Prevotella nigrescens, a Gram-negative black-pigmented anaerobic rod, is frequently isolated from periodontitis and periapical lesions. We characterized the chemical structure of purified exopolysaccharide (EPS) from clinicaliy-isolated EPS-producing P. nigrescens, strain 22, by methylation analysis. The results indicated that EPS has a highly branched structure and that linkages of mannose are mainly (1→2, 1→6), (1→2), (1→6), and (1→3). In addition, we studied the biological effects of EPS on abscess formation in mice and on the phagocytosis of peripheral blood polymorphonuclear leukocytes using strain 22, heat-killed strain 22, and a non-EPS-producing mutant, strain 328.
Although strain 22 and its heat-killed counterpart induced large abscesses in mice, strain 328 did not. Moreover, strain 328 recovered the ability of abscess formation by adding EPS purified from strain 22. EPS also exhibited anti-phagocytic activity in vitro. These results suggest that one of the functions of EPS produced by strain 22 is to protect the bacteria from the phagocytotic system in order to ensure a longer survival of the organism in the host.

View full abstract

We previously reported that the thickness of the reactive layer of commercially pure (CP) titanium castings could be decreased by using a sintering mold of phosphate-bonded investment that becomes vitreous on the surface when fired at a high temperature (1400℃). During this process Al₂TiO₅ is important in sintering. We fabricated phosphate-bonded investments containing three types of glass having different softening points to reduce the sintering temperature. Moreover, we also fabricated investment containing Al₂TiO₅ as a control. We evaluated the physical properties of the experimental investment and the reactive layers on the CP titanium castings that were produced with the experimental investments. Firing temperature conditions were 800, 900, 1000, 1100 and 1200℃.
In the control, compressive strength was increased significantly at 1100℃ and the thickness of the reactive layer was reduced at 1200℃. In the investment containing low softening point glass, compressive strength was increased significantly at 1000℃ and the thickness of the reactive layer was reduced at 1100℃. We found that the reactive layer on the casting could be reduced by using a phosphate-bonded investment with a low softening point that was sintered at a low temperature.

View full abstract

We obtained epithelial cells by cloning cells from the tongue mucosa of rats that were given 4-nitroquinoline 1-oxide for 4 weeks. After repeating the subculture 20 times, we transplanted the cells in subcutaneous tissue of nude mice. Firm tumors were formed, which histologically developed into squamous cell carcinoma. We observed telomerase activity. Telomerase reverse transcriptase (TERT), telomerase-associated protein 1 (TEP 1), c-Myc, p 16 and p53 expressed in these cells during the process of carcinogenesis in vitro. We also examined β-galuctosidase expression for cellular senescence.
We found an increase in telomerase activity and in the expression of TERT in the mRNA. The expression of TEP 1 remained stable regardless of passage. Although the expression of subculture p 16 and p53 also increased, a sharp decrease of p 16 was observed at passage 20. The expression of c-Myc increased at passage 8 and remained stable until passage 20. Although β-galuctosidase expression was strong in the control cells, it was not observed at all in the stimulated cells.
We concluded that the increase in telomerase activity and the decrease in p 16, which affects cellular senescence, were closely related to carcinogenesis in these cells.

View full abstract

We compared the histological effectiveness of treatment by platelet-rich plasma (PRP) and enamel matrix derivative (EMD) on rat periodontal defects. Palatal dehiscence defects were surgically created on the bilateral maxillary first molars in fifty rats. PRP was derived from allogenic blood and Emdogain^<[○!R]>-gel was used as EMD. Atelocollagen was used as a carrier for both. Both sides of the periodontal defects were filled with atelocollagen containing PRP (PRP group) or with atelocollagen containing EMD (EMD group). Moreover, both sides of the periodontal defects were filled only with atelocollagen in the atelocollagen control (AC) group. Five rats in each group were euthanized 2, 4 and 8 weeks after surgery. Histological analysis and histomorphometric measurements were then performed. Two and eight weeks after surgery, the rate of bone regeneration was greatest in the PRP group, and there were statistically significant differences between the PRP and EMD groups. Four and eight weeks after surgery, the rate of new cementum formation was largest in the EMD group, and there were statistically significant differences between the PRP and EMD groups. The results suggest that implanting PRP in periodontal defects significantly promotes bone regeneration. However the effect of PRP on the formation of new cementum was inferior to that of EMD.

View full abstract

We examined nose respiratory movements during swallowing and evaluated the usefulness of measuring these movements as a method of clinical examination in comparison with other conventional methods. Using a differential pressure-type air flowmeter, we determined nose respiratory movements in normal subjects. In addition, we measured EMG activity of the geniohyoid muscle, as well as laryngeal, thorax and abdomen vallum motions. We also examined the reliability of current differential pressure-type air flowmeters used for measuring nose respiratory movements. Our results showed that the dispersion was smaller for the time used for arrest of nose respiration than was that of other parameters (p<0.01). With an optimal volume for swallowing (20 mL), we found that nose respiration was arrested to retard the onset of electromyogram activity and the onset of laryngeal motion. It was initiated later than the offset of EMG activity and earlier than the offset of laryngeal motion (p<0.01). However, the results were different when swallowing volume exceeded 20 mL. These findings indicate that the current method of determining nose respiratory movements is more accurate and easier to use than other measuring devices, and is useful for clinical examinations of swallowing.

View full abstract

In order to examine changes in occlusion affect mandibular condylar cartilage, we studied the molecular biochemistry of proteoglycan changes that molar extraction induced in rat mandibular condylar cartilage. We removed all the left maxillary molars in eight-week-old male rat. Five weeks later proteoglycans were extracted from cartilage samples taken from the mandibular condyle. Analysis of the cartilage conducted by the western blotting method revealed the existence of the proteoglycans, aggrecan, decorin and fibromodulin as expected. We determined the amount of proteoglycan mRNA using the real-time PCR method. We found that there was a pronounced increase in all of the molecules on the side where the molars had been extracted. These results suggest that changes in occlusion accelerate the production of proteoglycans in mandibular condylar cartilage.

View full abstract

There are several varieties of mandibular shift. We attempted to classify mandibular shift cases that had mandibular protrusion, using frontal cephalograms and plaster models of the dentition. We measured indexes on cephalograms and oral models, and applied cluster analysis and statistical correlation. We found four groups of mandibular protrusion cases with mandibular shift, and applied correlation analysis to each group. Classified groups are fllowing. Group 1 is that Menton related with the position of the maxillary molars. Group 2 is that Menton related with few measurement index. Group 3 is that Menton related with AG line angle and Mo line angle. Group 4 is that Menton related with AG line angle. And AG line angle related with Zyg line angle, MX line angle, Cd line angle. We found that cases with mandibular shift could be categorized by cluster analysis and correlation analysis.

View full abstract

Osteoarthritis (OA) is a chronic disease that causes degeneration and loss of articular cartilage. Because the relative balance of matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) is thought to trigger OA, even slight deviations in gene expression can contribute to its progression. However, molecular biological techniques have not yet been able to demonstrate the relationship of OA with MMP-3 and TIMP-2 in the temporomandibular joint (TMJ). We used these techniques to investigate the expression pattern of MMP-3 and TIMP-2 during disease progression in the TMJ of male Institute for Cancer Research (ICR) mice, which are models for osteoarthritis. In addition, we observed the ets-1 gene, which is a transcription factor of MMP-3. The expression of MMP-3, TIMP-2 and ets-1 in the TMJ of ICR mice was examined using reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR. TIMP-2 disappeared in the cartilage as the disease developed, while MMP-3 and ets-1 increased. In contrast, RT-PCR and real-time PCR showed that levels of MMP-3, TIMP-2 and ets-1 increased in the synovium and disc. These results suggest that the balance between MMP-3 and TIMP-2 is disrupted in the osteoarthritic cartilage, and that this may trigger progressive osteoarthritis. Ets-1 expression may also play an important role in development of OA.

View full abstract

We did electrophysiological, histological and immnohistochemical investigations of the regenerative process of cat inferior alveolar nerves that had been severed and reconnected with a regeneration-inducing tube made primarily of pig skin collagen. Histological results showed that the nerve had regenerated by the twelfth postoperative week. Electropysiological results showed that latency of the mouth-opening reflex was not restored to the pre-surgery level after 24 weeks, although some recovery was noted in the regeneration group. Potential in the inferior alveolar nerve was evoked in the regeneration group 24 weeks after the operation. These results suggest that nerves may regenerate morphologically and functionally if a regeneration-inducing tube is placed at the time of nerve injury, and if the regeneration-inducing tube is of biologically compatible material.

View full abstract

We evaluated the tongue contacts with tooth surfaces at rest and on swallowing in patients with mandibular prognathism and in normal subjects. The tongue forces at rest and on swallowing were measured at the cervix and near the edge of the lingual surface on the maxillary and mandibular left central incisors, and on the left first molars. The maximum force and time quadrature of the force on swallowing were recorded for all measurement points. The force at rest, maximum force, and time quadrature for mandibular prognathism patients were compared with those of normal subjects using the Student's t-test. At rest the tongue forces on the cervix and near the edge of the mandibular left central incisors in mandibular prognathism patients were larger than in the normal subjects. On swallowing, forces of all measurement items on the cervix of the mandibular first molars were larger in the mandibular prognathism patients, while those on the cervix of the maxillary central incisors were smaller. These results suggest that the tongue position of the mandibular prognathism patient is lower at rest and during swallowing.

View full abstract

Receptor activator of NF-κB ligand (RANKL) is necessary for osteoclast formation. 1,25-dihydroxyvitamin D_3 (1,25-(OH)_2D_3) induces RANKL expression in osteoblast cells. It has been reported that protein kinase C (PKC) mediates RANKL expression induced by PMA. However, details of the role of PKC isozymes in RANKL expression are not clear. In order to clarify the involvement of PKC isozymes, we investigated the effect of various PKC inhibitors on RANKL expression induced by 1,25-(OH)_2D_3 in the bone marrow derived stromal cell line ST 2. Rottlerin, which inhibits PKC-δ specifically, was used to determine the function of PKC-δ on RANKL expression. Although rottlerin decreased 1,25-(OH)_2D_3 induced RANKL expression in ST 2, staurosporine, which is a nonspecific PKC inhibitor, did not decrease the expression. These results indicate that PKC-δ may be involved in 1,25-(OH)_2D_3-induced RANKL expression.

View full abstract

We investigated the test-retest reliability of two time measurements from the T-Scan II, which is an occlusal examination device. Occlusion time (OT) is the time required for 90% completion of maximum intercuspation, and disclusion time (DT) is the time from the intercuspal position to the completion of mandibular lateral excursion. The Bland-Altman method (the mean difference between measures (MD) and the 95% limit of agreement), and the intraclass correlation coefficient (ICC) with its 95% confidence interval were calculated for the two time parameters. The reliability for OT was high for same-day measurements and for different-day measurements, with the ICCs being above 0.8. When the Bland-Altman test was applied to measurements of OT, the MD was between -0.023 and 0.025 sec, and the 95% limit of agreement was between -0.096 and 0.100 sec for day one, between -0.114 and 0.067 sec for day two, and between -0.086 to 0.136 sec for measurements made on different days. The reliability for same-day and different day measurements of DT was low, with the ICCs being near 0.50. When the Bland-Altman test was applied to measurement of DT, the MD was between -0.015 and 0.018 sec, and the 95% limit of agreement was between -0.204 and 0.223 sec for day one, between -0.166 and 0.135 sec for day two, and between -0.184 and 0.219 sec for measurements made on different days. A more standardized protocol is needed for DT to produce reliable time analyses for lateral excursion using the T-ScanⅡ.

View full abstract

Using videofluoroscopic examination of swallowing, we investigated the effect of occlusal support on dysphagia and how it might be used to treat this dysfunction. We examined the relationship between dysphagia and sex, age, disease, period between diagnosis and hospitalization, degree of independence in daily life, rehabilitation period, number of remaining teeth, Eichner classification, and dental treatment. There was no correlation between dysphagia and any of the nine items. Patients whose dysphagia improved, showed improvement in the anticipatory and preparatory stages. Dysphagia improved in patients with a greater number of remaining teeth, in those with better occlusal support, and in those who had missing teeth replaced with fixed and removable dentures. We concluded that dentists should take an active role in treating dysphagia.

View full abstract

We compared the histological effectiveness of treatment by platelet-rich plasma (PRP) and enamel matrix derivative (EMD) on rat periodontal defects. Palatal dehiscence defects were surgically created on the bilateral maxillary first molars. Both sides of the periodontal defects were filled with atelocollagen containing PRP (PRP group) or with atelocollagen containing EMD (EMD group). Five rats in each group were euthanized 2, 4 and 8 weeks after surgery. The results suggested that implanting PRP in periodontal defects significantly promoted bone regeneration. However, the effect of PRP on the formation of new cementum was inferior to that of EMD.

View full abstract

We examined the effectiveness of various breath freshers, including 6 tablets, 4 sprays and 3 rinses, on 12 periodontal patients who were subjectively judged to have bad breath. Changes in breath ammonia were examined after administration of the breath fresheners. The tablets markedly lowered the ammonia for 30 minutes after administration, although their effectiveness then tended to decrease over time. The four sprays lowered the ammonia immediately after application, although it returned to its original value in about one or two hours. The three rinses lowered the ammonia immediately, although it returned to its original value after one hour.

View full abstract

We investigated the effect of the occlusal splint on motor evoked potentials (MEPs) of fatigued masseter muscles using transcranial magnetic stimulation (IMS). We compared the root MEPs (R-MEPs) and the cortex MEPs (C-MEPs) in 10 volunteers who performed continuous voluntary contractions without the splint, with a 2.0-mm splint, and with a 10-mm splint. The amplitude of both the MEPs was significantly decreased under all conditions. The ratio between the amplitude of the C-MEPs and that of the R-MEPs was significantly decreased without the splint. There were no changes in the other conditions. These findings indicated that the occlusal splint reduced reflex inhibition of peripheral feedback to the masseter muscle motor neurons during fatigue.

View full abstract

Using videofluoroscopic examination of swallowing, we investigated the effect of occlusal support on dysphagia and how it might be used to treat this dysfunction. We examined the relationship between dysphagia and sex, age, disease, period between diagnosis and hospitalization, degree of independence in daily life, rehabilitation period, number of remaining teeth, Eichner classification, and dental treatment. There was no correlation between dysphagia and any of the nine items. Patients whose dysphagia improved, showed improvement in the anticipatory and preparatory stages. Dysphagia improved in patients with a greater number of remaining teeth, in those with better occlusal support, and in those who had missing teeth replaced with fixed and removable dentures. We concluded that dentists should take an active role in treating dysphagia.

View full abstract

We previously reported that the thickness of the undesirable reactive layer of commercially pure (CP) titanium castings can be decreased by using a sintering mold of phosphate-bonded investment that becomes vitreous on the surface when fired at a high temperature (1400°C) . We used phosphate-bonded investments with various types of glass having different softening points to reduce the sintering temperature, and evaluated the reactive layers on the CP titanium castings that were produced. We found that the reactive layer on the casting could be reduced by using an investment with low softening point glass that was sintered at a low temperature.

View full abstract

I evaluated the effect of fluoride-releasing restoratives on caries prevention by measuring the amount of decalcified calcium ions dissolved from dentin that had been soaked in acetate buffer solution. The dentin was exposed to one of the following four conditions. 1) It was immersed in distilled water for 24 hrs. 2) It was immersed in an aqueous solution of NaF (fluoride concentration 10 ppm) for 24 hrs. 3) It was bonded to one of three types of fluoride-releasing restoratives. 4) It was bonded to a non fluoride-releasing restorative. The amount of decalcified calcium ions was significantly less from the dentin bonded to fluoride releasing restoratives. These results indicated that the decrease in demineralization could be attributed to the fluoride ions that leached into the solution around the dentin.

View full abstract

Although the Er: YAG laser has been shown to effectively remove dental hard tissues, reports have indicated that laser-irradiation markedly decreases the bond strength (BS) of composite resin to dentin. I investigated the effect of fluoride and glutaraldehyde on the BS of laser-irradiated dentin. NaF and APF were used as the fluorides, and aqueous solutions of 2, 5 and 1096 glutaraldehyde were employed. Laser irradiated dentin (LID) was prepared by irradiating polished human dentin at 100mJ and 10pps, followed by application of fluoride or glutaraldehyde. Clearfil AP-X (Kuraray, Japan) composite resin was bonded to the LID with Clearfil Mega Bond (Kuraray, Japan) and the BS was measured. Statistical analysis indicated that application of NaF or glutaraldehyde at 5 or 1096 significantly increased the BS to the laser-irradiated dentin.

View full abstract

We electrophysiologically and histologically investigated the regenerative process of cat inferior alveolar nerves which had been severed and reconnected with a regeneration-inducing tube made primarily of pig skin collagen. Histological results showed that the nerve had regenerated by the third postoperative month. Although latency of the mouth-opening reflex was not restored to the pre-surgery level after 6 months, some recovery was noted. These results suggest that nerves may regenerate morphologically and functionally if a regeneration-inducing tube is placed at the time of nerve injury.

View full abstract

We obtained epithelial cells from the tongue of rats treated with 4-nitroquinoline 1-oxide and transplanted cells that had been subcultured 20 times in the subcutaneous tissue of nude mice. A firm tumor was formed, that was histologically confirmed to be squamous cell carcinoma. We observed telomerase activity, TERT, c-Myc, p 16, and p 53 expression in these cells during the process of carcinogenesis. We also examined β-galactosidase expression. The results showed that telomerase activity and expression of TERT mRNA increased with the number of subcultures. Although p 16 expression also increased, a sharp decrease was obsearved after 20 subcultures. While the control cells showed strong β-galactosidase expression, this was not observed in all cells. We concluded that carcinogenesis had a direct effect on the increase in telomerase activitv and on the decrease in cellular senescence caused by p 16.

View full abstract

I analyzed the movement of the human maxillary first molar caused by orthodontic force. A three-dimensional finite element model of the tooth and surrounding alveolar bone was used to perform the linear static finite element analysis. I measured the stress distribution of the alveolar bone to analyze moments in the maxillary first molar. The results showed that the direction of the force on the tooth was different from the direction of movement.

View full abstract

Receptor activator of NF-KB ligand (RANKL) is necessary for osteoclast formation. 1,25-dihydroxyvitamin D_3 (1,25-(OH)_2D_3) induces RANKL expression in osteoblast cells. It has been reported that protein kinase C (PKC) mediates RANKL expression induced by PMA. However, details of the role of PKC isozymes in RANKL expression are not clear. In order to clarify the involvement of PKC isozymes, we investigated the effect of various PKC inhibitors on RANKL expression induced by 1,25-(OH)_2D_3 in the bone marrow derived stromal cell line ST 2. Rottlerin, which inhibits PKC-δ specifically, was used to determine the function of PKC-δ on RANKL expression. Although rottlerin decreased 1,25-(OH)_2D_3 induced RANKL expression in ST 2, staurosporine, which is a nonspecific PKC inhibitor, did not. These results indicate that PKC-δ may be involved in 1,25-(OH)_2D_3-induced RANKL expression.

View full abstract