Background of the Invention Upon treatment of patients with different bone fractures, the use of various types of fixation means has been known for a long time, which are implanted in the patient's tissue, for example in order to join different bone tissues, which com- pletely or partly have been separated through bone fractures. It is essential to choose a material and a design of these fixation means so that the body does not reject these fixation means, that inflammations do not occur, and that the fixation means are properly anchored in the bone tissue.

Various types of fixation means are implanted in patients'jaws, for exam- ple for patients with highly resorbed bone or very poor bone quality in the maxilla, i. e. the upper jaw. For these patients a double-anchoring fixation means is used, <BR> <BR> e. g. , which is anchored both in the maxilla and in the os zygomaticum, i. e. the zy- gomatic bone, which is located above the prominence of respective cheekbone towards respective ear. This double-anchoring fixation means is anchored subse- quent to drilling, during which drilling the maxilla is drilled through so that a through hole is formed, after which the drilling is continued through the sinus maxillaris, i. e. the maxillary sinus, and is stopped up in the os zygomaticum. Usually, the os zy- gomaticum always has good bone quality, which guarantees a good result. The alterative to this treatment of patients with above mentioned bone status is to take

a piece of bone from another part of the body, shape it and place it in the sinus maxillaries, to get a better support for the fixation means. Bone transplant involves a more extensive operation on a patient and a longer healing process.

SE 500 383 (EP 0 599 794) discloses a substantially cylindrical anchoring element for replacement of one or more teeth in the upper jaw, presenting two cy- lindrical portions having different diameters, which are provided with external threads having the same pitch. At one end the anchoring element has a mounting portion for the mounting of a denture or a dental bridge. The two cylindrical por- tions are intended for fixation in the zygomatic bone and the upper jaw, respec- tively.

However, the anchoring element according to SE 500 383, and other dou- ble-anchoring fixation means according to prior art, have several disadvantages.

Since it is important that a double-anchoring fixation element in the jaws is stable and firmly anchored, it is, besides a proper fixation in the os zygomaticum, essen- tial that the fixation element is also firmly anchored in the maxilla. This is problem- atic since the maxilla of patients with poor bone quality is often very thin. If there is a poor fixation in the maxilla, there is a major risk of inflammations and other com- plications. Prior fixation elements do not completely succeed in solving this prob- lem. Further, the fixation in the os zygomaticum of prior fixation elements is not strong enough. There is also a need for an effective double-anchoring fixation element upon other types of treatments, for example when two bones at another location in the body are to be joined after a complicated fracture. Fixation elements according to prior art neither solves the problem when the maxilla is completely or partly removed, for example as a consequence of cancer in the jaw region, and a dental bridge or a denture is to be arranged at the original position of the maxilla, and the only possibility of fixation is in the os zygomaticum. There is also a need for an effective single-anchoring fixation element for treatments at other locations in a patient's body.

The Object of the Invention The object of the present invention is therefore to provide an anchoring element, a dental anchoring member, and a dental anchoring unit which effectively are anchored in bone tissue, and join various separated bone tissues at various locations in the body with a low risk of inflammations and other complications.

Further, the object of the present invention is to provide an anchoring element and a dental anchoring member which improve and facilitate the fixation in the maxilla when a fixation shall be made in both the maxilla and the os zygomaticum, espe- cially on patients with poor bone quality. The object of the present invention is also to provide an anchoring element, a dental anchoring member, and a dental an- choring unit which improve the fixation in the os zygomaticum. A further object of the present invention is to provide a dental anchoring unit enabling the fixation of a denture or a dental bridge in the upper region of the maxillary sinus on patients without a maxilla.

Summary of the Invention The above mentioned objects of the present invention are attained by pro- viding an anchoring element of the kind defined in the preamble of claim 1, where the second fixation portion has the form of a truncated cone having the smaller basis adjacent to the intermediate portion and the larger basis forming the basis of the anchoring element. This conic shape of the second fixation portion provides for the anchoring element to be automatically wedged in the bore in the second bone tissue, and simultaneously provides for the apex of the anchoring element to be forced into the bore in the first bone tissue. The anchoring element is advanta- <BR> <BR> geously positioned in a patient's jaw, e. g. , the fist bone tissue being located in the os zygomaticum, and the second bone tissue being located in the maxilla, and an attachment means intended for a denture or a dental bridge is arranged at the ba- sis of the anchoring element. Advantageously, the attachment means comprises an attachment hole, which for example presents inner threads, and at least one contact surface for the denture or the dental bridge, and the attachment hole is ar- ranged at an angle to the longitudinal axis of the anchoring element.

According to an advantageous embodiment of the anchoring element ac- cording to the present invention, also the first fixation portion has the form of a truncated cone having the smaller basis adjacent to the apex and the larger basis adjacent to the intermediate portion. In this way the fixation in the first bone tissue becomes more effective. Inter alia for reasons of facilitating the production, it is also advantageous that the first and second fixation portions and the intermediate portion together have the form of a truncated cone having the smaller basis adja- cent to the apex and the larger basis forming the basis of the anchoring element.

According to a further advantageous embodiment of the anchoring ele- ment according to the present invention, the first fixation portion is threaded. In this way a firm fixation of the anchoring element in the first bone tissue is achieved when it is driven in by rotation. Advantageously, also the second fixation portion is threaded. An alternative to a threaded fixation portion is to provide the fixation por- tion with a rough surface, for example, which is attached to the bone tissue through pressure.

According to another advantageous embodiment of the anchoring element according to the present invention, the second fixation portion comprises at least one recess transverse to the threads and disposed at the intermediate portion, comprising a distinct edge transverse to the threads, which edge provides a groove forming cutting unit. Advantageously, there are several recesses, for ex- ample three, which are evenly distributed along the circumference. In this way, the second fixation portion becomes self-tapping since grooves are cut on the inside of the bore in the second bone tissue through the rotation of the anchoring ele- ment, in which grooves the threads of the second fixation portion subsequently engage. In order to avoid inflammations in non-bone tissue between the first and second bone tissues, the intermediate portion advantageously has a smooth outer surface. Sometimes the anchoring element is diagonally positioned to such an extent that it is positioned outside the maxilla, where there are, inter alia, mastica- tory muscles which could be irritated by the threads, and therefore the smooth outer surface is advantageous. If the intermediate portion is smooth and, in addi- tion, the fixation portions are threaded, it is advantageous that the outer surface of the intermediate portion, the surface limited by the valleys of the threads of the threaded first fixation portion, and the surface limited by the valleys of the threads of the threaded second fixation portion are portions of the envelope surface of the same truncated cone.

According to the present invention, a dental anchoring member of the kind defined in the preamble of claim 11 is also provided, where the second fixation portion comprises at least one recess transverse to the threads and disposed at the intermediate portion, comprising a distinct edge transverse to the threads, which edge provides a groove forming cutting unit. In this way, the second fixation portion becomes self-tapping since grooves are cut on the inside of the bore in the second bone tissue through the rotation of the dental anchoring member, in which

grooves the threads of the second fixation portion subsequently engage. Advanta- geously, the second fixation portion is provided with several recesses transverse to the threads, for example three, which for example are evenly distributed along the circumference. Advantageously, the attachment means comprises an attach- ment hole, which for example presents inner threads, and at least one contact surface for the denture or the dental bridge, and the attachment hole is arranged at an angle to the longitudinal axis of the dental anchoring member.

According to an advantageous embodiment of the dental anchoring mem- ber according to the present invention, the second fixation portion has the form of a truncated cone having the smaller basis adjacent to the intermediate portion and the larger basis forming the basis of the dental anchoring member. Advanta- geously, the first fixation portion has the form of a truncated cone having the smaller basis adjacent to the apex and the larger basis adjacent to the intermedi- ate portion, and advantageously the first and second fixation portions and the in- termediate portion together have the form of a truncated cone having the smaller basis adjacent to the apex and the larger basis forming the basis of the dental an- choring member.

According to a further advantageous embodiment of the dental anchoring member according to the present invention, the first fixation portion is also threaded, and suitably, the intermediate portion has a smooth outer surface to re- duce the risk of inflammations, and if the intermediate portion has a smooth sur- face, the outer surface of the intermediate portion, the surface limited by the val- leys of the threads of the threaded first fixation portion, and the surface limited by the valleys of the threads of the threaded second fixation portion are advanta- geously portions of the envelope surface of the same truncated cone.

According to the present invention, a dental anchoring unit of the kind de- fined in the preamble of claim 18 is also provided, where the fixations portion has the form of a truncated cone having the smaller basis adjacent to the apex and the larger basis adjacent to the end portion. As mentioned, the end portion is position- able in non-bone tissue between the os zygomaticum and the original position of the maxilla, i. e. where the maxilla would have been located but is removed as a result of injury or cancer. Advantageously, the attachment means comprises an attachment hole, which for example has inner threads, and at least one contact surface for the denture or the dental bridge, and the attachment hole is arranged

at an angle to the longitudinal axis of the dental anchoring unit. For all of the men- tioned attachment means, it is advantageous that the angle between the attach- ment hole and the longitudinal axis of the dental anchoring unit, member or unit is about 45°. The attachment hole can be replaced by a corresponding angled at- tachment pin. In this way, an effective and stable fixation of a denture or a dental bridge is achieved for a patient completely or partly without a maxilla.

According to an advantageous embodiment of the dental anchoring unit according to the present invention, the fixation portion and the end portion together have the form of a truncated cone having the smaller basis adjacent to the apex and the larger basis forming the basis of the dental anchoring unit.

According to a further advantageous embodiment of the dental anchoring unit according to the present invention, the fixation portion is threaded, and ad- vantageously, the end portion has a smooth outer surface. By threading, the effec- tive fixation is supported by the rotation of the dental anchoring unit upon the im- plantation, but instead of providing the fixation portion with threads, the fixation portion can, for example, be provided with a ragged and rough surface which is attached to the bone tissue through pressure. If the end portion is smooth, it is ad- vantageous that the outer surface of the end portion and the surface limited by the valleys of the threads of the threaded fixation portion are portions of the envelope surface of the same truncated cone.

Brief Description of the Drawings The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which: Fig. 1 is a side view of an embodiment of the anchoring element accord- ing to the present invention, Fig. 2 is a side view of an embodiment of the dental anchoring member according to the present invention, Fig. 3 is a side view of an embodiment of the dental anchoring unit according to the present invention, Fig. 4 is a schematic view of an example of the position of the anchoring element or dental anchoring member according to the present in- vention, in relation to the os zygomaticum and the maxilla, and

Fig. 5 is a schematic view of an example of the fixation of an embodi- ment of the anchoring element or dental anchoring member of the present invention in the os zygomaticum and the maxilla.

Detailed Description of the Embodiments Fig. 1 shows an embodiment of the anchoring element according to the in- vention, for fixation in a first bone tissue and in a second bone tissue, the first and second bone tissues being separated by non-bone tissue. The anchoring element comprises an apex 1 according to prior art, provided with elongated recesses 2 which function as cutting units when the apex 1 is screwed into the first bone tis- sue and thus form grooves in which the threads engage. Adjacent to the apex 1 there is a threaded first fixation portion 3 which together with the apex 1 is adapted for fixation in the first bone tissue, and has the form of a truncated cone having the smaller basis adjacent to the apex 1 and the larger basis adjacent to an intermedi- ate portion 4. Adjacent to the intermediate portion 4 there is a second fixation por- tion 5 adapted for fixation in the second bone tissue, and has the form a truncated cone having the smaller basis adjacent to the intermediate portion 4 and the larger basis forming the basis 6 of the anchoring element. At the basis 6 of the anchoring element, an attachment means 7 is arranged, intended for a denture or a dental bridge. The attachment means 7 advantageously comprises an attachment hole, which has inner threads, and two contact surfaces for the denture or the dental bridge. The attachment hole is arranged at an angle of about 45 ° to the longitudi- nal axis of the anchoring element. The outer surface of the intermediate portion 4, the surface limited by the valleys 8 of the threads of the threaded first fixation por- tion 3, and the surface limited by the valleys 9 of the threads of the threaded sec- ond fixation portion 5 are portions of the envelope surface of the same truncated cone. On the second fixation portion 5, there is a recess 10 transverse to the threads and disposed at the intermediate portion 4, comprising a distinct edge 11 transverse to the threads, which edge 11 provides a groove forming cutting unit.

Two additional such recesses are evenly distributed along the circumference of the second fixation portion 5, but are not visible in Fig. 1. The smaller basis of the first fixation portion 3 has a diameter of 4 mm, e. g. , and the larger basis of the second fixation portion 5 has a diameter of 5.3 mm, e. g.. The length of the first fixation portion 3 is 14 mm, e. g. , and the length of the second fixation portion is 12

mm, e. g. The total length from the top of the apex 1 to the larger basis of the sec- ond fixation portion 5 is 36,40, 44,48 or 52 mm, e. g. By choosing the total length, a certain slope of the cone shape is provided.

Fig. 2 shows an embodiment of the dental anchoring member according to the invention for fixation in the os zygomaticum and the maxilla, the os zygomati- cum and the maxilla being separated by non-bone tissue. The dental anchoring member is elongated and comprises an apex 12 according to prior art, as de- scribed in connection to Fig. 1, and a threaded first fixation portion 13 disposed at the apex 12, both adapted for fixation in os zygomaticum. The first fixation portion 13 has the form of a truncated cone having the smaller basis adjacent to the apex 12 and the larger basis adjacent to a smooth intermediate portion 14. The inter- mediate portion 14 is positionable in the non-bone tissue separating the os zygo- maticum and the maxilla. A threaded second fixation portion 15 is disposed at the basis 16 of the dental anchoring member and is adapted for fixation in the second bone tissue. The second fixation portion 15 has the form of a truncated cone hav- ing the smaller basis adjacent to the intermediate portion 14 and the larger basis forming the basis 16 of the dental anchoring member. The second fixation portion comprises three, of which only two are visible in Fig. 2, recesses 17, 18 transverse to the threads and disposed at the intermediate portion 14, each comprising a dis- tinct edge 19,20 transverse to the threads, respective edge 19,20 providing a groove forming cutting unit in the bore of the maxilla. At the basis 16 of the dental anchoring member an attachment means intended for a denture or a dental bridge is arranged, but enclosed by an dental anchoring member holder 21 which is re- moved when the dental anchoring member is anchored. The outer surface of the intermediate portion 14, the surface limited by the valleys 22 of the threads of the threaded first fixation portion 13, and the surface limited by the valleys 23 of the threads of the threaded second fixation portion 15 are portions of the envelope surface of the same truncated cone. The dimensions of the dental anchoring member are for example the same as for the anchoring element of Fig. 1.

Fig. 3 shows an embodiment of the dental anchoring unit according to the invention for fixation in the os zygomaticum, the dental anchoring unit being elon- gated and comprising an apex 24 according to prior art, as described in connec- tion to Fig. 1, and a threaded fixation portion 25 disposed at the apex 24, both adapted for fixation in the os zygomaticum, a basis 26, and an end portion 27 dis-

posed between the fixation portion 25 and said basis 26. The fixation portion 25 and the end portion 27 together have the form of a truncated cone having the smaller basis adjacent to the apex 24 and the larger basis forming the basis 26 of the dental anchoring unit. At the basis 26 of the dental anchoring unit, an attach- ment means 28 intended for a denture or a dental bridge is arranged. The attach- ment means 28 comprises an attachment hole, which has inner threads, and two contact surfaces for the denture or the dental bridge. The attachment hole is ar- ranged at an angle of about 45° to the longitudinal axis of the dental anchoring unit. The outer surface of the end portion 27 and the surface limited by the valleys 29 of the threads of the threaded fixation portion 25 are portions of the envelope surface of the same truncated cone.

Fig. 4 shows an example of the position of the anchoring element or the dental anchoring member of the present invention in a patient's jaw, where the first fixation portion 30 is anchored in os zygomaticum 31, and the second fixation por- tion 32 is anchored in the maxilla 33.

Fig. 5 shows a more precise example of the position of the anchoring ele- ment or the dental anchoring member of the present invention in a patient's jaw, where the first fixation portion 34 is anchored in os zygomaticum 35, and the sec- ond fixation portion 36 is anchored in the maxilla 37, and the smooth intermediate portion 38 is positioned in the sinus maxillaries 39.