Matthias von Walter

Development of Individual Three-Dimensional Bone Substitutes Using “Selective Laser Melting”

AbstractAim and Background:Scientific approach is the utilization of the newngenerative manufacturing process termed Selective Laser Meltingn(SLM) for the creation of biocompatible three-dimensional (3-D)nbone substitutes made of the titanium alloy TiAl6V4. The SLMntechnique enables direct transfer of virtual 3-D structures intonsolid metal materials with full serial characteristics andntypically great freedom of geometric design.Material and Methods:Individual 3-D CAD data which are derived from computedntomography models of anatomic structures are subdivided intonlayers of defined thickness. The actual part is generated by anrepeating process of applying TiAl6V4 powder in layers ofn0.003–0.1 mm on the process chamber platform transferring thenarea and contour information of each layer into the materialnusing a laser beam. The physical process is a complete remeltingnof the powder with a metallurgical bonding between the layersnyielding densities of approximately 100%. This operation isnrepeated step by step until the generation of the 3-D part isncompleted. We cultured human primary osteoblast-like cells onndifferent surfaces of SLMmanufactured TiAl6V4 parts to provenosteoblast compatibility. Proliferation, vitality, and alkalinenphosphatase (AP) activity of osteoblast cultures arenpresented.Results:It has become possible to produce complex 3-D geometriesnwith different surface properties within few hours.nCompatibility of the tested TiAl6V4 material with humannosteoblasts is demonstrated. The cultured cells attach andnproliferate on SLM substrates and show AP activity.Conclusions:The presented results demonstrate the potential offered bynthe SLM process. On the basis of scanned information, thengeneration of complex anatomic structures is realizable. Thenpresented promising advantages make this procedure interestingnfor the production of individual implants or bonensubstitutes.

The removal of Al2O3 particles from grit-blasted titanium implant surfaces: effects on biocompatibility, osseointegration and interface strength in vivo.

For the improvement of surface roughness and mechanical interlocking with bone, titanium prostheses are grit-blasted with Al(2)O(3) particles during manufacturing. Dislocated Al(2)O(3) particles are a leading cause of third-body abrasive wear in the articulation of endoprosthetic implants, resulting in inflammation, pain and ultimately aseptic loosening and implant failure. In the present study, a new treatment for the removal of residual Al(2)O(3) particles from grit-blasted, cementless titanium endoprosthetic devices was investigated in a rabbit model. The cleansing process reduces residual Al(2)O(3) particles on titanium surfaces by up to 96%. The biocompatibility of the implants secondary to treatment was examined histologically, the bone-implant contact area was quantified histomorphometrically, and interface strength was evaluated with a biomechanical push-out test. Conventional grit-blasted implants served as control. In histological and SEM analysis, the Al(2)O(3)-free implant surfaces demonstrated uncompromised biocompatibility. Histomorphometrically, Al(2)O(3)-free implants exhibited a significantly increased bone-implant contact area (p=0.016) over conventional implants between both evaluation points. In push-out testing, treated Al(2)O(3)-free implants yielded less shear resistance than conventional implants at both evaluation points (p=0.018). In conclusion, the new surface treatment effectively removes Al(2)O(3) from implant surfaces. The treated implants demonstrated uncompromised biocompatibility and bone apposition in vivo. Clinically, Al(2)O(3)-free titanium prostheses could lead to less mechanical wear of the articulating surfaces and ultimately result in less aseptic loosening and longer implant life.