PubMed · 12995365
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F N TEKENBROEK. 1952. [Dental materials. 5. Alloy elements].. https://pubmed.ncbi.nlm.nih.gov/12995365/
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The in vivo behavior of a porous Ti6Al4V material that was produced by a positive replica technique, with and without an octacalcium phosphate (OCP) coating, has been studied both in the back muscle and femur of goats. Macro- and microporous biphasic calcium phosphate (BCP) ceramic, known to be both osteoconductive and able to induce ectopic bone formation, was used for comparison purpose. The three groups of materials (Ti6Al4V, OCP Ti6Al4V and BCP) were implanted transcortically and intramuscularly for 6 and 12 weeks in 10 adult Dutch milk goats in order to study their osteointegration and osteoinductive potential. In femoral defects, both OCP Ti6Al4V and BCP were performing better than the uncoated Ti6Al4V, at both time points. BCP showed a higher bone amount than OCP Ti6Al4V after 6 weeks of implantation, while after 12 weeks, this difference was no longer significant. Ectopic bone formation was found in both OCP Ti6Al4V and BCP implants after 6 and 12 weeks. The quantity of ectopically formed bone was limited as was the amount of animals in which the bone was observed. Ectopic bone formation was not found in uncoated titanium alloy implants, suggesting that the presence of calcium phosphate (CaP) is important for bone induction. This study showed that CaPs in the form of coating on metal implants or in the form of bulk ceramic have a significantly positive effect on the bone healing process.
Rat bone marrow stromal cells were cultured on either Ra (0.14 microm) or Ra (5.8 microm) Ti6Al4V discs for 24 or 48 h. Cells on the Ra (0.14 microm) surface showed typical fibroblastic morphology, whereas cells on the Ra (5.8 microm) surface were in clusters with a more epithelial appearance. RNA was extracted from the cells at both time points, and gene expression was analyzed by using a rat gene microarray. At 24 and 48 h, a similar number of genes were both up- and down-regulated at least twofold on the Ra (5.8 microm) surface compared to the Ra (0.14 microm) surface. We analyzed the relative level of specific groups of genes related to bone and cartilage development, cell adhesion and extracellular matrix proteins, transcription factors, bone morphogenetic proteins, phospholipases, and protein kinases. Roughness did not appear to be a specific stimulator of osteogenesis because genes of both the bone and cartilage lineage were up-regulated on the Ra (5.8 microm) surface. The most prominent change among transcription factors was up-regulation of Hox 1.4 on the Ra (5.8 microm) surface. Up-regulation of phospholipase A2 and SMAD 4 indicate these genes are also involved in the response of cells to an Ra (5.8 microm) surface. Our data show surface roughness alters the expression of a large number of genes in marrow stromal cells, which are related to multiple pathways of mesenchymal cell differentiation.
Tissue factor (TF), a transmembrane glycoprotein, plays a role in the initiation of blood coagulation at sites of vascular injury. Activated products of coagulation may then enhance inflammatory responses. The present investigation assesses the ability of rat osteosarcoma (UMR-106) cells cultured on titanium alloy (Ti6Al4V) to express differential surface TF activity in response to cyclic mechanical strain. Strains ranged from -2000 micro-strain to +2000 micro-strain, and durations from 5, 10, and 20 min per day over 5 days to 24 h continuous stimulation. ROS cells exhibited significant TF activity as demonstrated by the conversion of Factor X to Factor Xa. Strains of +2000 micro-strain with 5-20-min duration exhibited decreased TF activity with duration from 1.4E-04 nM/cell to 8.7E-05 nM/cell. Additionally, ROS cells stimulated with calcium ionophore (A23187) exhibited at least twice the activity of nonstimulated cells. Strains of +1340 micro-strain with 5-20-min duration exhibited an increasing trend with 4.15E-05 nM/cell to 7.38E-05 nM/cell. Strain direction had no significant effect on TF activity. Thus, both mechanical and chemical stimuli induce differential expression of TF activity by ROS cells cultured on Ti6Al4V, a phenomenon that may potentiate or regulate the inflammatory responses associated with the implantation of orthopedic biomaterials.