Papers by Keyword: Osteoconductivity

Abstract: Effect of heat-treatment temperature on the osteoconductivity of the apatite derived from bovine trabecular bone was investigated. Three different heat-treatment temperatures (600, 800 and 1000 oC) were adopted in the experiment and their effects on the physical properties of apatite granules, which could affect on the osteoconductivity, were evaluated. The content of carbonate ions in the apatite structure was assessed by FT-IR and its crystallinity was evaluated by X-ray diffractometry. The microstructure was assessed by field emission electron microscopy. Apatite granules heat-treated at 600 oC and 1000 oC were implanted into the calvaria of New Zealand White rabbit for 4 weeks, respectively, and the undecalcified ground histologic specimens stained with multiple staining method was observed. As increasing the heat-treatment temperature, the crystal size and crystallinity of the apatite increased while the content of carbonate ions decreased. The apatite granules heat-treated at 600 oC showed much better osteoconductivity comparing to that heat-treated at 1000 oC. The results were explained in terms of the physical properties of apatite which could affect to the osteoconductivity.

Abstract: Deep-frozen morselized human bone grafts showed osteoconductivity and osteoinductivity when implanted into tibial window defects of nude rats. The osteoconductivity was assessed by measuring the total area of newly formed bone bridged by the implanted bone grafts in the entire defect area. The osteoinductivity was evidenced by the presence of active osteoblast-like cells and new bone formation around the implanted bone grafts, which were surrounded by soft tissues distant from the host cortex. Gamma irradiation at the doses of 15 or 25 kGray reduced the osteoconductivity (ANOVA and LSD tests, p<0.05) at 3 weeks post operation. The 25 kGray group had a significantly lower level of new bone formation compared with the 0 and 15 kGray groups. The evidences of osteoinductivity were only noted in the 0 and 15 kGray groups. Our data indicate that 25 kGray gamma irradiation reduces the osteoconductive and osteoinductive properties of the morselized human bone graft.

Abstract: We investigated the biocompatibility, osteoconductivity, and biodegradability of porous composite of Hydroxyapatite (HA) and Poly D/L-lactide (PDLLA). At 6weeks afterimplantation to rabbit femoral condyle, HA/PDLLA was covered with bone and contacted with bone directly. The amounts of newly formed bone in the pores had increased during the examined period. By 26weeks, bone remodeling of formed bone in the pores was seen and bone marrow tissue formation was seen in the pores of HA/PDLLA. Porous HA/PDLLA was resorbed much faster than porous HA as a control. Porous HA/PDLLA was resorbed constantly through the bone formation and bone remodeling but porous HA was hardly resorbed during the period. It might be one of the desirable materials for bone substitute. To evaluate for a scaffold, disc shaped blocks loaded with rat bone marrow cell were implanted in the subcutaneous pouch of the back of syngeneic rat. At 3weeks afterimplantation, newly bone formation in the pores was observed at ectopic site. It also suggested the availability of this material as cell scaffolds.

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.

Abstract: Two types of new bioactive polymethylmethacrylate (PMMA)-based bone cements containing nano−sized titania (TiO2) particles were prepared and evaluated to assess the effect of TiO2 content on their mechanical properties and osteoconductivity. We prepared two types of bioactive bone cement, ST50c and ST60c, which contained 50 wt% silanized TiO2 and 60 wt% silanized TiO2, respectively. Commercially available PMMA cement (PMMAc) was used as a control. The cements were inserted into rat tibiae and solidified in situ. After 6 and 12 weeks, they were taken out for evaluation of osteoconductivity by scanning electron microscopy (SEM), contact microradiography (CMR) and Giemsa surface staining. SEM revealed that ST60c and ST50c apposed to bone directly while PMMAc did not. The affinity index of ST60c was significantly higher than for the other cements at each time interval. The results showed that ST60c was a promising material, but its mechanical strength should be improved before application in prosthesis fixation.