The new type three-dimensional capillary - porous (TCP) of plasma coatings with adjustable through pores
The structure TCP of coatings consists of ripples and troughs. The structure TCP of coatings in essence differs from structure of conventional porous coatings, which one consist from feebly distorted of particles (such structure have low cohesive strength of particles in a coating). The surface area of these coatings is directly proportional to their thickness. This property has allowed to call these coatings three-dimensional. Basic porous volume of coatings is focused in troughs. The more shallow pores, capillary, are focused in ripples. The availability in designed coatings both large pores and capillary pores has allowed to call as their three-dimensional capillary - porous (ÒÑÐ). The thickness designed by us of coatings can reach several millimeters. Ripples and the troughs of our coatings shape macrostructure, and the rough walls of ripples shape microstructure. Under the literature data such porous structure by such pore (troughs) size is favorable for fixing a bone tissue in surface layer of an implants.
Adhesion and cohesion TCP of coatings have higher values than for conventional coatings. The allocation of pores for TCP of coatings has polimodal character. The first part of this allocation, the larger pores, compose troughs. Breadth of troughs is governed and reaches 1500 µ. The second part of allocation compose pores with the size smaller 10 microns. These pores are posed between a disk particles in the ripples. The blanket porosity ÒÊÏ of coatings reaches 70 %. Thickness of TCP coatings is 0,1-10 mm (can be and more). Designed TCP of coatings are intended for usage as metal (titanium) and ceramic (Al2O3, Ca10(PO4)6(OH)2 etc.) coatings for prostheses of a bone skeleton of the person. . The technology of plasma spraying of a porous coatings of a new type on tooth and coxofemoral prostheses is designed. The pore size in TCP coatings is optimal for fastenings of a bone tissue in a coating.
The special modes of process of spraying has allowed to increase the shear strength of linking of a titanium coating with a titanium prosthesis up to 30 êã/ìì2, that six times is higher than the data for conventional porous coatings.
Since February, 2000 year 700 substantial coxofemoral implants with ours ÒÑÐ titanium coatings set in the patients. We design technologies of spraying ÒÑÐ coatings on substantial implants and their machining jobs after spraying.
TCP of coatings can be utilised in others processes:
- Catalysis (as contact carriers);
- Heat exchange with change of a modular state refrigerant;
- Filtration (including molten metals);
- Absorption of a different radiation's.
We concluded investigating surface relief of our TCP coatings. This research confirmed significant differences of the TCP coatings from known porous coatings. The values Ra = 350 micron, Rz = 824 micron, Ra/Rz = 0.42, and V = 414 micron3/micron2, obtained for our coatings, are different from those reported by Dwayne D. Arola (Dwayne D. Arola, Mark K. McCain: "A New Method of Surface Preparation for Metal Orthopedic Implants", J. Biomedical Mater. Res. 2000, 53, 536-546).
Characteristics of implant surface after hydroabrasive treatment and after conventional plasma coating (from Dwayne D. Arola's article) are given in the table below. It is interesting to analize the experimental value V, which characterizes possible penetration depth of the growing bone in the coating. V for TCP coatings is 6 time greater than the corresponding value determined for conventional plasma coatings!
The structure TCP of coatings is explored for a wide range of materials, modes of spraying and views of industrial inventory.
|Method of Surface Formation
|Hydroabrasive treatment, USA*
|Plasma coating, USA*||28,9||144,9||71,0||0,155
|Plasma TCP coating,
* - Dwayne D. Arola, Mark K. McCain
Fig. 1.The TCP coatings with new type porous structure. Mark 100 µ.
Fig. 2. Real intrabone coxofemoral implants "leg" and "bowl" with three-dimensional is capillary - porous titanic coatings. Implants have passed successful clinical tests and are used at enterprise " ÝÑÈ "(Moscow).
Fig. 3. Structure of a surface three-dimensional capillary - porous titanic coating on real coxofemoral implants "leg" (it is increased in 5 times).