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.
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.
The purpose of this study was to examine the differences in immunohistochemical staining for transforming growth factor-α (TGF-α) and Lewisy 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 Ley 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.
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.