Biomedical Evaluation Of The Controlled Porous Titanium Alloy Scaffold Produced By Electron Beam Melting Technique

Reconstructing bone defects was still a major concern in the orthopaedic field.As we all know, autologous bone graft was considered to be the goldenstandard. However, the available autologous bone supplies were limited andadditional invasive surgical procedure may lead to donor site morbidity, chronicpostoperativepain, hypersensitivity and infection. Allogeneic grafts were widelyavailable and did not require an additional surgery on the patient. However,many negative effects limited the development of allogeneic grafts because ofslow intergration,poor remodeling, immunoreactions and disease transmission.Particularly , the negative effects cut down osteoinductive and osteoconductivepotential of the allograft . For these reasons ,tissue engineering approaches thatincorporated osteoblastic cells and porous biocompatible scaffolds as potentialalternatives .Although many researchers studied porous ceramics and polymers etc as bone graft scaffolds ,they could not satisfy the mechanical demands ofload-bearing orthopedic applications. In recent years, metallic scaffolds withcontrolled three-dimensional structures had drawn a lot of attention for itspotential applications such as tissue engineering. Metallic materials recognizedas a promising bone substitute material were widely used for orthopedic anddental implants. Metals were more suitable for loading–bearing applicationscompared with ceramics or polymeric materials due to their combination of highmechanical strength and fracture toughness. Among various metallicbiomaterials, titanium and its alloys were the most attractive metallicbiomaterials for orthopedic and dental implants due to their excellentmechanical properties, biocompatibility and good corrosion resistance.1. Three-dimensional culture of osteoblast seeded on titanium alloyscaffold with controlled internal structure fabricated using electronbeam melting techniques in vitro.The purpose of the present study was to explore the feasibility of culturingosteoblast on titanium alloy scaffold with controlled internal structurefabricated using electron beam melting techniques in vitro and to investigatethe effects of like-honeycomb scaffold with controlled porous structure. Adirect metal rapid prototyping (RP) fabrication technique, electron beammelting (EBM) process, was utilized to fabricate porous titanium alloyscaffold with fully interconnected and controlled internal pore structure.Osteoblasts were isolated from rabbit skulls,seeded on scaffolds,and culturedfor up to 1,7 and 14 days respectively. The experiment was divided intoexperiment group (cells were culture with scaffold) and control group (cellsalone ) . The growth of rabbit osteoblasts on the scaffolds were observed byinverted phase contrast microscope, scanning electron microscope, histological section staining method .Proliferation and differentiation ofosteoblasts was determined at different time points by MTT assay. The resultsshowed the osteoblasts on scaffolds grew well in vitro with biological andmorphological characteristics similar to those of normal osteoblasts. Goodadhension,proliferation and differentiation of the osteoblasts on the scaffoldcould be observed with the culture time prolonged. The number of cells onScaffolds was higher than the control group (P<0.05).2. Titanium alloy scaffold with controlled internal structure asosteoblast carrier to repair rabbit cranial defects.The aim of this study was to evaluate the feasibility of titanium alloyscaffold with controlled internal architecture as osteoblast carrier on boneresponse in rabbit cranial defects models. Electron beam melting process wasutilized to fabricate porous titanium alloy scaffold with fully interconnected andcontrolled internal pore architecture. Osteoblasts were seeded on scaffolds andcultured for up to 7 days .The growth of rabbit osteoblasts on the scaffolds wereobserved by scanning electron microscope. To evaluate the bone formation invivo ,the experiment was divided into four groups: group A (cell/scaffoldcomposite), group B(scaffold only) , group C (left empty) and D( autogenousbone implant).Scaffolds were transplanted into rabbit cranial defects after cultured in vitro for7 days .The animals were sacrificed at 4,8,12 weeks after implantation .Boneformation into the scaffolds was investigated by gross observation,histologyand histomorphometry of non-decalcified sections and fluorochrome markers.The results showed that confluent cell layer could be observed on scaffoldsurface and internal pores after 7 days of incubation in vitro．New Bone growthand revasc ularization could be observed not only at the margins of scaffold, but also insidethe central pores of the scaffold after 12 weeks .New bone formed along thecontrolled internal channel of scaffold .The scaffold were fully filled with thenew bone tissue and blood vessel. The group A had been found that extensivenew bone formation originating from host bone towards the implant comparedwith group B (P<0.05). The controlled scaffold in this study was good biocompatibleand accelerated healing of rabbit cranial defects and new bone formation.The controlled honeycomb-like architecture could guide and promote theformation of mineralization tissue.In summary, the results of above studies suggested that the controlled porousscaffold had not only good biocompatibility, but also could improve theadhesion, growth and proliferation of osteoblasts , showing no adverse effectson the cell functions .The controlled like-honeycomb pore structure welladjusted the distribution of osteoblasts on the scaffolds .The scaffold acceleratedhealing of rabbit cranial defects and new bone formation. The controlledhoneycomb-like architecture could guide and promote the formation ofmineralization tissue. A direct cellular response was produced from the hosttissue into porous scaffolds to form new bone and thereby improve fixation,osteointegration and long term stability of implants.