We investigated the effect of dental metals on cells from the perspective of genotoxicity. We did chromosome aberration tests, which are one of the main genotoxicity tests, using extracts of seven metals commonly used during dental treatment. The metal extracts were used in chromosome aberration tests and MTT assay, which used cultures of Syrian hamster embryo cells. Hg induced various chromosome aberrations and reduced cell viability below 20% at 69.81μM. Cu also induced chromosome aberrations and reduced cell viability below 60% at 900μM. Ag induced various chromosome aberrations at 150μM and cell viability at that level was about 50%. Ni and Co did not induce chromosome aberrations, but yielded few metaphases at concentrations that decreased cell viability to about 60%. Two other metals, Cr and Ti did not induce chromosome aberrations or cytotoxicity. Although these results are from in vitro experiments, they are considered important indicators of the effects these materials might produce in the oral cavity during clinical use.

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The paracellular pathway is a dynamic and a highly regulated transport route of salivary gland acinar secretion. In this study, the relationship between paracellular permeability and cytoskeletal proteins was investigated in order to clarify the nature of the sealing mechanism of the tight junction in mouse submandibular gland acini. Male Sic: ddy mice, weighing 60-70 g were used. Tight junctions were found impermeable to microperoxidase in the control gland. However, at 3 min after carbachol administration, tight junctions become permeable. In control acini, the tight junction protein, ZO-1 was highly concentrated at the luminal site of cytoplasm in company with occludin which was also found at the tight junction region. The distribution pattern of E-cadherin coincided completely with that of both β-catenin and vinculin. Cytoplasmic aggregates of F-actin were seen and were colocalized with both ZO-1 and vinculin. In the carbachol administered gland, expression of ZO-1 was expanded, not only to the tight junctional region, but also lateral membranes. The staining pattern of E-cadherin was not jagged or discontinuous as was the pattern observed for vinculin. Results indicate that secretory stimulation leads to alteration in the architecture of the adherens junction. Thus the adherens junction may well represent an intermediate link in the signaling pathway to the tight junction via the cytoskelton.

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I investigated changes in mandibular movement and tooth position caused by mandibular lip bumper treatment. Ten patients who received lip bumper therapy were studied. Study models, cephalograms, and records of mandibular movement were taken prior to and 6 months after lip bumper treatment. The incisal point was used as the analyzing point of mandibular movements. The analyzing points from the intercuspal position (ICP) to 0.5 mm opening level were calculated on closing path during the occlusal phase of mastication. A line from ICP to 0.5 mm opening level points, projected on each reference plane (coronal plane, horizontal plane and sagittal plane) and each projection angle (coronal plane projection angle, horizontal plane projection angle and sagittal plane projection angle) were calculated. Changes for the dental measurement items and for each projection angle before and after treatment were compared using the paired t-tests.
The relations between these changes were evaluated by Pearson's correlation analysis. All measured items for the dentition increased significantly in all cases after 6 months of lip bumper treatment. I also found a significant relationship between changes in arch width and the frontal and horizontal projection angle. This study showed that with lip bumper treatment, changes in arch development, especially arch width, resulted in masticatory movement changes in the lateral dimension.

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We investigated the expression of cytokeratin (CK) in the Vitamin A-deficient rat sublingual gland using biochemical and immunohistochemical techniques. We found that rats with vitamin A deficiency had decreased body weights. In addition, compared with the controls, the wet and dry weights of their sublingual glands and their serum retinol binding ing protein were decreased. Histological examination revealed an increase in the stratifing two-cell layer structure in the excretory duct of experimental group. Proteins were extracted from controls and vitamin A-deficient rats, and the expression of CK 5, 8, 10, 14, 17, 18 and 19 was evaluated using Western blotting and two-dimensional electrophoresis Two-dimensional electrophoresis profiles showed a marked increase in the expression of CK 10 and 14 in the vitamin A-deficient rats compared with the controls, and the expression of CK 8 was, conversely, lower than in the controls. In addition, stronger immunohistochemical CK reactions were observed in the sublingual glands of vitamin A-deficient rats.
These experiments demonstrated that CK expression was more pronounced in vitamin A-deficient rats than in normal ones.

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We evaluated the effect of sevoflurane anesthesia on cerebral autoregulation using a model of acute-phase infarction (within 48 hours after onset) induced by middle cerebral artery (MCA) occlusion in rats. The capacity for cerebral autoregulation, as assessed by the relative slope ratio (RS) between mean arterial pressure (MAP) and regional cerebral blood flow of the cortex, was evaluated in exsanguinated rats (Group I), rats under deep anesthesia with sevoflurane (Group II) and rats with MCA infarction under deep anesthesia with sevoflurane (Group III). Although the animals in Groups I and II exhibited similar RS values between 50 and 110 mmHg MAP, the values in Group III were higher than those in the other two groups (p<0.01). The changing point of RS, which represents the lower limit of autoregulation, was 50 mmHg in Group I and 40 mmHg in Group II, while in Group III no such changing point was noted and the slope was constant throughout the MAP range evaluated. These findings suggest that cerebral autoregulation deteriorates during the acute phase of cerebral ischemia.

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Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are often used for treatment of tissue defects. We investigated the ability of lyophilized periosteum (Dura Mater: DM) to induce GBR when combined with growth factors and when used alone. Three types of DM complexes were prepared: DM alone, DM with rhBMP-2, and DM with purified bovine TGF-β. Three experiments were performed: 1) periodontal ligament fibro- blasts (PDLs) were co-cultured with the three DM complexes and observed; 2) new-born mice muscle tissues were co-cultured with the three complexes, removed at 5, 7 and 10 days, and the samples embedded in paraffin, cut and stained with hematoxylin eosin (HE); 3) the three complexes were implanted in the thigh muscle pouches of mice, removed at 5, 7 and 10 days, embedded in paraffin, cut and stained with HE. We found that in experiment 1) almost all of the cells were dead after 5 days of co-culture. In experiment 2) chondroid tissue was found in the group with rhBMP-2 and bone or a cartilage-like matrix was found in the group with TGF-β. There were no such changes in the group with DM alone. In experiment 3) no bone or cartilage-like tissue/matrix was detected, although densely aggregated inflammatory cells surrounded the implants. We concluded that DM may have some cytotoxic effects on the host tissues resulting from immunologic rejection and low histo-compatibility. Immunoreaction of the host tissue to DM may have negative effects on the ability of DM and DM complexes to regenerate bone.

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Because the retentional lattice form is a factor in the deformation and fit of commercial pure(CP)titanium cast plates, we performed experiments to evaluate six forms (the mesh, ladder, and non-perforated types, each with the outline within or beyond the alveolar crest). Although dimensional changes were significantly smaller for the non-perforated type than for the mesh or ladder types, they were similar for the two latter types. We also found that, dimensional changes for the outline within the alveolar crest were significantly greater than for those beyond the alveolar crest. Dimensional changes were significantly smaller in the vertical direction than in the horizontal direction for all forms. Although the amount of elevation(discrepancy)in the palatal posterior margin was greatest for the mesh type irrespective of the position of the lattice outline, it was very little for the non-perforated and ladder types.
These results suggest that the ladder type, retentional lattice form with its outline within the alveolar crest is the most appropriate for CP titanium cast plates.

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