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Biomedical subjects

D Kawahara

Publications and source records attributed to D Kawahara.

14 recordsLinked to original sources
PubMed2006

Electron microscopic investigation on the osteogenesis at titanium implant/bone marrow interface under masticatory loading.

Electron microscopic investigation on osteogenetic process at the implant surface of threadless rod-type titanium implants with different surface roughness of Ra 0.4 +/- 0.01 microm, Sm 2.6 +/- 0.3 microm and Ra 2.0 +/- 0.12 microm, Sm 36 +/- 9.1 microm was performed at the early stage of 21 and 42 days post implantation into the jawbones of four beagles under the load bearing condition of functional mastication. The implant surfaces were covered with a blood clot and haematopoietic stem cells (HSC) including phagocytic monocytes immediately after the implantation. Successively, osteogenic stem cells (OSC) migrated from cortical and/or trabecular endosteum to the HSC-layer on the implant surface. The new bone formation at the implant/bone marrow interface was developed by collaboration of osteomediator cells (OMC) differentiated from monocytes of HSC and osteoblast phenotype cells of OSC derived from endosteum of cortical bone and/or trabecular. The new bone layer at the implant surface consisted of two layers, solution-mediated calcification layer of pseudo bone and cell (osteoblast) -mediated calcification layer of true bone. The pseudo bone was produced by solution-mediated calcification of OMC- and HSC-remnants near by the implant surface. The bone healing process at the implant/bone marrow interface depended upon two factors; the migration of OSC from cortical and/or trabecular endosteum to the implant surface and the healing potentiality. Topographic dependency upon the bone healing potential at implant/bone marrow interface was not confirmed in this experiment under the load bearing condition of functional mastication.

Animals↗
PubMed2006

No evidence to indicate topographic dependency on bone formation around cp titanium implants under masticatory loading.

In vitro studies have proved the topographic dependency upon osteogenesis on titanium plate by investigating the cell-adhesion, -shape, -proliferation, -differentiation, ALP activity and osteocalcin production of osteogenic stem cells, MG36, MC3T3-E1 and wild strains of bone formative cells from animal and human. However, this in vivo study on bone growth around cp titanium dental implants under masticatory loading did not demonstrate significant difference among the different surface roughness in the range of Ra 0.4-1.9 microm, Rz 2.8-11.2 microm, Rmax 3.6-28.1 microm and Sm 2.9-41.0 microm, which was estimated by measuring the bone contacts, bone occupancies and bone bonding strengths at the implant/bone marrow interface. It is revealed that the topographic dependency on the osteogenetic activity is apt to be covered with wide variation in bone healing potential under the clinical condition with functional biting load.

Animals↗
PubMed2004

In vitro study on bone formation and surface topography from the standpoint of biomechanics.

Effect of surface topography upon cell-adhesion, -orientation and -differentiation was investigated by in vitro study on cellular responses to titanium substratum with different surface roughness. Cell-shape, -function and -differentiation depending upon the surface topography were clarified by use of bone formative group cells (BFGCs) derived from bone marrow of beagle's femur. BFGCs consisted of hematopoietic stem cells (HSC) and osteogenetic stem cells (OSC). Cell differentiation of BFGCs was expressed and promoted by structural changes of cytoskeleton, and cell-organella, which was caused by mechanical stress with cytoplasmic stretching of cell adhesions to the substratum. Phagocytic monocytes of HSC differentiated to osteomediator cells (OMC) by cytoplasmic stretching with cell adhesion to the substratum. The OMC mediated and promoted cell differentiation from OSC to osteoblast through osteoblastic phenotype cell (OBC) by cell-aggregation of nodules with "pile up" phenomenon of OBC onto OMC. The osteogenesis might be performed by coupling work of both cells, OMC originated from monocyte of HSC and OBC originated from OSC, which were explained by SEM, TEM and fluorescent probe investigation on BFGCs on the test plate of cp titanium plates with different topographies. This osteogenetic process was proved by investigating cell proliferation, DNA contents, cell-adhesion, alkaline phosphatase activity and osteocalcine productivity for cells on the titanium plates with different topographies. The study showed increased osteogenic effects for cells cultured on Ti with increased surface roughness. Possible mechanisms were discussed from a biomechanical perspective.

Animals↗
PubMed1989

[Usefulness of collagen gel matrix culture for biological evaluation of dental materials (in vitro)].

Cytotoxicity of zinc oxide-eugenol cement was investigated using collagen gel matrix culture. Diffusibility of the main components into the collagen gel was measured by either atomic absorption or ultraviolet spectroscopy. The agar overlay culture method was also carried out for comparison. Results from solution cultures containing diluted collagen were similar to those with diluted agar. Longer culture with either cement liquid, eugenol, or zinc chloride solution, resulted in more depressed cell growth. The lower the powder/liquid ratio for mixing, the higher the cytotoxicity for all the materials tested in gelled collagen. Also, cytotoxicity levels were always lower in cultures with collagen than in those with agar. Diffusibility of the materials into collagen gel was similar to that into agar, but the of diffused components in collagen gel was less. Thus, the usefulness of collagen gel matrix culture for biological evaluation of dental materials was equivalent to that of agar overlay culture. However, it is suggested that collagen as a tissue matrix might provide a favorable environment for cell culture, and hence allow biocompatibility testing of biomaterials under simulated conditions.

Agar↗
PubMed1984

Ice cream in the diet of insulin-dependent diabetic patients.

We investigated the effect of ice cream ingestion on blood glucose control in conventionally treated and intensively treated insulin-dependent (type I) diabetic patients. After the ingestion of 100 g of ice cream, plasma glucose excursions as measured by the peak increment (90 +/- 30 mg/dL) and area under the curve (166 +/- 59 mg/dL X hour) were modest and not significantly different between the subgroups of intensively treated and conventionally treated diabetics. A small dose (3 to 5 units) of rapid-acting insulin given 30 minutes before ingestion of ice cream reduced the modest plasma glucose excursion. A modest amount of ice cream may be included in weight-maintaining diets of insulin-dependent diabetics. Small doses of rapid-acting insulin prevent any adverse effect of the ice cream on blood glucose control.

Adult↗
PubMedDate not supplied

Surface characterization of radio-frequency glow discharged and autoclaved titanium surfaces.

To characterize titanium surfaces treated with radio-frequency glow discharge (RFGD) after media exposure, surface chemical analyses were performed using x-ray photoelectron spectroscopy. Auger electron spectroscopy, and Fourier transform infrared-reflection absorption spectroscopy (FTIR-RAS). The RFGD treatments resulted in a cleaner surface as compared to as-sputtered or as-autoclaved titanium specimens. The oxide thickness of RFGD-treated titanium specimens was not statistically different from the as-autoclaved and as-sputter cleaned titanium specimens. Exposure to a phosphate-buffered saline solution revealed a greater deposition of calcium and phosphorous on the RFGD-treated surfaces. Auger electron spectroscopy depth profiles showed that calcium and phosphorous ions diffused into the titanium oxide layer. The calcium and phosphorous deposits were identified as amorphous calcium phosphate compounds using FTIR-RAS. These results suggest that RFGD treatments of titanium enhance calcium and/or phosphate affinity because of an increase in elemental interactions at the surface, thereby resulting in the formation of amorphous calcium phosphate compounds.

Buffers↗
PubMedDate not supplied

Morphologic studies on the biologic seal of titanium dental implants. Report I. In vitro study on the epithelialization mechanism around the dental implant.

To propose a mechanism for apical epithelialization at the implant-tissue interface, cell contact to titanium surfaces and adhesive strength of epithelial-like (HGE) and fibroblastic (HGF) cells derived from human gingiva were investigated under three different media conditions containing plaque extracts: nonfiltered, 5-micron pore filtered, and 0.22-micron pore filtered. The plaque extracts had a greater effect in decreasing the growth rate of the HGF than of the HGE. Similarly, the HGE exhibited greater adhesive strength than the HGF. These differences in the cells' resistance to plaque extracts were also observed using light and electron microscopy. Evidence from this study suggests that the difference in growth, contact, and adhesive strength of the HGE and HGF cells to titanium surfaces may promote apical epithelialization under the pathologic condition.

Adult↗
PubMedDate not supplied

Morphologic studies on the biologic seal of titanium dental implants. Report II. In vivo study on the defending mechanism of epithelial adhesions/attachment against invasive factors.

Clinical measurements on gingival indices and morphologic observations were performed in this study to verify the defending mechanism of gingival soft tissue against foreign invasions from the perspective of epithelial adhesion/attachment to implant surfaces in the monkey mandible. The following zones were observed using scanning electron microscopy: (1) plaque zone, suggesting susceptibility of the gingival tissue to bacterial invasion; (2) nude zone, demonstrating indirect adhesion of epithelial cells to the implant surface through the mucous layer and preventing bacterial invasion; and (3) epithelial cell attached zone, having greater bond strength of epithelial cells at the cell-implant interface as compared to cell-cell bonding within the epithelial cell layer. This study suggested that epithelial cell attachment/adhesion may play a dominant role in retaining the successful condition of a dental implant.

Animals↗