Three-week-old rats of Wistar strain were given calcium-deficient diet and experimental osteoporosis was induced in them. These rats were then given calcitonin (eel calcitonin) and its effect on the mandibular condyle, tibia epiphysis, and tibia metaphysis was examined radiologically and histopathologically. The results were as follows : I. Radiological findings A. A compact osseous layer was observed in the periphery of the mandibular condyle and of the tibia epiphysis. Trabeculae were increased, wider, and running vertically from the articular surface. B. In the tibia metaphysis, trabeculae were increased, wider, and running vertically and compactly from the surface of the tibia metaphysis. II. Histopathological findings A. Contact microradiographical findings 1. Granular trabeculae of primary spongiosa in the mandibular condyle were increased. Those of secondary spongiosa were also increased, uniform in width, and running more compactly. 2. Granular trabeculae of primary spongiosa in the tibia epiphysis were slightly increased. Those of secondary spongiosa were also increased, slightly wider, and running more compactly. 3. Trabeculae of primary spongiosa in the tibia metaphysis were increased, clearly distinguishable between longitudinal and lateral trabeculae, and running compactly. Trabeculae of secondary spongiosa were also increased slightly in quantity and width, and running. B. General histopathological findings 1. The cartilage layer in the mandibular condyle thickened because of increase in hypertrophic chondrocytes. Erosions of calcified matrix by chondroclasts were numerous ; however, the patterns of erosion were irregular. Incidence of subchondrocyte bone formation was also high. Trabeculae were wider and most of them constituted weakly-calcified layer. 2. In the tibia epiphysis, the cartilage layer thickened because of decrease in proliferative chondrocytes and increase in hypertrophic chondrocytes. Erosions of calcified matrix by chondroclasts and subchondrocyte bone formation were numerous. Trabeculae widened and most of them constituted weakly-calcified layer. 3. In the tibia metaphysis, the cartilage layer thickened because of increase in proliferative chondrocytes and hypertrophic chondrocytes. Erosions of calcified matrix by chondroclasts and subchondrocyte bone formation were numerous. Trabeculae widened and most of them constituted weakly-calcified layer. III Scanning electron microscope findings In the mandibular condyle, chondrocyte lacunae in the upper portion of the cartilage layer were composed of several calcospherites. The lacunae were 10-20μm in diameter and bowl-shaped, and calcospherites were 1-2μm in diameter. Trabeculae in the zone of subchondrocyte bone formation were wider, and collagen fiber networks and calcospherites were observed in the center of the zone. Several resorption lacunae were observed and collagen fiber networks were also observed extensively. On the basis of the foregoing findings, in the mandibular condyle, tibia epiphysis, and tibia metaphysis, administration of calcitonin facilitated bone formation by inhibiting chondroclasts ; however, most trabeculae constituted weakly-calcified layers. The effect on chondrocytes was the highest in the tibia metaphysis, with the mandibular condyle and tibia epiphysis following.

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With regard to the upper anterior teeth, many studies have been made on forms, sizes, standards for selecting colors, and state of dentition. However, little concern has been shown on the lower anterior teeth from the viewpoint of esthetics, although they are as clearly visible as the upper anterior teeth during speaking. Therefore, with 56 individually normal dentulous males, 20 to 40 years of ages, as subjects, incisal point, gingival point, and interdental papillary apex were measured and the horizontal and vertical relationships in position with aging among the measured items and changes in position of each measured item were examined. The prosthetic plane was used as the vertical base plane and the contact points of the lower left and right central incisors as the horizontal reference points. The results were as follows : 1. Incisal point, incisal embrasure apex, and gingival embrasure apex showed little changes horizontally and vertically with aging. 2. Gingival point showed a tendency to lower slightly with aging. For all ages, the gingival points of the central and lateral incisors were at about the same positions, and that of the canine was located at about 1.5mm below those points. 3. Interdental papillary apex lowered with a statistical significance with aging. The extent of lowering was about the same for all items. 4. Interdental papillary apex and gingival point both lowered vertically ; however, the former showed a greater tendency to lower with aging. 5. The coronal axis was positioned about vertically to the occlusal plane for the central and lateral incisors but inclined about 8°mesially for the canine. 6. The coronal twist angles of the central and lateral incisors and canine were 0°, 13-18°, and 31-35°, respectively. 7. Incisal embrasure area showed no changes with aging but gingival embrasure area tended to decrease with aging. 8. The clinical coronal lengths of the lateral incisor and canine were about the same for both the upper and lower jaws but that of the central incisors was greater for the upper jaw.

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Chemotherapy for oral cancer is an important treatment method next to surgical therapy and radiotherapy. It is therefore important to have a grasp of the cytocidal effect of anticancer agents on normal cells and tissues from the viewpoint of tumor-host-drug relationship. In chemotherapy, several anticancer agents have been combined in use or combined with non-antitumor agents to increase antitumor effect and to minimize side effects. Of these non-antitumor agents, vitamin A has lysosome stabilizing effect and membrane active effect, and has been reported to increase antitumor effect when combined in use with anticancer agents. While vitamin A increases antitumor effect, its influence on normal tissues is also expected. Therefore, Bleomycin (BLM) and Mitomycin C (MMC), frequently used in chemotherapy for oral cancer, were combined with vitamin A (V・A) and the effect of these combinations on the parotid gland of domestic rabbits was investigated histopathologically. The results were as follows : 1. In the terminal portion, both BLM-V・A and MMC-V・A combined administration cases showed marked atrophy and destruction of acinous cells, and pyknosis and deformation of nuclei, as compared with the cases of administration of BLM or MMC only. Between scattered acinous cells, stagnation and hyperemia were observed. Along with these regressive changes, PAS stainability, PAS positive substance and A・M stainable substance were considerably decreased. These findings were seen first in the peripheral part of the gland, and gradually passed to the middle of the gland with increase in the number of administration. In the 15 dose cases especially, these findings were observed markedly in the whole gland. 2. In the intercalated duct and striated duct, both BLM-V・A and MMC-V・A combined administration cases showed marked atrophy of epithelial cells of the ducts, and pyknosis and deformation of nuclei, in comparison with the cases of administration of BLM or MMC only. In the surrounding capillary vessels, dilation due to stagnation and hyperemia was observed. These findings increased in severity as the number of administration increased. 3. In the excretory duct, hardly any morphological changes were seen as compared with controls and the cases of administration of BLM or MMC only. 4. Regressive changes attributable to the combined use of vitamin A with BLM and with MMC were clearly recognized. However, no specific histological changes for medicine could be found in the experimental series. 5. On the basis of the foregoing experimental findings, both BLM and MMC caused in the parotid gland of domestic rabbits not only morphological changes but also functional changes in synthesis of secretory substance and excretion. The combined use with vitamin A in addition to its pharmacological peculiarity was thought to aid and promote regressive changes and reduction of function.

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Macroscopic, roentgenographic and histopathological studies were undertaken to evaluate the effectiveness of Hydroxyapatite Ceramics (HAP) and Polycrystal Alumina Ceramics (Al_2O_3) as a bone substitutes implanted in the extraction sockets where the periapical lesions were experimentally induced before extraction of teeth in Macaca fuscata fuscata and to compare the results with those for control sites which were not implanted. The results were as follows : 1. Macroscopic findings On the 14th postoperative day the postoperative reactive inflammation almost disappeared in both control and implantation groups. The narrowing of width of alveolar ridge and its lowering were observed after operation in the control group, but in both implantation groups the narrowing of width was scanty and the level of alveolar ridge was maintained high. 2. Roentgenographic findings The extraction sockets showed an increase of radio-opacity in process of time and the similar findings to those of the surrounding bone in the control group, but alveolar crest showed depression. In the implantation groups, HAP showed the granulated radioopaque image with large and small irregular in shapes, and Al_2O_3 showed smaller grobular granulated radio-opaque image than HAP. They existed at the level of ridges in extraction sockets. 3. Histopathological findings 1) On the 1st postoperative day of blood clotting stage the extraction sockets were filled with blood clots in the control group, whereas in the implantation groups they were filled with numerous HAP and Al_2O_3 granules, which exsisted at the high level of alveolar crest. On the 5th postoperative day the formation of new bone trabeculae in the extraction sockets floor were seen in the control group, but in the implantation groups it was seen on the 7th postoperative day. The amount of bone formation was greater in HAP implantation group than in Al_2O_3 implantation group. In both control and implantation groups the residual inflammatory lesions were observed in the extraction sockets floor with reduction in extent of inflammatory infiltration in process of time. 2) On the 14th postoperative day of the granulation tissue stage the extraction wounds were completely covered with epithelium in both control and implantation groups. In the extraction sockets of control group, the coronal about one-half layer consisted of granulation tissue, whereas about one-half of apical layer consisted of new bone trabecula. In the HAP group, greater part of layer consisted of granulation tissue with new bone trabeculae in about one-fifth of the apical layer, whereas in the Al_2O_3 implantation group the amount of regions occupied with new bone trabeculae was less. HAP and Al_2O_3 granules exsisted in large numbers within the granulation tissue and new bone trabeculae, reaching the portion directly underneath the epithelial layer. The inflammatory lesions in the extraction sockets were indistinct in both control and implantation groups. 3) On the 21th and 28th postoperative day of trabecula stage, the formation of new bone trabeculae proceeded in both control and implantation groups, but it was fairly delayed in the implantation group as compared with that of control group. In the implantation group, the amount of bone formation in HAP implantation group was greater than that in Al_2O_3 implantation group. HAP and Al_2O_3 granules were observed in large numbers within granulation tissue and new bone trabecula of extraction sockets, existing in the portion directly underneath the epithelial layer. No inflammatory cellular infiltration was observed around HAP and Al_2O_3 granules, and their cementing granulation tissue and new bone trabecula were dense. 4) On the 60th postoperative day of healing stage, the epithelia of extraction wounds were nearly normal in both control and implantation groups. The extraction sockets were filled with trabeculae which proceeded in

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The endotoxin of Gram-negative bacteria has various biological activities and many studies show evidence to support this. Especially in the initial lesion in periodontitis, endotoxin plays an important part in complement cleavage. The aim of this study was to investigate changes with time in complement and immunoglobulins in the gingiva and serum by inoculating the gingiva of rats with endotoxin from E. coli. The results were as follows : 1. The immunofluorescent technique for locating C3 deposits in the periodontal tissue after LPS inoculation showed strong immunofluorescent stain in the blood vessel walls and the surrounding areas adjacent to the site of inoculation three hours after inoculation. The immunofluorescent stain decreased greately six hours after inoculation. 2. The values of C3 in the gingival extracts were about 3.8 times higher at three hours, about 1.2 times higher at six hours, and about 1.8 times higher at 24 hours than the normal value, and were about normal at 168 hours. 3. No marked changes in C3 were observed in the serum. 4. The values of C3_c in the gingival extracts were about 3.7 times higher at one hour, about 1.8 times higher at six hours, and about 3.4 times higher at 24 hours than the normal value, and were about normal at 72 hours. A diphasic change was seen in increase and decrease. 5. No marked changes were seen in C3_c in the serum. 6. No marked changes were seen in complement titer of serum (CH50). 7. As to immunoglobulins in the gingival extracts at one hour, IgG was 1.4 times higher, IgM 1.2 times higher, and IgA 1.1 times higher than the normal values, showing a slight increase. The values however were about normal in three to six hours. 8. No marked changes were found in whole IgG, IgM, and IgA in the serum. 9. With regard to anti-LPS immunoglobulins in the serum, no marked changes were seen for anti-LPS IgM and a definite increase was observed at 168 hours. A slight increase was seen for anti-LPS IgM at 72 hours and a definite increase was seen at 168 hours. On the basis of the foregoing, the infiltration of LPS into the tissue led the complement at site to an abrupt cleavage through the alternative pathway. The direct effect of LPS and indirect effect through cells and others resulted in a biphasic change in increase and decrease. However, the complement in the serum circulated through the circulatory system did not show any changes. Only anti-LPS immunoglobulins showed changes in 72∿168 hours.

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For the purpose of studying contamination of prosthetic restoration, daily changes in the amounts of protein adhering to the denture basal surface and of immunoglobulins (IgA, IgG) in the saliva, factors of the formation of initial denture plaque, were measured and their correlation with adhesion and deposition of microorganisms was investigated and the formation of initial denture plaque was examined. The basal surface of the upper full denture and the adjacent surfaces of the abutment tooth of the partial denture were selected as the sites for study. The results were as follows : 1. The amount of protein adhering to the basal surface of the upper full denture showed an increasing tendency with time. By site, the anterior and posterior regions of the basal surface tended to show greater amounts of protein adhesion than the central region. 2. The amount of protein adhering to the adjacent surfaces of the abutment tooth of the partial denture increased abruptly on the first and the second day after insertion of the denture and tended to decrease slightly on the third day. The amount of adhesion was higher than that to the basal surface of the upper full denture. 3. On the basal surface of the upper full denture, microorganisms began to adhere to the basal surface on the second day after insertion of the denture and division and proliferation were observed on the third day. A greater number of microorganisms were found in the anterior and posterior regions of the basal surface than in the central region. 4. On the adjacent surfaces of the abutment tooth of the partial denture, microorganisms began to adhere to the surfaces on the second day after insertion, but no division or proliferation was seen on the third day. 5. The amount of immunoglobulin IgA in the resting saliva was about the same for the subjects with the full or the partial denture. The subjects with natural dentition showed lower values in IgA. The amount of immunoglobulin IgG was higher for the subjects with the partial denture than for those with the full denture. The IgG values for those with natural dentition was about the same as that for the subjects with the full denture. 6. The amounts of immunoglobulins in the resting saliva in the subjects with a denture varied by sex and age. In the subjects with the partial denture, those with more teeth remaining tended to show greater amounts of immunoglobulins (IgA, IgG) in the resting saliva. 7. Between the changes in the amount of immunoglobulins in the resting saliva and the amount of protein adhering to the denture surface, correlation was found in the subjects with the partial denture but not in the subjects with the full denture. 8. The teeth remaining in the subjects with the partial denture tended to show greater amounts of gingival crevicular fluid and of IgA, IgG, and Type I collagen in the gingival crevicular fluid than the teeth with healthy periodontal tissue. This tendency was more marked for the abutment tooth in comparison with the teeth at the same site. On the basis of the foregoing findings, it was suggested that the oral environment of a denture after its insertion and the environment of the site of plaque adhesion greatly affected plaque formation. Also, although plaque formation varied to some extent, the basis for plaque was confirmed to be formed on the third day after insertion of the denture.

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The composite resins have been widely applied for posterior restorations in place of amalgam since their compressive strength and wear resistance were markedly improved. One of the problems with amalgam is its large creep rate associated with marginal fracture of the restoration. In this study, therefore, the posterior composite resins were compared with amalgam in terms of static and dynamic creeps up to 6 months aging, and deterioration caused by the repeated compressive loading. The 24-hour creep was determined by applying compressive load (100kg/cm^2) to the specimen for 24 hours in water at 23℃ and storing it for 3 hours more without loading to make it almost completely recover from the elastic part of deformation. The static creep values of posterior composite resins were 1/4-1/10 times as small as those of amalgams. Among the composites, the hybrid type resins containing larger size and amount of fillers showed lower creep than the microfilled resins. The chemicalcured resins also tended to show lower creep than the light-cured. The creep was markedly decreased with increase in aging of the specimen from 1 hour to 3 hours in the composites and from 1 hour to 1 day in the amalgams. Little or no decrease was found thereafter in both materials. These creep behaviors might well reflect the polymerization or setting rates of the materials. The dynamic creep caused by repeated compressive loading was significantly larger than the static creep. It was notable that the repeated loading appeared to severely affect the creep of the amalgams even after their setting was almost completed. The compressive strength of the specimens after the creep test was not significantly different from that of the specimens after being stored without loading for the same period as the creep test. When the center of the restoration filled in the extracted tooth was subjected to repeated loading with steel ball, a depression was observed in all the materials. Some protrusions were found just outside the depression in the amalgams and the microfilled resins having higher creep, but not in the hybrid type resins showing lower creep. Distinguishable fracturing aspects by repeated loading were recognized between the amalgams and the composite resins. Namely the fractures occurred at the margin apart from the loaded area in the amalgam restorations, while in the composite resin restorations cracks were initiated just at the depression by the direct compressive loading.

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Ceramo-metal restorations are widely used because of their superiorities in esthetics, biocompatibility, toughness, and resistance to chemical attack. However, the dental professionals have long been concerned with the problem of a difficulty in harmonizing the color of ceramo-metal restorations with that of the patient's natural dentition. The purpose of this study was to confirm the mutual migration of the enamel and dentin porcelain particles during condensation process and its effects on the color changes of the ceramo-metal restorations. The porcelain slurry was condensed with four kinds of condensers : experimental condenser utilizing a revolving pulley (EC), Le Cron carver (LC), ultrasonic condenser (UC), ultrasonic condenser combined with hot air (UH). The migration of the enamel particles through the enamel-dentin interface during condensation was estimated by the penetration of the fluorescent particles contained in the enamel powder into the underlying dentin layer, which was detected with an epifluorescence microscope. Among the condensers used, EC exhibited the maximum penetration distance of the enamel particles and UH the minimum. For color analysis, dentin and enamel layers were built up in several different proportions of thickness so as to be 1.2mm thick in total. The porcelain was fired by two-different procedures : one-step firing technique in which the molded dentin and enamel were fired simultaneously, and two-step technique in which the dentin was molded and fired first and then the enamel was molded and fired. The enamel particles, therefore, could penetrate into the dentin layer in the one-step technique but not in the two-step technique. By comparing the ceramo-metal specimens fired by these two techniques, it was found that their colors were affected by the particle migration. The values of luminous reflectance and chromaticity coordinates were significantly increased with the particle migration when EC, LC, or UC causing larger migration were used. In the case of UH showing smallest particle migration, the luminous reflectance was also increased but the chromaticity coordinates were not significantly changed by the migration. This indicates that the luminous reflectance may be more markedly affected than the chromaticity coordinates by the particle migration. Color differences also appeared in the range of "trace" or "slight", although a definite relationship between the color difference and the particle migration could not be recognized.

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The oral cavity with such articulatory organs as the lips, tongue, uvula, and soft palate which are very versatile in mobility plays an important role of articulatory function in producing various sounds by changing their forms. When many teeth are lost by surgery or periodontosis, it is well known by experience that the articulatory function of the oral cavity is greatly impaired and speech impediment is induced. In practice in prosthodontics, therefore, it is very important to restore the articulatory function, as well as esthetic and occlusion, by carrying out a prosthetic treatment at the region with a tooth-loss. In view of the articulatory function, it is important to examine the relation between artificial tooth position and articulation. Four types of experimental dentures with over bite and over jet varied were therefore prepared for the cases of a tooth-loss at the lower anterior region. Five syllables of "S" followed by a vowel in Japanese (Sa, Si, Su, Se, So) were designated as the target syllables and analyses of "S" position on Mandibular Kinesiograph and of the voice on a sound spectrograph were made. Then, the effect of the changes in the artificial tooth position in the lower anterior tooth region on articulation was examined in detail. The results were as follows : 1. With the standard-type experimental denture with over bite at 2mm and over jet at 2mm, no positional changes in the anteroposterior "S" position were found in any of the "S" syllables. 2. The up-down "S" positions differed among the target syllables. The positions for "So" showed the greatest difference in comparison with other syllables. 3. The effect of increase in over jet on the anteroposterior "S" position was greater in comparison with the up-down "S" position, and the anteroposterior "S" position tended to be displaced forward. However, with the experimental denture with over bite at 4mm and over jet at 6mm, the tendency toward forward displacement of the anteroposterior "S" position decreased. 4. The effect of increase in over jet on the up-down "S" position was rather small, and no fixed patterns were seen in the displacement direction of the up-down "S" position. 5. The consonant duration differed among the target syllables. It was comparatively long for "Si" and "Su" and was the shortest for "Sa". 6. The effect of the artificial tooth position in the lower anterior region on the consonant duration was small. 7. The average amplitude differed among the target syllables. It was comparatively large for "Si" and "Su" and was the smallest for "Sa". 8. The effect of increase in over jet on the average amplitude was very marked. Although the average amplitude showed a decreasing tendency, the experimental denture with over bite at 4mm and over jet at 6mm, showed a decline in the rate of decrease. 9. Analyses of frequency showed that the energy level tended to decline in the hlgh frequency range form 4, 500∿5, 000Hz to 9, 500∿10, 000Hz for all target syllables of "S" with an increase in over jet. However with the experimental denture with over bite at 4mm and over jet at 6mm, the declining tendency of energy level decreased.

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An anthropological study of the oral cavity in various areas of Japan and neighboring country has been conducted to clarify racial lineage. This study examined the dental arches of 114 males and 117 females living in northern Shikoku and of 364 males and 422 females living in Kyushu in whom impressions were taken and plaster models made. The data on the two populations were compared with those of the populations in various areas of Kyushu, Okinawa island and Shimonoseki (Yamaguchi prefecture), obtained in other investigations. The length and the breadth of the dental arch in the northern Shikoku population tended to be longer and smaller, respectively, than those of the Shimonoseki and northern Kyushu populations, but were similar to those of the southern Kyushu and Okinawa populations. The height of the palate in the northern Shikoku population tended to be greater than those of the Shimonoseki and northern Kyushu populations, but tended to be smaller than those of the Okinawa population, especially in the anteriority of the palate. The length of sutura palatina mediana in the northern Shikoku population tended to be longer than that of the Shimonoseki and northern Kyushu populations, but tended to be shorter than that of the southern Kyushu and Okinawa populations. These findings indicate that the dental arch and palate in the northern Shikoku population differ in morphology from those of the populations in various areas of Kyushu, Okinawa and Shimonoseki.

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The mechanism for the insolubilization of exogenous 1, 6-α-D-glucan as a primer with 1, 3-α-D-glucan synthase from serotype g Streptococcus mutans was examined. Glucan produced by 1, 3-α-D-glucan synthase was methylated, degraded, and analysed by gas chromatography and quadrupole type gas chromatograph mass spectrometry (GC/MS). The structure of the water-insoluble glucan (IG) produced by 1, 3-α-D-glucan synthase was determined by methylation analysis using GC/MS. It was confirmed qualitatively that four kinds of the partially methylated alditol acetates were derived from the nonreducing terminal residue, 1, 3-α-linked residue, 1, 6-α-linked residue, and branched residue. 1, 3-α-D-glucan synthase was incubated with sucrose and dextran for a given time and only IG was harvested. By repeating the above method using the residual supernatant, five varieties of IG were obtained by changing the reaction time, and their structures were examined. In the glucan insolubilized immediately after initiating the reaction, side chains of 1, 3-α-D-glucan attached closely to 1, 6-α-D-glucan as the main chain. However, the glucan whose side chains were sparsely branched did not insolubilize unless these side chains were extended by further incubation. In other words, the more closely the side chains attached to the main chain, the sooner the glucan insolubilized.

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Ca(OH)_2-pulpotomy of the deciduous teeth in young dogs was performed with FC and the changes in the nerve fibers in the remaining living dental pulp after pulpotomy of the ends of the pulp nerve were examined neurohistologically. The results were as follows : 1. Three days after operation, the pulp directly under the necrosed layer showed slight inflammatory change, with several lymphocytes that were found the free ribosomes and several mitochondria in cytoplasm under the electron microscope. Findings of atrophy of the nuclei of pulp cells were seen in the surrounding tissues. The nerve fibers in this region were degenerated and an electron microscopic observation showed marked destruction of myelin of the myelin sheath and decrease in the microtubules in axon. 2. From seven to ten days, calcified tissue was observed in the cut surface of the pulp. In the adjacent pulp, large and spindle cells concentrated. The region of calcified tissue contained proper pulp tissue and degenerated nerve fibers were seen. An electron microscopic observation of the regenerated nerve fibers directed toward the calcified tissue showed myelinated nerve fibers which appeared to have undergone degeneration during regeneration, and the axon was approximately normal. 3. At 14 days, a finding of the initial formation of the dentin barrier was seen and a formation of slightly eosin-stained pre-dentin was seen in the innermost of the barrier. The radicular pulp was healthy. The nerve fibers under the electron microscopic obervation myelinated nerve fibers with sheaths, the nuclei of Schwanns cells, and nonmyelinated nerve fibers only with nerve processes. 4. At 21 days, the barrier was more compact in constitution than it was at 14 days and a continuous formation of pre-dentin from the peripheries to the mid-pulp was seen. In the dental pulp below the dentin barrier, minute nerve fibers began to appear. 5. At 35 days, formation of a thick dentin barrier was seen in the cutsurface of the pulp. No marked changes were seen in the pulp upto the root apex. Branches of nerve fibers began to appear in the pulp directly below the barrier. The nerve fibers in the pulp under the electron microscopic observation showed myelinated and non-myelinated nerves, and a large number of dense collagen fibers were seen between the nerve fibers. In the axon, neurofilament, microtubles, and mitochondria were always seen.

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The state of root canal obturation at various portions of the canal was examined in this study. Ten extracted human teeth were used and the canals were filled by two methods, the lateral condensation method (LCM) and vertical condensation method (VCM). Degree of canal obturation and reaching of the guttapercha point to the apical seat were examined on radiograms and obturation of various portions of the canal (mid-canal, apical third, and root apex) was observed by scanning electron microscopy. The results were as follows : 1. On radiograms, obturation was poor at the mid-canal portion in many cases for both LCM and VCM. At the apical third and root apex portions, obturation was good except for one case of VCM. 2. Reaching of the guttapercha point varied widely with cases of "flush", "over" and "under" for LCM. For VCM, the cases were either "flush" or "under". 3. Scanning electron microscopically, obturation was rather poor or poor at the midcanal and apical third portions in many cases for both LCM and VCM. At the root apex portion, obturation was good in two cases, and poor in one case for LCM. For VCM, all cases were good.

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Observations were made on the changes in the nerve fibers of the dental pulp in jaw tumor. Two teeth were taken from the tumor lesion diagnosed as a being myxoma, and investigated histopathologically. Nerve fibers were observed clearly, and were unaffected by the myxoma lesion. Whether such findings are dependent upon a benign tumor could not be concluded because of the limited materials.

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It is known that quantity of Ia antigen on the surface of macrophages increases in the presence of stimulated T cells in cell culture. Murine spleen T cells and thymus T cells were stimulated with Concanavalin A. The T cells were injected in murine peritoneum, and then the quantity of Ia antigen on the surface of peritoneal macrophages was measured using the method of enzyme-linked immunosorbent assay (ELISA). The results were as follows ; 1. In the presence of stimulated thymus T cells, the quantity of Ia antigen did not increase on the surface of macrophages. 2. In the presence of stimulated spleen T cells, the quantity of Ia antigen increased on the surface of macrophages. 3. On the surface of resident macrophages, the quantity of Ia antigen did not increase after injection of stimulated T cells. 4. On the surface of Pepton-induced macrophages, the quantity of Ia antigen increased rapidly, but soon decreased, after injection of stimulated spleen T cells. 5. On the surface of LPS-induced macrophages, the quantity of Ia antigen decreased slightly, and then increased gradually, after injection of stimulated spleen T cells. These results showed that stimulated spleen T cells had the capacity for increasing the quantity of Ia antigen on the surface of macrophage in mice. The expression of Ia antigen on the surface of macrophages differed with the conditions of macrophages.

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Until now, sensory mechanism of coding the taste quality in the nerve has not become clear completely. In the previous studies of comparison of receptor potentials and nerve impulses to taste stimuli, simultaneous records of the above two potentials have not been carried out in the same preparation. In the present study, the simultaneous records from a taste cell and the glossopharyngeal nerve were carried out in the frog, Rana catesbeiana. The similarity and differences in these two responses, and coding taste quality were investigated. The main results were as follows. 1. Receptor potential to 0.5M NaCl attained to its maximum and subsequently decayed to the level of resting potential gradually, and that to 10mM HCl reached a peak quickly, then fell down a little, went up again and reduced to resting potential level finally. The forms of receptor potentials to 0.5M NaCl and 10mM HCl looked somewhat like a gently-sloping hill and M shape of alphabet respectively. The change in frequency of nerve impulses to 0.5M NaCl and 10mM HCl with lapse of time paralleled to that of the receptor potential. The curve of receptor potential induced by 20mM quinine-HCl resembled that of 0.5M NaCl. However, the frequency of nerve impulses reached the maximum as soon as the stimulus was carried out before receptor potential rose to a peak response. 2. The amplitude of receptor potential evoked by 10mM HCl was markedly larger than those of 0.5M NaCl and quinine-HCl. 3. The frequencies of nerve impulses to 0.5M NaCl and 10mM HCl were proportionated to the amplitude of those receptor potentials. However, the frequency of nerve impulses to 20mM quinine-HCl was markedly high although the amplitude of receptor potential to 20 mM quinine-HCl was lower than that of any other stimuli.

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Several types of tooth-colored restorative materials such as composite resin, glass ionomer cement and porcelain have been developed and followed by various techniques for esthetical restoration of the dentition. The porcelain laminate veneer technique consists of firing a thin porcelain shell and bonding it directly to the prepared enamel surface using light-curing composite resin. The purpose of this article is to explain the clinical procedures for porcelain laminate veneer technique as well as to describe its advantages and problems.

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The porcelain laminate veneer and inlay are fabricated by the indirect methods in which the porcelain powder is molded on the refractory investment cast and fired in the furnace. The purpose of this study is to evaluate the ability of the investment material to reproduce the impression surface by examining the surface roughness of the investment cast as well as the contact angle of the investment slurry with various impression materials. It was found that the surface roughness became smaller when the investment was cast into the rubber base impressions than into the hydrocolloid impressions. It is recommended from the results to use rubber base impression materials for these techniques. However, great care must be taken in casting the investment since they showed poorer wettability with the investment slurry.

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Occlusal force is one method for preventing elevation of the cast crown at cementation. For the purpose of examining changes in occlusal force with time, this study was designed to measure continuous occlusal force and to compare the occlusal force of male and female, and of the left and right upper first molars. In addition, the relation of the habitual side of occlusion with momentary individual occlusal force, and with magnitude of continuous occlusal force was examined. The results were as follows ; 1. When continuous occlusal force was compared between male and female, a rapid decrease occurred immediately after mesurement in the case of female. In addition, continuous occlusal force decreased to less than 15kg after about 50 seconds in the case of male, and after about 20 seconds in the case of female. 2. When continuous occlusal force was compared between the left and right upper first molars, the left side showed a slightly higher tendency than the right side. But no significant difference was found. 3. On the relation of the habitual side of occlusion with momentary individual occlusal force and with magnitude of continuous occlusal force, about 59% agreement was found in the former and about 45% agreement in the latter.

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Psychosedation is widely applied to dental patients to relieve their anxiety and fear and to make smooth dental treatment possible. In particular, inhalation sedation with nitrous oxide under 30 per-cent and oxygen is of the highest safety and is easy to use. This inhalation sedation with nitrous oxide is said to have light analgesic effect also. This sedation has rarely caused uncomfortable feeling by improper techniques. It is reported that the patient shifts to excitation from sedation with a higher concentration. This study reports the nitrous oxide concentrations, the blood gas analysis in arterial blood, and psychosedative conditions in volunteers who inhaled nitrous oxide.

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