Titanium plasma spray

Fig. 1 Photograph of (a) femoral hip stem with (b) inset of the microbeaded surface, (c) Photomicrograph of a plasma-deposited calcium phosphate coating on a hip stem (image kindly provided by Smith Nephew, Memphis, TN, USA), (d) Dental implant with (e) inset showing a titanium plasma-sprayed surface coating...

When high-impact resistance is needed, bioceramic materials such as hydroxyapatite can be coated by plasma spraying on to metals like titanium. Plasma-sprayed calcium phosphate coatings on to steel pins, when used with implants, greatly reduce pain experienced in hip joints. Bone adhesion is also improved [68,69],... 

The Salto Talaris Anatomic Ankle (Tomier, Edina, Minnesota, US A) is ametal-on-UHMWPE, semi-constrained cemented TAR (Figure 11.15). It has been in clinical use since 2006 [88]. The device consists of two mating components a CoCr tibial base in association with a conforming UHMWPE insert and a CoCr talar resurfacing component [89]. The bony interface of the metal components are coated with titanium plasma spray, although the device is intended for cemented use only in the United States [89]. 

The ProDisc-C, produced by Synthes, is a cervical version of the lumbar ProDisc II and employs CoCr-on-UHMWPE articulation (Figure 12.10). In contrast to the lumbar design, in the ProDisc-C, the UHMWPE component is provided already inserted into the inferior endplate by the manufacturer. Bone-implant fixation is achieved by a combination of a keel and titanium plasma sprayed surface, similar to the ProDisc II. Naturally, the size and proportion of the keel and articulations are much smaller in the ProDisc-C as compared with the ProDisc-L, but the technology underlying both designs is identical. Synthes completed a prospective randomized clinical trial with the ProDisc-C for the FDA and received clearance to market the device in the United States in 2007. 

Despite the progress outlined in this chapter, much work remains to be done in the metal surface preparation arena. For example, there is still no ideal surface preparation method that does for steel what anodization processes do for aluminum and titanium. The plasma spray process looks encouraging but because it is slow for large areas and requires rather expensive robot controlled plasma spray equipment, its use will probably be limited to some rather special applications. For more general use, the sol-gel process has potential if future studies confirm recently reported results. 

In the field of metallic powder applications, a method of plasma spray coating suitable for biomedical materials has been developed using titanium and calcium phosphate composite powder. By means of the mechanical shock process, the appropriate composite powder was prepared, and plasma sprayed on Ti substrate under a low-pressure argon atmosphere. A porous Ti coating layer was obtained in which the surface and the inside of the pores were covered thinly with hydroxyapatite. This surface coating is expected to show excellent bone ingrowth and fixation with bone (21). 

Plasma spray coatings have been evalnated as snrface treatments for aluminnm, titanium and steel snbstrates prior to adhesive bonding. These treatments are environ-... 

PiatteUi A, Scarauo A, PiatteUi M, Bertolai R, Panzoni E. Histologic aspects of the boue aud soft tissues surrounding three titanium uou-submerged plasma-sprayed implants retrieved at autopsy a case report. J Periodontol 1997 68(7) 694-700. 

Different methods used to prepare titanium diboride have been reviewed by Samsonov et al. (1975). At present, it is mainly produced as a powder by thermochemical reduction of boron and titanium oxides followed by hot pressing and sintering to process the final product. The less costly alternative appears to be to coat suitable substrate materials with TiB2 or TiB2-based composites by hot pressing, plasma spraying, chemical vapor deposition, etc. 

Muzzarelli et al. (2000) described a method for coating prosthetic articles with chitosan-oxychitin. Plates of titanium (Ti) and its alloys were plasma sprayed with hydroxyapatite and glass layers, and subsequently a chitosan coat was deposited on the plasma-sprayed layers using chitosan acetate. These layers were treated with 6-oxychitin to form a polyelectrolytic complex. This complex was optionally contacted with l-ethyl-3-(3-dimethylami-nopropyl) carbodiimide at 4°C for 2 hours to form amide links between the two polysaccharides, or acetylation with acetic anhydride in methanol to obtain a chitin film. In all cases, the modified coats were insoluble, uniformly flat, and smooth. Prosthetic materials coated with chitosan-oxychitin were capable of provoking colonization by cells, osteogenesis, and osteointegration. 

During plasma spraying of hydroxyapatite onto titanium alloy substrate surfaces minor amounts of highly reactive CaO are being formed by thermal decomposition that react with the native titanium oxide layer to form calcium titanate, CaTiOs. This thin reaction layer has been implicated to be an important... 

Demnati, I., Parco, M., Grossin, D., Fagoaga, I., Drouet, C., Barykin, G., Combes, C., Braceras, I., Gonsalves, S., and Rey, C. (2012) Hydroxyapatite coating on titanium by a low energy plasma spraying mini-gun. Surf. Coat. Technol., 206, 2346-2353. 

Podlesak, H., Pawlowski, L., Laureyns, J., Jaworski, R., and Lampke, T. (2008) Advanced microstructural study of suspension plasma sprayed titanium oxide coatings. Surf. Coat. Technol., 202 (15), 3722-3731. 

Early bone apposition in vivo on plasma -sprayed and electrochemically deposited hydroxyapatite coatings on titanium alloy. Biomaterials, 27 (23), 4192—4203. 

Figure 6.14 shows that a plasma-sprayed hydroxyapatite coating on a porous titanium layer covering the titanium alloy surface (solid bars) will improve the interfacial bond strength compared to uncoated porous titanium (light bars)... 

Figure 6.14 Comparison of early stage interfacial bond strength of porous titanium with (solid bars) and without (light bars) a plasma-sprayed hydroxyapatite coating (Cook, 1991. (Modified after Hench (1991).)...

Figure 6.17 Formation of a thin CaSi03 (or CaTiSi05) reaction layer adjacent to the titanium alloy substrate surface of an atmospheric plasma-sprayed Ti6AI4V...

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