I examined osseous healing after placement of HAP granules (APACE-RAM G^®) and HAP blocks (APACERAM B^®) in mandibular segmental defects of 8×4×3mm in rabbits. An ultrasonic scalpel was used to preserve the preexisting vessels from the inferior alveolar artery. Sequential changes in the histological structures and microvasculature were investigated on microvascular corrosion castings under light and scanning electron microscopy.
     One week after the operation new bone formation, which was similar for both the granules and blocks, was seen on the bone marrow side of the defect. In the HAP granule group, the granules were surrounded by new sinusoidal capillaries which developed to form a new capillary network at two weeks. Newly-formed bone spread between the new capillary network and impacted the granules at four weeks. Spaces of less than 50μm were observed between the granules, new bone formation was delayed, and fibrous tissue remained. In the HAP block group, new capillary networks and new bone formation were observed in the larger pores (greater than 200μm) at two weeks. At three weeks, one new capillary was observed entering a l00-200μm pore where new bone formation had been delayed.
     These results suggest that new capillary and bone formation occur when the spaces between the HAP granules is greater than 50μm and when the pores in the HAP blocks are greater than 50μm.

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We investigated biochemically and immunohistochemically the age-related changes in type III collagen and tenascin in the rat submandibular gland. The DNA content tended to decrease beginning at 14 weeks after birth. The total protein content decreased with age while the Hyp content gradually increased. The amount of type III collagen, which is distributed in interlobular connective tissue, gradually decreased after 14 weeks, as did the ratio of type III to type I collagen. Tenascin, which is distributed in the basement membrane of ducts and vessel walls, decreased markedly between 14 to 21 weeks after birth.
     These findings suggest that collagen and tenascin remain in the tissues after completion of functional differentiation, although their quality and quantity change with age. They are both instrumental in the construction of the infant submandibular gland during the first 14 weeks of life.

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Using SAMR l and SAMP 8 mice, we studied the relation between learning impairment and senescence, individual variations in senility, and the effects of oral administration of docosahexaenoic acid (DHA, n-3 PUFA) on learning and memory impairment.
     When we studied learning and memory impairment as a model of disorders using the passive avoidance task, we found that mice with a lower grading score were more successful at achieving learning. Changes in learning and memory ability were related to age as well as senescent characteristics, and the turning point for the senescent process in SAMP 8 mice was between 27 and 42 weeks of age. When SAMP 8 mice were fed diets containing DHA, the incidence of learning impairment was decreased.
     These results indicate that we should correct experimental data in chronological age for differences in individual biological age (senescent characteristics). DHA was found efficacious against learning and memory impairment in the SAMP 8 mice, and was able to delay the onset of senility.

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We investigated the growth and morphological characteristics of the cranium and face of Han Chinese children with normal occlusion and compared them with Japanese children. We selected 180 school children (90 males and 90 females) from 2,518 pupils at four primary schools in Xicheng District, Beijing, China. The children were divided into six groups following Hellman's developmental stages (IIIA, IIIB and IIIC). We did statistical calculations on angular and linear measurements using tracings of head X-rays.
     We found that the direction of facial growth in the Han Chinese children was forward and downward. Boys showed less growth change than girls in developmental stages IIIA and IIIB, while both boys and girls showed marked growth in stages IIIB and IIIC. Girls showed two growth peaks and a tendency to grow slightly earlier than boys. The facial pattern of growth was more prominent in the mandible than the maxilla. The lengths of the anterior cranial base and mandibular body in the Han Chinese children were about the same as Japanese. While the Gonial angle and Mandibular plane angle of Han Chinese children were smaller than those of Japanese, the former had a greater tendency for prominent maxillas and mandibles.

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Using strain gauges, we investigated the effect of an extraoral anchorage appliance on two dry human skulls of Hellman's developmental stage VA that had different palatal plane angles. We set an edgewise appliance and palatal bar on the skull and measured the strain when a 3kg force was applied to short, medium and long outer bows of a face bow headgear. The strain on the sutures was greater than the strain on the bone around the sutures. Compared to the skull with a high palatal plane angle, in the skull with a low palatal plane angle even downward traction by the face bow headgear produced backward and upward distortion of the maxilla with counterclockwise rotation. We concluded that the orthopedic effects of the face bow headgear operates chiefly on the sutures, which are the main growth centers of the maxillofacial complex. The skeletal patterns of patients and the purpose of the face bow headgear must be considered when determining the position and direction of traction.

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β-Lactamase is closely related to the mechanism of β-lactam resistance in Prevotella intermedia from odontogenic infections. We studied the efficacy of β-lactamase inhibitors to design compounds of β-lactams and β-lactamase inhibitors with the most potent activity against β-lactamase producing clinical isolates of Prevotella intermedia. The minimum inhibitory concentration (MIC) of the β-lactamase inhibitors clavulanic acid (CVA), sulbactam (SBT) and tazobactam (TAZ) was in the range 0.06〜8.00μg/ml against fifteen β-lactamase producing clinical isolates of Prevotella intermedia. In penicillin G with 0.5〜2.0μg/ml of β-lactamase inhibitors, the efficacy of the inhibitors that caused a marked reduction in growth of β-lactamase producing clinical isolates of Prevotella intermedia was 79〜94% for β-lactamase producing the clinical isolates for CVA, 73〜100% for SBT, and 86〜100% for TAZ. Combinations of each inhibitor and cephalexin, cefteram, cefaclor, ampicillin, cefazolin, and piperacillin were also effective β-lactamase inhibitors against clinical isolates. We found the therapeutic efficacy of combinations of β-lactams and β-lactamase inhibitors was stronger than that of penicillins and cephems against odontogenic infections with β-lactamase producers of prevotella intermadia.

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We investigated biochemically and immunohistochemically the age-related changes in type III collgen and tenascin in the rat submandibular gland. Tha DNA content tended to decrease beginning at 14 weeks after birth. The total protein content decreased with age while the hydroxyproline content gradually increased. The amount of type III collagen, which is distributed in interlobular connective tissue, gradually decreased after 14 weeks, as did the ratio of type III to type I collagen. Tenascin, which is distributed in the basement membrane of ducts and vessel walls, decreased markedly between 14 to 21 weeks after birth. These findings suggest that collagen and tenascin remain in the tissues after completion of functional differentiation, although their quality and quantity change with age. They are both instrumental in the construction of infant submandibular glands during the first 14 weeks of life.

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Using SAMR 1 and SAMP 8 mice, we studied the relation between learning impairment and senescence, individual variations in senility, and the effects of oral administration of docosahexaenoic acid (DHA, n-3 PUFA) on learning and memory impairment. When we studied learning and memory impairment as a model of disorders using the passive avoidance task, we found that mice with a lower grading score were more successful at achieving learning. Changes in learning and memory ability were related to age as well as senescent characteristics, and the turning point for the senescent process in SAMP 8 mice was between 27 and 42 weeks of age. The incidence of learning impairment was decreased when SAMP 8 mice were fed diets containing DHA. These results indicate that we should correct experimental data in chronological age for differences in individual biological age (senescent characteristics). DHA was effective against learning and memory impairment in SAMP 8 mice, and delayed the onset of senility.

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I examined the immunohistochemical localization of type I, type II and type X collagens, and hyaluronic acid binding protein (HABP) in the mandibular condylar cartilage of SAMR l (senescence accelerated mouse, resistant) and SAMP 8 (senescence accelerated mouse, prone). With ageing, the staining of type I collagen decreased in the intermediate and hypertrophic zone. Type II collagen was present throughout the cartilage. Type X collagen was present around chondrocytes in the articular zone. The staining of HABP decreased in the intermediate and hypertrophic zone. These immunohistochemical changes were observed in the SAMP 8 strain earlier than in SAMR l. These results indicate that this characteristic response may be related to accelerated senescence.

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I examined how the progression of diabetic microangiopathy in streptozotocin-induced diabetic rats affected tooth extraction wound healing. Using microvascular corrosion castings (Ohta et al., 1990), I investigated successive changes in histological structures and microvasculature after extraction of maxillary first molars. Six weeks after induction of diabetes, healing in the experimental group was similar to that of the controls. However, when the extraction was done 16 weeks after induction, the blood clot was still visible in the socket center one week after the operation, and the vascularization was a sinusoidal network without any bone trabecular formation. The socket was still not completely filled with newly-formed capillaries at two weeks. In conclusion, microvascular patterns during extraction wound healing played an important role in new bone formation and development. Vascularization and new bone formation was delayed in the diabetic groups at the microangiopathy advanced.

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Programed cell death (apoptosis) is an active process of self-destruction, as opposed to accidental cell death (necrosis). It has been reported that apoptosis is closely related to proliferation and differentiation. Ceramide, a fundamental structure of sphingolipids which are a basic construction unit of the cell membrane, has been reported to be a lipid second messenger. I investgated the interrelation between differentiation, proliferation and apoptosis, and the role of ceramide in the signal transduction pathway in cancer cells. The results indicated that ceramide controls cell differentiation and proliferation through apoptosis by activating the nuclear transcriptional factor AP-1.

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We investigated the effect of temperature and humidity on the tensile bond strengths (TBS) to human and bovine dentin for a conventional and two light-activated glass ionomer cements (L-GIC). With Glas Ionomer-F and Vitremer, very low TBS was obtained even when the adherent was dry, irrespective of the adherent. With Fuji Ionomer Type II LC, high TBS was obtained with wet human dentin. Higher TBS was obtained at 32O℃ and 92% ralative humidity than in room temperature. We found that the TBS between L-GIC and dentin was influenced by the type of adherent and the moisture on it, as well as by the temperature and humidity during the bonding procedure.

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I evaluated the effect of ViaSpan, sterile saline, human resting saliva, and pasteurized milk as storage media for tooth replantation on intra-cellular LDH activity, growth activity, and morphological changes in human periodontal ligament cells. ViaSpan and pasteurized milk were superior to sterile saline and human resting saliva in their effect on intra-cellular LDH activity and cell growth activity. Human resting saliva had the greatest influence on morphological changes among the four media. There was correlation between the osmolality o f the storage media, intra-cellular LDH activity, and growth activity o f the periodontal ligament cells.

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We investigated sequential changes with age in the microvasculature of the periodontal ligament of male rat mandibular molars at one month intervals up to 24 months of age. Capillary loops around the root surface generally changed form a hairpin type to an arcade form. During this time the formation of cementum also advanced cervically from the apical region, and considerable new cementum was deposited. Age changes in the microvasculature of the rat periodontal ligament appears closely related to capillary loop and cementum formation.

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I investigated changes in collagen localization for types I, II and X collagen in rat mandibular cartilage during growth using immunohistochemistry. Sections were stained with hematoxylin eosin and immunostained using the labelled streptavidin biotin method. Collagen in the rat mandibular cartilage was localized in the extracellular matrix of the particular cell layer that played a role in each component, and was thought related to growth functions in the temporomandibular joint.

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We used the finite element method to compare the mechanical behavior in bone around IMZ implants when the implants were splinted to teeth and when they were free standing. The muscle activity from the masseter, anterior temporal and anterior belly of the digastric muscles was evaluated by electromyographic linear envelops (EMG profiles). Deflection and stresses generated in bone around the implant and on the surface of the implant were less when it was splinted than when not. Regardless of whether the implants and teeth were splinted, EMG profiles of the masticatory muscles varied with each chewing stroke before placement of the superstructures, although they were stable after placement. These findings suggest that splinting IMZ implants to natural teeth poses little risk mechanically and functionally.

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I assessed how changes in gum texture during chewing affected masticatory function. Masticatory movements and EMG activity were analyzed during gum chewing in 12 normal subjects and 8 people with masticatory muscle disorders. Comparisons were made between the early stage of chewing, when the texture varied widely, and the late stage, by time the texture had stabilized. In normal subjects, there was considerable variation in masticatory movement and EMG activity between strokes during the early stage. The cycle durations, however, were relatively constant throughout the chewing. In those with masticatory muscle disorders, the cycle durations were constant, and masticatory movement and EMG activity did not vary between the early and late stages. The results showed that although the output of the central pattern generator is influenced by sensory feedback in normal subjects, it is not in people with masticatory muscle disorders.

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I used normalized electromyographic linear envelopes (EMG LEs) to investigate differences in coodination patterns of masticatory muscles during gum chewing on the preferred and nonpreferred sides (PRC and NPRC). Ten asymptomatic volunteers were used in the experiment. EMG LEs normalized with respect to EMG amplitude and stroke were generated from surface EMG signals of the bilateral anterior temporal, posterior temporal and masseter muscles, and movement of the incisal point of the mandible. The coordination patterns of EMG LEs for the masticatory muscles were evaluated by cluster analysis. There were differences between PRC and NPRC in the phasic behavior for the non-working masseter muscle.

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We investigated the influence of vibratory stimuli on mandibular position during opening and closing movements. Eight subjects were instructed to memorize different reference positions from intercuspal position (ICP). They were then required to open and close 20 times between each reference point and a point just short of maximum opening. A l00Hz vibratory stimulus was then applied for 20 second to the mentalis and the above jaw movements were repeated. After application of the stimulus, the opening was generally less. Next, the subjects were requested to cycle between the reference points and a position just short of ICP. After application of the stimulus, the opening was generally greater. We found that the mandibular position sense was affected by vibratory stimuli.

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I quantitatively evaluated the degree or palatonasal closure for maxillary prostheses. The subjects included five healthy males aged 24 to 25 years, and 8 subjects with partial defects in the maxilla. Quantitative evaluation of the palatonasal closure level was possible by measuring and comparing the maximum pressure, the stable pressure inside the mouth, and the stable pressure maintenance interval and the pressure attenuation time while blowing and sucking before and after placement of the maxillary prosthesis.

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I examined electromyograms (EMG) during tapping movements to determine the effect of local pressure on mucosa underlying free-end saddle partial dentures in 6 denture wearers. EMG of the bilateral anterior temporal and masseter muscles were recorded together with mandibular kinesiograph motions. Four plates of different diameters and thicknesses were fixed inside the dentures to apply pressure. There was significant variation in the EMG time parameters and integrated EMG for the different experimental conditions. The results suggest that compatibility of the denture base and mucosa is important to function.

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I recorded and analyzed electromyographic activity, incisal movement and condylar movement in 5 subjects to investigate the effect of the anterior guide angle on electromyographic activities in the inferior head of the leteral pterygoid muscle (Lpt) and the anterior belly of the digastric muscle (Dig). Increasing the angle significantly changed the electromyographic activities of Lpt and Dig. Significant correlation was found between electromyographic activity in Lpt and translation of condylar movement, and between Dig and mandibular rotation. It was found that protrusive movement could be performed smoothly by coordinating Lpt and Dig to accomodate changes in the anterior guide angle.

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I investigated histochemical changes in the masticatory muscles and morphological changes in the cranium induced by elevating the vertical dimension of occlusion in growing rats. One hundred and forty-four 4-week-old male Wistar rats were divided into three groups. In the experimental group, the vertical dimension of occlusion was elevated 1mm and 1.5mm bilaterally at the maxillary molars. The weight of the masticatory muscles and the mean diameter of II B fibers had decreased at 7 weeks of age in the experimental animals, the percentage of II B fiber in those muscles had increased, and the height of the mandibular angle had significantly decreased at 7 and l0 weeks of age. These results suggest that elevating the vertical dimension of occlusion retards growth of the masticatory muscles and cranium, and that these changes might be related to a decrease in the diameter of, and an increase in the percentage of, type II B fibers.

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We measured the vertical force transmitted through a palatal bar to the maxillary first molars during swallowing in 22 subjects with normal occlusion and a mean age of 22.3 years. The measurements produced biphasic wave forms. The maximum vertical forces were 1,844g for 5ml or water, 1,446g for saliva, and 1,293g for 180ml of water. The maximum durations of continuous force were 2.0sec for 5ml of water, 2.6sec for saliva, and 14.8sec for 180ml of water. The maximum integrals of force over time were 1,412g・sec for 5ml of water, 1,515g・sec for saliva, and 5,234g・sec for 180ml of water. These results suggest that the palatal bar effectively controls vertical forces on the maxillary molars during orthodontic treatment.

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We used adult and child dried human skulls to investigate the effect of chin caps on the direction of traction forces. The strain gauge method was used to measure the strain distribution on the temporal bone and surrounding sutures, and in the maxilla and mandible. The chin cap affected the craniofacial skeletons and sutures not only through the condyle, but also through the occlusal surfaces of the molars. The chin cap force extended to the temporal bones and surrounding sutures, and the direction of the traction forces created by the chin cap produced different effects on the mandible and temporal bone.

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We used strain gauges on a dried adult human skull to measure the effect of headgears on the force system of multi bracket appliances. The face bow headgear produced distal movement in the maxillary dental arch by rotation centered in the region between the apices of the first premolar and canine, as well as enlargement of the dental arch. The J-hook headgear produced the greatest compressive strain when force was applied to hooks placed between the maxillary lateral incisors and canine. These results suggest that the headgear is an effective auxiliary to multi bracket appliances.

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We used the finite element method to analyze stresses and displacement during trauma to the maxillary primary central incisors, alveolar bone, and the successive permanent tooth germs for different degrees of primary root resorption. We found that the teeth and alveolar bone were displaced more for teeth that had greater resorption. We also found that greater resorption resulted in less stress in the tooth, although it produced greater stresses in the alveolar bone.

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We investigated the surface characterizations of apatite plates synthesized by the method of Abe, and of sintered apatite plates, and examined adsorption isotherms of protein to these plates. An x-ray refraction apparatus showed the sintered apataite plate to have high crystallinity. Chemical analysis by electron spectrometer for chemical analysis showed that the peaks for calcium, phosphorous, oxygen and carbon were in the same positions for the apatite plate as they were for powdered hydroxyapatite. Scanning electron microscopy and atomic force microscopy showed that the surface structure in the sintered apatite plate was flat because of polishing, and that the synthetic apatite plate was comprised of overlapping layers. The zeta potential of the surface of the apatite plate in protein solution (human serum albumin and salmon protamine) increased with increasing protein concentration, and the plateau value of the sintered apatite plate was closer to the charge of protein than was that of the synthetic apatite plate. We found the sintered apatite plate useful for experiments on the adhesion o f protein and bacteria.

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Using the microdialysis method, we evaluated the effect on the prefrontal cortex of noxious stimulation during anesthesia, and the role of 6-amino-3 hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptors. We also examined the effect of preemptive analgesia (PA) on the dopaminergic neuron system in the prefrontal cortex. Electric stimulation of the dorsum pedis decreased dopamine (DA) by 20% (p<0.05), while electric stimulation after addition of 6-cyano-7-nitroquinoxaline-2.3-dione, an AMPA/kainate receptor antagonist, to the dialyzing solution futher decreased DA. These findings suggest that noxious stimulation during general anesthesia, unlike during arousal, decreases DA in the prefrontal cortex, and that AMPA/kainate receptors inhibit this decrease. In addition, although noxious stimulation during anesthesia decreased DA in the prefrontal cortex, epidural anesthesia inhibited this decrease.

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[in Japanese]

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