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ABSTRACT: We have developed a bioactive bone cement that consists of apatite and wollastonite containing glass-ceramic (AW-GC) powder and bisphenol-a-glycidyl dimethacrylate (Bis-GMA)-based resin. In this study, we made three types of composite (designated AWC, HAC, and TCPC) consisting of AW-GC, hydroxyapatite (HA,) or beta-tricalcium phosphate (beta-TCP) powder as the inorganic filler and Bis-GMA-based resin as the organic matrix. The proportion by weight of the filler mixed into the cement was 70%. Rectangular plates (10 x 15 x 2 mm) of each composite were made and abraded with 2000 alumina powder. These composites were implanted into tibial metaphyses of rabbits. Specimens were prepared 10 and 25 weeks after implantation and examined using transmission electron microscopy (TEM). AWC was in direct contact with bone 10 weeks after implantation, and AW-GC particles were partially absorbed at the surface. HAC was in contact with partially mineralized extracellular matrix 10 weeks after implantation. In TCPC-implanted specimens, randomly oriented mineral was observed 10 weeks after implantation; however, collagenous extracellular matrix rarely was observed. In 25-week specimens, AW-GC particles were completely absorbed and replaced by new bone, and there was no intervening soft tissue. Both HAC and TCPC were in contact with bone at 25 weeks. These results indicate that AWC has higher bioactivity than either HAC or TCPC.
Journal of Biomedical Materials Research 11/2001; 57(1):101-7.
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ABSTRACT: Previously we developed a composite consisting of apatite and wollastonite containing glass-ceramic (AW-GC) powder and bisphenol-a-glycidyldimethacrylate (Bis-GMA)-based resin (designated AWC), and demonstrated that AWC showed direct contact with living bone. Another new composite consisting of mainly the delta-crystal phase of alumina bead powder and Bis-GMA-based resin (designated ABC) was developed. Although alumina ceramics are bioinert and a composite filled with the pure alpha-crystal phase of alumina powder (designated alphaALC) did not allow direct bone formation in vivo, ABC was shown to have excellent osteoconductivity. One purpose of this study was to investigate whether AW-GC powder in a composite promotes osteoblastic differentiation of rat bone marrow cells as AW-GC bulk did. Another purpose was to evaluate the effects of the delta-crystal phase of alumina powder in a composite on osteoblastic differentiation. In a cell culture with dexamethasone, alkaline phosphatase (AP) activity at both days 7 and 14, and the levels of osteocalcin mRNA and alpha1(I) collagen mRNA at day 14 and osteopontin mRNA at day 7, were highest on AWC, followed by ABC, and finally alphaALC. Scanning electron microscopy showed more abundant mineralized globules and a fibrous collagen matrix on AWC at day 14, followed by ABC. In a cell culture without dexamethasone, AP activity at both days 7 and 14, and the level of osteopontin mRNA at day 7, were higher on ABC than on any other composite, whereas osteocalcin mRNA could not be detected. These results indicate that AW-GC powder in a composite promotes osteoblastic differentiation of bone marrow cells intensively when supplemented with dexamethasone. The delta-crystal phase of alumina powder in a composite promotes greater osteoblastic differentiation than the alpha-crystal phase of alumina powder.
Journal of Biomedical Materials Research 06/2001; 55(2):164-76.
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ABSTRACT: The purpose of this study was to investigate the bone-implant interface of high-strength hydroxyapatite (HA)/poly(L-lactide) (PLLA) composite rods. As reinforcing particles, two types of HA particles-calcined HA (c-HA) and uncalcined HA (u-HA)-were applied to allow comparison of their suitability as bioactive fillers. Four types of composites (c-HA30, c-HA40, u-HA30, and u-HA40), which contained 30 or 40% by weight of each HA particle, were used. Unfilled PLLA rods were used as controls. A hole was drilled in the distal femora of 50 rabbits, and a composite or unfilled PLLA rod was implanted in a press-fit manner. Two, 4, 8, and 25 weeks after implantation, the samples were examined histologically by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An image analyzer was used for histomorphometric analysis of the bone-implant interface. An affinity index was calculated for each material; this was the length of bone directly apposed to the rods expressed as a percentage of the total length of the rod surface. In all the composites, histologic examination showed new bone formation at 2 weeks after implantation. The bone gradually grew along the composite surface. SEM showed direct bone contact with the composites without intervening fibrous tissue. During follow-up, the affinity indices of all the composite rods were significantly higher than those of the unfilled PLLA rods (p < 0.01; two-way ANOVA). The maximum affinity index (41%) was attained at 4 weeks in c-HA40 rods. In contrast, little bone contact was seen in unfilled PLLA rods. The only significant difference in affinity indices among the composites was that c-HA40 had a higher affinity index than u-HA40 (p < 0.05 at 4 weeks). No disintegration of rods or polymer debris, which could elicit inflammatory tissue reactions, was observed even at 25 weeks. Our results indicate that osteoconductive bone formation on composites could enhance the stability between bone and implant in fracture repair.
Journal of Biomedical Materials Research 06/2000; 50(3):410-9.
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ABSTRACT: We developed a composite (ABC) consisting of alumina bead powder as an inorganic filler and bisphenol-a-glycidyl dimethacrylate (Bis-GMA)-based resin as an organic matrix. Alumina bead powder was manufactured by fusing crushed alpha-alumina powder and quenching it. The beads took a spherical form 3 microm in average diameter. The proportion of filler in the composites was 70% w/w. The composite was implanted into rat tibiae and cured in situ. Specimens were prepared 1, 2, 4, and 8 weeks after the operation and observed by transmission electron microscopy. The results were compared with those of a bone composite made of alpha-alumina powder (alpha-ALC). In ABC-implanted tibiae, the uncured surface layer of Bis-GMA-based resin was completely filled with newly formed bonelike tissue 2 weeks after implantation. The alumina bead fillers were surrounded by and in contact with bonelike tissue. No intervening soft tissue was seen. In alpha-ALC-implanted tibiae, a gap was always observed between the alpha-ALC and the bonelike tissue. These results indicate that the ABC has osteoconductivity, although the precise mechanism is still unclear.
Journal of Biomedical Materials Research 02/2000; 49(1):106-11.
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ABSTRACT: We developed a bioactive bone cement (BABC) that consists of apatite and wollastonite containing glass ceramic (AW-GC) powder and bisphenol-A-glycidyl dimethacrylate (Bis-GMA) based resin. In the present study, the effectiveness of the BABC for repair of segmental bone defects under load-bearing conditions was examined using a rabbit tibia model. Polymethylmethacrylate (PMMA) bone cement was used as a control. A 15-mm length of bone was resected from the middle of the shaft of the tibia, and the tibia was fixed by two Kirschner wires. The defects were replaced by cement. Each cement was used in 12 rabbits; six rabbits were sacrificed at 12 and 25 weeks after surgery, and the tibia containing the bone cement was excised and tension tested. At both the intervals studied, the failure loads of the BABC were significantly higher than those of the PMMA cement. The BABC was in direct contact with bone, whereas soft tissue was observed between the cement and bone in all PMMA cement specimens. Results indicated that the BABC was useful as a bone substitute under load-bearing conditions.
Journal of Biomedical Materials Research 01/2000; 47(3):353-9.
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ABSTRACT: We analyzed the mechanisms of the efficient bone formation on the osteoconductive surface of apatite- and wollastonite-containing glass-ceramic (AW) by using an in vitro system. AW releases Ca ions and bonds to bone via a submicron-thick hydroxycarbonate apatite (HCA) layer. AW disks were conditioned with simulated body fluid (SBF) to grow HCA layers, and the amount of released Ca ion was regulated by modulating the conditioning time from 24 to 240 h. Surface-transformed AW disks increased alkaline phosphatase (AP) activity in osteoblastic ROS17/2.8 cells by 1.5- to threefold over unconditioned disks. AW disks conditioned for 24 h [AW(24)], which had a homogeneous, submicron-thick apatite layer and increased extracellular ionized Ca concentration ([Ca(2+)](e)) in the culture medium to the greatest extent, enhanced the AP activity the most. High [Ca(2+)](e) promoted osteogenic differentiation in ROS17/2.8 cells: It increased AP activity in a dose-dependent manner by up to 1.6-fold, and up-regulated the expression of AP, osteocalcin (OC), and transforming growth factor-beta1 mRNAs in dose- and time-dependent manners. AW(24) enhanced AP activity in ROS17/2.8 cells as much as AW disks conditioned with SBF containing serum to exhibit in vivo surface-structure changes. AW(24) increased AP activity in ROS17/2.8 cells by 1.6-fold and enhanced the expression of AP and OC mRNAs significantly, compared with sintered hydroxyapatite (HA). After implantation of AW and HA in the distal metaphyses of rabbit femurs, thin, newly formed bone lined with cuboidal, osteoblast-like cells was characteristically observed adjacent to the AW surface within 8 days. These results provide evidence for the hypothesis that AW stimulates bone formation on its surface by increasing [Ca(2+)](e) to promote the HCA layer formation and the differentiation of osteogenic cells.
Journal of Biomedical Materials Research 12/1999; 47(2):176-88.
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ABSTRACT: We developed a bioactive bone cement that consists of apatite and wollastonite containing glass-ceramic (AW-GC) powder and bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin. In this study, we made three types of cement (designated AWC, HAC, and TCPC) consisting of either AW-GC, hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder as the inorganic filler and Bis-GMA based resin as the organic matrix. These cements were implanted into rat tibiae and cured in situ. Specimens were prepared 1, 2, 4, and 8 weeks after the operation and observed using transmission electron microscopy. Each of the bone cements was in direct contact with the bone. In AWC-implanted tibiae, the uncured surface layer of Bis-GMA based resin was completely filled with newly formed bone-like tissue 2 weeks after implantation. The AW-GC particles were surrounded by bone and were in contact with bone through an apatite layer. No intervening soft tissue was seen. In HAC-implanted tibiae, it took 4 weeks for the uncured layer to completely fill with newly formed bonelike tissue. The HA particles were also in contact with bone through an apatite layer. In TCPC-implanted tibiae, it took 8 weeks for the uncured layer to fill with newly formed bone-like tissue. The new bone that formed on the TCPC was not as dense as that on the AWC or HAC, and an intervening apatite layer was not evident. Results indicated that AWC had higher bioactivity than either HAC or TCPC.
Journal of Biomedical Materials Research 07/1999; 45(4):277-84.
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ABSTRACT: We have developed a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW glass-ceramic powder), silica glass powder as an inorganic filler, and bisphenol-a-glycidyl methacrylate (bis-GMA) based resin as an organic matrix. The efficacy of this bioactive bone cement was investigated by evaluating its pressurization in a 5-mm hole and small pores using a simulated acetabular cavity. Two types of acetabular components were used (flanged and unflanged sockets) and a commercially available polymethylmethacrylate (PMMA) bone cement (CMW 1 Radiopaque Bone Cement) was selected as a comparative control. Bioactive bone cement exerted greater intrusion volume in 5-mm holes than PMMA bone cement in both the flanged and unflanged sockets 10 minutes after pressurization (p < 0.05). In the small pores the bioactive and PMMA bone cements exerted almost identical intrusion volumes in flanged and unflanged sockets 10 min after pressurization. The intrusion volume in the flanged socket 10 minutes after pressurization was greater than that in the unflanged socket in all groups (p < 0.05). These results show that bioactive bone cement intrudes deeper into anchor holes than PMMA bone cement.
Journal of Biomedical Materials Research 02/1999; 48(1):43-51.
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ABSTRACT: We have investigated the applicability of a simple and inexpensive osteoclastic assay system using bone-like apatite-coated polyethyleneterephthalate (PET) disks. A 1 microm thick apatite layer, uniform and homogeneous bone-mineral-like with no organic components, was made on PET disks using a biomimetic process. As substrates for an osteoclastic assay, these coated disks were compared with dentine as well as with bone-like or heat-treated apatite of various thicknesses on apatite- and wollastonite-containing glass ceramic (A-W GC) disks. The unfractionated bone cells, including osteoclasts, of a neonatal rabbit were seeded onto these substrates. By scanning electron microscopic examination, the resorption lacunae of the thick bone-like apatite clearly showed track-like shapes at various depths, similar to those of dentine although the border between the A-W GC and the apatite was unclear. In contrast, those of heat-treated apatite showed small and shallow shapes with irregular margins, quite different from those of dentine. By reducing the thickness of bone-like apatite to 1 microm as well as using PET as its substrate, the margins of the resorption lacunae became quite clear, and with the use of phase-contrast microscopy during culture, osteoclasts and resorption pits could be precisely observed. The resorbed area, easily measured with the aid of bright-field microscopy and an image analyzer, was found to have increased in a time-dependent manner and at the end of 4 days of culture was not statistically different from that of dentine.
Journal of Biomedical Materials Research 12/1998; 42(2):278-85.
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ABSTRACT: We have developed a new drug delivery system using porous apatite-wollastonite glass ceramic (A-W GC) to treat osteomyelitis. A-W GC (porosity, 70% and 20% to 30%), or porous hydroxyapatite (HA) blocks (porosity 35% to 48%) used as controls, were soaked in mixtures of two antibiotics, isepamicin sulphate (ISP) and cefmetazole (CMZ) under high vacuum. We evaluated the release concentrations of the antibiotics from the blocks. The bactericidal concentration of ISP from A-W GC was maintained for more than 42 days, but that from HA decreased to below the detection limit after 28 days. The concentrations of CMZ from both materials were lower than those of ISP. An in vivo study using rabbit femora showed that an osseous concentration of ISP was maintained at eight weeks after implantation. Osteoconduction of the A-W GC block was good. Four patients with infected hip arthroplasties and one with osteomyelitis of the tibia have been treated with the new delivery system with excellent results.
Journal of Bone and Joint Surgery - British Volume 06/1998; 80(3):527-30. · 2.83 Impact Factor
