Key Engineering Materials Vols. 309-311

Abstract: The bioactivity of a composite of titania and hydroxyapatite was studied in vitro in this paper. After the titania ceramics was added 10% HA, it could induce apatite formation in simulated body fluid in 2d, while the pure titania ceramics could not induced apatite formation even after 14d. After the composite of titania and HA was subjected to alkali-heat treatment, it has a faster speed for apatite formation in SBF than the composite without treatment. When the osteoblast was cultured on the materials, the amount of osteoblasts attaching on the composite was more than that on the pure titania ceramics. It has the most osteoblasts cells on the composite subjected to alkali-heat treatment. These results showed that the composite of titania and HA is a bioactive materials, while the alkali-heat treatment could improved the bioactivity of this composite.

Abstract: A novel material, namely, TiO2-HDPE (TiO2/high density polyethylene) composite was developed by our research group. Its mechanical properties are similar to those of the human cortical bone; hence, we examined the possibility of using it as a bone substitute. We prepared two groups of TiO2-HDPE; one was subjected to ultraviolet irradiation for 0.1 h and the other for 9 h. In bone bonding ability test, the former indicated a lower ability than the latter, which showed approximately 7 to 8 N of failure load. The bone bonding ability of the latter group alone is not sufficient for clinical application; on the other hand, the biocompatibility test was carried out. In the biocompatibility test, the group that was irradiated for 9 h revealed neither a major inflammatory response nor formation of neoplasm. We have to further examine alternate types of polyethylene or TiO2 particles in order to improve the bone bonding ability.

Abstract: Rutile films were deposited on polytetrafluoroethylene (PTFE) substrates using 1.5 M titanium tetrachloride aqueous solution at 60 °C. The rutile films exhibited excellent in vitro bioactivity as they induced apatite deposition in a simulated body fluid (SBF) within 2 days. Chlorine incorporated in the rutile films did not inhibit apatite deposition.

Abstract: Biological sealing is a key factor for successful development of percutaneous device (PD). A new device with arc-perforated flange as subcutaneous part and groove-shaped percutaneous part, was intended to improve integration of soft tissue and implant. Material and surface properties are known to have great impact on tissue-implant integration. To understand how a material and its surface property can influence tissue reaction, and to find the appropriate material for PD fabrication, five different kinds of materials were prepared for in vivo animal tests with corresponding histological evaluation. Results revealed that a more stable junction was formed between the soft tissue and HA coated titanium implant than other combinations.

Abstract: The purpose of this study was to examine if the application of custom-made porous titanium membranes combined with bone graft materials promotes exophytic bone formation in rabbit calvaria. For this purpose, round decorticated calvaria sites were created using a round carbide bur. In the control group, rectangular parallelepiped-shaped porous titanium membranes (RPTMs) were placed on the decorticated sites and fixed with metal pins. In the experimental groups, RPTMs were filled with one of the following bone graft materials prior to fixing with metal pins: bovine bone mineral (BBM), demineralized freeze-dried human cortical bone (DFDB) or freeze-dried human cancellous bone (FDB). Animals were sacrificed at 8 and 12 weeks after surgery, and new bone formation was assessed by histomorphometric as well as statistical analysis. The results indicate that at 8 and 12 weeks, all the experimental groups demonstrated exophytic bone formation. At 12 weeks, DFDB group revealed the most new bone formation (p<0.05) and resorption of grafted materials (p<0.05). On the basis of these findings, we conclude that RPTMs may be used as an augmentation membrane for guided bone regeneration and DFDB as an effective bone-inducing graft material.

Abstract: The biocompatibility of zirconia-alumina composite was evaluated with HOS osteoblast like cell models. A total of 18 zirconia-alumina composite disc (diameter: 19mm and thickness: 1.5mm) were prepared and divided into two groups. Half of the discs were sandblasted with 50µm alumina particles. Mean values of surface roughness (Ra) were 0.1 µm and 0.9-1.48 µm for smooth and sandblasted sample respectively. The cell attachment, proliferation, and differentiation on the specimen were evaluated by the Real-Time Polymerase Chain Reaction (RT-PCR), Methylthiazole Sulfate (MTS) analysis, Alkaline Phosphatase (ALP) activity, and Scanning Electron Microscopy (SEM). There was no significant difference in cellular response between two groups. The analysis of the RT-PCR showed that the amount of Cyclin D1(mRNA expression) was not statistically significant different between two groups after 24 hours as well, however markedly decreased in the smooth surface after 72 hours. This indicated that the rough one might have a more favorable cellular proliferation compared to smooth one in long term evaluation. Further study will be necessary.

Abstract: The osseointegration rate of a new zirconia/alumina composite ceramic implant material, (Y,Nb)-TZP/ alumina, was compared with conventional titanium implant in the rabbit model. Four different groups of threaded implant were compared after 4 and 6weeks healing period. The bone implant contact ratio and bone volume was evaluated by undecalcified histologic sections. The surface of each implant group was observed under SEM. Within the limitations of this study, Zr/Al composite ceramic implants demonstrated favorable bone response compared to titanium implant. This material demonstrated a possibility of an alternative to titanium dental implant. Further studies are needed to confirm this result.

Abstract: The gelation kinetics of two water-based gel-casting systems, made from reagents with very low acute toxicity, has been investigated. The zirconia particles greatly enhance the gelation rate, thus reducing both the temperature and time required for complete gelation. Binder burnout is complete and comparison of the pyrolysis of the net gel and the zirconia-based gel-cast parts revealed that the presence of zirconia particles accelerates the pyrolysis of the gel.

Abstract: Bioactive Mg-PSZ composites were developed by using wollastonite ceramics either as a constituent of the composite formulation or as a bioactive bed during the biomimetic treatment in simulated body fluids. The zirconia composites were prepared by uniaxial pressing of powder mixtures and sintered at 1550oC in air. Wollastonite containing zirconia/alumina composites were also sintered at 1350oC. The composites were immersed in SBF for 7 days on a bed of wollastonite powder and then re-immersed in 1.5SBF for 7 days. Tests were also performed with no wollastonite bed. A highly bioactive surface was observed on the Mg-PSZ/CaSiO3 and Mg-PSZ/Al2O3 composites. A homogeneous apatite layer was detected on the Mg-PSZ/CaSiO3 composites immersed for only 7 days in SBF. No apatite was formed on the Mg-PSZ/Al2O3/CaSiO3 composite. During the sintering mechanism at either 1550 or 1350oC small amounts of aluminosilicate phases are formed. These phases inhibited the apatite formation.

Abstract: The in vitro biocompatibility of aragonite material obtained from inner and out layers of four different molluscs was tested. After grinding and sieving, the obtained fine powders were put in contact with primary osteoblasts derived from rat calvariae. The viability of the cells increased at about 10% in the presence of powders derived from Vennus Gallina outer layer and from Pecten Jacobaeus inner layer. In the case of the presence of the other 6 tested powders, there was no statistical difference in cells’ viability. With regard to alkaline phosphatase production, all the tested powders induced a decrease of the production of this enzyme by osteoblasts. There was no evidence of any alterations in collagen production.