Benefits of Tantalum for Orthopedics Implants
Featuring the CVDVP200
Ta metal offers benefits that can enhance preexisting implant systems. Worth noting, is that given the high density of Ta, and the difficulty of machining Ta using traditional means, whole Ta implants are impractical. However, CVD processing can uniquely enable the use of Ta for implants, without compromising the novelty of the manufacturer’s orthopedic system.
Ta can be coated evenly onto a complex 3D shape by CVD. This even coating may serve as mechanical sealant to protect roughening beads/particles from disintegrating over time, reducing the odds of implant loosening. Additionally, such a sealing layer, in combination with the ‘low ion release’ property of Ta may prevent unwanted leaching of metal ions (from metallic implant substrate components such as CoCrMo), allowing for a more predictable, stable implant performance in the long term.
Importantly, Ta is biologically innocuous similarly to Ti, but like HA, and more so than Ti, Ta is bioactive. HA, however, suffers from eventual cracking and delamination, and ex-situ testing of Ti coatings have shown a similar loss of Ti layer coverage on simulated implants. We anticipate that ductile Ta will outperform both HA and Ti with regard to resisting cracking, especially when the Ta coating is CVD-coated. Further, higher surface energy of Ta, as compared with Ti may explain why initial cell interaction and proliferation is faster on Ta.
- Excellent corrosion resistance
- Good wear resistance for joints. For instance, Ta coated on CoCrMo has demonstrated better characteristic than DLC coated on CoCrMo.a
- Alpha (α)-Ta can be obtained by CVD with the appropriate recipe, perhaps directly, or obtained irreversibly by post-deposition annealing of the deposited β-Ta.b α-Ta is known for having noteworthy ductility.c Meanwhile, implants coated by Ti-thermal spray have been shown to suffer from a ~30% loss of implant coverage during ex-situ impact testing.d The ductility of α-Ta could prove to be an improvement upon long-term implant durability as compared with a coating of the typical thermal-sprayed Ti.
- Observed cell proliferation on the various surfaces (where greater is better): Ta > HA > Tie,f
- Ta features low ion release, and as such, may serve as a good chemical ‘sealant’ when uniformly coated onto metal alloys such as CoCrMo.g Co and Cr ions, are not bioinert, and have been shown to illicit an unwanted biological response.h
- Initial cell attachment onto tantalum has been observed to be comparable to that of hydroxyapatite (HA).f However, there are concerns about the long term durability of HA-coated implants, as HA is known to exhibit cracking, delamination, and undergoes phase change to its lesser preferred amorphous phase.i
- Ta biologically bonds to bone.a,e,f
- Better cellular adhesion than Ti – Tantalum has a higher surface energy than titanium, enhancing cell-material interaction on Ta.e
- A statistically significant, higher density of proliferated cells have been observed on the surface of Ta as compared with a similarly pretreated Ti surface, also having a similar morphology.e
(a)Sci. Technol. Adv. Mater., 2014, 15 (1), 014402 (b)Inorg. Mater., 2017, 53 (10), 1064-1068 (c)Surf. Coat. Technol., 2004, 177–178 (30), 44–51 (d)Spine J., 2018, 18 (5), 857–865 (e)Acta Biomater., 2010, 6 (8), 3349–3359 (f)JOM, 2010, 62 (7), 61-64 (g)Mater. Sci. and Eng. C, 2012, 32 (4), 887–895 (h)J. Orthop. Res., 2013, 31 (9) 1484-1491 (i)Biomaterials, 1996, 17 (5), 537-544
Chemical Vapor Deposition Tantalum Processing
Chemical vapor infiltration (CVI) is a chemical vapor deposition (CVD) process that is performed at low pressures to allow for coating the internal surfaces of porous materials having complex shapes and geometries. Using heat and low pressure, precursor vapors penetrate the pores or fibers of the material and deposit to form a conformal coating on the internal surfaces.
CVI System Features & Options
- Dual or multi chamber configuration for improved productivity
- Substrate temperatures 800 to 1200 degrees Celsius
- Cascade temperature control using external (furnace) and internal (process) thermocouples for real time continuous in-situ control of temperature profiles
- CVDWinPrC™ system control software for real time process control, data logging, and recipe editing
- Process pressure control with automatic pressure adjustment during the process to control infiltration and uniformity
- Wet scrubbing and neutralization treatment of hazardous process exhaust gasses
powered by CVDWinPrC™
Operated through our CVDWinPrC™ process control software, the systems automatically log data and graphically show time-dependent values of user-selected parameters. CVDWinPrC™ also allows users to load preprogrammed recipes, modify, check and create new recipes, and view realtime or saved process data.
The systems have application configured safety protocols embedded into relay logic, PLC, and CVDWinPrC™ software.