Papers by Author: Pierre Layrolle

Abstract: An hydrated putty was prepared by mixing submicron particles, rounded particles and granules of Biphasic Calcium Phosphate (BCP) ceramics composed of HA and β-TCP phases. The material filled entirely critical sized defects in the femoral epiphysis of NZW rabbits. After 3, 6 and 12 weeks, histology revealed that submicron particles were rapidly degraded by multinucleated TRAP-positive cells. This osteoclastic resorption stimulated bone ingrowth while the large BCP particles served as scaffold supporting bone healing by osteoconduction.

Abstract: This paper reports on the research into multiphase bone substitutes carried out by laboratories from the ‘Pays de la Loire’ region in France. This collaborative research was funded by both the French Government and the Regional Council in the period 2000-2007. Calcium phosphate bioceramics, polymers and combinations have been developed as bone substitutes for various maxillofacial and orthopaedic applications. These bone substitutes should support and regenerate bone tissue and resorb after implantation. In the bone tissue engineering area, they have been combined with autologous bone marrow cells or bioactive factors. The bone substitutes were tested in various animal models mimicking clinical situations or under pathological conditions (osteoporosis). In order to complete our research, the multiphase materials were also evaluated in clinical trials.

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: This study aims at evaluating bone growth in critical-sized femoral defects of rats filled with macro micro porous biphasic calcium phosphate ceramic (MBCP) cylinders surrounded or not by a resorbable collagen membrane. Femoral defects left empty (control) exhibited partial bone ingrowths after 3 and 6 weeks and were completely healed at 12 weeks. The defects filled with the collagen membranes appeared partially healed suggesting that the membranes constraint bone ingrowth. Bone formation occurred around the collagen membrane which partially degraded over time. In the MBCP/membrane group, bone has grown inside the macro pores of the MBCP cylinders. Bone ingrowth was more rapid and abundant in the defects filled with MBCP alone. The combination MBCP/collagen membrane may be beneficial for the reconstruction of large bone defects without using repetitive surgeries and autologous bone grafting.

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: Autologous bone chips are widely used in orthopedic surgery to fill large defects due to osteoinductive property but are limited in quantity. Several groups have reported the formation of mineralized bone after implantation of bioceramics in ectopic sites of different animals. However, osteoinduction by bioceramics has not yet proved to be equivalent to those of autologous bone. In this study, we compare the bone inducing capability of autologous bone chips and synthetic biphasic calcium phosphate (BCP) ceramics granules sintered at various temperatures. Both materials were implanted in muscles and femurs of goats inside hollow containers for 6, 12 and 24 weeks and analyzed by histology. This study showed that bone tissue formed in contact with micro porous ceramics sintered at low temperature as well as autologous bone chips both in ectopic and intrafemoral sites of goats.

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.