Usually, Tomes' process pits on the intact enamel surfaces show a circular or a cross-sectioned prism-shaped outline. In this scanning electron microscopic study, we found that smaller Tomes' process pits showed various irregular outlines including incompletely closed pits on the supracervical enamel surface in a premolar tooth. The crystal density in these pit margins was lower than that of the surrounding enamel. These results suggest that the final matrix deposition by ameloblasts occasionally continues for a short time after the formation of Tomes' process pits which have shown a usual outline. Such a formation differs from the formation of a small dome-shaped projection within the pit.

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Previously, we found the fine incremental laminate lines with a prismless structure running transversely on the enamel surfaces in human teeth after phosphoric acid etching. In this scanning electron microscopic study, similar laminate structures ranging from about 0.5 to 1.5 μm in intervals were found on the enamel surface of a human permanent tooth after EDTA etching, although the structures were only formed on the small surface-overlapping projections which were present with Tomes' process pits. The laminate lines on the projections formed by the final stage of matrix deposition are probably the result of the sequential completion of ameloblast activity at the final stage, as the fine incremental lines on the enamel surfaces.

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The purpose of this study was to examine the differences in immunohistochemical staining for transforming growth factor-α (TGF-α) and Lewis^y antigen (Le ^y) in pathologic specimens of squamous cell carcinoma (SCC), leukoplakia, and epithelial dysplasia. For this purpose, ten cases of SCC developing from oral leukoplakia and thirty-five cases of leukoplakia with epithelial dysplasia, yet to develop into SCC, were investigated immunohistochemically. Proliferating cell nuclear antigen (PCNA) staining was used as a marker of cell proliferating activity. The results showed that the expression of TGF-α and PCNA increased, whereas that of Le ^y decreased with the malignant transformation into SCC. In case of leukoplakia with epithelial dysplasia, the expression of PCNA, TGF-α and Le^y did not show an obvious correlation with the grade of epithelial dysplasia. These results suggest that TGF-α and Le ^y may be concerned with tumor growth, but not with the progression of epithelial dysplasia.

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Adaptation of crowns and bridges is a significant factor in secondary caries or periodontal disease. In this study, in vivo and in vitro adaptations of full cast crowns were investigated with three different impression methods. Seven premolars that would be extracted for orthodontic treatment were used for in vivo study. and 15 epoxy dies were used for in vitro study. The cement thickness was measured with a profile projector. The results were as follows : 1. The marginal cement thickness showed no significant difference between the in vivo and in vitro studies. 2. Crowns fabricated by the individual tooth tray method exhibited the thinnest marginal cement of all impression methods. 3. There were no significant differences among the marginal cement thicknesses of the various tooth surfaces. The results suggest that all impression methods investigated in this study are clinically acceptable and that the individual tooth tray method is the most accurate and stable of the three methods.

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The aim of this study was to evaluate the clinical effects of guided tissue regeneration technique which used expanded polytetrafluoroethylene (ePTFE) membrane. Eleven teeth in 11 patients (45-59 years old, 4 males and 7 females) with adult periodontitis participated in this study. After initial preparation, probing pocket depth and clinical attachment level were measured. Following flap elevation, root was planed and granulation tissue was removed. The ePTFE membrane was placed over the defect and sutured. Four to six weeks after surgery, the membrane was removed. Three to six months after surgery, clinical measurements were carried out. At the postsurgical evaluation, probing pocket depth was decreased and clinical attachment level was gained. This study suggests that guided tissue regeneration technique using the ePTFE membrane is effective in the treatment o f intrabony defect and furcation involvement.

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In the present study, the authors investigated the three-dimensional organization of matrical collagen fibrils in the adult mandibular condylar cartilage by scanning electron microscopy (SEM) and additionally attempted to ascertain whether or not they showed the same fibril organization as that in experimental animals. Adult human bodies for anatomical dissection were used for this study. The bodies having teeth maintained entirely or almost entirely to the second molars were selected. Tissue preparation with both Triton X-100 and enzymatic treatment after freeze-cracking displayed precise fibril organization by high-resolution SEM. Light microscopy revealed cellular division : fibrous, proliferative and cartilaginous zones, and subchondral bone occurred in sequence from the surface of the condylar cartilage. The fibrous zone making up about two thirds of the total thickness of the condylar cartilage contained dense fibril bundles running parallel to the articular surface. But with increasing distance from the articular surface the fibril bundles arranged in a downward direction. These bundles reached the uppermost part of the proliferative or cartilaginous zone directly below the fibrous zone, in which a fibril network composed of sparse thin fibrils was evident, and almost all intruded into their zonal fibrillar matrices. In the fibrous zone, the fibril organization may serve to resist abrasion and diffuse load-stress toward the lower part of condylar cartilage. Fibril bundles in the cartilaginous zone, except in its uppermost part, were interlaced three-dimensionally. This differed remarkably from the fibril organization in the rat condylar cartilage arranged in a simple direction. The articular surface of the condylar cartilage had undirectionally interlaced fibril bundles covered with a fibril network. The fibril organization in the adult condylar cartilage differs in every zone and provides load-carrying modulation submitted to various extrinsic stresses.

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The purpose of this study was to evaluate the clinical effectiveness and usefulness of the recently developed Er : YAG laser (Luxar Co., U.S.A.). For this study, 60 teeth of 40 patients including caries, cervical WSD and 11 teeth with cervical hypersensitive dentine were used. The wave length was 2.94 μm, and the maxim energy was about 500 mJ/pulse. The following results were obtained :
1. Class V cavity preparation on 48 of 60 teeth was carried out without pain. Slight pain was produced in 2 teeth and moderate or severs pain in 10 teeth. 2. No patients experienced unpleasant feelings or tenderness during cavity preparation by Er : YAG laser. 3. There were no side-effects, such as allergic reactions. 4. The duration of cavity preparations ranged from 10 seconds to 3 minutes. 5. Clinical follow-up found no clinical symptoms in the 30 days after the procedure. Cavities prepared by Er : YAG laser were filled with composite resin. These results suggest that cavity preparation by Er : YAG laser at a setting of 8 Hz and 250 mJ/pulse is clinically useful.

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[in Japanese]

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