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Biomedical subjects

T Kitsugi

Publications and source records attributed to T Kitsugi.

At least 37 records · Page 2Linked to original sources
PubMed1992

Influence of substituting B2O3 for CaF2 on the bonding behaviour to bone of glass-ceramics containing apatite and wollastonite.

Glass-ceramics containing crystalline oxy-fluoroapatite (Ca10(PO4)6(O,F2)) and wollastonite (CaSiO3) (designated AWGC) are reported to have a fairly high mechanical strength as well as the capability of forming a chemical bond with bone tissue. The chemical composition is MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, and CaF2 0.5 in weight ratio. In this study the influence of substituting B2O3 for CaF2 on the bonding behaviour of glass-ceramics containing apatite and wollastonite to bone tissue was investigated. Two kinds of glass-ceramics containing apatite and wollastonite were prepared. CaF2 0.5 was replaced with B2O3 at 0.5 and 2.0 in weight ratio (designated AWGC-0.5B and AWGC-2.0B). Rectangular ceramic plates (15 x 10 x 2 mm, abraded with No. 2000 alumina powder) were implanted into a rabbit tibia. The failure load, when an implant detached from the bone, or the bone itself broke, was measured. The failure load of AWGC-0.5B was 8.00 +/- 1.82 kg at 10 weeks after implantation and 8.16 +/- 1.36 kg at 25 weeks after implantation. The failure load of AWGC-2B was 8.08 +/- 1.70 kg at 10 weeks after implantation and 9.92 +/- 2.46 kg at 25 weeks after implantation. None of the loads for the two kinds of glass-ceramics decreased as time passed. Giemsa surface staining and contact microradiography revealed direct bonding between glass-ceramics and bone. SEM-EPMA showed a calcium-phosphorus rich layer (reaction zone) at the interface of ceramics and bone tissue. The thickness of the reaction zone was 10 to -15 microns and did not increase as time passed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Enhancement of bone bonding to bioactive ceramics by demineralized bone powder.

In an attempt to enhance the bonding of bone to bioactive ceramics, allogeneic demineralized bone powder (DBP) was used in combination with bioactive ceramic implants in rabbit tibiae. Rectangular plates (10 x 15 x 2 mm) made of apatite-wollastonite-containing glass ceramics were implanted in the proximal metaphyses of the bilateral tibiae of 20 rabbits, with DBP packed into the medullary cavity. In the control group, only the plates of A-W GC were implanted in the bilateral tibiae of 20 rabbits. Four rabbits from each group were killed at two, four, eight, 12, and 25 weeks after implantation for the tensile test. Results of the tensile test and histologic examination of the undecalcified specimens by Giemsa surface stain and contact microradiography confirmed that DBP significantly accelerated the process of bone bonding to the implant and increased the strength of bone-implant bonding.

Animals↗
PubMed1991

Bone bonding mechanism of beta-tricalcium phosphate.

It has been proposed that the formation of a surface apatite layer in vivo on surface active ceramics is an essential condition for chemical bonding between ceramics and bone tissue. To clarify the difference in bone-bonding mechanisms between surface active ceramics and bioresorbable ceramics, two experiments were performed using plates of dense beta-tricalcium phosphate (beta-TCP). First, plates of beta-TCP were implanted subcutaneously in rats for 8 weeks. Surface change due to bioresorption was observed with scanning electron microscopy. Formation of the apatite layer on the surface was investigated using thin-film x-ray diffraction and Fourier transform infrared reflection spectroscopy. Second, plates of beta-TCP were implanted in tibiae of rabbits for 8 and 25 weeks and subjected to the detaching test to measure bone-bonding strength. beta-TCP bonded strongly to bone. Undecalcified sections of the interface of bone and beta-TCP were examined with SEM-EPMA. However, by physicochemical methods, no formation of surface apatite layer was observed. These results suggest that beta-TCP bonds to bone through microanchoring between bone and rough surface of resorbed beta-TCP.

Animals↗
PubMed1990

Analysis of A.W glass-ceramic surface by micro-beam x-ray diffraction.

The purpose of this study is to examine the formation of hydroxyapatite on the surface of glass-ceramics (chemical composition: SiO2, 34.2; P2O5, 16.3; CaO, 44.9; MgO, 4.6; CaF2, 0.5 in weight ratio). Two experiments were performed. In the first experiment, plates (2 x 25 x 25 mm) of glass-ceramics containing apatite-wollastonite (designated A.W-GC) were used. In the second experiment, plates (15 x 10 x 2 mm) of A.W-GC and its parent glass (designated G) were used. In each experiment, two paired specimens of identical material, one tied with silk thread, the other not tied, were implanted subcutaneously into rats. In both experiments, bonding to each other of both tied and untied specimens was observed one month after implantation. A pattern resembling hydroxyapatite was identified on the detached surface of the bonded A.W-GC by micro-beam x-ray diffraction. The weak crystalline pattern was also observed on the detached surface of bonded G samples. Analysis of the interface by SEM-EPMA showed that a calcium-phosphorus rich layer formed between the two bonded surfaces in both experiments. It is suggested that the bonding between the two materials was formed by the calcium-phosphorus rich layer, and that the calcium-phosphorus rich layer is virtually identical to hydroxyapatite.

Animals↗
PubMed1990

Ca,P-rich layer formed on high-strength bioactive glass-ceramic A-W.

Glass-ceramic A-W, containing crystalline apatite and wollastonite in a MgO-CaO-SiO2 glassy matrix shows high bioactivity as well as high mechanical strength, but other ceramics containing the same kinds of crystalline phases in different glassy matrices do not show the same bioactivity. In order to investigate the bone-bonding mechanism of this type of glass-ceramic, surface structural changes of the glass-ceramics after exposure to simulated body fluid were analyzed with various techniques. A solution with ion concentrations which are almost equal to those of the human blood plasma was used as the simulated body fluid, instead of Tris-buffer solution hitherto used. For analyzing the surface structural changes, thin-film x-ray diffraction was used in addition to conventional techniques. It was found that a bioactive glass-ceramic forms a Ca, P-rich layer on its surface in the fluid but nonbioactive ones do not, and that the Ca, P-rich layer consists of carbonate-containing hydroxyapatite of small crystallites and/or defective structure. These findings were common to those of Bioglass-type glasses. So, we conclude that the essential condition for glass and glass-ceramic to bond to bone is the formation of the surface apatite layer in the body environment but it is not essential to contain apatite within the material. Bioactivity of glass and glass-ceramic can be evaluated in vitro by examining the formation of the surface apatite layer in the simulated body fluid described above.

Apatites↗
PubMed1990

Surface reactions of calcium phosphate ceramics to various solutions.

The surface reactions of calcium phosphate ceramics have been thought to play an important role in bonding with living bone. Hydroxyapatite (HA), tricalcium phosphate (TCP), and two kinds of apatite-containing glass ceramics were immersed in three types of solutions with different chemical constituents. The first solution was a physiological saline, the second contained phosphate (PO4), and the third was a balanced salt solution consisting of calcium (Ca), magnesium (Mg), and PO4. After serial incubation periods, changes in the solutions were assessed by measurement of total Ca, Mg, and PO4. The ceramic surfaces were studied using scanning electron spectroscopy, infrared reflection spectroscopy, and thin-film x-ray diffraction. The surface reactions of the ceramics were greatly affected by the chemical compositions of the surrounding media. In the complete solution with both Ca and PO4, a carbonated apatite layer was formed on the surfaces of HA, TCP, and the glass ceramics. In comparison to HA and TCP, the glass ceramics were characterized as Ca-releasing materials, the dissolved Ca creating an apatite layer on the surfaces in a few days, in conjunction with PO4 stock in the surrounding media. The immersion test with various solutions proved to be a simple and effective method of assessing surface conditions of ceramic materials.

Biocompatible Materials↗
PubMed1990

Solutions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-W.

High-strength bioactive glass-ceramic A-W was soaked in various acellular aqueous solutions different in ion concentrations and pH. After soaking for 7 and 30 days, surface structural changes of the glass-ceramic were investigated by means of Fourier transform infrared reflection spectroscopy, thin-film x-ray diffraction, and scanning electronmicroscopic observations, in comparison with in vivo surface structural changes. So-called Tris buffer solution, pure water buffered with trishydroxymethyl-aminomethane, which had been used by various workers as a "simulated body fluid," did not reproduce the in vivo surface structural changes, i.e., apatite formation on the surface. A solution, ion concentrations and pH of which are almost equal to those of the human blood plasma--i.e., Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl- 148.8, HCO3- 4.2 and PO4(2-) 1.0 mM and buffered at pH 7.25 with the trishydroxymethyl-aminomethane--most precisely reproduced in vivo surface structure change. This shows that careful selection of simulated body fluid is required for in vitro experiments. The results also support the concept that the apatite phase on the surface of glass-ceramic A-W is formed by a chemical reaction of the glass-ceramic with the Ca2+, HPO4(2-), and OH- ions in the body fluid.

Biocompatible Materials↗
PubMed1990

Replacement of the lumbar vertebrae of sheep with ceramic prostheses.

We prepared a prosthesis for the replacement of the lumbar vertebrae of sheep, using apatite- and wollastonite-containing glass-ceramic. The material is stronger than human cortical bone and has the special feature of chemical bonding to bone. Ten sheep underwent replacement of L3 and L4 vertebrae, without bone grafting. The animals were killed at intervals from three months to 27 months after operation, and the interface between the prosthesis and bone was examined radiologically, histologically and crystallographically. Bone bonding with the prosthesis had occurred in half the implants. It took at least one year for bonding to be complete, but an apatite layer on the surface of the prosthesis was observed as early as three months after the operation, suggesting the possibility of much earlier bone bonding if more rigid fixation of the prosthesis had been provided.

Animals↗
PubMed1989

Bone bonding behavior of MgO-CaO-SiO2-P2O5-CaF2 glass (mother glass of A.W-glass-ceramics).

In this study, it was found that a Ca-P layer and a Si layer were formed on the interface of the mother glass of apatite-wollastonite containing glass-ceramics (designated AW) and bone tissue. The dissolution of Si, Ca, and P from glass (MgO-CaO-SiO2-P2O5-CaF2) is necessary to form a chemical film (a Si layer and a Ca-P layer). The three kinds of glasses used were 1) a mirror surface of the mother glass (MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF 0.5 weight ratio) of AW (designated G-AW (mirror], 2) an abraded surface of G-AW (designated G-AW (#2000)), 3) a mirror surface SiO2 glass (designated G-Si, 100% SiO2). The glass plates (15 mm x 10 mm x 2 mm) were implanted into the metaphysis of tibia of mature male rabbits for 10 and 25 weeks. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a detaching test and the interface of glass/bone was observed by SEM-EPMA. Failure loads in G-Si, G-AW (mirror), and G-AW (#2000) 10 weeks after implantation were 0.18 +/- 0.24, 3.06 +/- 1.29, and 2.94 +/- 1.77 kg, respectively. Those in G-Si, G-AW (mirror), and G-AW (#2000) 25 weeks after implantation were 1.30 +/- 1.18, 3.88 +/- 1.06, and 3.55 +/- 1.51, respectively. The failure loads in G-Si vs. G-AW (mirror) and those in G-Si vs. G-AW (#2000) differed significantly (P less than 0.01). There were no significant differences in the failure load according to the surface roughness of G-AW. As shown by SEM-EPMA observation, a Si layer next to G was adjacent to a Ca-P layer next to the bone. The chemical film showed no increase in thickness as time passed. A Ca-P layer did not form on the interface of Si-G and bone.

Biocompatible Materials↗
PubMed1989

The influence of calcium phosphate ceramics and glass-ceramics on cultured cells and their surrounding media.

The cytotoxicity of hydroxyapatite (HA), tricalcium phosphate (TCP), and two types of apatite-containing glass-ceramics designated A.W-GC and A.W.CP-GC was evaluated by the direct contact method using V79 cells. Compatibility of the cells was assessed as a function of cellular attachment and subsequent growth using scanning electron microscopy. Although all of the tested materials have surfaces available for cellular attachment, cell growth was markedly inhibited by HA sintered at 600 degrees C and 900 degrees C, and slightly inhibited by HA sintered at 1200 degrees C, TCP and the glass-ceramics. In attempts to clarify the cause of this toxicity, the interactions of the ceramics with culture medium was assessed by measurement of calcium (Ca), inorganic phosphate (P), magnesium (Mg), pH and albumin content in the medium. The grade of toxicity corresponded to the degree of reduction of Ca, P, and albumin in the medium. Furthermore, surface reactions of the ceramics were demonstrated to vary in both mode and degree depending on their chemical structure and level of microporosity. Thus, the surface reactivity of ceramic materials should be always taken into account in discussing their biocompatibility in vivo.

Animals↗
PubMed1989

The bonding of glass ceramics to bone.

In this study the bonding behaviour of glass ceramics, containing apatite and wollastonite, to bone tissue is shown to vary depending on the amount of alumina they contain. We have experimented with three types of material: A.W-GC, AW-6 and AW-AL. Rectangular plates were implanted into the tibiae of rabbits. Ten weeks later a segment of bone around the plate was removed for examination, and the load of breaking by traction (failure load) was measured by an autograph. This was lowest for AW-AL and highest for A.W-GC (with AW-6 in between), and the figures differed significantly from each other (P less than 0.01). The interface was examined by a scanning electron micro-analyser and an energy dispersive X-ray micro-analyser (SEM-EPMA) and the reactive zone, the calcium-phosphorus rich layer, was assessed. Silicon and magnesium decreased, the calcium did not change, and the phosphorus increased. The reactive zone of A.W-GC was wider than that of AW-6. A Ca-P rich layer was not present between AW-AL and the bone. It is suggested that the strong bonding between glass-ceramics and bone was made through the formation of the Ca-P rich layer.

Animals↗
PubMed1989

Normal somatomedin-C activity measured by radioimmunoassay in Perthes' disease.

In recent years, the association between somatomedin and Perthes' disease has been investigated. Somatomedin activity measured by different methods (i.e., bioassay and radioreceptor assay) has generated variable results. The purpose of this study was to examine plasma somatomedin-C activity in Perthes' disease using radioimmunoassay. Somatomedin-C activity in affected boys and girls between six and 11 years of age was normal compared to the standard data on normal children. It is difficult to prove a functional pituitary somatomedin target axis. Therefore, caution is advisable before hypothesizing an etiology of Perthes' disease on the basis of results of plasma somatomedin concentration.

Child↗
PubMed1989

Bonding behavior of a glass-ceramic containing apatite and wollastonite in segmental replacement of the rabbit tibia under load-bearing conditions.

Glass-ceramic implants containing apatite and wollastonite were studied under load-bearing conditions in a segmental replacement model in the tibia of the rabbit. Alumina-ceramic implants were used as a control. A sixteen-millimeter segment of the middle of the shaft of the tibia was resected at a point distal to the junction of the tibia and the fibula. The defect was replaced by a fifteen-millimeter-long hollow, cylindrical implant that was fixed by intramedullary nailing using a Kirschner wire. Two groups of eight rabbits each (one group with a glass-ceramic implant and the other with an alumina implant) were killed twelve weeks after implantation. Two similar groups were killed twenty-five weeks after implantation. The segment of the tibia that contained the implant was excised and tension-tested. The load to failure of glass-ceramic implants containing apatite and wollastonite increased with time. The loads to failure of the glass-ceramic and alumina implants at twelve weeks after implantation were 19.8 +/- 7.06 and zero newtons, respectively. The loads to failure of glass-ceramic and alumina implants at twenty-five weeks after implantation were 126.4 +/- 32.54 and 19.6 +/- 13.92 newtons, respectively. No glass-ceramic implants broke. A calcium-phosphorus layer at the interface of the glass-ceramic and the bone was observed by scanning electron microscopy and electron-probe microanalysis. There was no interposition of soft tissue between the glass-ceramic and the bone, as observed by Giemsa surface staining.

Aluminum Oxide↗
PubMed1988

Apatite-wollastonite containing glass ceramic-fibrin mixture as a bone defect filler.

The purpose of this study was to evaluate the usefulness of a mixture of apatite-wollastonite containing glass ceramic (A-W.GC, 42-60 mesh in granule size) with fibrin as a bone defect filler. A bone defect was drilled in the proximal metaphysis of the rat tibia and was filled with (1) fibrin glue, (2) A-W.GC granules, or (3) A-W.GC-fibrin mixture. Nothing was placed in the defect of the controls. The animals were serially sacrificed until 8 weeks after the operation, and the defect site was histologically examined and histomorphometrically analyzed for quantitative evaluation of newly formed bone and blood vessels. The use of fibrin glue as the binder markedly increased the ease of handling the A-W.GC granules. In the controls, little trabecular regeneration was observed in the defect site. Early vascularization (confirmed by microangiography) increased and the repairing process was accelerated in the defects filled with fibrin. In these defects filled with A-W.GC granules, good bone formation was observed around the granules. Bone formation was accelerated in the defects filled with A-W.GC fibrin mixture. Thus, the mixture showed good osteoconductive potential as well as acceleration of the repair process. Therefore, A-W.GC-fibrin mixture is considered to be a useful bone defect filler.

Animals↗
PubMed1988

Strength of bonding between A-W glass-ceramic and the surface of bone cortex.

We examined the bonding strength of apatite- and wollastonite-containing glass-ceramics (A-W.GC) to the surface of bone cortex. Semi-column-shaped blocks of A-W.GC were fixed with screws on the surface of the tibiae of rabbits. The blocks of alumina-ceramic were used as the control. The load required to detach the implant from the surface of bone cortex was measured 2, 4, 8, and 25 weeks after the implantation. The bonding strength between A-W.GC and the surface of bone cortex increased with time. It increased remarkably 4 weeks after the implantation, suggesting that the chemical bonding advanced rapidly between 2 and 4 weeks after the implantation. The tensile strength of bonding reached a maximum of 15.1 +/- 3.1 kg/cm2 25 weeks after the implantation. The shear strength of bonding reached a maximum of 17.1 +/- 2.3 kg/cm2 25 weeks after the implantation. From these studies, we conclude that A-W.GC has a capability of making relatively quick bonding to the surface of bone cortex.

Animals↗
PubMed1988

Bonding behavior of three types of hydroxyapatite with different sintering temperatures implanted in bone.

The present study suggests that bonding does not vary in hydroxyapatite (HA) with different sintering temperatures implanted in bone tissue. The apparent unimportance of strict temperature regulation greatly simplifies HA processing. Three samples of HA (15 mm x 10 mm x 2 mm, abraded with 2000 alumina powder), of which sintering temperatures and microporosity were 800 degrees (45%), 1000 degrees (4.8%), and 1200 degrees (0.4%), respectively, were prepared. They were implanted into the metaphysis of tibia of mature male rabbits. Segments of the tibia containing the HA were excised and prepared for the detaching test. The failure load, when an implant detached from the bone or the bone broke, was then measured. Failure loads in HA (800 degrees), HA (1000 degrees), and HA (1200 degrees) ten weeks after implantation did not differ. Those in HA (800 degrees), HA (1000 degrees), and HA (1200 degrees) 25 weeks after implantation were 2.58 +/- 1.88 kg, 6.46 +/- 1.43 kg, and 6.50 +/- 2.71 kg, respectively. The failure load in HA (800 degrees) versus HA (1200 degrees) and that in HA (800 degrees) versus HA (1000 degrees) differed significantly (p less than 0.05). The lower failure load of HA (800 degrees) 25 weeks after implantation can be explained by its weakened mechanical strength due to high porosity. Bonding between bone tissue and three types of HA did not vary as observed by contact microradiography, Giemsa surface staining, and scanning electron microanalyzer-energy dispersive X-ray microanalyzer.

Animals↗
PubMed1987

Aging test and dynamic fatigue test of apatite-wollastonite-containing glass ceramics and dense hydroxyapatite.

The purpose of this study is to examine the changes in mechanical strength of two bioactive ceramics in living tissue. An aging test and dynamic fatigue test were performed using apatite-wollastonite-containing glass ceramics (A X W-GC) and dense hydroxyapatite (HA). Specimens (5 mm X 5 mm X 25 mm, abraded with No. 2000 Al2O3 powder) were implanted into subcutaneous tissue of rats for varying periods of time. The bending strength of aged samples was measured by the three-point loading method. The bending strength of A X W-GC was greater than that of HA (P less than 0.001). There was no reduction in bending strength for both A X W-GC and HA in living tissue. The n value of both A X W-GC and HA did not decrease significantly after implantation as assessed by the results of the dynamic fatigue test according to analysis of covariance. SEM-EPMA showed that Si and Mg contents decreased, Ca content did not change, while P content increased in the surface of A X W-GC. The area where x-ray intensity changed increased moderately after implantation. There were no changes in Ca and P at the interface between HA and soft tissue. In macroscopic and microscopic observations, specimens were found to be encapsulated with a thin layer of connective tissue. Foreign body giant cells, osteoblasts, or osteoclasts were not observed in the soft tissue. There was no bonding between ceramics and soft tissue.

Animals↗