Implant coated with net-shaped or island-shaped low-crystallized hydroxyapatite and method for coating same

Abstract

The present disclosure relates to a method for coating a surface of a titanium implant with low crystalline hydroxyapatite having network- or island-like morphology and to an implant coated by such method.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional application of U.S. patent application Ser. No. 13 / 378,029, filed Dec. 22, 2011, now pending, which is a U.S. national stage application filed under 35 U.S.C. §371 of International Patent Application No. PCT / KR2010 / 003132, file May 18, 2010, which application claims priority to Korean Patent Application No. 10-2009-0054315, filed Jun. 18, 2009.BACKGROUND[0002]1. Technical Field[0003]The present disclosure relates to the field of coated titanium implants, which have been widely used as grafting materials. The present disclosure relates in particular to a method for coating a surface of a titanium implant with low crystalline hydroxyapatite having bioabsorbability, and to an implant coated by such a method.[0004]2. Description of the Related Art[0005]In recent years, hydroxyapatite has been widely used as an artificial biomaterial capable of replacing hard tissues such as bones or teeth. Hydroxyapatite is a ...

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Benefits of technology

[0013]The present disclosure provides methods for coating titanium or titanium alloy implants with hydroxyapatite and implants coated by such methods. The methods disclosed can achieve superior productivity by relatively simple processes at low cost, without requiring temperature and / or pH control or elevated temperatures. The implants coated by the methods disclosed herein may show superior incorporation into bone and may thus have improved properties and lifespan over implants coated by conventional methods.

[0015]Implant coating methods described herein provide low crystalline hydroxyapatite-coated implants that may be used for long periods of time while not being isolated from new bone, such that the implants are absorbed by osteoclasts in vivo, thereby taking part in remodeling processes of bone. Methods and implants disclosed herein thereby overcome limitations of conventional methods for forming hydroxyapatite coating layers having high crystallinity and the resulting implants.

[0016]Further, coating methods providing low crystalline hydroxyapatite according to the present invention are relatively simple compared to conventional wet methods. The coating methods are also economically favorable due to the absence of requirements for strict control of reaction conditions such as temperature and / or pH and for elevation of reaction temperature, while imparting excellent bioactivity.

[0017]Implants formed according to coating methods disclosed herein have an advantage of being usable for a long period of time while not being isolated from new bones, in such a way that the implant is absorbed by osteoclasts in vivo, thereby taking part in a remodeling process of bones.

[0018]Further, an implant coating method according to the present disclosure is capable of enhancing success of a titanium implant in such a way that the bioactivity imparted to a surface of the implant results in strong interfacial bonding between the implant and bone tissues or teeth tissues, and the promotion of osteoconductivity or osteogenesis. Furthermore, separation of an implant resulting from peeling of the surface coating layer is prevented due to bioabsorbability of the coating layer formed from low crystalline hydroxyapatite.

[0019]Further, an implant coating method according to the present disclosure enables the production of an excellent dental implant by very simple processes at low cost. The method allows control of thickness and morphology of the coating layer, as necessary, such as a thin coating layer, a thick coating layer, and co-exposed surfaces of titanium and a coating layer. Therefore, the present invention can be applied to a variety of biomaterial fields in accordance with desired uses, for example, the orthopedic area as well as the dental area.

Problems solved by technology

However, titanium disadvantageously exhibits poor biocompatibility as compared to ceramic materials such as hydroxyapatite, and undergoes dissolution of metal ions upon long term residence thereof in the human body, which consequently results in the formation of in vivo inorganic substances.

Plasma spraying which has been most commonly used among the above-mentioned methods has shortcomings such as non-uniformity of a coating layer due to instantaneous exposure to a high temperature of 10,000° C. or higher, and a difficulty to achieve a coating having a thickness of less than about 10 μm.

Further, this method has a problem of very low biological reactivity in that hydroxyapatite coated on the surface of titanium undergoes decomposition in vivo due to a very high crystallinity or is refractory to removal by osteoclasts.

Even after a functional bone is generated, the coating film exists and decomposes into by-products having different phases, which contributes to peeling of the coating film from the surface, finally resulting in the separation of an implant.

Further, sputtering or ion implantation, apart from high-priced equipment for this purpose, has suffered from various problems such as complex shapes, poor uniformity of the coating layer formed on irregular parts, and detachment of implants due to the peeling-off phenomenon in the human body.

The above-exemplified coating processes involve complicated steps or require a long coating time.

Generally, it is difficult for a supersaturated solution of calcium phosphate to maintain a constant concentration, due to spontaneous precipitation (see H. B. Wen, et al., J. Biomed. Mater. Res.

Further, a process which is performed under a limited condition of maintaining about 37° C. may take a long period of time, about one month or more, depending on conditions of the surface.

In addition, these methods also do not overcome limitations of a complex and long process time (Korean Patent Application No. 1999-38528 to Kim Hyun-Man, et al., and Korean Patent Application No. 2000-51923 to Kim Se-Won, et al., both assigned to Oscotec Inc.

Therefore, an initial process should proceed at a low temperature of 2° C. to 5° C., and it is very difficult to obtain a coating film of calcium phosphate as well as a colloidal solution of calcium phosphate without the elevation of temperature.

As discussed above, conventional wet coating methods utilize differences in the solubility of calcium phosphate in response to changes in temperature, and thus are limited by the need to control temperature and / or pH, the need to use elevated reaction temperature, and the complex procedures required for formation of calcium phosphate coating films.

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