The invention relates to a method for producing a rigid supporting prosthetic structure of the kind that is seen in the preamble of claim 1.

The invention also relates to a device for the production of a prosthetic structure of such kind, according to the preamble of the appended independent device claim.

A requirement for a prosthetic structure to correctly rest against fixtures, for instance implants, is that no sig¬ nificant stresses should occur in the structure when the same is connected to the fixtures. Such stresses can estab¬ lish forces, which tend to displace the fixtures mutually, whereby the patient may experience them as negative. Such stresses may also lead to an incomplete alignment between co-operating support surfaces on the prosthetic structure and the respective fixture/implant, so that a tightened mounting screw can get a tendency of becoming threaded out when the structure is subjected to varying loads.

The fixtures usually comprise implants, for instance a den- tal implant. Usually, a model of the jaw of the patient is manufactured using implant analogues. On the same, a tubu¬ lar member is releasably mounted by means of a fixing screw, which extends through the member and having a head that rests against a seating in the member. The threaded end of the fixing screw engages by a thread in the im¬ plant/the implant analogue in order to bring the support surfaces of the member and the implant analogue, for instance ring-shaped support surfaces, stably into solid contact with each other around the fixing member. Between adjacent pairs of such members along a line of implants, for instance dental implants in one of the jaws of a patient, bars are now to be bridgingly mounted on the mem-

E2005/001481

2 bers releasably carried by the implant analogues, without introducing any stresses. After that, the formed mounted structure is to be fixed in the substantially stressless state thereof. The intention is that the structure then may be provided with a superstructure of a conventional kind per se, for instance corresponding to a dental prosthesis and/or teeth, in order to, without problems, i.e., without introduction of stresses, subsequently be allowed to be connected to the implants in the patient by means of said members and the appurtenant fixing screws.

A previously known technique ("DynaStar") includes that the implants have cup-shaped upper surfaces and that the bars are telescopic and have ball-shaped end bodies, which are articulately received in the recesses of the implants. The ball-shaped end portions of the bars have a throughput opening each for a fixing member, which with the threaded portion thereof is received in a central threaded boring in the implant and which by means of the head thereof clamps the ball down in the recess of the implant. In the mounting operation, the telescopic bar may be given a chosen length, and furthermore, the telescopic bar parts should be mutu¬ ally fixed by welding, for the formation of a rigid and stiff structure that may be dismounted from the implants/ /the implant analogues.

A problem of the previously known structure is, however, that the balls of the bars should rest on the cup-shaped upper ends of the implants, whereby the possibility of dis- placement of the connection point of the bar along the axis of the implant cannot be attained in a simple way.

Another drawback is that the structure relies on telescopic bars, which means difficulties when the distances between adjacent implants are small.

An object of the invention is, therefore, to provide a method and a new device by means of which said drawbacks may be obviated entirely or partly.

The object is attained by the invention.

The invention is defined in the appended independent claims .

Embodiments of the invention are defined in the appended dependent claims .

Important features of the invention is that a body having a throughput channel is mounted on and displaced along a tubular member, which is releasably mounted on an implant/ /implant analogue at a desired axial position along said member. The body defines the position of the connection points of the connecting bars. This position may, in other words, be set by a chosen displacement of the body along the tubular member. The tubular member and the body should co-operate by a certain friction, for instance with a threaded joint or a frictional fitting, allowing the body to be displaced along the member by means of manually pressed forces into a chosen position.

When the distances between adjacent implants/implant ana¬ logues are relatively great, it may be advantageous to utilize axially extensible/shortenable ("telescopic") bars, the end portions of which are, for instance, cup-shaped, concave and co-operate with the (for instance, convex) sur¬ face portions of the bodies adapted thereto, in order to adjust the same bars to the correct length and into shape- wise bonding to the bodies . But when the distances between the implants/the implant analogues are relatively short, instead it may be advantageous to utilize bars having fixed length. Thus, a bar may be selected from a set or series of

bars of different length. One of the two bodies to which the bar is to be joined, may have an oval shape.

In relation to the previously known structure, which also requires that the screw head and the ball have articulately- co-operating surfaces having a centre of curvature that substantially coincides with the centre of curvature of the co-operating fusion faces of the ball and the implant, the invention also offers the advantage of allowing a greater range of deflection between the implant axis and the axis of the connecting bar.

In the structure according to the invention, at least one of the balls may have a protruding arm that forms a corbel- ling-out part of the structure, for instance for the exten¬ sion of a dental prosthetic structure.

In the following, the invention will be described by way of examples, reference being made to the appended drawing.

Fig. 1 schematically shows a side view of a prosthesis as mounted on implants or implant analogues.

Fig. 2 shows a view taken along the line II-II in Fig. 1.

Fig. 3 schematically illustrates an implant having a tubular member mounted thereon and a body mounted thereon.

Figs. 4 and 5 show in axial section two different embodiments of a bar, which may be used in the invention.

Fig. 6 schematically illustrates a fixed bar, as joined between two adjacent bodies, one of which is oval.

Fig. 7 schematically illustrates an alternative embodi¬ ment of the co-operating surface sectors of the body and of the bar.

Fig. 8 shows a view taken along the line VIII-VIII in Fig. 7.

Fig. 9 shows a variant of the object of Fig. 7.

Fig. 10 shows a view taken along the line X-X in Fig. 9.

Figs. 1 and 2 illustrate a prosthetic structure carried by three implants. Each implant 10 carries a tubular member 20 that rests against the implant 10 and is releasably con¬ nected to the same by a fixing member 21, which by means of a thread engages in a threaded boring 11 in the implant 10. The member 20 has a step 22 that forms a seating for the head 23 of the fixing member 21. The tubular member 20 has a substantially constant outer cross section along the length thereof. A ball 30 has a throughput opening 31 and is threaded on the member 20. The wall of the opening 31 may, for instance, be in the form of a thread, which threadably engages with a corresponding outer thread (not shown) on the outside (circumference surface) of the member 20, so that the ball 30 may be displaced axially along the member 20 and assume a substantially stable axial position along the same. As an alternative to the thread, the wall 31 of the throughput opening and/or the circumferential surface of the member 20 may have scores or a surface roughness offering a limited frictional coupling between the ball and the member, whereby an operator may displace the ball 30 manually along the member 20 into a chosen position, where the ball stays. As an additional alterna- tive, the ball and the member may have a mutual fit that offers a similar frictional binding.

The throughput channel of the ball is shown to have widened sections 32 at the ends in order to facilitate for the ope¬ rator to thread the ball 30 onto the member 20.

The implant 10 is shown to have a thread 12, by means of which the implant is anchored in bone tissue 13, for in¬ stance in the jawbone of a patient when the implant 10 is to support a dental prosthesis.

Figs. 1 and 2 illustrate three structures corresponding to Fig. 3, a bar 40 being shown inserted between adjacent pairs of bodies 30, which are shown in the form of balls. The bar 40 has opposite end portions 37, which are cup- shaped by a radius substantially corresponding to the ra- dius of the balls 30. As can be seen in Figs. 1 and 2, the bars 40 are shown to be axially adjustable in respect of the length, in order to, in a relatively short state, be possible to be inserted between two adjacent balls 30, and there be expanded until the cup-shaped end surfaces thereof come into surface-extended contact with the balls on the sides thereof facing each other.

As shown in Fig. 4, the bar 40 may comprise two parts 42, 43 that mutually are axially directed for linear motion, for instance by the fact that one part 43 has a protruding pin 44, which is received in a corresponding guiding chan¬ nel 45 in the other part 42. Preferably, the parts 44, 45 may engage by a certain limited friction against each other so that the bar 40 may be adjusted manually into chosen the length and keep this length, as inserted between a pair of balls 30. As another alternative, a spring, for instance a compression spring 47, may be received in the channel 45 between the bottom thereof and the pin 44, for prestressing the bar 40 toward the maximal length thereof, preferably defined by co-operating stop faces on the two parts. In this way, an operator may compress the bar 40 before the same is inserted between two adjacent balls 30, and subse-

quently the bar is released and allowed to expand, under the effect of the spring 47, into contact with the respec¬ tive ball.

Fig. 5 shows an axial section through another embodiment of a bar 40, comprising two parts 42, 43, one of which has a bar 44 that is received in a boring 45 in the other part 42. In Fig. 5, the bar 44 and the channel 45 are shown to have co-operating screw threads 51, 52. Alternatively, the threads 51, 52 may be replaced by scores or surface irregu¬ larities allowing the parts 42, 43 to be mutually axially displaced and to keep the adjusted length up to a certain axial load.

It will be appreciated that the structure 60 shown in Fig. 1 after the building up thereof and after the fitting of the included members to each other, substantially has no stresses that tend to deform the structure, in particular the members 20 away from their set positions on the im- plants 10. Furthermore, it will be appreciated that the building up of the structure may include that the balls 30 are displaced along the members 20 into chosen axial posi¬ tions along the members 20, i.e., to chosen distances from the implants 10. Next, the fitted structure according to Figs. 1 and 2 may be fixed by the fact that the bars 40 are fixed in the adjusted length and by the fact that the bars 40 are fixed/joined to the balls 30 and the balls 30 are fixed to the members 20. The fixation may be provided by means of glue joints, welded joints, soldered joints. In the case of welded joints, the parts may first be jointed to each other by welding by means of welding spots and then the same are supplemented with welding seams.

In a particularly preferred embodiment, the cup-edge may be chamfered in the respective end of the bar 40, such as shown at 48 in Fig. 3, in order to define, with the surface 36 of the ball 30, a circumferential V-shaped gap 49, which

facilitates establishment of a welding seam or glue joint between the bar and the ball. The chamfering in the ends of the throughput channel 31 of the ball also allows facili¬ tated accessibility to the joint between the channel wall 31 of the ball and the outer circumference of the member, for the assurance of, for instance, a welding seam.

In a few embodiments, axially adjustable bars 40 may bridge over a great distance range between adjacent balls 30, but when the distance between adjacent balls 30 becomes small, in certain cases it is preferred to form the bars 40 to have constant length. In order to, in a such case, be able to insert such bars 40' between two balls in a simple way, one of the balls 30 may have an elliptical shape, i.e., have a varying radius around the circumference thereof in relation to the axis of the throughput channel 31, so that the ball has at least one substantially spherical bulge 38 of advanced radius R. When the bulge 36 extends substan¬ tially perpendicularly from the connecting line between two adjacent balls 30, a bar 40' of fixed length may be inser¬ ted between the balls in order to then be fitted shape-wise bondingly in between the same by turning the oval ball 30' into alignment to the axis of the bar 40' . Alternatively, the body may be entirely round, but have a throughput opening that is eccentrically located in relation to the envelope surface of the body.

Fig. 1, finally, shows a ball 30 that is mounted at one end of the prosthesis, and may have a cantilever arm 39, which is intended to provide an extension of the prosthesis arc that is built up past the last implant 10 in the row.

A person skilled in the art appreciates that the structure 60 does not necessarily need to be built up on the implant 10 in the jaw of a patient, but may be built up on an implant analogue in a model of the jaw of the patient. When the structure 60 has been fixed, a prosthesis may be built

up on the same, wherein the prosthesis, for instance, may comprise tooth members and prosthesis parts, when the con¬ struction is a dental prosthesis. It will be appreciated, however, that the prosthesis shows general use, even if it primarily has been developed in order to provide dental bridge constructions and the like, which should be releas- ably fixed to the implant 10.

Thanks to the invention, the structure 60 may easily be given a shape that does not have any built-in stresses and that, therefore, does not have any tendency to deviate from the shape it has been given in the building up on the im¬ plants/the implant analogues.

Figs. 8-10 illustrate that the bodies 30, as an alternative to a convex ball cap area for the co-operation with a con¬ cave end surface of the bar, may have a rounded recess that receives a corresponding rounded convex end part of the bar, for the formation of a ball-and-socket-like joint between the body and the bar.

In the embodiment according to Fig. 6, where the bar has a fixed length and a concave end surface for the co-operation with a convexly rounded, preferably spherical surface sec- tor of the body 30, and because this surface sector has a centre of curvature that coincides with the axis of rota¬ tion of the body (and the end surface of the bar has a cor¬ responding curvature) , the fitting of the bar to the body may be effected by the fact that the body is rotated while the ^' bar is kept aligned to the axis of rotation of the body.

Suitably, the bodies have two substantially diametrically opposed surface sectors for the co-operation with a respec- tive bar end.

In other cases (Figs. 8-10), it is, in the fitting of bars having fixed length, suitable to ensure that the bar turns around the opposite end thereof that rests against an adja¬ cent body at the same time as the freely movable end there- of' follows the surface sector in question of the body during the turning motion of the body for the shape-wise bonding engagement. In this way, a shape-wise bonding between the body and the bar end is offered, also when the central portion of the bar has a fixed length corresponding to the free distance that can be adjusted between two bod¬ ies .

The concave surface portion of the bar end, for instance, is suitably cup-shaped and lacks undercut, the cup-shape receiving the convex surface portion of a radially protrud¬ ing part of the body in such a way that it is possible to change the direction of the bar end in relation to the body. For instance, the concave surface has a greater ra¬ dius than the convex one. When the first bar end is re- ceived on a first body, the co-operating surface portions of the second body and of the other end of the bar should be able to move into engagement with each other during turning, about in the same way as a cog and a gash of two co-operating cogwheels .

As can be seen in Fig. 3, the bar end may have a concave surface 37, which co-operates with the generally spherical outer surface of a body 30 formed as a ball. Alternatively, the radially protruding portion 38 of the body may have a curved surface that offers a surface-extended contact with the cup-shaped surface 37 of the bar end. Naturally, the body 30 may have, for instance, two generally diametrically opposed protruding portions 38.