Bio-Medical Materials and Engineering - Volume 7, issue 1

Authors: Wen, Xuejun | Zhang, Ning | Li, Xiaohe | Cao, Zhengwang

Article Type: Research Article

Abstract: By means of electrochemical and quantitative histomorphometric methods, the corrosion resistance and tissue biocompatibility of Ti50 Ni50 and Ti50 Ni50-x Cux (x = 1, 2, 4, 6, 8) were investigated. It is discovered that the repassivation potential of Ti50 Ni50-x Cux (x = 2, 4, 6, 8) alloys is about 200 mV higher than that of Ti50 Ni50 alloy. Namely, the addition of Cu raises the repassivation potential of TiNi shape memory alloys and improves their corrosion resistance. Pitting potentials of Ti50 Ni50 and Ti50 Ni50-x Cux (x = 1, 2, 4, 6, 8) …alloys increase with solution pH value, but the repassivation potentials keep constant. The adding of Cu has no obvious influence on pitting potential (Epit ) of TiNi alloys, meanwhile, the corrosion potential and corrosion rate of Ti50 Ni50-x Cux (x = 1, 2, 4, 6, 8) alloys are irrelevant to its Cu content and the values are almost the same as those of TiNi alloys. The connective tissue layer covering the plates is statistically significantly thicker for Ti50 Ni42 Cu8 plates (p < 0.05) than that of Ti50 Ni50 , Ti50 Ni48 Cu2 , Ti50 Ni44 Cu6 plates after one month. The numbers of connective tissue cells, polynucleated cells, macrophages and round cells are higher for Ti50 Ni42 Cu8 plates than those of the other three types of plates, but no statistically significant differences are detected. There are no significant differences on tissue reaction parameters after two and three months among four alloys. After one, two and three months implantation, no corrosion is observed on the plates surfaces. A preliminary conclusion can be drawn that Ti50 Ni50-x Cux (x = 2, 6, 8) shape memory alloys have good biocompatibility. Show more

Keywords: Shape memory alloy, electrochemistry, corrosion, biocompatibility, histomorphometry

DOI: 10.3233/BME-1997-7101

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 1, pp. 1-11, 1997

Authors: Oshida, Yoshiki | Fung, Leo W. | Isikbay, Serkis C.

Article Type: Research Article

Abstract: Commercially pure titanium (CPT) substrate was subjected to porcelain firing and bond strengths under three-point bending mode (span length: 15 mm; crosshead speed: 0.5 mm/min) were evaluated. Experimental variables included surface treatments of CPT and porcelain firing schedules. Variables for the surface treatments were (1) sandblasting, (2) mono- and triple-layered nitridation, and (3) mono-layered chrome-doped nitridation. Variables for the porcelain firing schedule included (4) bonding agent application, (5) bonding agent plus gold bonding agent application, and (6) Procera porcelain application. All together eleven sample groups were prepared with different combination of aforementioned experimental variables. Statistically all of them exhibited no …significant differences. Hence, we employed two further criteria; (I) the minimum bond strength should exceed the maximum porcelain strength per se, and (II) the CPT substrate should not be heated close to the ,β-transus temperature. After applying these criteria, it was concluded that mono-layered nitridation and mono-layered application of chrome-doped nitridation on both (with and without) sandblasted and non-sandblasted surfaces were the most promising conditions for a successful Titanium-Porcelain System. Show more

Keywords: Nitrided pure titanium, porcelain firing, bond strength, bonding criteria, metal ceramic system

DOI: 10.3233/BME-1997-7102

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 1, pp. 13-34, 1997

Authors: Hong, Ye | Chirila, Traian V. | Fitton, J. Helen | Ziegelaar, Brian W. | Constable, Ian J.

Article Type: Research Article

Abstract: Poly(1-vinyl-2-pyrrolidinone) (PVP) and copolymers of 1-vinyl-2-pyrrolidinone are insoluble in water when crosslinked but they can absorb very large amounts of water to become syringe-injectable hydrogels. Such gels have been investigated recently as potential substitutes for the vitreous humour in the eye. In this study, during the cytotoxic evaluation by sulforhodamine B colorimetric assay of variously crosslinked PVP gels, it was found that many of them showed protective/growth promoting effects on 3T3 mouse fibroblasts in static cultures, a phenomenon encountered previously only with aqueous solutions of a limited number of natural or synthetic polymers. Particularly, the gels crosslinked with diethylene glycol …dimethacrylate (DEGDMA) induced a significant enhancement of cell proliferation, especially in serum-free cultures. No correlation between this effect and the essential gel properties (chemical composition, viscoelasticity and equilibrium water content) could be established. The study demonstrated that crosslinked PVP hydrogels showed a serum-like growth promoting effect on an anchorage-dependent cell line, which may be due to physical protection, inability of the insoluble gels to penetrate cell membranes, and their ability to mimic the extracellular matrix. Show more

Keywords: Poly(1-vinyl-2-pyrrolidinone), hydrogels, fibroblast static cultures, sulforhodamine B colorimetric assay, growth-promoting effect, dynamic viscosity

DOI: 10.3233/BME-1997-7103

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 1, pp. 35-47, 1997

Authors: Yoshikawa, Takafumi | Ohgushi, Hajime | Dohi, Yoshiko | Davies, John E.

Article Type: Research Article

Abstract: With the aim of in vitro production of bone fragments more closely resembling autogenous bone, rat cultured bone marrow cells were combined with porous hydroxyapatite (HA) discs and cultured in the presence of dexamethasone (Dex). Bone marrow cells were collected from the femoral diaphyses of a 7-week-old male Wistar rat, and primary culture was performed for six days. Then, cell suspensions were prepared by trypsin treatment, and combined with the porous HA discs. After a 2-hour incubation, the composites were additionally cultured for up to 4 weeks (subculture) in the presence of Dex. In a control group, the subculture was …performed without Dex. After 1, 2, 3 and 4 weeks of subculturing, the HA discs were removed, and alkaline phosphatase (ALP) activity, bone Gla protein (BGP), and DNA were quantitated. A portion of the disc was prepared for scanning electron microscopy (SEM), from which bone formation was evaluated morphologically. ALP activity peaked at 2-3 weeks and decreased at 4 weeks. BGP levels began to increase at 3 weeks. In the SEM study, mineralized collagenous extracellular matrix was noted at 3 and 4 weeks. In the control group, neither significant ALP activity nor increased BGP was detected. These biochemical and morphological results suggest that with the culture technique, active bone formation in the pore regions of HA can be fabricated in vitro. It is anticipated that when composites are sub cultured in this way they will function as a bone graft with properties similar to those of autogenous bone. Show more

Keywords: Bone Gla protein, hydroxyapatite, scanning electron microscopy, osteogenesis, in vitro

DOI: 10.3233/BME-1997-7104

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 1, pp. 49-58, 1997

Authors: Besong, A.A. | Hailey, J.L. | Ingham, E. | Stone, M. | Wroblewski, B.M. | Fisher, J.

Article Type: Research Article

Abstract: Damage to polished femoral heads in vivo can cause increased wear of acetabular cups. Oxidation and ageing after sterilisation by gamma irradiation in air, can also change the mechanical properties and wear resistance of ultra high molecular weight polyethylene (UHMWPE). This study investigated the combined effect of these changes in material properties on the wear of UHMWPE for different counterface roughnesses, representative of new femoral heads and those damaged in vivo. Wear rates were studied on a tri-pin-on-disc tribometer in a protein-containing solution. A comparison was made of the wear, using three different counterface roughnesses, of specimens that were manufactured …from polyethylene acetabular cups of different shelf ages (3–120 months) after gamma irradiation in air but never implanted. These were compared to the wear of control specimens that were manufactured from cups that had not been sterilised. The wear surfaces were tested 1 mm below the initial articulating surface of the cup, the position of high degradation. The wear rate of UHMWPE which had been sterilised by gamma irradiation in air was shown to increase significantly with ageing time on the shelf for all counterface conditions. The wear rate of all materials increased markedly as the counterface roughness increased, but to different extents depending on the age of the material. The combined effect of ageing and increase in counterface roughness had a dramatic effect (as high as 2000 fold increase) on the wear rate. Both ageing of the polymer and damage to the femoral head have been cited as causing increased wear in vivo. The results of this study demonstrate that these variables can act synergistically to markedly effect UHMWPE wear rate. Show more

DOI: 10.3233/BME-1997-7105

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 1, pp. 59-65, 1997

Authors: Zhou, Ping | Akao, Masaru

Article Type: Research Article

Abstract: A new modified thermal decomposition method is described for preparing a double layered coating on titanium plates which includes an initial perovskite (CaTiO3 ) layer followed by a hydroxyapatite (HA) layer on top. The characterization of the coating was studied by X-ray diffractometry and infrared spectroscopy and indicated that the double layer consisted of carbonate HA and CaTiO3 and the thickness of the layer was 4 μm. The coating was performed on the inner surfaces of 50-200 μtm sized pores and was also consistent in the smallest of the pores even those of 50 μm. Bone formation was examined …in canines at 2-32 week intervals and was dominant on coated plates and in large-sized pores before 16 weeks. However, after 16 weeks bone ingrowth was similar in non-coated and coated plates and in all pore sizes. The results indicated that HA could only influence early bone ingrowth, though good bone ingrowth into small pores indicated that HA exhibited enhanced osteocompatibility. Our methodology ensured the stability of the HA layer consequently minimizing the problems associated with HA loss. Show more

Keywords: Hydroxyapatite coating, thermal decomposition method, X-ray diffractometry, infrared spectroscopy, osteocompatibility

DOI: 10.3233/BME-1997-7106

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 1, pp. 67-81, 1997