BONE IMPLANT

Abstract: The invention concerns an implant for guided or controlled bone tissue regeneration. The implant consists essentially of a three-dimensional material having a form that allows bone cells to attach to it or can be modified to allow cells to attach to it and which allows cells to grow in more than one layer. According to the invention, the material essentially consists of a biocompatible, fibrous material.

Description: BONE IMPLANT The present invention concerns an implant for guided or controlled bone tissue regeneration. Guided tissue regeneration is a known technique for creating new periodontal attachment to real teeth. This technique is based on the assumption that only some of the cell types in the jaw have a positive effect on the creation of supporting tissue, whereas other types have a negative effect. The latter, i.e. the epithelium, connective tissue and bone cells, should be prevented from reaching the tooth, whereas the former, mostly from the periodontal ligament, should have free access thereto. To keep away the undesired cells, "cell-tight" filters or membranes placed near the tooth are used. The membrane, which is soft, is applied or applies itself to the tooth. A much-used membrane consists of expanded PTFE and is sold under the tradename of GORE periodontal membrane (Gottlow et al J. Clin. Periodontology 1984; 9: 494-503; Pontoriero, R. et al J. Clin. Periodontology 1988; 15: 247-254; Pontoriero, R. et al J. Clin Periodontology 1989; 16: 170-174; Gottlow, J. et al 1986; 13: 604-616; Becker, W. et al Int. J. Periodont . Rest. Dent. 1988; 3: 2-16) . When modified, this technique is said to be useful in connection with fixtures. The flat membrane is applied to the top of the fixture, under the flap (Dahlin et al Int. J. Oral Maxillofac. Implants 1989; 4(1): 19-25; Becker, W. et al Int. J. Periodont. Rest. Dent. 1990; 10: 93-102). However, it has been found that this technique gives no satisfactory regeneration of bone tissue. As disclosed in the patent publication PCT/SE91/00216 it has however been found that soft, cell- tight membranes are not suitable for recreating bone tissue in connection with fixtures, i.e. coronally of (above) the surrounding bone level. Instead it was found that cells in the jaw that previously were considered disadvantageous in the recreation of bone tissue are ac ¬ tually extremely advantageous in this process. Therefore bone cells from the periosteum and the bone edge should be given access to the operation area round the fixture. This accessibility can be created by the rigidity and the perforations of the device according to this patent publication. This technique is also disclosed in an article by S. Jovanovic et al in Volume 10, No. 1, 1995 of The International Journal of Oral and Maxillofacial Implants. According to this article, supracrestal bone formation was demonstrated by a submerged membrane therapy in a dog model. The bone formation was obtained by using rein- forced e-PTFE membranes with titanium. These membranes preserved their original form during the investigation, provided a large space for blood-clot stabilisation and resulted in more bone when compared to the use of standard membranes. It has now been found that sufficient rigidity and space-providing ability can be obtained if the mesh used according to the article by Jovanovic et al is replaced by a fibrous material, preferably in the form of wool. The publication WO 9007308 discloses a barrier which could be in the form of a fibrous material. The barrier is intended for regeneration of bone supporting tissue and is said to give a predictable healing sequence including a regeneration of firstly, periodontal ligament tissue, secondly, surrounding alveolar bone tissue and, thirdly, gingival connective tissue and epithelium. It is critical that the barrier is used in combination with a separating means including e.g. protuberances. Furthermore, it is recommended that the barrier should consist of a biodegradable material. In contrast to this known material which should give a specific healing sequence of different cells, the fibrous material according to the present invention is intended for use as an implant for guided or controlled regeneration or growth of primarily or essentially only bone cells in surgically intervened areas. No separating means of the kind necessary according to the patent publication WO 9007308 is required. Furthermore, according to the present invention, the guided growth or regeneration of the bone cells is determined by the shape and the material of the implant and depends on the damage to be remedied. In practice the shape of the implant is determined by the person performing the surgery. The new implant according to the present invention essentially consists of a three-dimensional, space- creating, porous, biocompatible, non-biodegradable material having a form that allows bone cells to attach to it or which can be modified to allow cells to attach to it and which allows cells to grow three-dimensionally . It is critical that the material is fibrous, and preferably in the form of wool. Especially preferred forms are wool strings or pads, which can easily be tailored to the desired form by the surgeon. The new material according to the invention should have a sufficient strength to withstand the pressure prevailing in the region of the body where it is to be inserted and it should also have a suitable porosity. The actual diameter of the fibre may vary depending on the site in body and the required strength. Normally this diameter will be less than 1 mm, preferably less than 0.5 mm and most preferably less than 0.1 mm. As regards the porosity it is obvious that the more porosity the more the bone cells will be formed within the space of the implant. If, however, the porosity is too large the ability of the implant to withstand pressure exerted by the adjacent tissues will decrease. If, on the other hand, drilling operations are to be expected, e.g. for the fixation of screws, in the newly created bone, the porosity should not be too low. The optimal porosity will therefore depend on the place where the fibrous material is to be used and is easily determined by the person skilled in the art. The new biocompatible implant preferably consists of titanium or titanium-coated fibres. Preferably the fibres are in the form of titanium wool. Other types of material are ceramic materials.. Furthermore the new material can be provided in the form of strings or pads, which optionally can be at least partially covered by a film or membrane of e.g. polylactic acid in order to avoid optional fibre penetration through the mucous membranes. In comparison with the devices known from the PCT/SE91/00216 publication and the above article by Jovanovic et al, the device according to the present invention confers several advantages. Thus the new device can be obtained in almost any shape and more or less tailored for the intended use. The new material also provides an increased surface for rapid bone regeneration, as it has been proved that newly formed bone cells have a tendency to climb on a surface, thereby increasing the proliferation of the bone cells. Another advantage is that the device can be manufactured without expensive production equipment. Other advantages concern the possibility of coupling bone morphogenic proteins (BMPs) to fibres according to the invention. The new device can also be useful in areas other than teeth prosthetics, where there are problems with replacing parts of the skeleton that have lost their original shape. After a traffic accident, crushed or caved-in skeleton parts of the face may have to be replaced, and in bone neoplasm therapy, it is sometimes necessary to surgically remove skeleton parts which may need to be replaced. The method of using the implant can be described as follows : The area in which the implant is to be installed is first uncovered by raising one or two separate mucoperiostal flaps. Minor perforations (0.5-1 mm in diameter) are done in the bone tissue in order to perforate the compact bone wall and facilitate bleeding into the wound area. This technique improves the bone regeneration procedure in the area to be regenerated. The area is inspected by the surgeon and a proper implant size is chosen. The implant will thereafter be trimmed in order to fit the defect morphology. The implant is, if necessary, fixated to the bone. For example, small screws could do this in different ways. The soft tissues are trimmed and placed over the implant in such a way that this is completely covered by the flaps. The flaps are sutured and the area is left for healing. During the healing phase the area should be protected from external forces. This means that if the implant is used in the mouth, removable dentures should not be worn during the phase of healing.

Claims: CLAIMS 1. A new implant essentially consisting of a three- dimensional, essentially non-biodegradable, space- creating, porous, biocompatible material having a form that allows bone cells to attach to it or which can be modified to allow such cells to attach to it and which allows primarily bone cells to grow three-dimensionally, c h a r a c t e r i s e d in that the implant essentially consists of a fibrous material. 2. The implant according to claim 1, c h a r a c t e r i s e d in that the fibrous material essentially consists of titanium or titanium-coated fibres . 3. The implant according to claim 1, c h a r a c t e r i s e d in that it is at least partially covered by a bioresorbable membrane. 4. The implant according to any one of the preceding claims, c h a r a c t e r i s e d in that it is in the form of titanium wool strings or pads. 5. The implant according to any one of the preceding claims, c h a r a c t e r i s e d in that it also includes bone morphogenic factors. 6. Use of an implant which allows primarily bone cells to grow three-dimensionally and which essentially consists of a three-dimensional, essentially non- biodegradable, space-creating, porous, biocompatible material having a form that allows bone cells to attach to it or which can be modified to allow such cells to attach to it and which essentially consists of a fibrous material . 7. Method of providing selective bone tissue regeneration or growth, c h a r a c e r t i s e d in that a defined space for bone tissue growth is provided by surgical intervention, that an implant essentially consisting of a three-dimensional, essentially non- biodegradable, space-creating, porous, biocompatible material having a form that allows bone cells to attach to it or which can be modified to allow such cells to attach to it and which essentially consists of a fibrous material, is arranged in the selected implant area, and that soft tissues are trimmed and replaced over the implant in such a way that the soft tissue after suturing completely covers the implant.

Inventors: RENVERT STEFAN, RENVERT, STEFAN
Applicants: MIGRATA U K LTD, RENVERT STEFAN, MIGRATA U.K. LTD., RENVERT, STEFAN
Application year: 1998
Main classification: A61C8
IPC codes: A61C8, A61F2, A61L27