Radiation therapy is an effective method of treatment, which has shown competence in the treatment of malignant tumors of the oral region. On the other hand, there have been many reports stating radiation therapy have caused injury to various tissues of jaw bones. Many of the studies concerning radiation injury so far has been carried out either employing clinical observation or experimental observation using animals which predisposition of species differs from that of human being. Also there has been a few reports on changes of human jaw bone tissues. However, all of them were surgical cases, and they did not take account of predisposition of age and the effect caused by local lesion. It is well known that decalcifying method is not appropriate for cytological observation, because leaving no exception, decalcification gives severe damage on tissue. In this study the author observes the changes in jaw bones caused by radiation therapy for malignant tumors of the oral region. Thirty-nine bones of autopsy cases which were obtained from the Department of Pathology, Kyushu Dental College, were examined roentgenologically and pathohistologically, using undecalcified specimens which are suitable for cytological observation. The results obtained were as follows : 1. Initial changes of osteoradionecrosis could not be found on roentgenograms. 2. Morphological changes of osteocytes caused by irradiation could be observed as atrophy, swelling, clearing, necrosis, destruction and empty lacuna. Those findings were clearly recognized when radiation dose was more than 1200 R. 3. Changes in osteocytic process (decreasing, disappearance) and the appearance of spherical corpuscles around the osteocyte were characteristic, especially the jaw bone was irradiated more than 1200 R. A deep-stained area around lacuna was observed distinctly in all of the radiated group, except the case of 900 R. These histologic changes were confirmed by using microradiogram as in the state of low calcification. 4. Bizarre resorption is considered to be produced by fusion of enlarged lacuna centering around the Haversian canal. And this is not a characteristic change in radiation injury, but irradiation accelerates the resorption. 5. In lamella, deep-stained part and vague-stained part were observed in all cases. 6. Deep-stained layers were evident in the alveolar bone, the apex of residual ridge, the thickened part of endosteum in substantia spongiosa, and the area adjacent to the periosteum at the bottom of the jaw bone. 7. Osteoblasts and fibroblasts in the periosteum were decreased in number and the periosteum was thickened with hyalinization. 8. Necrosis of osteocyte occured even in 1200 R and osteoradionecrosis is considered to be aseptic necrosis. 9. Slight fibrosis of bone marrow was found in all of the cases. However, this may have other causes besides radiation. 10. Osteomyelitis occurs due to the secondary infection and is not due to the direct effect by radiation. 11. Osteosclerosis was not found. Radiation injury of bones is considered to be mainly due to regressive tissue changes. 12. Characteristic changes of blood vessels by radiation was not found. 13. No remarkable relationship between the variation dose of radiation and tissue changes was recognized. However, frequency of bone injury tended to increase slightly with the increment of dose. 14. From the above findings, it may be suggested that the osteocyte has high radiosensitivity, and the fundamental tissue changes in radiation injury of bone is severe disturbances of metabolism of osteocyte which leads to halisteresis.

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Investigation of biomechanical behavior of the temporomandibular joint of persons with stabilized occlusion was made to establish a means for determining whether the mandible has stabilized in its new position after its anterior or posterior displacement due to orthodontic treatment. For this purpose, an apparatus which enables detailed measuring of the anterior or posterior positional change of the mandible was devised. Measurements with the apparatus were taken of adults with normal occlusion first and studied. The results obtained were as follows : 1. The extents of the anterior displacements brought about by the subjects' own muscles were 7.4 to 12.9mm (average : 10.8mm) on Frankfort Horizontal Plane. The posterior displacements were 0.1 to 1.9mm (average : 1.2mm). These values were 82.9 to 99.2% (average : 90.0%) and 0.8 to 17.1% (average : 10.0%) of the total mandibular displacements respectively. 2. When the mandible was pulled using a chin-retractor toward Pogonion to Porion direction, the extents of the posterior displacements of the mandible were 0.11 to 0.37mm (average : 0.27mm) on the Pogonion to Porion line with the traction load of 2, 000g. With the traction load of 4, 000g, the figures were 0.23 to 0.84mm (average : 0.59mm). With an increase in the traction load, the extents of the movements also increased. The extents of increase, however, showed individual differences. 3. As to the biomechanical behavior after the removal of the traction load, every subject showed viscoelastic movement consisting of instant and creep recovery. The behavior could be shown by 3 element model with the spring and voigt model in series. The biomechanical behavior of the temporomandibular joint showed elastic behavior in which a full recovery was made when the application time of the external force was quite short (about 2 minutes). 4. Observations of the extent of displacements (creep recovery) of the mandible after the removal of the traction load showed that individual differences in full creep recovery time were great even among the subjects with normal occlusion, and that the time varied from very short (4 to 6 seconds) to relatively long (4 to 6 minutes). 5. In every subject, the higher the traction load and the longer the traction time, the longer was the full creep recovery time after the removal of traction load. 6. The biomechanical behavior of the temporomandibular joint was similar to the behavior of the supporting tissue of the teeth, which has already been reported.

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The blade implants were embedded on the 70th day after the extraction of the lower fourth premolars of the dogs, and the superprostheses, which connected the implants to the first molars, were cemented in place. From 14 to 180 days after the implantation of the blades, the implant sites were examined clinically and histopathologically. Results were summerized as follows. 1. By the 17th to 70th day after the implantation, the healing process as studied in the present implantation wounds seemed to follow the same pattern as usual tooth extraction wounds. The implants were well covered by newly formed bone trabeculae. 2. By the 90th day after the implantation, however, the development of a fibrous connective tissue between the implant and bone was observed. 3. By the 120th day after the implantation, the fibrous connective tissue surrounding the implant was enlarged, and roentgenographically, there was the evidence of radiolucent areas around the implant. 4. Nevertheless, it was noticeable that there were not distinguishable differences between 120-day and 180-day specimens roentgenographically and histopathologically. 5. The fibrous connective tissue surrounding the implant was composed of dense collagenous fibers, and simulated the periodontal ligament. The fibers were arranged parallel to implant contours, but this arrangement changed where the fibers were embedded in bone. 6. The average thickness of fibrous connective tissue surrounding the implants was 0.72mm at vent, 0.43mm at shoulder, 0.38mm at inferior apex, 0.32mm at arm in 120-day specimens, and 0.70mm at vent, 0.45mm at shoulder, 0.34mm at arm, 0.28mm at inferior apex in 180-day specimens (periodontal membrane of lower fourth premolars : 0.17-0.22mm). 7. Of the prostheses of the "sanitary" type, the inflammatory cell infiltration around the implant-posts was mild. On the other hand, of the prostheses designed in such a manner as to prevent from keeping "self-cleansing", the enlargement or the erosion of epithelium occured and the inflammatory cell infiltration was more visible than that of the "sanitary" prostheses. 8. On both types in this present study, the amount of epithelial downgrowth along the implant-posts was minimal and the extention of inflammatory infiltration to periosteum did not occur.

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In the present study, the comparison of the measurement in the lateral dimensions of the cranio-maxillo-facial complex of forty normal females and twenty-seven cleft female patients with complete unilateral cleft of the lip, alvcolus and palate (Hellman dental age over IV A) were carried out using the posteroanterior cephalograms with the following results : 1. The control group showed symmetry in the cranio-maxillo-facial structures, however, the mean ratio indicated a tendency that the right side width is wider than the left side. 2. In the cleft group, CN (the center of nasal septum), UI (proximating point of the central incisors) and Me (Menton) were displaced to the cleft side and NS (nasal spine) shifted to the normal side. 3. Cleft patients showed that BL (mandibular body length) in the cleft side was smaller than that of the normal side. 4. Bizygomatic width, CMo-CMo' and Bigonion were smaller in the cleft patients. 5. Widening of the nasal and interorbital width were not observed in cleft patients when compared to the normal samples. 6. Concerning the Mx-Mx' (intermaxillary width) of the cleft samples, neither asymmetry nor contraction tendency was not found. 7. CMo points (retromolar portion) of both the small and large segments were equally inclined to the midline dircction. 8. In the cleft samples, dimensions of the Biporion, Bimaxillare and Bigonion among others indicated correlation with the CMo width to which the contraction by the cleft anormaly is prominent. 9. It is presumed that the mechanical factors of the contraction to CMo-CMo' and to Bizygomatic width are different, since no correlation on them was found. 10. It is suggested that the prenatal abnormality and the postoperative lesion in the nasal septum must be one of the important factors to the growth retardation of the maxilla. 11. Deviation of the nasal septum was observed in the whole sample and the extent is so severe in the cleft group, while 23% with mild degree in the normal females.

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1. The patients had few complaints, although soft dentin arose widely from the multiple surface caries, producing the destruction of the dentin in the crown. 2. By means of histopathlogical views, the secondary dentin was observed in all the cases, while the destruction of dentin was observed in many cases. 3. In many cases the inflammation was observed mainly in the dental pulp in the crown and the upper part of the pulp in the middle of the roots, but the cases having inflammation of dental pulp extending to the apical part were rare. 4. The results obtained from a the histopathological approach had a very similar property in many cases of the present study, although the actual number of the cases was not enough from statistical point of view. 5. In conclusion, the appropriate method of restoration of the crown decayed by multiple surface caries at final period of deciduous dentition was discussed in the present paper.

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I found a case of the human lower right first premolar which had 2 separate roots in male of 45 years old. In this case, the roots are separated into the buccal and the lingual side by the deep fissure. In the mesial surface of the root, the fissure begins about 1/3 below the cervical line and runs toward the apex along the nearer side of the lingual than the central part of the root. Therefore, the root separates completely into bucco-lingual side at the upper 1/3 part of the apex. The distal surface of the root is almost flat, and there is a vertical shallow groove on the cental part of the root, and it separates completely into bucco-lingual root at the upper 1/3 part of the apex. The buccal root is slightly longer than the lingual root as a whole. In the lower premolar, the root is sometimes separated into two or three. And in case of two roots, they are separated into buccal and lingual side, or mesial and distal side. As for frequency of the supernumerary roots, it does not occur constantly. In the end I should like to say that the factors of supernumerary root of the lower premolar should be not only in the theory of atavism from phylogenetic problem, but also in ontogeny as being the result of a morphological disturbance that occurred in the dental lamina. But, I think this case is not ascribed to atavism of the tooth.

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市販国産(山浦製)の未使用探針, 7種類について, その先端の太さを計測し, 次のような結果を得た.1. Parfitt standard explorer No.6より直径が大きい探針はNo.3が先端から0.1mm点, No.9が先端から0.05mm点, No.25が先端から0.1mm点, No.25'が先端から0.1mmより太くなっていた.ほぼ同様の太さの探針はNo.5, No.8, No.23で, 細い探針はNo.8'で先端から0.2mm点より細くなっていた.2. 同種類の探針にも, その先端の大きさにはある程度のバラツキがみられ, また先端の変形したものがあった.3. 探針の形態, 先端の大きさの程度については, 小窩裂薄の形態や大きさと比較検討の上, 適当な探針の選択が必要であり探針の規格化が痛感された.

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The instrumentation with reamers is one of the important parts in root canal therapy and it is necessary to have the knowledge of them so as to get a successful result. The authors use MAILLEFER's hand-reamer mainly, besides ZIPPERER's, COLORINOX's and PIERCE's, and studied diameter and length of each part, taper of four Kinds of hand-reamers. The results are as follows. 1. The lengths of the blades of PIERCE were 12.7∿14.5mm, while those of MAILLEFER, ZIPPERER and COLORINOX were 14.2∿15.9mm. 2. The effective lengths were about 25mm, but ZIPPERER's #20, #30 and #35 were slightly shorter than 25mm. 3. The diameters of top of PIERCE without #25 were close to the standers of the U.S. numbering system, but the difference between #25 and #30 was 0.1mm. ZIPPERER without #30 was close to PIERCE. COLORINOX was smaller than the standers of the U.S. numbering system, and there was no differense between #20 and #25. MAILLEFER was similar to COLORINOX, while the transition from smaller to larger size was on an average. 4. The diamenters of wires of PIERCE without #35 were similar to the standers of U.S. numbering system. From No.1∿No.4 of MAILLEFER were about 0.6mm, No.5 and No.6 were about 0.8mm. Those without No.4 were larger than the standers of U.S. numbering system. COLORINOX was similar to MAILLEFER, while ZIPPERER was about 0.78mm. 5. The taper (d_2-d_1/1) and its transition from #15 to #40 of ZIPPERER were decreas from 0.0423 to 0.0264. COLORINOX were decrease between #15 and #40, but #15 and #40 were about 0.03. MAILLEFER were about 0.027, and PIERCE were about 0.021.

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