Improved Biological Responses of Titanium Coating Using Laser-Aided Direct Metal Fabrication on SUS316L Stainless Steel

Direct metal fabrication (DMF) coatings have the advantage of a more uniform porous structure and superior mechanical properties compared to coatings provided by other methods. We applied pure titanium metal powders to SUS316L stainless steel using laser-aided DMF coating technology with 3D printing. The purpose of this study was to determine the efficacy of this surface modification of stainless steel. The capacity of cells to adhere to DMF-coated SUS316L stainless steel was compared with machined SUS316L stainless steel in vitro and in vivo. Morphological in vitro response to human osteoblast cell lines was evaluated using scanning electron microscopy. Separate specimens were inserted into the medulla of distal femurs of rabbits for in vivo study. The distal femurs were harvested after 3 months, and were then subjected to push-out test and histomorphometrical analyses. The DMF group exhibited a distinct surface chemical composition, showing higher peaks of titanium compared to the machined stainless steel. The surface of the DMF group had a more distinct porous structure, which showed more extensive coverage with lamellipodia from osteoblasts than the machined surface. In the in vivo test, the DMF group showed better results than the machined group in the push-out test (3.39 vs. 1.35 MPa, respectively, p = 0.001). In the histomorphometric analyses, the mean bone-to-implant contact percentage of the DMF group was about 1.5 times greater than that of the machined group (65.4 ± 7.1% vs. 41.9 ± 5.6%, respectively; p < 0.001). The porous titanium coating on SUS316L stainless steel produced using DMF with 3D printing showed better surface characteristics and biomechanical properties than the machined SUS316L.

Comparative analysis of titanium coating on cobalt-chrome alloy in vitro and in vivo direct metal fabrication vs. plasma spraying

Abstracts Background Titanium surface coating on cobalt-chromium (CoCr) alloy has characteristics desirable for an orthopedic implant as follows: strength, osteointegrative capability, and biocompatibility. Creating such a coated surface takes a challenging process and two dissimilar metals are not easily welded. In our study, we utilized additive manufacturing with a 3D printing called direct metal fabrication (DMF) and compared it to the plasma spraying method (TPS), to coat titanium onto CoCr alloy. We hypothesized that this would yield a coated surface quality as acceptable or better than the already established method of plasma spraying. For this, we compared characteristics of titanium-coated surfaces created by direct metal fabrication method (DMF) and titanium plasma spraying (TPS), both in vitro and in vivo, for (1) cell morphology, (2) confocal microscopy images of immunofluorescent assay of RUNX2 and fibronectin, (3) quantification of cell proliferation rate, (4) push-out biomechanical test, and (5) bone histomorphometry. Method For in vitro study, human osteoblast cells were seeded onto the coated surfaces. Cellular morphology was observed with a scanning electron microscope. Cellular proliferation was validated with ELISA, immunofluorescent assay. For in vivo study, coated rods were inserted into the distal femur of the rabbit and then harvested. The rods were biomechanically tested with a push-out test and observed for histomorphometry to evaluate the microscopic bone to implant ratio. Result For cell morphology observation, lamellipodia and filopodia, a cytoplasmic projection extending into porous structure, formed on both surfaces created by DMF and TPS. The proliferation of the osteoblasts, the DMF group showed a better result at different optic density levels (p = 0.035, 0.005, 0.001). Expression and distribution of fibronectin and Runx-2 genes showed similar degrees of expressions. The biomechanical push-out test yielded a similar result (p = 0.714). Histomorphometry analysis also showed a similar result (p = 0.657). Conclusion In conclusion, DMF is a method which can reliably create a proper titanium surface on CoCr alloy. The resulting product of the surface shows a similar quality to that of the plasma spraying method, both in vivo and in vitro, in terms of biological and mechanical property.

Comparative analysis of titanium coating on Cobalt Chrome alloy in vitro & vivo- direct metal fabrication vs. plasma spraying

Background Titanium surface coating on Cobalt-Chromium (CoCr) alloy has characteristic desirable for orthopedic implant; strength, osteointegrative capability, biocompatibility. Creating such coated surface takes challenging process and two dissimilar metals are not easily welded. In our study, we utilized additive manufacturing with 3D printing called direct metal fabrication (DMF) and compared it to plasma spraying method (TPS), to coat titanium onto CoCr alloy. We hypothesized that this would yield a coated surface quality as acceptable or better than already established method of plasma spraying. For this, we compared characteristics of titanium coated surfaces created by direct metal fabrication method (DMF) and titanium plasma spraying (TPS), both in-vitro & in-vivo, for (1) cell morphology, (2) confocal microscopy images of immunofluorescent assay of RUNX2 and fibronectin, (3) Quantification of cell proliferation rate, (4) push-out biomechanical test, and (5) bone histomorphometry.Method For in vitro study, human osteoblast cells were seeded onto the coated surfaces. Cellular morphology was observed with scanning electron microscope. Cellular proliferation was validated with ELISA, immunofluorescent assay. For in vivo study, coated rods were inserted into distal femur of rabbit and then harvested. The rods were biomechanically tested with push out test and observed for histomorphometry to evaluate microscopic bone to implant ratio.Result For cell morphology observation, lamellipodia and filopodia, a cytoplasmic projection extending into porous structure, formed on both surfaces created by DMF and TPS. Proliferation of the osteoblasts, the DMF group showed better result at different optic density levels (p = 0.035, 0.005, 0.001). Expression and distribution of fibronectin and Runx-2 genes showed similar degrees of expressions. Biomechanical push-out test yielded similar result (p = 0.714). Histomorphometry analysis also showed similar result (p = 0.657).Conclusion In conclusion, DMF is a method which can reliably create proper titanium surface on CoCr alloy. The resulting product of the surface shows similar quality to that of plasma spraying method, both in vivo and in vitro, in terms of biological and mechanical property.Keywords: Titanium surface coating, Direct metal fabrication, Osteointegration, 3D printing.

Comparative Analysis of Titanium Coating on Cobalt Chrome Alloy in Vitro & Vivo-Direct Metal Fabrication vs. Plasma Spraying

BackgroundTitanium surface coating on Cobalt-Chromium (CoCr) alloy has characteristic desirable for orthopedic implant; strength, osteointegrative capability, biocompatibility. Creating such coated surface takes challenging process and two dissimilar metals are not easily welded. In our study, we utilized additive manufacturing with 3D printing called direct metal fabrication (DMF) and compared it to plasma spraying method (TPS), to coat titanium onto CoCr alloy. We hypothesized that this would yield a coated surface quality as acceptable or better than already established method of plasma spraying. For this, we compared characteristics of titanium coated surfaces created by direct metal fabrication method (DMF) and titanium plasma spraying (TPS), both in-vitro & in-vivo, for (1) cell morphology, (2) confocal microscopy images of immunofluorescent assay of RUNX2 and fibronectin, (3) Quantification of cell proliferation rate, (4) push-out biomechanical test, and (5) bone histomorphometry. MethodFor in vitro study, human osteoblast cells were seeded onto the coated surfaces. Cellular morphology was observed with scanning electron microscope. Cellular proliferation was validated with ELISA, immunofluorescent assay. For in vivo study, coated rods were inserted into distal femur of rabbit and then harvested. The rods were biomechanically tested with push out test and observed for histomorphometry to evaluate microscopic bone to implant ratio. ResultFor cell morphology observation, lamellipodia and filopodia, a cytoplasmic projection extending into porous structure, formed on both surfaces created by DMF and TPS. Proliferation of the osteoblasts, the DMF group showed better result at different optic density levels (p = 0.035, 0.005, 0.001). Expression and distribution of fibronectin and Runx-2 genes showed similar degrees of expressions. Biomechanical push-out test yielded similar result (p = 0.714). Histomorphometry analysis also showed similar result (p = 0.657).Conclusion In conclusion, DMF is a method which can reliably create proper titanium surface on CoCr alloy. The resulting product of the surface shows similar quality to that of plasma spraying method, both in vivo and in vitro, in terms of biological and mechanical property.

Taking a Powder

This article focuses on the use of laser in conjunction with metal powder. The use of the laser in conjunction with metal powder could be regarded as an extension of rapid prototyping, which has involved plastic parts almost exclusively. However, terms such as ‘direct metal fabrication’ and ‘rapid manufacturing’ suggest that developers have much more ambitious goals in mind for powder metals. Lockheed Martin Tactical Aircraft Systems in Fort Worth, Texas, is operating a research facility based on the laser engineered net shaping (LENS) process on the same factory floor where the F-16 fighter is assembled for the US Air Force. Optomec Design Co. in Albuquerque builds machines for use with the LENS process. Tests of Sandia National Laboratories' laser engineered net shaping process take place in a tank at Lockheed Martin Tactical Aircraft Systems. Much can be done in direct metal fabrication to improve the thermal conductivity of tooling for injection molding and die casting. The result can be increases in cycle times of as much as 80 percent.