Recently, carboxylate and acrylate have been extensively used as dental cement. However, the viscoelastic behavior of these cements has ever scarcely been elucidated. So the authors measured the dynamic viscoelasticity of two kinds of commercial resin cements (acrylic resin cement and unsaturated polyester resin cement) and discussed their rheological behavior. (1) The influence of the mixing ratio of powder and liquid could not be recognized in the curve of dynamic modulus versus temperature. (2) The glass transition temperature of the cements soaked in water (37℃) for 7 to 21 days was higher than that of the unsoaked cements.

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Martin's classification is currently favored for Genus Candida which depends chiefly on the modes of chlamydospore formation and sugar fermentation. The author undertook a series of study on the modes of white ring formation of the Genus candida by use of SCLT medium (Akisada) and PT medium (Akisada), of which the former has recently been proved very efficient in promoting the chlamydospore formation and the latter in promoting the white ring formation. The composition of the former medium is as follows. soluble starch 10 g corn meal extract 330 ml liver extract (300 g/500 ml) 40 ml Tween 80 8 ml agar 20 g distilled water 630 ml Adjusted to pH 7.4 with NH_3 The composition of the 2nd medium is as follows. peptone 10 g Tween 80 8 ml agar 20 g distilled water 1000 ml Adjusted to pH 6.6 It was noticed with use of these two media, that some species of Candida produced white ring around periphery of colonies and others did not. The present study concerned with the detailed cultural conditions and possible mechanisms to explain the phenomenon, and results were summarized as follows. 1. Of seven species of genus Candida, C. albicans, C. tropicalis and C. stellatoidea produced the white ring, while C. pseudotropicalis, C. krusei, C. parakrusei and C. guilliermondii failed to do so. This would seem to provide a convenient method for the preliminary differentiation of the organisms. 2. Of the ring-forming organisms, C. tropicalis produced the strongest white ring, while C. stellatoidea and C. albicans produced weaker ones. Of the latter two, C. stellatoidea produced the ring more distinct than the one produced by C. albicans. 3. The optimum conditions for the ring formation were first to use the fresh culture of the organisms on Sabouraud glucose agar maintained for 24 to 48 hours at 37 C. The optimum pH was 7.4 for SCLT medium and 6.6 for PT medium and 25 C was required for optimum growth in these media. 4. When Tween 40, Tween 20, lard oil, olive oil were used respectively instead of Tween 80, similar ring formation was observed. 5. When Tween 80 and other fatty substances were removed from the medium, the ring formation was never observed. 6. When sucrose was added to SCLT and PT media to see its effect on the ring formation, C. albicans and C. tropicalis failed to produce the white ring by sucrose consentrations of 0.5 % in the former and 0.8 % in the latter, while no inhibition of ring formation was observed with C. stellatoidea at the concentration of 1.0 %. Evidences showed that the inhibitory effect of sucrose addition derived from lowered pH of culture medium by sucrose addition rather than any direct action of sucrose itself. 7. A possible mechanism for the white ring formation was regarded to be the activity of lipase which is present in-and outsides of these three species of Candida.

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Experimental apical infections were established in the teeth of dogs inoculated with known amount of a strain of Streptococcus viridans that was isolated from apical infected lesion of human teeth. The infected root canals were filled with the commercial filling materials such as AH 26, N_2 and Canals, and the effects were examined radiologically and pathohistologically. The findings were summarized as follows. 1. The cell suspension of Streptococcus viridans in the amount of 0.02 ml containing 4×10^3 of cells inoculated to the teeth of dogs produced an acute inflammation in the tissues about the root tip by approximately 3 weeks. 2. When the Penicillin paper point of 10 units was applied to the infected root, the acute exudative inflammation in the root tip was subsided in the course of about 1 week and granular tissue started to proliferate. The lesion eventually became localized and showed the picture of chronic lesion. 3. When each of the above filling materials was applied to the chronic lesion and the effect compared with that of non-treated controls, distinct improvement was observed in the healing process of the treated cases. 4. In non-treated cases, there remained more or less an extensive region of chronic inflammation even 9 weeks after treatment, while in the treated cases there remained only traces of inflammatory foci that were localized in the root tip region. 5. Comparison of relative merit of these 3 canal filling materials in the healing of apical lesion showed that AH26 was most excellent, followed by N_2 and Canals. 6. In order to achieve the best use of these filling materials, it is advised to fill the root canal completely and not to leave any space unfilled within the canal.

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The developmental process of mandibular molar teeth was studies histologically using rabbits at its varying developmental stages from 15 fetal days to 30 postnatal days and adulthood. Results were summarized as follows. Histology 1. Each molar tooth was characterized by the presence of a large indentation beginning from the buccal surface and dividing the tooth body into mesial and distal halves which were connected at the middle of the lingual surface. Both halves of the tooth were consisted of greater part of dentin which was filled with an osseous cementum substance which fused itself with the enamel layers of both halves of the tooth. 2. Of the molar teeth examined, the 1st premolar was the largest in size and most complex in structure with two indentations of small size, one incised on the buccal side of the mesial half of tooth and other on the middle of the mesial side of tooth. These indentations were also filled with an osseous cementum substance. 3. In the 1st premolar, the distal half of the crown lacked the enamel layer at distolingual side, but the rest of molars lacked the enamel layer even wider so that the lacked area extended from the middle of the lingual side toward the mesial side of the mesial half of the crown. The cementum substance directly covered the dentin layer in such regions. 4. The structure of the basal end of individual molars except the 1st premolar showed an incorporation of two tooth anlages. This means that, located in the middle of the basal end mesio-distally, there was present the compound enamel organ that is responsible for the formation of early phages of enamel in both distal side of the mesial half and mesial side of the distal half of the individual teeth. The tooth anlage of the mesial half of the 1st premolar was further divided into two parts, representing future cusps. The basal end was devoid of enamel and osseous cementum substances, and instead there was seen the cementblastic tissue, the dental sac. Genesis 1. By 15 fetal days the dental lamellae of deciduous molars (Pm_1, Pm_2) came into existence, and by 25 fetal days hard tissues were seen to be formed in these lamellae. Eruption of the newly formed teeth started by 3 postnatal days. On the other hand, there were seen signs of resorption in the roots of the teeth that were just being formed. 2. By 5 postnatal days, a greater part of the tooth crown came into eruption, but the root that had been well grown was largely resorbed, except its apical part which was yet to be fully completed. As mechanisms of the root resorption, two kinds of process were observed, of which the one acting through the osteoclasts that attacked from outside and the other from inside the root through spontaneous decalcification of the pulpal wall. 3. Over 20 days after birth the deciduous molars began to be shed and these were replaced by the rootless successors (PM_1, PM_2). 4. Order of these rootless teeth to erupt was as follows : M_1 (15 postnatal days), M_2 (20 postnatal days), PM_2, PM_1 and M_3. 5. Through entire process of development as above described, it was observed that no enamel was formed at every cuspal tips for both rooted and rootless teeth.

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Using a total of 30 samples of eel, Anguilla japonica, mode of blood supply in the head was studied, and detailed observations were made on the blood supply in the upper and lower jaw teeth, vomerine teeth and their surrounding tissues. Besides using conventional technics, the scanning electron microscope was used to observe the actual shape of individual teeth, their mode of standing and to know the three dimensional relationship between the blood supply and the teeth. Results were summarized as follows. 1. The main artery supplying the region is A. carotis communis that derives from A. branchalis efferentes I. This artery branches into A. carotis externa and A. carotis interna, and the latter branches into A. cerebri and A. ophthalmonasalis. The latter artery further branches into A. ophthalmica and A. maxillaris and finally turns into A. nasalis. A. carotis externa, on the other hand, makes a turn in the orbit and sends out A. facialis mandibularis, then, after further sending out R. dentalis superior posterior becomes to be A. mandibularis. A. mandibularis sends out two branches, A. dentalis inferior anterior that runs along the inside wall of the mandible, and A. dentalis inferior posterior that runs within the mandibular canal. 2. The vomerine teeth group is supplied by the arterial branches sent out from ventral side of A. nasalis and distributing there from outside. The maxillary teeth group is supplied by A. dentalis superior anterior steming from A. maxillaris and by A. dentalis superior posterior steming from A. nasalis. Besides, these teeth group is distributed by R. dentalis superior posterior coming from A. mandibularis. The mandibular teeth group is supplied by A. dentalis inferior anterior and A. dentalis inferior posterior, both stemed from A. mandibularis. 3. Observations on the mode of arterial distribution in the teeth and their surrounding tissues revealed that there are two kinds of distribution whereby some branches go directly to the periodontal tissues and others once enter into the bone and then proceed to the pulp of individual teeth for distribution. It was particularly noticed with the latter branches of artery that they are ramified at the intervals of every 5 to 6 teeth, and, on reaching near the dental pedicles, a part of the branches is distributed to the dental pulp and the rest enters into small pits between the bone and the pedicles to be distributed to the successive teeth and the surrounding tissues.

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Many studies have been reported about the existence of afferent fiber in the hypoglossal nerve of some species of animals. Liou, et al. reported afferent impulses in the hypoglossal nerve of the frogs. It is the main purpose of the present study to investigate the generation of the afferent impulses by a variety of stimuli given the hypoglossal nerve of frog's tongue. Both the afferent impulses in the hypoglossal and the glossopharyngeal nerve generated by stimulation to the tongue were recorded simultaneously by a cathode ray oscilloscope. The afferent impulses of the hypoglossal nerve were compared with that of the glossopharyngeal nerve with respect to the frequency of the impulses, the threshold concentration and the latent time. Changes in the afferent impulses of the hypoglossal nerve were investigated for the period of 90 days after cutting the unilateral glossopharyngeal nerve. The results are summarized as follows : 1. Mechanical stimulation, such as light touch with cotton fibers or a horse-tail hair, applied to the surface of the tongue elicited afferent impulses in the glossopharyngeal nerve, but not in the hypoglossal nerve. Stimulation by pressure and traction with a glass rod applied to the tongue elicited afferent impulses in both the glossopharyngeal and the hypoglossal nerve. In this case, the afferent impulses of the hypoglossal nerve were of lower frequency with long latent time as compared to those elicited in the glossopharyngeal nerve. 2. When the horse-tail hair stimulations were given indiscriminately to'different parts of the tongue, the glossopharyngeal nerve responded similarly, regardless of parts stimulated, while the hypoglossal nerve responded more effectively the stimulation at the root than at the apical and central parts of the tongue. 3. Stimulation by warm or cold Ringer's solution could generate afferent impulses of the glossopharyngeal nerve only in the temperature range from 25℃ to 45℃ and from 5℃ to 0℃. No response was obtained from the hypoglossal nerve with the same experiment. 4. When the tongue was stimulated either by water or Ringer's solution, the fomer generated afferent impulses of much more frequency than did the latter in the glossopharyngeal nerve, while these stimulations elicited no such response in the hypoglossal nerve. However, solutions containing NaCl, sucrose, acetic acid and quinine hydrochloride produced afferent impulses in both nerve. The hypoglossal nerve could produce the afferent impulses only with much higher threshold concentrations of substances tested and the impulses produced was of lower frequency as compared to the glossopharyngeal nerve. The hypoglossal nerve also showed relatively longer latent time in responding the stimulations by the above substances except acetic acid. 5. When the glossopharyngeal nerve in one side of the tongue was cut and stimulation given by solutions of NaCl, sucrose and acetic acid, afferent impulses were generated from the hypoglossal nerve at lower concentrations of the substanses tested in the cut side than in the control side. Such phenomenon was not observed with use of quinine hydrochloride.

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We experienced three cases of supernumerary teeth in which found rarely in the premolars. Case 1, there were two supernumerary teeth present on the upper left, and was one on the upper right, and was one on the lower left side. Case 2, there was one supernumerary tooth present on the lower left, and were two supernumerary teeth on the lower right side. Case 3, there were two supernumerary teeth present on the lower left, and was one on the lower right side. These three cases were rare on the regions and numbers in the supernumerary teeth.

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The author experienced the patient, a 69-years-old-man, with chronic osteomyelitis of the mandible. It was said that the patient had allergy for the antibiotics, and he was no given it. We tried to examinate the allergy test for the antibiotic agents (Carb enicillin, Chloramphenicol, Lincomycin, Tetracycline and Oleandmycin), but we could not recognize it. For this case, we did medicinal substances therapy and surgical radical operation, and he was cured. The patient today, a year after the osteomyelitis therapy, is alive and free of the disease.

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