During the evolution of the Equoidea, the histological structures of the teeth have become more complex as the molars have become hypsodont in form. The straight Hunter-Schreger bands of Hiracotherium have evolved into a more complex pattern in Equus. The enamel prisms changed from an arched form (about 5μm in diameter) with an alternating pattern in Hiracotherium to an oval form (about 2 μm width) arranged in straight rows in Equus. In Equus the rows of prisms are separated by interprismatic sheets. This pattern may have increased the architectural strength of the enamel, and is related to the later hypsodont molar teeth. With regard to the enamel, it is suggested that the number of ameloblasts increased whereas their size decreased during the evolution of the Equoidea. As to the dentine, on the other hand, the peritubular dentine was little observed in Hyracotherium, but evolved in Mesohippus and Equus. A transitional pattern between these two structures is observed in Mesohippus molars, which are not hypsodont. These changes in the histology of tooth structure may have preceded the changes in molar shape during evolution.
Immunoglobulin estimations by the single radial diffusion technique were performed using serum from 100 subjects comprising 50 patients with recurrent aphthous stomatitis, 25 with Behçet's syndrome and 25 normal controls. The data were subjected to multivariate analysis methods including Hotelling T2 statistics and the Roy-Bose simultaneous confidence interval. Raised levels of IgA and IgM were found in patients with recurrent aphthous stomatitis in comparison with normal controls, but there was no difference in IgG. In Behçet's syndrome, only the IgM titers showed a difference, IgG levels being insignificant.
A study was made of the detail reproduction test and roughness of the smooth surface of dental stone as a preliminary approach for examination of the surface reproduction of dental stone models made through combination of various impression materials. Measurement of the detail reproduction test was based on ISO 1563, while that of surface roughness was carried out using both an improved non-contact photogenic surface roughness analysis system and a contact surface roughness analysis system. The study produced the following findings : 1) It was clarified that almost all dental stones were capable of reproducing features 20 μm in size. 2) There was a correlation between the relative reflection (RR) of the model surface and its arithmetic average roughness (Ra). A correlation was also found between RR and average angle (R Oa), and between RR and average wavelength (Rλa).