Increasing attention has been paid in recent years to odontoparallaxis in deciduous teeth. The primate spaces, developmental spaces, and interdental spaces between the maxillary deciduous canine and first deciduous molar were examined three consecutive times annually in 520 kindergarten pupils.
We found that :
1. The incidence of spacing in the arch decreased with age.
2. The incidence of primate spaces was higher in the maxilla than in the mandible, and decreased with age.
3. The incidence of interdental spaces between the maxillary deciduous canine and first deciduous molar tended to increase in both boys and girls from age four to five and then to decreased from five to six.
4. The incidence of developmental spaces was higher in children with primate spaces than in those without.
5. In terms of chronological changes in spaces, of the three types, dentition that did not change was the most common.
These results provide a clear understandings of the interdental spacings in deciduous teeth, which is considered necessary for normal composition of the permanent dentition. Furthermore, it is evident that the incidence of interdental spacing as well as the distances of the interdental spaces decrease with age. For these reasons, treatment of the deciduous dentition should be carried out as early as possible.

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Jarabak analysis based on Björk analysis has been modified and added as a part of Tweed, Steiner and Ricketts analysis, as well as others. The main features of this method are that it can be divided into skeletal and denture components, and growth direction can be analyzed in detail by the skeletal component. It is recognized as an optimal cephalometric analysis for tracing cranio-facial skeletal growth.
We investigated and traced the growth changes in the cranio-facial skeleton from childhood to adolescence in 15 boys and 14 girls between 10 and 15 years of age using Jarabak analysis, taking cephalometric radiographs once a year for six years. Average values and annual increments were obtained for the Jarabak analysis of this group of Japanese children.
We found that the Japanese cranio-facial growth pattern either had a slight inclination from the straight downward type or tended to the counterclockwise growth type.

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I attempted to establish a method of evaluating sweet preference. Seven different concentrations (1, 2, 4, 8, 16, 32 and 48%) of sucrose solution were used with the sip and expectorate method. The sweet preference point corresponds to the lowest concentration of surcrose solution that the subject feels too sweet and unpleasant. All tests were carried out with liquid at room temperature, after lunch, and smoking was not permitted prior to testing.
When reliability and comparability were examined in 15 subjects between 19 and 23 years of age, eight men and seven women, the sweet preference point showed better results than threshold values or the most preferred solution.
Five hundred fifty-six males and four hundred ninety-three females between 6 and 49 years of age were tested. They completed questionnaires and were examined for dental caries. A larger proportion of the younger subjects had high sweet preference points, although no sex difference was observed. Subjects who had high sweet preference points in general favored sweet foods and tastes, and tended to eat sweet foods more often. The relationship between sweet preference point and caries experience was not significant, although subjects who had high sweet preference points tended to show greater caries experience.
These results indicate that the sweet preference point accurately reflects the subject's preference for sweets. They also imply that sweet preference might affect caries status to the extent that it affects dietary habits.

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We studied the changes caused by phospholipids [phosphatidylethanolamine (PE) and phosphatidylserine (PS)] in the physicochemical properties and hydrogen ion diffusion of glycoprotein. Six types of glycoprotein were injected into the sample port and hydrogen ion diffusion was measured. A fluorescent probe with 8-anilino-1-naphthalene sulfonate was used to determine changes in the hydrophobicity and surface potential of the above glycoprotein.
The permeability of the glycoprotein membrane was inversely related to the concentration of phospholipids in the glycoprotein layer. It was found that the permeability of glycoprotein associated with PS is lower than that of glycoprotein associated with PE. PS and PE had different hydrophobicity and surface potential.
These findings suggest that phospholipids in the glycoprotein layers play an important role in retarding hydrogen ion diffusion, creating increased hydrophobicity and maintaining surface potential in the glycoprotein layer.

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We investigated age related changes in the arrangement of the collagen fiber network of palatal mucosa using female Sprague-Dawley strain rats between 3 and 90 weeks of age. A cell-maceration/scanning electron microscope method was employed to demonstrate the three-dimensional architecture of the collagen fibers.
At low magnification, the connective tissue papillae on the rugae become enlarged and more complex in shape with age until ten weeks, but become less complex after 32 weeks. At high magnification, exposed collagen fiber networks of the connective tissue surface were observed in all specimens. Numerous microridges made up of interwoven collagen fibers were observed on the connective tissue surface, and two types of microridges were found : large wall-like and small bundle-like microridges.
Differences in the number and shape of microridges by location were observed at the same age. The microridges increased in number and extended towards the epidermis with age until 10 weeks, and the shape of the microridges became more complex until 32 weeks. At 90 weeks, the microridges decreased in number and size. The collagen fiber network on the connective tissue surface became tighter with age until 32 weeks, but it loosened at 90 weeks.
These results indicate that rat palatal mucosa have different collagen fiber architectures by location, and their structures change with age.

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A non-invasive, continuous measurement of blood flow through the periodontal membrane in cats was attempted using laser Doppler velocimetry (LDV). I examined whether the LDV readings reliably reflected the blood flow in the test region by simultaneous measurment of the periodontal membrane blood flow by the hydrogen clearance method.
Nine adult cats were used. A laser was applied through the wall of the cavities prepared in the upper canines to measure blood flow by LDV. At the same time, an 80 μm electrode was inserted into the periodontal membrane for blood flow measurement by the hydrogen clearance method.
It was found that LDV allowed the recording of oscillatory changes in blood flow synchronous with cardiac rhythm. Blood flow was reduced by local adrenaline treatment. Percent changes in periodontal membrane blood flow, measured by LDV, correlated well with those measured by the hydrogen clearance method, indicating that the LDV readings reliably reflected actual blood flow.
Thus, LDV allowed continuous measurement of changes in periodontal membrane blood flow. LDV seems to provide a useful means of assessing changes in the periodontal membrane circulation caused by various stimuli such as orthodontic forces and drugs.

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I cultured the cell line MG-63, which is derived from human osteosarcoma, and retains osteoblast characteristics, with and without hydroxyapatite (HAP). I examined the histocytochemistry, biosynthesis of the extracellular matrix of fibronectin, type I and type III collagen, and osteocalcin synthesis as a function of mineralization. An ACAS570, laser cytometer revealed that after one week of culture fibronectin caused the osteoblasts to adhere securely to the HAP surface. In addition, type I and type III collagen were synthesized after about two to three weeks. Synthesis of the extracellular matrix and subsequent mineralization were both substantially enhanced in the culture cells around of the HAP. These results suggest that the HAP implant surface may act as a substrate to permit cell growth that improves bone formation at bone defects.

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The migratory ability in collagen gel of cells from the periodontal ligament (PDL), alveolar bone and gingiva of monkeys were compared. In addition, the cell attachment to cementum and dentin were examined ultrastructurally. The migratory ability of PDL cells was less than that of cells from bone and gingiva. Although the migrated bone and gingival cells produced fibrillar materials on the cementum, the PDL cells could not establish an ideal attachment to either cementum or dentin. The decreased function of the PDL cells suggests that they do not respond to various stimulating factors.

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A long-term study on soft tissue healing to acid-treated root surfaces in monkeys and dogs was carried out. The experimental teeth including gingiva and bone were extracted at 2, 3 and 4 weeks after surgery, and undecalcified specimens were prepared routinely for TEM. In dogs, complete interdigitation between exposed fibrils and newly-formed ones was seen two weeks after surgery. In monkeys, however, inflammatory cells were still identifiable in the wound even at three weeks, and weak interdigitation occurred as late as four weeks. The results showed profound differences between monkeys and dogs in the response of healing tissue to exposed fibrils.

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I recorded and analysed mandibular arch width changes between the right and left first molars during opening and protrusive jaw movement, together with incisal movements and electromyograms of the inferior head of the lateral pterygoid muscle (LPt). In five subjects, the average maximum mandibular arch width decrease was 397.7μm during opening, and 585.0μm during protrusion. There was a significant correlation between the decrease in mandibular arch width and electromyographic activity of the LPt (p<0.01). The results suggest that the LPt is the primary cause of decreases in the mandibular arch width during opening and protrusion.

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I studied biochemically and immunohistochemically the kinetics of collagen and tenascin during progression of a human gingival carcinoma xenograft line, GK-1, in nude mice. Total collagen content increased during progression of the tumor. Although the ratio of composition of type I collagen did not change after transplantation, type IV collagen, which localized in patchs in the basement membrane of the tumor nest, and type V collagen, increased gradually from five weeks after transplantation. Type III collagen decreased. Tenascin with subunits molecular weights of 220kDa and 130kDa localized in the stroma of the tumor mass and partially in the basement membrane of the tumor nest. There were little changes in its content from week to week. These findings indicated that collagen functions as a scaffold and a host response to tumor cell proliferation, and tenascin functions to maintain a suitable environment for the progressing tumor tissue.

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We carried out experiments on anesthetized adult monkeys where electrical stimulation was applied to the masseter and temporalis muscles to study the dynamic response of the maxilla to occlusal force. Regardless of the tooth where occlusal forces were imparted, virtually all forces propagated in the direction of the maxillary process and zygomaticomaxillary suture region. Bone sutures are very effective at dispersing occlusal force, while the maxillary sinus easily deformed in response to the force. Since there are very few regions in the maxilla where stresses concentrated, we concluded that the maxilla has excellent mechanisms for buffering occlusal forces.

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Nociceptive neurons were recorded from the intralaminar nuclei of the cat. We investigated the effects of stimulating either the periaqueductal gray (PAG) or the nucleus raphe dorsalis (NRD) on responses obtained from these neurons. Conditioning electrical stimulation of either PAG or NRD inhibited responses to some nociceptive neurons. The same conditioning stimulation also inhibited short latency responses to electrical stimulation of the mesencephalic reticular formation on these inhibited nociceptive neurons. These data suggest that PAG or NRD stimulation-produced inhibition of these neurons may be partially mediated by an ascending pathway, in addition to the well-known descending pathways.

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A non-invasive, continuous measurement of blood flow through the periodontal membrane in cats was attempted, using laser Doppler velocimetry (LDV). I examined whether the LDV readings reliably reflected the blood flow in the test region by simultaneous measurement of the periodontal membrane blood flow by the hydrogen clearance method. It was found that LDV allowed the recording of oscillatory changes in blood flow synchronous with cardiac rhythm. Blood flow was reduced by local adrenaline treatment. Percent changes in periodontal membrane blood flow, measured by LDV, correlated well with those measured by the hydrogen clearance method, indicating that the LDV readings reliably reflected actual blood flow.

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I investigated the influence of water immersion and repeated load on the deterioration of composite resins. Specimens loaded repeatedly for 100,000 times were subjected to long-term immersion in 37℃ or 60℃ water. The sectioned specimens were observed by SEM and their flexural properties were determined. Although repeated loads created superficial cracks and fractures in the microfilled resin, long-term immersion had little effect. Neither repeated loading nor long-term immersion significantly affected the flexural properties, regardless of the type of composite resin. The water temperature had little effect on deterioration of the material.

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We compared the deformation of maxillary complete dentures polymerized under conventional water bath curing and four different conditions of microwave irradiation. In the regions where there were artificial teeth, there was considerable deformation in the dentures polymerized by microwave irradiation because of large anterior/posterior shrinkage compared to small lateral shrinkage. However, there was little deformation in the dentures polymerized by conventional water bath curing. On the other hand, compared with polymerization by conventional water bath curing, there was less shrinkage and little deformation in the mucosal surface region in the dentures polymerized by three minutes of irradiation from the mucosal side, or 90 seconds of irradiation from the occlusal surface side followed by 90 seconds from the mucosal surface side. The shrinkage of all of the dentures decreased between 7 and 30 days after polymerization.

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Magnetic resonance spectroscopy (MRS) has been used to evaluate the metabolic process in skeletal muscles during exercise. Varying phosphocreatine, inorganic phosphate and intracellular pH, I investigated the metabolism in the rat masseter muscle during masticatory movements during feeding, making use of ^<31>P-MRS. During normal masticatory movements during feeding, the supply of ATP is carried out in an aerobic environment. This suggests that energy metabolism in the rat masseter muscle is related to the masticatory cycle and force.

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I investigated the human masseteric jaw jerk reflex mechanism using an electrode array in the stomatognathic system. The response varied with location and contraction level, and there was no difference in latency between the two sides. I also investigated the relationship between motor nerves and masseter muscles. Electrical stimuli were applied to the masseteric nerve from the skin at the mandibular notch. I observed the M-wave, which is the so-called distal mother latency (DML), and M-wave peaks propagated from the motor end-plate. I found that the muscle fiber conduction velocity (MFCV) decreased with fatigue. DML and MFCV were useful parameters for estimating nerve and muscle conditions.

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I studied kinesiologically the variations in human habitual jaw movements without tooth contact when pressure was applied to the right or left maxillary canines from the lingual or labial direction. Applying this pressure caused lateral and anterior displacement of the jaw during movement. This reflex varied with changes in the direction and magnitude of the applied load. These results indicate that the periodontal receptors affect coordination of cranio-mandibular muscle activities during jaw movement.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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