Key Engineering Materials Vols. 284-286

Abstract: Radiotherapy is one of the effective treatments for cancers. This study presents a potential internal radiotherapy drug, radioactive calcium-phosphate micron-sized particles (RCPMP). The interaction of calcium-phosphate micron-sized particles (CPMP) with hepatoma cells and the cytotoxicity of RCPMP to hepatoma cells were evaluated. The CPMP having the eutectic composition of the CaO-P2O5 system (CaO-47wt% P2O5) was prepared and subsequently subjected to neutron irradiation in a nuclear reactor to yield RCPMP. The main nuclide in the RCPMP was P-32. RCPMP could be stably retained in a serum and culture medium. These CPMP had a high affinity with HepG2 human hepatoma cells. Cells climbed onto the larger CPMP particles, surrounding and embedding them within several days. The submicro-sized CPMP were endocytosed and retained in HepG2 cells. The dose dependent killing effect was obtained in RCPMP treated HepG2 cells. Cells were killed and detached from the flask with little morphological changes under a high dosage of RCPMP treatment. Meanwhile, treating HepG2 cell cultures with a lower dosage of RCPMP led to morphological changes before cell death. This RCPMP was biocompatible and had high killing effect on hepatoma cells.

Abstract: Alumina is excellent biomaterial and used in hip prostheses, dental implants and so on. Wollastonite particles were deposited in pores of porous alumina by electrophoretic deposition and an alumina-wollastonite composite was produced. Apatite was formed both inside the pores and on the surface of the composite of the alumina-wollastonite composite by soaking in a simulated body fluid. It was indicated that the deposited wollastonite particles induced the apatite formation. Novel composite material with both excellent mechanical properties and high bioactivity was developed.

Abstract: With the bone impaction grafting technique, a 50/50 volume mix of morselized cancellous bone (MCB) with TCP-HA granules was used to reconstruct a critical sized acetabular defect in the goat. The biological activity of the MCB/TCP-HA mix was assessed after 15 weeks. Defects filled with 100% MCB, currently the gold standard for this technique, were used as controls. In the 100% MCB defects, a new trabecular bone structure was found in which scarce incorporated remnants of the original graft material were present. In the MCB/TCP-HA defects, MCB was also resorbed or incorporated into new bone. Deep in the MCB-TCP-HA defects, large TCP-HA granules were generally totally osseous-integrated with new bone. Superficially, more fragmented TCP-HA granules of various sizes were present in the medullar tissue or in the interface with the cement layer. Here, the crushed TCP-HA granules were generally surrounded by osteoclasts and giant cells. The soft tissue interface between the reconstruction and cement did not differ between both groups. In conclusion, from a biological point of view, this short-term follow-up study suggests that TCP-HA granules can be safely used in a mix with MCB as bone graft extender in acetabular revision surgery with the bone impaction grafting technique.

Abstract: The erosion of dental glass infiltrated aluminum ceramics by sandblasting was evaluated. The variations of wear depth, surface roughness and bending strength after blasting were of particular interest. The sandblasting parameters of working pressures, times and erodent size came from routine manufacturing procedures. The results showed the erodent size affects the bending strength and pressure affects mainly the wear depth. The surface roughness increased significantly after sandblasting, but the differentiations with various blasting parameters were not apparent. Fatigue cracking characterized the mechanisms of erosion of dental glass infiltrated ceramics.

Abstract: BonelikeÒ graft that mimics the inorganic composition of bone tissue has been developed and characterized over the last decade. To evaluate the osteoconductivity of BonelikeÒ two granule size ranges, one ranging from 150-250µm and the other from 250-500µm were implanted in the femurs of New Zealand White rabbits, aiming at being clinically used in different medical applications, such as dentistry and orthopaedics. In order to facilitate the medical application of the BonelikeÒ graft the use of a commercially available polymeric vehicle was also analyzed. Radiological examination, histological studies and scanning electron microscopy (SEM) analyses revealed that the surface of Bonelike® granules was almost completely surrounded by new bone formation after 12 weeks of implantation, which proves its highly osteoconductive behaviour.

Abstract: The purpose of this study was to evaluate the behavior of nano-hydroxyapatite/ poly(D,L)lactide (n-HA/PDLLA) composite in vivo. The composite rods containing about 40wt% n-HA and control HA rods with a diameter of 2mm and a length of 6mm were implanted into the femora of 16 New Zealand rabbits. Composite wafers with a diameter of 5mm and a thickness of 1mm were implanted into the dorsal subcutis of 18 Wistar Albino rats. After definite intervals, the histological analysis was completed by light microscopy and the degradation behavior was observed by scanning electron microscopy. The histological analysis showed no obvious difference between n-HA /PDLLA composite and pure HA that had good biocompatibility and osteoconductivity. SEM analysis of the surface and cross section of the samples showed that the degradation of the composite started from surface, then into the inner gradually and formed multiple pores at surface. The pore size and porosity gradually increased along with time and a porous network may be formed.

Abstract: In clinical practice arises an increasing need for bone substitute materials. The main inorganic part of bone is the hydroxyapatite (HA). A new hydroxyapatite formula was created by a sol-gel-process at low temperature level [4]. The aim of this investigation was to test the biodegradation and the induction of bone formation by this new material and to compare these versus conventional fabricated HA and ß-TCP. 30 one-year-old Goettingen minipigs were divided into five groups. Critical size defect (>5 m3) in the mandible was treated differently in all 5 groups:-group I- filling with pure HA, which was fabricated by sol-gel-technique, group II- control, only gelatinous material was given, group III- conventional ß-TCP [Cerasorb®], in group IV- conventional HA [Endobone®] and in group V [Targobone®], a non denatureted bovine collagen matrix was used. Macroscopical and microscopical investigations of the former defects were made eight months postoperatively. The bone formation was superior in the sol-gel-HA-group (group I) in comparison with the control groups (group II) and the conventional fabricated ceramics groups (III and IV). In the sol-gel-HA group, the biodegradation of this new biomaterial was considered to very good with a resorption rate of more than 98%; eight months postoperatively. In this group complete bone formation was seen in former defects. In the control group, only an incomplete bone formation with 48.4% of the defect area was noted. This difference was significant (p<0,001). A less bone formation was also observed in group III and IV with 57.6% and 56.9%. The bovine non-denaturated collagen matrix (group V) leads to only 20% of new formed bone. The new calcium phosphate formula made by a sol-gel method seems to be superior and suitable for filling bone defects.

Abstract: Resorbable calcium phosphate glasses offer interesting solutions in the biomedical field, as bone cavity fillers, drug delivery systems, biodegradable reinforcing phase in the case of composites for bone fixation devices and tissue engineering scaffolds. In this work, two different glass formulations in the systems 44.5CaO-44.5P2O5-(11-X)Na2O-XTiO2 (X=0or 5) have been elaborated. It is known that the incorporation or TiO2 into the vitreous system reduces considerably the solubility of the glasses. To study the material solubility effect on the in vivo response, glass particles of the two formulations were implanted in rabbits. Results showed that both glasses elicited a similar biological response and good biocompatibility. The percentage of new bone formation in the glasses was comparable to that obtained for the autologous bone (control) after 12 weeks of implantation. The materials showed to have an osteoconductive potential. Finally, this study showed that in spite of the solubility difference of the studied glasses, there were no significant differences in the in vivo response.

Abstract: Large negative charges induced by electrical polarization on hydroxyapatite (HA) ceramics has been demonstrated to enhance their osteoconductivities. The newly formed bones in the vicinities of the negatively charged surfaces were investigated in the views of crystallography and histology. The newly formed bone layers accompanied by mono-layered osteoblastic cells showed 4 perfect extinction positions in a 360° rotation, parallel and perpendicular to the HA surfaces by the optically polarizing images. The observation revealed that the newly formed bone layers directly bonding to the N-surface were consisted of the well-crystallized and highly orientated HA. Therefore, it was presumed that the enhanced osteobonding by negative surface charges was ascribed to the activation of myeloid cells and the intensified attraction of the HA nuclei by the electrostatic force.