Yukio Kakudo

Basic Biological Sciences: Secretion and Re-absorption of Glucose in Rat Submandibular and Sublingual Saliva

Glucose permeation from blood to saliva appeared to follow the paracellular pathway in rat submandibular and sublingual glands, and the permeability was much higher in the sublingual than in the submandibular gland. The duct system re-absorbed glucose in the submandibular but not the sublingual gland. The glucose concentration in sublingual saliva was inversely related to the flow rate.Glucose permeation from blood to saliva appeared to follow the para cellular pathway in rat submandibular and sublingual glands, and the permeability was much higher in the sublingual than in the submandibular gland. The duct system re-absorbed glucose in the submandibular but not the sublingual gland. The glucose concentration in sublingual saliva was inversely related to the flow rate.

Effect of Streptozotocin Diabetes on Gingivitis in Plaque-susceptible Rats

The periodontal pocket probing depths of mandibular incisors of plaque-susceptible (Sus) rats, which spontaneously exhibit gingivitis with accumulation of plaque, were increased 20 days after injection of streptozotocin (70 mglkg, i.v.). The accumulated plaque weights were also increased in Sus rats with streptozotocin diabetes, and a positive correlation was found between the plaque weights and the pocket depths. Histological findings showed that this inflammatory reaction in gingival tissue was higher and more extensive in diabetic Sus rats than in control Sus rats. These findings suggest that the accumulated plaque is the important factor for the severe breakdown of gingival tissue in this experimental model.

Measurements of Deformations of Teeth and Mandibles due to Occlusal Forces

When occlusal or masticatory forces were applied to teeth and mandibles, three dimensional (3-D) displacements of their deformations were measured quantitatively by double-exposure holographic interferometry. The mandibles were extracted from adult dogs. As measuring places, buccal surfaces of the teeth and mandibles were selected. When vertical load was applied to the first retromolar (M1), a tiltlike deformation was observed. By this the tooth was displaced to the buccal direction. Experimental observation of a sagittal section shows that deformations of the tooth are larger than that of the corresponding mandible. When a lateral load acted on M1, the buccal surface of M1 was displaced into the upper direction of the tooth axis from the dental socket. In these experiments, two kinds of tensile forces, 100 gm and 200 gm were applied to M1. When the buccal surface of the mandible in the neighbourhood of M1 was partly scraped, the same surface of the tooth was displaced further to the upper direction of the tooth axis. The mandible in the neighbourhood of M1 was displaced in the same direction. These results show that the periodontal membrane plays the role of a buffer and will be valuable to considerations of deformations of human teeth and periodontal diseases.

Holographic Investigation of Tooth Deformations

A bad approximal contact may cause food impactions between teeth by masticatory forces. This may give rise to caries or other paradental diseases. Many studies on approximal contact relation have been presented based on clinical experience [1] and considered from a morphological standpoint [2] up to now. However, there have been only few studies on approximal contact relation investigated from a functional viewpoint. Therefore, investigations of the deformations of teeth subjected to occlusial or masticatory forces and the mechanical effect to their adjacent teeth are very important. Deformations have been measured, until now, with mechanical instruments [3], [4] such as dial gauges and strain gauges. Recently, double-exposure holographic interferometry has been found useful to measure three-dimensional deformations of teeth [5], [6]. This method, however, is restricted to the measurement of deformations within a certain time interval. Real-time holographic interferometry, on the other hand, allows measuring such deformations continuously.