We analyzed the three-dimensional occlusal force vectors during intercuspation in normal adults. Silicone occlusal registration and pressure-sensitive sheets were recorded for ten subjects during clenching with medium force and maximum force. A non-contact, three-dimensional measuring device digitized the silicone occlusal registration and occlusal forces were measured using pressure-sensitive sheets. After the occlusal contact position had been identified, the three-dimensional occlusal force pattern was synthesized from the data. The contact points, contact areas, resultant forces and moments for the molars were significantly different from those for the premolars. The inclination of resultant forces were almost vertical to the occlusal plane in the frontal and sagittal view. There was also a significant difference in the contact points, contact areas, resultant forces and moments when clenching with medium force was compared with clenching with maximum force. However, there was no consistant tendency in the inclination of the resultant forces.

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A beautiful smile is one of the goals of dentistry. We did a three-dimensional analysis of the human face to examine the effect of oral myofunctional therapy (MFT : face athletics, tongue athletics and facial exercise) on the health of the face. Examinees were divided into the physical exercise group, which performed daily MFT, and a control group. Changes in the face were measured by a non-contact three-dimensional system (VIVID 900, Minolta, Japan) and the somatic fat rate and somatic fat volume were measured by a body fat monitor (HBF-301, Omron, Japan). Faces of the subjects in the physical exercise group changed significantly compared with the controls during the first 6 months (p<0.05). Somatic fat content and volume decreased significantly during this period in the physical exercise group (p<0.05), even though somatic weight remained unchanged. Based on these results, we concluded that continuous MFT can result in changes to the face and body fat.

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We evaluated the healing process of experimental periodontal tissue defects in rats after the application of enamel matrix derivative (EMD). Palatal dehiscence defects were surgically created on the bilateral maxillary first molars in forty rats. EMD was applied to cover both sides of the denuded dentin surfaces in the experimental group, while none was applied in the control group. Rats were sacrificed at 1, 2, 3 and 4 weeks after surgery, and biopsies of the tooth, gingiva and bone were examined for the appearance and kinetics of tartrate-resistant acid phosphatase (TRAP)-positive cells by histopathology, histometrical and enzyme-histochemistry. In the experimental group, there were more TRAP-positive cells on the new bone surfaces and the denuded dentin surfaces, and the rate of bone regeneration and limited junctional epithelial down growth were also greater than in the control group. These findings suggest that TRAP-positive cells have the potential to promote new attachment formation and new bone formation.

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We have reported that clinically isolated Prevotella nigrescens strain 22 (strain 22) produced large amounts of exopolysaccharide (EPS) and that this EPS might play an important role as a virulent factor. However, EPS production decreaces with repeated subcultures. In this study, we attempted to establish a method of animal passage that maintains the EPS production of strain 22 at high levels. We also examined the protein expression patterns of strain 22 before and after animal passage using 2-D electrophoresis. EPS production of strain 22 increased after the first animal passage, and continued to increase until the third passage. Mesh-like structures around the cells became significantly denser after animal passage. N-terminal sequence analysis of proteins revealed that three conspicuously up-regulated spots on a 2-D gel after animal passage were the homologs of bacterial heat shock proteins : chaperonin protein DnaK (HSP 70), 60kDa chaperonin (GroEL), and 10kDa chaperonin (GroES). We concluded that this method of animal passage could be used to maintain EPS production of P. nigrescens at a high level, and that the bacterial heat shock protein homologs up-regulated by the animal passage might be involved in a regulatory pathway of EPS production in P. nigrescens under stressful conditions.

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To develop reliable dental implants, we measured the cytocompatibility of human osteoblast-like cells (Saos-2) and cells obtained from the periodontal ligament on titanium irnplanted with nitrogen or carbon (pulse voltage : 5kV and 10kV, 90min) and on titanium coated with diamond-like carbon (DLC). We also examined bacterial attachment to the materials. X-ray photoelectron spectroscopy did not show the presence of titanium nitride or carbide. The methylthiazole sulfate test showed that neither implantation with nitrogen or carbon, nor coating with DLC affected cell attachment or viability after 72hours of culture. The average ALP and the mRNA expression levels for ALP, type I collagen, and osteocalcin were the same whether the titanium was treated or not. However, when assessed by Streptococcus mutans, there was less bacterial attachment when the titanium was implanted with nitrogen or carbon or when it was coated with DLC than when untreated. The results indicated that the three types of surface treatment did not deteriorate the biocompatible characteristics of commercially pure titanium and did not create a favorable situation with bacteria. The results show possibilities for the next generation of dental implants.

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I examined the β-lactamase gene of Prevotella intermedia (P. intermedia) in order to better understand the β-lactam-resistance mechanism. The polymerase chain reaction (PCR) performed on β-lactam resistant P. intermedia gave a product the same size as one previously reported, as well as another product not previously observed. The PCR products of the CfxA 2 and CfxA 3 β-lactamase gene primers were amplified into products that had high homogeneity with the CfxA 2 and CfxA 3 β-lactamase genes. These results suggest that β-lactam resistant β-lactamase producers have genes that resemble the CfxA 2 and CfxA 3 genes, and that these genes are seen throughout the strain. However, Escherichia. coli transformed by the PCR product did not show resistance to β-lactams. This may be the result of inactivation by mutation of a sequence, or the existence of a specific phenotype.

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We investigated the influence of the shape of the temporary anchorage device (TAD) on stress distribution in the surrounding jaw bone using the three-dimensional finite element method to examine four different types of TAD screws (straight, slender, short and conical). The results demonstrated that the different TAD shapes produced significant variations in stress distribution in the bone. The slender type had distinctly higher stress per unit area in the bone than did the others, and the conical type had lower stress per unit area. Moreover, the diameter of the TAD seemed a more important factor for anchorage stability than was the total length.

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I fabricated implants covered with a thin film of hydroxyapatite (HAp) using the pulse laser-deposition technique (PLD). They had good mechanical properties, crystal structure, and homogeneity in composition, all of which are needed for good clinical results. I performed animal experiments to evaluate the osteoconductivity and did quantitative analysis on implants with a 50nm and a 300nm ultra thin film of HAp. I found that bone conduction by the film was adequate in the early stages, even though it was thin, suggesting that this technique might improve clinical results. I confirmed that the PLD technique produces an HAp film with improved mechanical properties, such as increased tensile strength and decreased film thickness.

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We investigated the influence of the shape of fiber-reinforced composite (FRC) on the flexure strength of bridges. Four different FRC bridges were fabricated with laminating hybrid composite resin and one was fabricated with hybrid composite resin alone. Flexure strength was determined by mechanical loading on the center of the pontic using a universal testing machine. Both enlarging the width of the FRC from 3mm to 6mm, and bending the FRC apically increased the flexure strength by about 400N, respectively (p<0.01). We found that it is desirable to enlarge the width of the FRC and to bend it apically when using this material for making bridges.

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We investigated the use of two types of digital image analyses for the objective evaluation of gingival condition. The subjects were 15 adults with a mean age of 24±2 years who were informed about the goals of this study and agreed to participate. Photographs of the gingiva were taken with an oral digital camera and the images were analyzed with a quantitative light-induced fluorescence system. Subjects were told not to brush for 7 days and then were reexamined by the same methods after days 1, 2, 3, 5 and 7. Analysis of the gingival digital images revealed changes in the subjects' gingival swelling when the surface shape was expressed in three-dimensions. When images of the gingiva were analyzed with the QLF system, it was found that changes in the color of the gingiva were more objectively expressed with red in the gingiva than with the green fluorescence of the sound surface of teeth. We found that this apparatus could be useful for the objective evaluation of gingivitis because it could express changes quantitatively.

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We used functional magnetic resonance imaging (fMRI) to examine the relationship of the activation region of the cerebral cortex during mastication with the language dominant hemisphere. Twelve healthy subjects were asked to chew a special gum 50 times on each side of the mouth, the gum changed color, becoming a deeper red, as it was chewed. The depth of red of the chewed gum was used to ascertain the habitual masticatory side. Measurements were also performed on a conventional whole body 1.5 T clinical scanner using a single shot, multislice echo-planar imaging sequence. The subjects were asked to masticate first on the right side, and then on the left side. As well, they were instructed to do a shiritori test, which is a word game. Computer analysis of the fMRI was done using SPM 99 software (p<0.001, paired t-test). We found that the sensorimotor cortex activated by masticatory movements always contains language dominant hemisphere.

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When a tooth is avulsed out as a result of trauma, the residual periodontium can be preserved for a short period of time if it is placed in a suitable storage solution as soon as possible. This is an important factor for successful replantation. We investigated the viability of the periodontium with regard to changes in the activity of alkaline phosphatase (ALP), which is a marker enzyme for calcification. We used human periodontal ligament (PDL) cells and two readily available storage solutions : pasteurized milk and physiological saline. For comparison, we used the culture solution Dulbecco's Modified Eagle's Medium (DMEM). In addition, because tooth replantation should be performed as soon as possible, the duration of storage was kept short, ranging between 30 and 360 minutes. The results showed that although ALP activity decreased after 30 minutes in all three storage solutions, in milk it increased after 240 minutes and in DMEM it increased markedly after 60 minutes. However, the ALP activity in physiological saline decreased with time and did not recover. The relationship between storage time (30 or 120 minutes) and PDL proliferation was also investigated. The results showed that on day 10 of culture, the ALP activity was greatest for PDL cells that had been stored in DMEM for between 30 and 120 minutes. This was followed by PDL cells that had been stored in milk. In addition, when the morphology of cells was observed, complete recovery was seen in the ALP activity of PDL cells that had been stored in either DMEM or milk. However, ALP activity was low with physiological saline, and morphological analysis revealed little cell proliferation. The above findings confirm that milk is an effective storage solution for PDL cells, and may facilitate recalcification of periodontal cells following replantation.

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We examined how the use of carboxymethyl-chitin sponge in the extraction sockets enhanced recovery and maintained bone mass. The experimental animals were euthanatized at 1, 2, 4 and 8 weeks by administration of excessive anesthetic drugs. Plastic was injected into the circuratory system, which was then observed by scanning electron microscopy. Sockets That had not received any treatment after extraction were examined as a control. We concluded that carboxymethyl-chitin sponge enhanced osteogenesis and helped maintain bone mass.

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We studied periodontal tissue regeneration following application of platelet-rich plasma (PRP) on monkey buccal dehiscence defects. Buccal dehiscence defects were surgically created on both sides of the maxillary first and second premolars of four monkeys. PRP was derived from the blood of each animal, and atelocollagen was used as a carrier. The periodontal defects on the left side were filled with atelocollagen containing PRP (PRP group) and those on the right with only atelocollagen (control group). Histological analysis and histomorphometric measurements were then performed on the euthanized monkeys 6 and 12 weeks after surgery. The rates of bone regeneration and new cementum formation were greater in PRP group than in the controls at all observation periods. Apical migration of the junctional epithelium was lower in the PRP group than in the controls, and the new cementum of the PRP group contained cementocytes. The results suggest that implanting PRP in periodontal defects has a significant effect on the promotion of bone regeneration and new cementum formation. However, the new cementum was reparative cementum.

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We evaluated the healing process of experimental periodontal tissue defects in rats after the application of enamel matrix derivative (EMD). Palatal dehiscence defects were surgically created on the bilateral maxillary first molars in forty rats. EMD was applied to cover both sides of the denuded dentin surfaces in the experimental group, and none was applied in the control group. Rats were sacrificed at 1, 2, 3 and 4 weeks after surgery, and biopsies of the tooth, gingiva and bone were examined for the appearance and kinetics of tartrate-resistant acid phosphatase (TRAP)-positive cells by histopathology and enzyme histochemistry. There were more TRAP-positive cells on the new bone surfaces and the denuded dentin surfaces in the experimental group than in the control group. This suggests that TRAP-positive cells have the potential to promote new attachment formation and new bone formation.

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We fabricated implants covered with a thin film of hydroxyapatite (HAp) using the pulse laser-deposition technique (PLD). They had good mechanical properties, crystal structure, and homogeneity in composition, all of which are needed for good clinical results. We performed animal experiments to evaluate the osteoconductivity and did quantitative analysis on 50 nm ultra thin film. We found that bone conduction by the HAp film was adequate in the early stages, even though it was thin, suggesting that this technique might improve clinical results. We confirmed that the PLD technique produces an HAp film with improved mechanical properties, such as increased tensile strength and decreased film thickness.

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We used functional magnetic resonance imaging (fMRI) to examine the relationship of the activation region of the cerebral cortex during mastication with the language dominant hemisphere. Twelve healthy volunteers were selected for this study. Measurements were performed on a conventional whole body 1.5 T clinical scanner using a single shot, multislice echo-planar imaging sequence. The subjects were ask to masticate on the right side, and then the left side. As well, they were instructed to perform capping tasks. Computer analysis of the fMRI was done using the SPM 99 software. The results showed that the language dominant hemisphere might influence the activation region of the sensorimotor cortex during mastication. This study was supported in part by a Grant-in-aid for Scientific Research (B) (No.14370650) from the Japan Society for the Promotion of Science.

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We evaluated the retentive force and energy of partial denture retainers using a tensile testing machine. We tested the RPI clasp, clasps with no guide plane (NP clasps), clasps with guide planes (GP clasps), the Magmax-C 600, the Magdome C, the cone crown telescope (Konus), the Bona 604, the Bona 604 A and the Rothermann. We measured the displacement before (DBP) and after (DAP) the peak retentive force, and calculated the retentive energy before (EBP) and after (EAP) the peak. The NP clasp had a larger retentive force, DBP and EBP than did the other clasps. This suggests that preparation of a guide plane reduces the load on the abutment tooth. Magnetic attachments had characteristics effective in preserving abutment teeth because of a shorter DBP and lower retentive energy. The Konus crown also had similar retentive properties, but a shorter DAP.

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We investigated the influence of the shape of the temporary anchorage device (TAD) on stress distribution in the surrounding jaw bone. We used the three-dimensional finite element method to examine four different types of TAD screws (straight, slender, short and conical). The results demonstrated that the different TAD shapes produced significant variations in stress distribution in the bone. The slender type had distinctly higher stress per unit area in the bone than did the other types, and the conical type had lower stress per unit area. Moreover, the diameter of the TAD seemed a more important factor for anchorage stability than was the total length.

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Water cooling is necessary when cutting with the Er : YAG laser. Perfluorocarbon (PFC) has also been used to increase the cutting efficiency (CE) of human bone. I investigated the influence of PFC on bovine dentin. Three types of PFC, whose boiling points were 56, 80 and 102℃, were used for cooling when cutting polished dentin. The CE, thickness of the denatured layer and bond strength of the composite resin were investigated. I also studied the effect of increased irradiation and etching by phosphoric acid. The use of PFC with boiling points of 56 and 80℃ increased CE. The lower the boiling point, the thicker the denatured layer. Although the use of PFC lowered the bond strength, additional irradiation with water cooling and etching increased it.

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We undertook three-dimensional analysis of the human face and examined the effect of oral myofunctional therapy (MFT) on the health of the face. Examinees were divided into the physical exercise group, which performed daily MFT, and a control group. The faces of subjects in the physical exercise group displayed significant changes compared with the controls from 0-6 months (p<0.05). Somatic fat content and volume decreased significantly from 0-6 months in the physical exercise group (p<0.05), even though somatic weight remained unchanged. Based on these results, we concluded that continuous MFT can result in changes to the face and body fat.

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We investigated the use of two types of digital image analysis to objectively evaluate gingival condition. Digital images were taken of gingiva using two special CCD camera systems. The subjects were requested not to brush for 7 days. Analysis of the gingival images showed that changes in the surface form and color could be objectively expressed. We found that this apparatus could be useful for the objective evaluation of gingivitis because changes could be expressed quantitatively.

View full abstract

We attempted to establish a method of animal passage for keeping the exopolysaccharide (EPS) production of Prevotella nigrescens strain 22 at high levels, and examined the protein expression patterns before and after animal passage by 2-D electrophoresis. The EPS production of strain 22 increased and the mesh-like structures around the cells became denser after animal passage. N-terminal sequence analysis of protein revealed that the expression of a few heat shock protein homologs were up-regulated in response to the stress of animal passage, suggesting the relation between a regulatory pathway of EPS production in Prevotella nigrescens with a heat shock response.

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We investigated the effect of photocatalytic reactions of titanium dioxide finepowder on rat tongue carcinoma cells induced by 4-nitroquinoline 1-oxide. Three types of titanium dioxide finepowder, anatase type ST-41, rutile type TP-3 and mixed type P-25, were added separately to culture fluid and were cultured for 48 hours. Each mixture was then exposed to 254 nm ultraviolet light. The cell survival rate was decreased in the cells cultured with any type of titanium dioxide finepowder, and the decrease was marked in the cells cultured with ST-41. Furthermore, the cell survival rate was decreased in correlation with irradiation time and concentration in the ST-41 group. We found an apoptosis ladder pattern which suggests that the apoptosis was concerned with the mechanism of cultured cell kill. These findings indicate that the photocatalytic reactions of ST-41 titanium dioxide finepowder may develop a new modality for cancer treatment.

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I examined the β-lactamase gene of Prevotella intermedia (P. intermedia) in order to better understand the β-lactam-resistance mechanism. The polymerase chain reaction (PCR) performed on β-lactam-resistant P. intermedia gave a product the same size as one previously reported, as well as another product not previously observed. The PCR products of the CfxA 2 and CfxA 3 β-lactamase gene primers were amplified into products that had high homogeneity with the CfxA 2 and CfxA 3 β-lactamase genes. These results suggest that β-lactam-resistant β-lactamase producers have genes that resemble the CfxA 2 and CfxA 3 genes, and that these genes are seen throughout the strain. However, Escherichia. coli transformed by the PCR product did not show resistance to β-lactams. This may be the result of inactivation by mutation of a sequence, or the existence of a specific phenotype.

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