84.6, H^* : 38.8-108.0, C^* : 0.6-22.2 upper 1……L^* : 57.9-91.4, H^* : 55.8-93.4, C^* : 8.7-28.0 4. The difference between the shade guide and the natural teeth a. Because the children's teeth were examined in this study, high brightness shade guide was insufficient. And the average hue of teeth was little redder than shade guide. b. The natural teeth only showed the correlation between L^* and C^* But the shade guide showed the correlation among all the cases. c. In the case of natural teeth, the lightness at central part was the highest. But in the case of the shade guide, the lightness and chromaticness decreased from the cervical part to the incisal edge.

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Recently new types of all-ceramic restoration systems have been developed and clinically applied. Since the core or porcelain material has been much improved in strength, it may be possible to apply the systems not only to single crown but also to short span bridge. When clinically applied to the connected crowns, however, they have often presented a problem of poor fit although satisfactory fitness has been demonstrated for single crown by several reports. In the present study, therefore, the factors affecting the fit were examined at the stages after the green core casting and some experimental approaches were evaluated for fabricating better fitting all-ceramic connected crowns using Alceram^<TM> system. The results obtained were as follows : 1. All-ceramic connected crowns fabricated according to the manufacturer's standard firing schedule (control specimen) showed poor fit having large marginal gap on the working die although each component crown itself separately exhibited good fit to its die. 2. It was found that the connected crowns were distorted as a whole into mesio-distally warped shape and that most of the distortion might have been caused during firing for core sintering due to the release of inner stresses of the green core. No significant changes were observed at the stage of the porcelain firing. 3. The use of a sprue modified into webbed-shape slightly restrained the distortion of the connected crowns while no significant reduction in the average marginal gap was recognized. 4. A modified design having vertically enlarged connection between the crowns showed marked decrease in warped-shape distortion and marginal gap. 5. When the core firing was prolonged for 30 minutes at the maximum temperature of the standard schedule, the resultant core showed better fit with marginal gap as small as half the control specimen. 6. By introducing a preheating treatment of the green core at 200℃ as it was seated on the working die prior to the standard firing, the marginal gap reduced to half the control. 7. When the core was fired as the sprue was left uncut, the good fit of the green core on the working die was almost maintained even after firing and sprue cutting. It might be due to the stress relief annealing reaction by this treatment. It was suggested from the foregoing results that it would be the best way for improving the fit of the all-ceramic connected crowns to cut sprue after core firing although it might have a risk of fracturing the brittle core.

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The present study was carried out to compare the characteristics of EMG activites of the anterior and posterior parts of the tongue and to investigate changes of EMG activities of these parts after the severance of the lateral or medial branches of the hypoglossal nerves in the rat. Bipolar electrodes of 50 μm stainless steel wire coated with Teflon^[○!R] were placed internally on the muscles of the anterior and posterior parts of the tongue and led to a connector fixed on the center of the cranial bone. In recording EMG, the terminal of connector and the amplifier were connected with other thin wires and rat could move and eat freely in the cage. Control EMG was recorded after 3 and 7 days from setting the electrodes and a connector. The postoperative EMG was recorded after 3 and 7 days from severance of the lateral or medial branches of both sides of the hypoglossal nerves. EMG pattern and muscle activities that were indicated as 100, relative value of integrated value of EMG during feeding, in the anterior and posterior parts of the tongue, and those after severance of the lateral and medial branches were compared. The main findings were summarized as follows. 1. During feeding of intact rats, several small amplitude bursts were generated when the biting sound by incisor was heard, and immediately about 20 bursts with semilarge amplitude and brief interval, and following rhythmical bursts when rat masticated with molar were elicited. The rhythmical bursts of the anterior and posterior parts were composed of burst generated with semilarge and large amplitude alternately. The freguency of burst of the anterior parts was twice that of the posterior parts. 2. The cycle of rhythmical bursts of the posterior parts during mastication was about 214 msec. On the other hand, the cycle (C2, C3) from first burst (A1) to next first burst (A1), and from second burst (A2) to next second bursts (A2) were bout 214 msec. The interval (I1, I2) from A1 to A2 and from A2 to A1 were 91 and 114 msec respectively. 3. The hythmical bursts of the posterior parts during mastication always preceded slightly those of the anterior parts. The time lag (P-A1, P-A2) from burst of the postrior part and first bursts (A1), and to second bursts (A2) of anterior parts were about 14, and 105 msec. The duration of semilarge and large bursts were same and about 100 msec. The duration of A1 and A2 of the anterior part were about 54 and 76 msec. The A1 and A2 differed in amplitude and duration of the rhythmical bursts during chewing. 4. EMG patterns of the anterior and posterior parts during licking differed. EMG pattern of the anterior parts was almost rhythmical. The cycle and duration of the anterior parts were about 162 and 106 msec and shorter than those during mastication. 5. After severance of both the lateral branches of the hypoglossal nerves, EMG pattern did not change, but cycle of the anterior and posterior parts was shortened significantly and the time lag of the posterior and anterior parts, too. 6. After severance of both the medial branches of the hypoglossal nerves, rhythmical bursts during feeding disappeared and bursts with small amplitude continued. The rhythmical bursts of the posterior and anterior parts during grooming reduced and those during licking were shortened in time elicited and irregular. 7. In intact rat, the muscle activities of the posterior parts during feeding, grooming, licking, exploring, and resting were 100, 110, 107, 63 and 37, and those of the anterior parts, 100, 128, 132, 65 and 36, respectively. The muscle activities during these behavior after severance of lateral and medial branches reduced about 29&acd;56% and 7&acd;40%.

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The purpose of this research was to assess the role of undifferentiated mesenchymal cells after pulpotomy using calcium hydroxide method (CHM) and formocresol method (FCM) during the pulp healing process. Bilateral maxillary 1st molars of 25 male Wistar rats were employed for the investigation in this study. The rats were sacrificed for histological examination at 1, 3, 7, 14 and 28 days postoperatively. Three hours before sacrifice, vinblastine sulfate (0.3 mg/ 100 g b. w.) was injected into the abdominal cavity for arresting the mitotic undifferentiated mesenchymal cells (MUM cells) of the residual pulp in metaphase. The MUM cells were calculated and statistically evaluated. Both CHM and FCM reached a maximum peak of the number of MUM cells at 3 rd day. When CHM and FCM were compared from 14 th day to 28 th day, the former showed that the significant (p< 0.05) reduction of MUM cells was more rapid and the number of MUM cells was relatively lower throughout the residual pulp. Residual inflammation at the wound surface and incomplete closure by osteodentin were found in FCM at the end of this study. These observations demonstrated that "Inflammation stimulates the proliferation of MUM cells and influcences morphological differentiation of MUM cells". Thus, the following conclusion can be made : Continual inflammation will give rise to a delayed healing of formocresol pulpotomy.

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Diabetic dysgeusia has been revealed since the first Fox's report (1932). In diabetes mellitus, however, ultrastructural study of the taste buds has not reported yet. In this point of view, the present study was perfomed to investigate morphological changes of the taste buds in foliate papillae in streptozotocin (STZ) induced diabetic rats. Diabetes was induced by intra abdominal injection of STZ (60 mg/kg b. w.). After raising for 3 months, 6 months and 12 months, the foliate papillae were collected and observed by means of electron microscopy. The results were as follows : 1. The taste buds of STZ rats were characterized by swelling cytoplasm, vacuole formation, and enlarged nerve fiber. The swelling taste buds contrasted strikingly with the atrophied foliate papillae in the whole STZ rats group. 2. Vacuole formation and pyknosis were seen in the taste buds in 3-month STZ rat group, and 6-month STZ rat group. Increased lipid droplets and a lot of filament bundles are seen in 12-month STZ rat group. 3. A great number of autophagic vacuoles were recognized morphologically as membranous cytoplasmic body (MCB) and zebra body. 4. Swelling mitochondria, rough ER, Golgi apparatus were observed as change of organelle. 5. Intragemmal fibers were enlarged and myelin-like body appeared in subsurface cisternae (ssc) in the Type II cell. Plasma membrane of the nerve ending degenerated in the afferent synapse in the type III cell. On the contrary, afferent synaptic contacts were observed in 12-month STZ rat group as well. 6. Dense substance in the taste pore decreased remarkably in 3-month STZ. It was suggested environment of taste pore changed in the early stage. With the foliate papillae atrophying, taste pore was apt to show stricture. There were also many imperfolate taste pore in 12-month STZ rat. 7. Diabetes showed strong infectiosity. Many taste pores infected with bacteria were observed. On account of these changes in taste buds and nerve element in STZ rats, functional disorder of taste buds were suggested in diabetes mellitus.

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Congenital lateral cervical cysts usually occurring on the lateral side of the neck are believed to be derived from the branchial arch organ and from the epithelial inclusion within the cervical lymph node. A 16-year-old girl noticed a swelling with tenderness in the right lateral cervical region about 3 days before visiting the hospital. At the time of the initial examination, this swelling was an elastic hard, pigeon-egg-sized localized tumor. The contained fluid was aspirated in an exploratory puncture. The cyst was surgically resected under the general anesthesia, and the prognosis is uneventful.

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