Papers by Author: Marco A. Lopez-Heredia

Abstract: Titanium dental implants presenting different blasted surfaces and an OCP coated surfaces have been implanted in the femoral epiphysis of rabbits. A comparable osseointegration has been observed for the titanium implants blasted either with alumina or biphasic calcium phosphates particles whatever the delay of implantation (2 or 8 weeks). A higher bone to implant contact has been observed for the SLA and OCP coated implants as compared to the grit-blasted groups.

Abstract: Porous Titanium Scaffolds were produced by using a rapid prototyping technique. These scaffolds were either coated or not with a calcium phosphate coating via an eletrodeposition method. Rat bone marrow mesenchymal stem cells were cultured on the scaffolds at a density of 106 cells/scaffold for a period of 3 days. Cell proliferation was measured by using the Alamar Blue assay. The scaffolds were observed by SEM and polarized light microscopy. Constructs were then implanted subcutaneously for 4 weeks in syngenic rats. Cells proliferated well after seeding. After subcutaneous implantation, histology and SEM revealed the presence of uniform coatings as well as Ca and P deposits in the non-coated scaffolds suggesting mineralization.

Abstract: Calcium phosphates coatings were deposited onto titanium discs via en electrodeposition method. Discs were blasted with calcium phosphate particles and etched in a mixture of sulfuric and fluoric acids. Temperatures from 25 to 80°C and current densities from 8 to 120 mA/ cm2 were used. Deposition times tested were between 10 and 120 min. The electrolyte consisted of a super saturated solution stirred at 250 rpm. The amount of magnesium (Mg2+) and carbonate (HCO3-) ions was varied from 0 to 1 mM. Coatings increased in thickness by increasing deposition time. The different amounts of Mg2+ and HCO3- affected the homogeneity and morphology of the coatings. Main factors affecting the deposition were temperature of electrolyte and current density.

Abstract: Two porous titanium implants with interconnected pore size of 800 and 1200 m in diameter, were fabricated by a rapid prototyping method. Their dimensions and structure accomplished the expected design with accuracy and reproducibility. The porosity of titanium was around 60%. The compressive strength and Young’s modulus were comparable to those of cortical bone with values around 80 MPa and 2.7 GPa, respectively. The implants were implanted bilaterally in the femoral epiphysis of 12 New Zealand Rabbits. After 3 and 8 weeks, abundant bone formation was found in the titanium porous structure. This work demonstrates that macroporous titanium with controlled shape and porosity is a good candidate for orthopaedic and maxilofacial applications.

Abstract: A titanium base alloy and a cobalt base alloy have been subjected to a biomimetic process. Samples of titanium and cobalt alloys have been immersed in 10M and 5M NaOH solutions, respectively, then the samples have been heat treated and finally, immersed in either a simulated body fluid (SBF) with ionic concentration close to human blood plasma or in a simulated body fluid with an ionic concentration 1.5 times that of the SBF (1.5SBF) for a period of 21 days. An apatite layer has been observed after the immersion of the samples in SBF for both Ti and Co base alloys. The apatite layer observed on the Ti alloy samples is more homogeneous and thicker than that observed on the Co alloy samples. However, the apatite layer on both samples is not continuous and homogeneous along the surface. The layer of apatite formed is thicker on samples immersed in 1.5SBF. This is attributed to the higher ion concentrations, mainly of calcium and phosphorus. The Ca/P ratios measured in the apatite layers are close to that of bone.