Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2002-02-28
2004-05-04
O'Connor, Cary E. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023600
Reexamination Certificate
active
06730129
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an implant for application in bone, for example the jaw bone, primarily of the human body. The implant comprises a unit which can be applied in the bone in question and which is made of biocompatible material, preferably titanium. At least on its surface parts cooperating with the bone, the unit is provided with a coating (or coatings) as will be described below. The invention also relates to a method for producing such an implant and to the use of such an implant.
PRIOR ART
It is already known to coat implants with films or layers on those parts which are directed towards the bone in question, for example the jaw bone. The coating is intended to initiate and stimulate bone growth where the implant has been implanted or screwed into place. It is known to use hydroxyapatite or HA in the coating. The said HA can be produced by various methods, of which one advantageous method has been found to be a method called RF sputtering, with subsequent heat treatment. It is known to use calcium phosphate compounds to achieve different release times during which the agent migrates from the layer to the surrounding bone material/jaw bone material, using different degrees of crystallization. The higher the degree of crystallization, the longer the release time, and vice versa.
Reference may be made to WO 98/48862 from the same Applicant as in the present case. The said publication gives examples of methods for applying layers of this type, and layer structures which are applicable in the present invention.
Reference may be made in purely general terms to WO 88/08460 and WO 94/25637. Reference is also made to the publications “Biomaterials, Volume 17, No. 4, 1996, K. Van Dijk et al., Influence of annealing temperature on RF magnetron sputtered calcium phosphate coatings, page 405 to page 410” and “Journal of Biomedical Materials Research, Volume 28, 1994, J. G. C. Wolke et al., Study of the surface characteristics of magnetron-sputter calcium phosphate coatings, page 1477 to page 1484” and “Phosphorus Research Bulletin, Volume 6, 1996, Kimihiro Yamashita et al., Bone-Like Apatite Coating of Alumina and Zirconia by RF-Magnetron Sputtering, page 123 to page 126”.
In connection with titanium implants, it is also known to arrange thick, porous titanium oxide layers which are used as depots for, inter alia, bone-growth-stimulating agents/substances (TS). In this connection, reference may be made to Swedish Patent Application No. 99 01971-3 filed on the same day and by the same Applicant, and which starts from the known arrangements according to the publications “Journal of Biomedical Materials Research, by Dann et al., Gentamicin sulfate attachment and release from anodized TI-6A1-4V orthopedic materials, Vol. 27, 895-900 (1993)” and “Journal of Biomedical Materials Research, by Hitoshi Ishizawa and Makoto Ogino, Formation and characterization of anodic titanium oxide films containing Ca and P, Vol. 29, 65-72 (1995)”.
Reference is made in purely general terms to U.S. Pat. Nos. 4,330,891 and 5,354,390.
Technical Problem
At the present time, considerable efforts are being made to further develop and refine the implants, methods and uses in question here. Particularly in the case of a bone/jaw bone in which it is not entirely certain that the implant will incorporate in the bone, it is preferable to be able to call upon and use all the possibilities at present available in the areas in question, inter alia the dental area. The invention aims to solve this problem, among others.
There is a need to be able to control more exactly the release times for the transfer of the agents/substances from the implant layer to the surrounding bone tissue. Thus, for example, it may be necessary to achieve a better controlled release function during a defined or optimum time for the agents or the substances. The invention solves this problem too.
In certain cases, it is preferable for the implant surface cooperating with the bone structure to still have the prescribed degree of fineness even after the coating or coatings have been applied, in order, in certain implant cases, to be able to maintain relatively small tightening forces/screwing forces, for example for a tooth implant in a hole in the jaw bone. The invention solves this problem too.
Using a relatively coarse porosity can increase the tightening force considerably, which may be advantageous in certain cases but which should be avoided in other cases, especially in connection with hard bones. It may be noted here that improved healing processes in soft bones are needed. The invention solves this problem too.
It is also preferable to be able to use proven methods for producing the relevant type of implant despite the fact that the implant has better properties from the medical point of view. The invention solves this problem too.
It is often necessary to be able to accelerate the healing time for an implant. This can be controlled by suitable choice of coating or coatings. There are also problems in being able to correctly balance the initial bone growth stimulation and the long-term maintenance of the established bone growth. If bone growth is too rapid, this may give rise to bone fractures and other complications in bone growth. A long-term stimulation or the maintenance of bone growth are important for an implant which is to function for a long time or for many years without the implant needing to be changed. The invention solves this problem too.
In accordance with the invention, a bone-growth-stimulating substance or agent, here called TS, is to be used. Examples which may be mentioned are those substances belonging to the superfamily TGF-&bgr;, for example BMP (
B
one
M
orphogenetic
P
roteins). There may be problems in preventing the said rapid release of the TS in question. It is also preferable to be able to obtain a functionally reliable support for TS upon application to an implant surface which from the outset is amorphous or heat-treated and partially crystalline. The invention solves this problem too.
There is also a need to have access to a wider range and choice of implant types which will be able to satisfy different applications on the market, cf. implants for soft bone and hard bone, etc. The invention solves this problem too.
Solution
The feature which can principally be regarded as characterizing an implant according to the invention is that the coating or coatings comprise a CaP coating with added TS. (CaP=calcium phosphate, and TS=growth-stimulating substance).
In embodiments of the inventive concept, the time for the said agent in the said coating or coatings to be released to the surrounding bone or tissue is chosen by setting the release time for CaP and the release time for TS in relation to each other. The release time for CaP is chosen with the aid of the degree of crystallization in CaP. The total release time can be chosen within the range from a few days to several months. In one embodiment, TS is applied on top of CaP. In one embodiment, the CaP coating can have a thickness in the range of between a few angstroms and 10 &mgr;m. In another illustrative embodiment, values in the range of between 0.1 &mgr;m and 20 &mgr;m can be used. All those areas of the said unit which cooperate with or are facing the bone material are preferably coated with the coating or layer in question. Each TS layer can have a thickness in the range of between a few angstroms and 1 &mgr;m.
In one embodiment, the coating or coatings comprise one or more layers of calcium phosphate compounds and one or more layers of bone-growth-stimulating substance. Agents of the release-retarding type, for example hyaluronic acid, can be interleaved with the said layers. In a further illustrative embodiment, one or more layers of CaP can have a high degree of crystallization, for example 75-100%, which means that the layer or layers have the principal role of functioning as supports for the layer or layers of TS and possibly the release-retarding agent or agents. In a further embodiment, one or more layer
Connolly Bove & Lodge & Hutz LLP
Melson Candice C.
Nobel Biocare AB
O'Connor Cary E.
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