We did light and electron microscopic observations of interproximal gingival tissue to clarify which cases require surgery after initial preparation. The samples were biopsies from adults who had undergone initial preparation. While the gingiva exhibited no macroscopic signs of gingivitis, a certain degree of inflammatory infiltration remained under the junctional epithelium even after the initial preparation. On the other hand, infiltration was localized and formation of new collagen was seen in some areas. Furthermore, the pocket epithelium reattached coronally to the planed root surface. These results suggest that periodontal surgery might not always be required after initial preparation.

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We studied the role of the cartilaginous nasal septum in maxillofacial growth by expanding the maxillary arch of 100 growing rats, and comparing them with 50 controls. We took measurements on serial cephalograms and prepared histological sections of both groups.
     There was no significant difference in weight gain between the experimental and control animals. The direction of maxillofacial growth changed from downward-forward to forward, with the greatest directional change being at 2-4 weeks. Although histological changes were seen in the cartilaginous nasal septum and surrounding tissues of the expanded animals at 1-4 weeks, no changes were seen after 7 weeks.
      The present experiment proved that the cartilaginous nasal septum plays an important role in the craniofacial growth of the young rat.

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We examined whether application of a long spinner culture of periodontal ligament cells to the root surface before reimplantation is capable of creating new attachment. Premolars were extracted from a monkey and cells from the periodontal ligaments were cultured. The maxillary central incisors were then extracted, the cementum and pulps removed, and the root canals filled. After culturing the periodontal ligament cells on the planed root surface of the right central incisor, the tooth was maintained in a spinner culture for 4 weeks. The left central incisor, which was preserved without exposure to the cells, served as a control. The teeth were then reimplanted to their original sockets. After 6 weeks the seeded root surface was covered with fibrillar tissues. However, epithelial downgrowth, root resorption and ankylosis were observed in the control. These results indicate that this new technique may promote the formation of new connective tissue attachment.

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We evaluated the growth characteristics of cells derived from bone side (BP), middle (MP) or cementum side (CP) of human periodontal ligament. The cells were from mandibular right third molar and first premolar. Fifth and 15th passage cultured cells were grown in Dulbecco's modified Eagle medium containing various concentrations (5, 10 and 20%) of fetal bovine serum (FBS), and the cells were counted at 5 and 10 days. The growth ability of the CP cells was the lowest in all examined. BP, MP and CP cells showed different growth patterns at each concentration of FBS. These results suggest that cells from different areas of the periodontal ligament produce different proliferative responses.

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We investigated the effect of surface potential energy on the adhesion of bacteria to hydroxyapatite (HAp) using a theoretical calculation of the surface potential energy with the interaction of electrical double layer forces (Vel) and van der Waals forces (V_A) between HAp, protein-coated HAp and oral bacteria.
      Vmax between the HAp and bacteria with a low zeta potential was smaller than that between HAp and bacteria with a higher one. These results show that oral bacteria can be divided into two groups-those that easily adhere to HAp and those that do not.
      The van der Walls forces between protein-coated HAp and bacteria caused them to repulse one another because the Hamaker constant of protein is smaller than that of water. However, surface potential energy was affected more by Vel. It is easy for bacteria that have a low zeta potential to adhere to protein-coated HAp. On the other hand, it is difficult for bacteria with a high zeta potential to adhere to protein-coated HAp because of electrostatic repulsive forces.
      These results suggest that it may be possible to prevent adhesion of bacteria with a high zeta potential to HAp by changing the surface potential energy between bacteria and HAp.

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Since mastication depends on the physical properties of foods, it is very important to know how food texture changes with chewing. We assessed how the texture of gum changed during chewing. Eleven normal subjects and 6 with masticatory muscle disorders were asked to chew gum and the texture (hardness, cohesiveness, stickiness and gumminess) was measured by a texturometer at 10, 20, 30, 60, 90, 120, 180 and 240 seconds. The cohesiveness and the stickiness of the gum during chewing was similar for the two groups. The only difference was that the hardness and the gumminess of the gum was less for the normal subjects at 10 seconds. This suggests that special attention should be paid to the early stages of chewing.

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We conducted clinical tests of Hybrid Ceramics (HCC-4S), a newly developed crown material, by observing the clinical course of patients immediately after placement, at one week, and at three months. Forty-seven subjects, 10 males and 37 females, were selected. The restoration sites included one anterior tooth, 22 premolars and 24 molars. The condition of gingival margins generally improved after placement. Although occlusal wear of the crowns and was almost nonexistent, shiny spots were noticed in two cases. Three of the crowns fractured, two during temporary fitting and one after placement. We concluded that the Hybrid Ceramics (HCC-4S) is appropriate for the coronal restoration of posterior teeth. It has excellent strength, biocompatibility and esthetic properties.

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Previous studies have shown that amorphous structures, which are glycoprotein in nature, surrounding vesicle-like structures in non-fimbriated Prevotella intermedia strain E18 may mediate hemagglutination. We attempted to purify a hemagglutinin from hemagglutination-active fraction A by sucrose density ultracentrifugation at 35,000 rpm for 20h. The active fraction was eluted from an arginine agarose 4B column using 1M arginine. Activity was found at the second peak on a Sepharose CL-4B column when equilibrated with 10 mM tris-HCl containing 6M urea. A single band at approximately 70kDa was obtained by SDS-PAGE. These results indicate that this protein may be a hemagglutinin.

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In order to study the function of the extracellular matrix (ECM) in the bovine periodontal ligament, I carried out biochemical investigations of the collagen and glycosaminoglycans in this tissue from 6 mandibular anterior teeth (APL) and 6 maxillary posterior teeth (PPL). The GAG from both locations consisted of the same 4 molecules: dermatan sulfate (DS), chondroitin sulfate, hyaluronic acid, and heparin sulfate. However, there was significantly more DS in the APL than in the PPL. Investigation of the unsaturated disaccharide component of DS revealed significantly more ΔDi-4S from the DS in the APL than in the PPL. Also, there was significantly more collagen (hydroxyproline) in the APL, although the chemical composition for this component was the same for both regions. These results indicate that the APL has a stronger tendency than the PPL to form fibers, and that metabolism in the ECM changes in response to the support function of the periodontal ligament.

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We investigated the effect of combined regional hyperthermia with injection of absolute ethanol into human oral carcinoma (KB cells) transplanted subcutaneously in the leg of BALB/cA nude mice. Combined regional hyperthermia with injection of absolute ethanol seemed to have a potential inhibitory effect on the growth of the KB cells. In addition, the anti-tumor effect of hyperthermia with injection of 0.3ml/g absolute ethanol at 43℃ was nearly 5.8 fold that at 41℃ We concluded that combined regional hyperthermia with injection of absolute ethanol is an effective treatment.

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Using microradiography and light and scanning electron micrograpy, I examined the histological changes around hydroxyapatite- (HAP-) coated shape memory alloy implants placed in the mandibular premolar and molar regions of Japanese monkeys. No connective tissue could be found between the HAP-coated layer and newly-formed bone, although they formed a tight bond similar to ankylosis. In the portion not coated with HAP, newly-formed bone tissue was in close apposition with the Ti-Ni alloy without interpositioning fibrous elements. This study suggests that these implants may stimulate osteogenic activity and maintain good stability and fixation with bone.

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We examined whether seeding a culture of long spinner periodontal ligament cells on the root surface is capable of creating new attachment. Premolars were extracted from a monkey and cells from the periodontal ligaments were cultured. The maxillary central incisors were extracted, the cementum and pulps removed and the root canals filled. After culturing the periodontal ligament cells on the planed root surface of the right central incisor, the tooth was maintained in a spinner culture for 4 weeks. The left central incisor, which was preserved without exposure to the cells, served as a control. The teeth were transplanted to their original sockets. After 6 week the seeded root surface was covered with fibrillar tissues. However, epithelial downgrowth, root resorption and ankylosis was observed in the control. These results indicate that this new technique may promote the formation of new connective tissue attachment.

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Using microvascular corrosion casts and scanning microscopy, we studied the microvasculature of the lingual papillae in primates (humans, common squirrel monkeys, common marmosets and tree shrews) and insectivores (large Japanese moles and dwarf shrews). The lingual papillae were well-developed in humans but their size and number decreased in primitive monkeys and insectivores. The microvasculature of the papilla is also much simpler in primates and insectivores, in that order. We found that both the external features and microvasculature of the papillae differed between animal species. It was possible to classify the pattern of microvasculature based on the animal species.

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We elucidated the relationship between osseous healing and microvascular changes utilizing light and scanning electron microscopic observations of osseous-microvascular corrosion castings. At one week, neovascularization was observed from pre-existing vessels of the inferior alveolar artery and mandibular periosteum. Newly-formed trabeculae at the fundus of the defect spread between new sinusoidal capillaries. At 4 weeks, the defect were filled with the newly-formed bone that approached the level of the mandibular border. We concluded that use of the ultrasonic blade to preserve pre-existing vessels of the inferior alveolar artery is beneficial to new bone formation.

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We investigated the relationship between the mandibular symphysis and measurement points on the craniofacial skeleton used in orthodontic diagnosis and treatment by surveying the area of the symphysis and analyzing cephalograms of 120 patients with high developmental skeletal values. We found a close relationship between the height of the symphysis and total anterior facial height. Inclination of the mandibular incisors was in proportion to that of the alveolar region, but the mandibular site of the symphysis was not affected. We found that the symphysis could be divided into alveolar and mandibular regions.

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We studied the role of the cartilaginous nasal septum in maxillofacial growth by expanding the maxillary arch of 100 growing rats. We took measurements on serial cephalograms and prepared histological sections. We found no significant difference in weight gain between the experimental and control animals. The direction of maxillofacial growth changed from downward-forward to forward. Although histological changes were seen in the cartilaginous nasal septum and surrounding tissues of the expanded animals at 1-4 weeks, no changes were seen after 7 weeks.

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Control of cutting load during cavity preparation is seldom taught in dental colleges. I developed an apparatus that recreates the minute movements of the handpiece during high-speed dental cutting without actually doing any cutting. I analyzed the characteristics of load control by the fingertips, and investigated the effectiveness of practice with this apparatus. Four types of feedback information were established for the experimental subjects who used this apparatus. It was found that the information used in controlling the load varied for each subject. The simulator was employed as a trainer for fourth-and fifth-year dental students, and for dentists with two years of clinical experience. Using the simulator during the early stages of dental education was found effective in improving control of cutting load.

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I studied the ability of inflamed granulation tissue to prevent systemic diffusion of bacterial endotoxin in dental periapical lesions. Inflammatory reactions were induced in the wall of the subcutaneous air pouch of rats by administration of endotoxin. I then examined the endotoxin density of the circulating blood and the endotoxin volume of the air pouch fluid. Endotoxins were also injected intravenously in other rats. Endotoxins in the circulating blood decreased to normal levels more rapidly in the group injected in the air pouch than in the group injected intravenously. However, the endotoxin volume in the air pouch maintained a high level during all experimental periods. These results suggest that inflammatory tissue may act as a barrier to diffusion of endotoxins from the focus of a lesion to the body.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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