A pathohistological investigation of age chages of the jaw bone was conducted with 53 non-extracted mandibles, of 36 males and 17 females ranging from 17 to 84 in age. In order to prevent intervention of the general and local effects to the jaw bone other than of time, the materials for the investigation were carefully chosen. The undecalcified sections of all the tooth regions of half-mandible in each case were prepared. Microscopic observation revealed the following results. 1. Downgrowth of epithelial attachment was observed at an age as early as 17. The maximum age for epithelial attachment locating at cemento-enamel junction was 33. 2. Recession of the gingival margin and epithelial attachment did not necessarily show a parallel relation with the extent of gingivitis and was recognized as agechanges. The gingival margin and the location of epithelial attachment migrated yearly toward the root apex by 0.056 mm and 0.062 mm respectively. 3. The average depth of the gingival sulcus was 0.89 mm, the length of the epithelial attachment 0.88 mm and the length of the connective tissue attachment 1.05 mm. No significant difference of the gingival thickness was observed among all age cases without exudative change or fibrosis. 4. Normal alveolar bone was observed at a tooth region in two cases, one of 17 years old and the othe 24 years old. Horizontal or vertical resorption of the alveolar bone was observed in all tooth regions in the remaining cases. 5. Horizontal resorption of the alveolar bone did not necessarily show a parallel change with gingivitis. A yearly horizontal resoptrion, as age-changes, of 0.06 mm occurred in adults. 6. Resorption of the alveolar bone was mainly osteolysis. Osteoclasis accounted for 17 % of all the resolved lesions and the majority was observed in the areas adjacent to inflammations. 7. Osteoporosis of the mandible was not observed as age-changes. 8. Horizontal resorption of the alveolar bone was observed prior to downgrowth of the epithelial attachment. 9. Narrowing index of the main branches of the mandibular arteries was observed as a change with age. Narrowing index of the small branches showed a little correlation with age, when compared with that of the main branches, a correlation with horizontal resorption of the alveolar bone was observed. 10. Incidence frequency of periodontitis showed a tendency to increase with age and higher incidence was observed in the posterior teeth than in the anterior teeth, and in the lingual side than in the labial side. Based on the histological findings, the aging of the periodontium which plays an important role in pathogenesis of periodontal diseases has been discussed.

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The degree of infection caused by Streptococcus mutans JC-2 (S. mutans) smeared experimentaly on animal teeth and gingiva was examined. In addition, the effect of antigen-antibody reaction on humoral immunity in the gingival tissue was investigated. The results obtained were as follows. 1. The fluorescence antibody technique was superior in the formulation of colony of S. mutans in gingival tissue to Gram's stain technique. 2. The caries incidence rate based upon the dental plaque formed by S. mutans decreased on lower saccharide content of feed. 3. The S. mutans fixed by forming high viscous polysaccharide was observed in the gingival tissue. 4. The antibody of S. mutans was observed within polymorpho-cyte formed in the epithelial and connective into tissue which S. mutans infiltrated. 5. The immune globulin (IgG) was observed in plasma cells which infiltrated into the connective tissue which lay directly under the epithelial tissue. 6. The antibody titer increased with the appearance of plasma cells of immune globulin (IgG).

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Temporomandibular joint dysfunction has increasingly been treated in the province of the dental medicine. To establish the etiology of temporomandibular joint dysfunction, many fundamental and clinical studies have been undertaken. In the field of dental radiology, also, some investigations have been made on the temporomandibular joint from the radiological view points but suffered from the lack of appropriate means to analyze the morphology of the mandibular fossa. In 1976, Ohba et al. attempted to express the morphology of the mandibular fossa as a single function using Fourier Progression. In 1977, Kashiwagi actually used Fourier Progression to express the shape of the female's mandibular fossa revealed by lateral oblique radiograph. In this paper, the morphology of the male's mandibular fossa revealed by radiograph was analyzed using Fourier Progression. The study was done on 65 males' radiographs which showed no pathological findings of the temporomandibular joint. Ages of the subjects ranged from eleven to fifty. The radiographs were divided into four groups by age : I ; 11-20, II ; 21-30, III ; 31-40, IV ; 41-50. Each group was compared for existence of right and left difference, age difference, and sex difference. The results obtained are as follows : 1. Morphologic difference between the right and left mandibular fossa was seen in the First and Third Groups. The difference in the First Group was due to the fact that the anterior part of the left mandibular fossa was deeper than the right one. In the Third Group, the posterior part of the left mandibular fossa was shallower than the right one. 2. Sex difference of the right mandibular fossa was seen in all of the groups except in the comparison of the Third with Fourth Groups. The male's mandibular fossa increases in depth in proportion to aging till thirties. The morphology of the mandibular fossa of the First Group was asymmetric but it becomes symmetric in the Fourth Group. 3. Sex difference was seen in the morphology of the mandibular fossa. Female's fossa of the First Group was deeper than the male's, and both showed asymmetry in the morphology. In the comparison of the Second Group of both sexes, only the asymmetry of the morphology differed. Male's fossa of the Third Group was deeper than the female's. In the comparison of the Fourth Group of the both sexes, only the asymmetry of the morphology differed.

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The compressive and diametral tensile strength, and hardness were measured for a single phase spherical alloy of non-γ_2 type, Dialloy, and a conventional spherical alloy, Hiatomic M. Fracture surface was also observed in order to study the relationship of the fracture to the microstructure. The variation of the mercury content from the standard one significantly decreased the compressive strength and hardness. The compressive strength dropped markedly when the alloy was mixed with 27 and 29% of mercury for Dialloy and Hiatomic M, respectively, as well as with 62 and 60% of mercury for each. The γ phase particles in the set amalgam were much more porous and softer than the original unreacted one, and could not be materially the same as the unreacted γ phase. These particles remained in the set amalgam should not be defined as the unreacted γ phase particles. At lower M/A ratio, the fracture occured through the matrix in a collapsing manner because of the embrittlement due to the poor matrix formation. At the standard or higher M/A ratio, the fracture passed preferentially through the voids, γ_2 phase in Hiatomic M, and the grain boundaries of the γ_1 phase in the matrix, and the porous and brittle residual alloy particles. The fracture seemed to be unlikely to pass the γ_1 phase. Clear differences can not be detected in both the two amalgams.

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[in Japanese]

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[in Japanese]

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A follow-up research, before and during 2 years after pharyngeal flap surgery, of 30 patients was undertaken in order to investigate the auditory changes, nasal air escape and the roentgenographical changes in velopharyngeal function and shape. The results were as follows ; 1. Both nasality and nasal air escape disappeared during about the same period. 50% of the subjects showed disappearance of nasality and nasal air escape at 2 months after operation, and 83.7% of them showed disappearance within a year after operation. All of the other subjects, with the exception of those who could not accept the follow-up research, also showed disappearance of nasality and nasal air escape within 18 months after operation, indicating remarkable improvement. The effectiveness of pharyngeal flap surgery was reaffirmed from this. 2. After the pharyngeal flap surgery, the velar length showed an increase but the tendency to constriction was not recognized. However, the velar elevational angle on phonation showed relatively lower degree until 3 months after operation than before operation. 3. The greatest change in the velopharyngeal function and shape, before and after pharyngeal flap surgery, was the reduction of the minimal velopharyngeal distance at the time of rest and phonation. 4. Within a month after operation, the depth of the posterior pharyngeal wall revealed the maximum constriction (forward protrusion) in the area of middle and lower pharynx, and later, within 6 months after operation, revealed the tendency to returning to the pre-operative shape. Coincident with this period of extention, nasality, nasal air escape and "snore" after operation disappeared or reduced, though the upper pharynx above the level of the palatal plane showed no change or a tendency to constriction, which was supposed to be the change caused by existence and growth of adenoid. 5. Pharyngeal flap base showed a tendency to descending until 9 months after operation. The average distance of descending was about 5 mm. The area of flap attached to soft palate also showed much the same tendency to descending until 6 months after operation. 6. Contrary to the descending of the flap base, the elevational mobility of the flap base showed an increase until 9 months after operation, but no striking change was recognized after that. This elevational movement was closely connected with the velar elevation. The coopertive movement between M. constrictor pharyngis superior and M. levator veli palatini was considered with much importance. 7. It seems proper that judgement of results after operation should be done later than 9 months after operation, since, as mentioned above, the velopharyngeal function and shape revealed considerable changes until 9 months after pharyngeal flap surgery. These changes in function and shape are considered to be affected most by the scar tissue. 8. Analysis of the manner of velopharyngeal closure and the improvement after pharyngeal flap surgery showed that pharyngeal flap base should be placed at the level of the palatal plane and in the area containing Passavant's ridge, and that it is difficult to expect successful results if the pharyngeal flap base is placed above the palatal plane. 9. Age, speech training, function of velopharyngeal muscle and shape of upper pharynx were pointed out as factors on improvement of results after pharyngeal flap surgery. In other words, successful results will be obtained regardless of surgical technique in younger patients with pre-operative speech training, Passavant's ridge as well as fairly good function of palatopharyngeal muscle, smaller palatopharyngeal distance, parallel type of nasal air escape and smaller velopharyngeal area as well as "non box-shaped" upper pharynx.

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The checkbite technique, which is one of the methods of recording the condylar guide inclination, is simple and easy, so it is commonly used with semiadjustable articulators. In this report, we recorded the lateral condylar guide inclination using the wax checkbite method with six dentulous subjects on Tsubone's articulator in order to discuss the precise degree of wax checkbite records. The wax checkbite method was found to be effective. The lateral and sagittal condylar guide inclinations therefore were recorded with eighty edentulous patients whose dentures were constructed using Tsubone's articulator. The relationship of the lateral and sagittal condylar guide inclinations and these inclinations by age were compared. Results were summarized as follows : 1) The wax was evenly softened, the amount of the condylar rod movement on the articulator was limited to 5 mm, and patients were made sure this relation. Giving attention to the above, we could accurately measure the condylar guide inclination. 2) The sagittal condylar guide inclination of the right side was 21.8 ± 6.7°, and that of the left side was 22.4 ± 5.3°. The lateral condylar guide inclination of the right side was 22.3 ± 5.3°, and that of the left side was 22.1 ± 5.9°. 3) The sagittal and lateral condylar guide inclinations that were recorded from eighty edentulous patients have no significant differences. 4) No significant differences were noted between the right side and left side condylar guide inclinations. 5) The sagittal and lateral condylar guide inclinations according to the ages were compared, and no significant differences were noted.

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Seven root canal sealers were examined for their hardness affecting radiopacity, adhesion to root dentin, consistency and removal. The results were as follows : 1. AH26, N_2, Kri 1 and Canals were strongly radiopaque, followed by Neodyne for root canal filling. Triozinc pasta and Calvital were slightly radiolucent. 2. AH26, N_2, and Calvital showed strong adhesive properties to root dentin, followed by Neodyne for root canal filling. Triozinc pasta, Kri 1 and Canals showed weak adhesive properties to root dentin. 3. Neodyne for root canal filling, N_2, AH26 and Canals exhibited strong consistency, followed by Kri 1 and Calvital. Triozinc pasta was porous. 4. AH26 was the hardest, followed by Neodyne for root canal filling, Canals and N_2. Triozinc pasta, Calvital and Kri 1 were too soft to be tested.

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Because of the recent progress and expansion in the modern industries, a variety of new chemicals and engineering techniques have been introduced and verious changes have been brought about in the working environment and operations in the factories. Various kinds of health hazards are frequently the inevitable results of such situation. The authors experienced a case of teeth erosion resulting from an exposure to fluoride acid, as an occupational disease, and cases of teeth abrasion with teeth erosion are rare. The teeth abrasion had an appearance of a whistle mouthpiece. Combining the conventional macroscopic examination with the replica method made detection of teeth erosion in its early stages possible. Consequetly, workers upon detection can be protected from aggravation by effecting positive measures for prevention, improing working conditions, and transfer.

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