Changes in the microcirculation after irradiation by Nd : YAG laser were evaluated using the “rabbit ear chamber” method. Morphological changes of the vascular network related to time elapsed after irradiation was observed by a microscope-video system. Findings such as vascular shrinkage, degeneration, coagulation and stasis associated with irradiation were recognized shortly after Nd : YAG laser was applied. Damage increased with irradiation energy increase. Expansion of the stasis region and appearance of hemorrhagic spots were observed on the 1st day after irradiation. On the 3rd to 5th days, the hemocytes of hemorrhagic spots decreased, and vascularization began. On the 7th to 10th days, the damaged region was restored by a newly formed capillaly network. When no change was noticed microscopically in the case of low-energy irradiation, transient increase of blood flow, determined by laser doppler flowmeter, was observed. The results suggest that the effects of Nd : YAG laser irradiation are primarily thermal, it has good hemostatic and coagulation ability, and some of the changes are nerve-mediated by low-energy irradiation.
Disaccharidases of oral bacteria, especially α-glucosidase and β-fructofuranosidase, are considered to play an important role in the induction of dental caries. Upon the examination of disaccharidases from several strains of saccharolytic cral bacteria, we found all of those bacteria to be capable of hydrolyzing the glycosidic linkage of sucrose. One species of bacteria, Rothia dentocariosa, was found to contain a single disaccharidase, α-glucosidase. This enzyme was partially purified by ammonium sulfate precipitation, gel filtration and ion-exchange column chromatography. The optimum pH and temperature for the enzyme activity was found to be 6.8-7.0 and 40°C, respectively. The enzyme activity was strongly inhibited by Ag+, Hg2+, Cu2+, Fe2+ and Tris (Hydroximethyl) aminomethane.