EP1957000A1

EP1957000A1 - Orthodontic anchoring screw

Info

Publication number: EP1957000A1
Application number: EP06818849A
Authority: EP
Inventors: Holger Zipprich; Björn Ludwig
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-11-27
Filing date: 2006-11-27
Publication date: 2008-08-20
Also published as: DE102005056119A1; DE102006051082A1; US20090240289A1; WO2007060005A1

Abstract

An orthodontic anchoring screw (1, 1', 1'), with a shank formed integrally on a screw head (2) and provided with a thread (8), is intended to ensure a particularly secure and permanent hold after insertion into the jaw bone. For this purpose, according to the invention, the thread (8) is provided with at least one thread parameter that does not remain constant along the longitudinal axis of the shank (4).

Description

Description Orthodontic anchorage screw

The invention relates to an orthodontic anchoring screw with a screw head formed on a threaded threaded shaft.

In orthodontics, the main therapeutic goal is the targeted and controlled movement of teeth. Such a translational or rotational movement of a tooth is only possible by a force is applied to the tooth to the appropriate extent, which can move this against the jaw. This force is then applied over suitable fixing means over comparatively long periods of time on the respective tooth, until it assumes the desired positioning and / or orientation in the oral cavity. However, a suitable support of the force-exerting element in the oral cavity is necessary for targeted application of a tooth with such a suitably chosen force, for example via brackets, wires, rubbers or other suitable force-exerting elements.

Usually, such a support of the force-applying elements is made on a further tooth, for example, two suitably positioned teeth are connected to each other via a clamping element, which is then biased to train. However, such an approach has the disadvantage that it conceptually two teeth are applied symmetrically with forces, but this is actually intended and desired only for one of the teeth. The targeted repositioning of the one tooth is thus inevitably associated with an undesirable or only conditionally acceptable change in position of the other tooth.

In order to counteract this, an anchoring via one-piece temporary screws, the so-called orthodontic anchoring screws, can also be carried out, which are temporarily introduced into the jawbone and removed again after the tooth has been displaced. In contrast to dental implant materials, which are designed for a permanent integration in the jawbone and the longest possible stable ingrowth, such Anchoring screws are thus introduced so that a later removal from the bone remains possible. In contrast, when using such anchoring screws but necessarily to be noted that during the active therapy phase, ie during the actual application of force of the desired forces in the tooth requiring treatment, a reliable and resilient fit of the respective, provided as counterpoint anchoring screw is essential.

It should be noted that the anchoring screw after screwing has a strength in the bone, which is based on the tension of the screw with the bone. This strength is also called primary stability. However, as the bone responds to mechanical stresses and reorganises itself, this strength initially decreases as a result of the rearrangements with increasing wearing time. On the other hand, from the colonization of the screw material with cells, especially bone cells, on the other hand, a further strength builds up over the composite of the cells with the screw material. This is called Oseointegration. The strength in the bone should be sufficient during the entire insertion period to be sufficient as an abutment for the displacement of at least one tooth. However, as in previous systems, the primary stability significantly reduced before it comes to a sufficient bond to the bone, it can come in an intermediate phase to a significantly reduced strength compared to the primary stability. In this phase there is the undesirable possibility that the screw can no longer transfer the necessary forces and is lost or pulled out of the bone.

The invention is therefore based on the object, an orthodontic

Specify anchoring screw of the above type, with a particularly high and lasting strength after insertion into the jaw bone is reached.

This object is achieved by the thread of

Anchoring screw is designed with at least one seen over the longitudinal axis of the threaded shaft not constant thread parameters. The invention is based on the consideration that for the desired, over the entire treatment period sufficiently high strength of the introduced anchoring screw in particular that time interval before the finally onset oseointegration should be considered as the basis for the system design in which said reduction in strength occur can. It should be noted that this reduction in strength is primarily a consequence of transposition or adaptation processes in the surrounding bone in the manner of microstructural changes in response to the introduced screw. To avoid excessive strength reduction, these effects should therefore be at least partially targeted reduced, in addition, additional mechanical retention should be offered. This can be done in particular by creating different conditions in different spatial areas, by which the strength in its entirety can be increased. For this purpose, it is provided to perform the thread along the longitudinal axis of the threaded shaft suitably uneven.

As a thread parameter, that is, as for the characterization of the thread particularly suitable information, come here a plurality of parameters into consideration. In particular, a thread is usually defined by the thread parameters thread pitch and thread depth. The thread pitch is defined as the position change in the longitudinal direction of the thread axis per revolution, so that the thread pitch can be regarded as the measure with which a screw penetrates per revolution in a material. Another thread feature is the thread depth. The thread depth indicates how deep the thread geometry is cut into the material and thus gives a measure of the profile depth of the thread. The larger the thread depth, the smaller the thread core of the

Bolzens or the screw. Advantageously, the thread pitch and / or the thread profile are provided as those thread parameters which are not constant over the longitudinal axis of the threaded shaft.

In view of the desired increase in strength, in particular an unevenly executed thread pitch is advantageous, by means of which suitable tensions in the bone tissue can be induced, which have the effect of increasing the strength. In particular, the bone in which the temporary - A -

Anchorage screw is screwed in, in the direction of insertion of the thread either compressed or stretched. Due to the resulting additional tension of the bone with the screw, the contact pressure between the temporary screw and the bone is increased, which has a direct effect on the strength.

By alternatively or additionally advantageously provided variation of the thread profile as a non-constant held thread parameters can be achieved that the bone in the pre-cut or cut by the screw itself thread in the longitudinal direction of the threaded shaft is compressed unevenly. As a result, this results in the bone over the temporarily introduced screw undercuts, which increase the retention and counteract a rotational movement.

The cross-section of the orthodontic anchoring screw, in particular in the region of its threaded shaft, can be designed in the manner of ordinary screw designs rotationally or cylindrically symmetrical and thus almost circular. In a particularly advantageous embodiment of the threaded shaft but also in the region of its cross-section is specifically adapted to the design goal of high strength after insertion of the screw. In this case, it is expedient to take into account the fact that within a certain period of time after the introduction of the screw, a remodeling process takes place in the bone, within which it adapts to the contour of the inserted screw, whereby the clamping effect originally fixing the clamping force in the surrounding bone material is increasingly reduced. In this state, a rotationally symmetrical configuration of the threaded shaft with an approximately circular cross-section of a rotational movement of the screw, which could ultimately lead to a detachment of the screw, at best only low resistance. Significantly higher strengths can be achieved in this phase, in that the screw in the region of its threaded shaft is advantageously designed for rotational inhibition via positive engagement with the surrounding bone material. This can be achieved by the threaded shaft is designed to be unsymmetrical with respect to rotation about its longitudinal axis. Particularly advantageously, the threaded shaft is executed in cross section in approximately triangular or in the form of a Triovals. Such a design thus corresponds to the case that as a thread parameter, the distance of the thread from the central axis of the threaded shaft is not constant.

As a further non-constant held thread parameters, for example, an impression of structures or holes in the thread flanks into consideration. These can be introduced into the thread flanks by suitable production methods, such as, for example, cutting or shaping techniques.

The variation of the non-constant held thread parameter with the position along the longitudinal axis of the threaded shaft can in particular be continuous, for example linear or following another function, once or sequentially repeating, uniformly or non-uniformly varying. In a particularly advantageous embodiment, the threaded shaft but a number of seen in its longitudinal axis successively arranged main zones, in which the thread is carried out in each case with approximately constant thread parameters. Within a main zone thus has the thread and thus in this area, the surrounding bone tissue homogeneous properties. During the transition from one main zone to the adjacent main zone, the respective non-constant thread parameters change discontinuously or suddenly. By a suitable choice and dimensioning of the individual main zones a particularly individual adaptation to the conditions in the jaw area can be achieved.

In a particularly advantageous embodiment, the threaded shaft has two main zones, wherein the thread in the first main zone catchy and in the adjacent second main zone zweigängig with otherwise the same

Thread parameters such as thread pitch and thread profile is configured. In this case, the first main zone as the lower main zone, ie adjacent to the cutting tip of the threaded shaft, and the second main zone as the upper main zone, so positioned between the first main zone and the screw head, particularly preferably with a shaft length of the second main zone of about 2 to 3 mm, configured be. By such a construction, namely, the bone structure in the jaw can be taken into account in a particularly favorable manner, which is also considered to be particularly desirable in a failure of the screw a Screw fracture - in contrast to the fact that the thread flanks are sheared off in the threaded hole or the screw or that the material of the threaded hole stretches so much that the thread slips - absolutely avoid.

For this purpose, the overall system should thus be designed so that in the manner of an integrated safety reserve in case of doubt, the thread fails in the bone before the screw fractures. For this purpose, the thread of the screw should be largely matched to the material pairing bone / titanium. Since all common self-cutting screw types fracture with good bone quality before the thread fails in the bone, the thread should be specifically weakened for the said safety margin in the bone, the functionality of the screw thread is achieved with targeted use of the anatomical conditions of the human jaw. The primary thread - in the area of the first main zone - is located after insertion of the screw namely in the bone area of the Sprongiosa. There is no risk of fracture of the screw, as the cancellous bone is too soft. The secondary thread - in the area of the second main zone -, however, is adapted to the conditions of Kompakta located above the Sprongiosa, which usually has a thickness of 2 to 3 mm. This shows a comparatively greater hardness, so that must be expected in this area with increased stress on the screw and risk of breakage. In order to counteract this, the thread in this area is purposefully weakened by the double-flighted design, since the latter in particular is weakened by the resulting increased material removal from the bone substance. So there are two types of threads for two processes (safe screwing and increasing the

Fracture resistance) and two bone types (Sprongiosa and Kompakta). By still maintaining thread pitch in both main zones additional tension in the bone substance are also avoided, so that the thus designed screw is particularly suitable for use in this area.

The anchoring screw should be designed for a particularly easy handling. In order to do the targeted application of a tightening torque and thus to facilitate the actual introduction of the screw particularly, the screw head is advantageously in its outer contour with a polygonal contour, preferably with an octagonal contour executed.

In a particularly advantageous embodiment, the orthodontic

Anchorage screw suitable for common use with customary in the therapy fixative. These include, for example, staples, wires, springs and / or rubbers. Advantageously, the anchoring screw is therefore designed so suitable that said commercial fixative can be fixed without further effort on the screw head. These are, in particular, rectangular wires with a width of 0.018 and 0.022 ".The screw head is advantageously provided in its roof surface with a number of, preferably with two intersecting, continuous profile depressions / or regarding its dimensioning to a dental therapeutic

Adjusted clamp element of the type mentioned. The profile recesses thus correspond in design and function to the so-called "slots" fixing slots for such fixatives, as they are used for example in the so-called "brackets" which are glued directly to the teeth for dental treatment.

In a further advantageous embodiment of the screw head is provided on its side surface with a circumferential fixing groove. This can serve as an undercut to attach fixing rubbers for the guided in the profile depressions wires or fixatives suitable.

Advantageously, the orthodontic anchoring screw is made of titanium as a base material.

The advantages achieved by the invention are in particular that targeted locally different conditions in the bone mass can be adjusted by the varying thread parameters, which favor the strength of the introduced anchoring screw. The described design of the thread carries to increase the primary stability and / or to increase the strength through the oseointergation.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

Fig. 1 to 3 each an orthodontic anchorage screw

Fig. 4 shows the threaded shank on the orthodontic anchoring screw in cross section, and

5 shows the screw head of the orthodontic anchoring screw in FIG

At sight

The same parts are provided in all figures with the same reference numerals.

The orthodontic anchoring screw 1 according to FIG. 1 is intended for temporary or temporary introduction into the jawbone of a patient. Here, the anchoring screw 1 is to serve in the manner of a repository for reliable and resilient attachment of fixing or other force-exerting elements over the course of the proposed therapy translational or rotational forces are exerted on the tooth in need of treatment, so that this into a desired position is moved. After successfully completed treatment, the connecting screw 1 can then be removed from the jaw again. In view of the good compatibility with human tissue, the connecting screw 1 is made entirely of titanium.

The connecting screw 1 comprises a threaded shaft 4 integrally formed on a screw head 2 and carrying a circumferential thread 8 above a cutting tip 6. The screw 1 can be designed in the manner of a countersunk screw, in which the cutting tip 6 can introduce directly into untreated bone. Alternatively, it may also be designed for use in predrilled channels, wherein the cutting tip 6 is designed accordingly. In view of the typical in the proposed orthodontic treatment resulting boundary conditions, such as reliable load capacity over a long period of time, the anchoring screw 1 for a particularly reliable, especially in the medium term particularly tight fit in the jaw bone after their introduction is particularly designed. The connecting screw 1 is specifically designed to strengthen the achievable strength after insertion into the bone (so-called primary strength) in that the bone structure is clamped by the introduced screw targeted and thus the strength is particularly increased. For this purpose, one or more of the thread parameters of the thread 8 seen over the longitudinal axis of the threaded shaft 4 or seen over the threaded portion 10 or the thread length is not kept constant, but vary depending on location.

As thread parameters are in particular the thread pitch, the thread profile, a surface contour on the thread (in the thread flanks introduced holes or grooves) or the number of threads of the thread into consideration. The variation of the respective thread parameter can be continuous or not continuous. For example, therefore, a continuous variation of the respective thread parameter, for example linear, according to a particular function, once or repeatedly, uniformly or non-uniformly varying, with a substantially continuous variation along the longitudinal axis of the threaded shaft 4 can take place. Alternatively, however, it can also be provided in the manner of abruptly changing parameters that the threaded shaft 4 has a number of main zones 12 arranged one behind the other in its longitudinal axis, wherein thread parameters are kept constant within a main zone 12, and wherein when changing from a main zone 12 in the adjacent main zone 12, a sudden change in a thread parameter takes place.

In the exemplary embodiment according to FIG. 1, it is shown by way of example that the thread pitch of the thread 8 varies continuously in the direction of the longitudinal axis of the threaded shaft 4 as a non-constant thread parameter. By such a configuration, so seen by a variation of the thread pitch in the longitudinal direction of the screw 1, is reached that the bone into which the anchoring screw 1 is screwed, is either compressed or stretched in the insertion of the thread 8. By this additional tension of the bone with the anchoring screw 1, the contact pressure between the anchoring screw 1 and the bone is increased. Due to the increase in the fitting pressure between the anchoring screw 1 and the bone increases the adhesion and the Gleitreibungsmoment between them, which is necessary after screwing to release the anchoring screw 1 again.

In the embodiment of FIG. 2, however, the one case is shown that the thread parameters kept constant in segments and only abruptly changed between adjacent segments or main zones 12 of the threaded shaft 4. As can be seen from the illustration in FIG. 2, a further main zone 12 is arranged in the longitudinal direction of the threaded shaft 4 between two main zones 12, each with a comparatively steep thread pitch, which has a comparatively much flatter thread pitch.

3 again shows an orthodontic anchoring screw 1 ^" , in which the threaded shaft 4 has a plurality of-in this case, two-major zones 12 in which the thread parameters are kept constant in each case Main zone 12 is provided, which has a thread 8 with the same pitch and the same thread profile compared to the underlying further main zone 12. However, these threads, which are identical in themselves, in the main zones 12 differ from each other in that the thread 8 in the lower main zone 12 is single-handed and The thread 8 in the upper main zone 12 thus has exactly twice as many thread ribs per unit length as the thread 8 in the lower main zone 12. The upper main zone 12 comprises while a length of about 2 to 3 mm.

The anchoring screw 1 ^" shown in the embodiment of FIG. 3 is particularly suitable for use in the jaw bone while maintaining high Safety precautions designed. It is based in particular as a design target that an absolutely inevitable case in case of failure of the anchoring screw 1 is the screw break, in which the screw head 2 breaks off and the remaining screw body stuck in the jawbone and then would have to be milled out. In order to avoid this case specifically and safely, the anchoring screw 1 ^"is specifically designed so that failure instead of a screw failure, not the screw body, but rather the thread or its anchoring fails in the bone.Accordingly, the thread contour and the zoning is targeted to a typical A human jaw has a comparatively hard upper layer, the so-called Kompakta, which has an average thickness of about 2 to 3 mm, beneath which the so-called "sprongiosa", a comparatively softer bone zone, can be found Conditions is the anchoring screw 1 ^" according to FIG. 3 specifically adapted. After the anchoring screw 1 ^{"has been} screwed in, the upper main zone 12 in the jaw lies approximately in the region of the compacta, as indicated by the auxiliary lines 14. Opposite this, the lower main zone 12 lies in the area of the cancellous bone the Sprongiosa a subordinate problem, since this usually when storing the anchoring screw 1 ^" does not provide sufficient strength to withstand a load to break the bolt in case of doubt can. This could possibly be done in the field of Kompakta. In the field of Kompakta, however, due to the provided two threads, the density of the thread profiles is twice as high, which ultimately weakens the grip and strength of the thread as such in this area. This specifically ensures that the thread is dimensioned sufficiently weak in this area, so that before a screw breakage, the thread would initially give in this bone area. Incidentally, the threads in both main zones 12 have the same thread pitch, so that otherwise a particularly harmonic and undisturbed screwing in of the anchoring screw 1 ^" can take place.

Alternatively or additionally, however, the location-dependent varying thread parameters can also lie in the fact that the distance of the thread profile from the main axis of Anchoring screw 1, 1 ', 1 ^"is changed depending on the location An embodiment of this is shown in Figure 4, wherein there, the cross-section of the threaded shaft 4 is shown, the threaded shank 4 has approximately a tri-oval cross-section, so that: -... As shown by the Arrows 16 is indicated - depending on the position in the thread and thus also dependent on the position in the longitudinal direction of the

Anchoring screw 1, 1 ^' , 1 ^" adjusts a different distance of the thread profile of the screw axis 18. By such a triangular or triovale contour of the cross section can also be achieved that increased even after the adaptation processes in the bone tissue after insertion of the screw Firmness in the seat of the anchoring screw 1, 1 ^' , 1 ^" reach. This is achievable by the fact that beyond the normal sliding or adhesive fit in such an embodiment, a form-fitting is reached, which also supports the strength of the screw used even after the incoming microstructural changes in the bone tissue.

As can be seen in the plan view in Fig. 5, the screw head 2 is executed with an octagonal contour, thus facilitating the assembly and disassembly of the screw in the jaw using appropriate tools. In addition, the screw head 2 is provided in its roof surface with two intersecting continuous profile recesses 20. These are rectangular in cross-section and in terms of their dimensions - a typical width of 0.018 "or 0.022" is provided - adapted to the usual manner used in orthodontic treatments Fixier- or Stellenlemente, such as brackets, wires, springs or rubbers. The profiled recesses 20 thus serve in the manner of so-called slots or cross braces for fastening the further fixing means, so that a reliable power transmission to the tooth requiring treatment can be achieved by anchoring to the jaw. It is also possible to adapt the dimensioning or contouring of the profile depressions 20 to the typical profiles and dimensions of these fixing means, in particular via the rectangular cross-section, so that the desired forces can be transferred particularly reliably and that both translational and rotational forces are transmitted and can be fixed. LIST OF REFERENCE NUMBERS

anchoring screw

screw head

threaded shaft

cutting tip

thread

threaded portion

main zone

ledger line

arrows

screw axis

profile depression

Claims

claims

An orthodontic anchoring screw (1, 1 ^' , 1 ^" ) having a threaded shank (4) formed on a screw head (2) and provided with a thread (8), in which the thread (8) bears at least one over the

Longitudinal axis of the threaded shaft (4) seen not constant thread parameters is executed.

2. Orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to claim 1, wherein the thread pitch and / or the thread profile over the longitudinal axis of

Threaded shank (14) are not designed to be constant.

3. orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to claim 1 or 2, the threaded shank (4) is executed in cross section in approximately triangular or in the form of a Triovals.

4. Orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to one of claims 1 to 3, the threaded shaft (4) has a number of seen in its longitudinal axis successively arranged main zones (12), in which the thread (8) each with Almost constant thread parameters is executed.

5. Orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to one of claims 1 to 4, the screw head (2) is executed in its outer contour with a polygonal contour, preferably with an octagonal contour,

6. Orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to one of claims 1 to 5, the screw head (2) is provided in its roof surface with a number of, preferably with two intersecting, continuous profile recesses (20).

7. An orthodontic anchoring screw (1, 1 ^' , 1 ^'' ) according to claim 6, wherein the or each profile recess (20) in terms of their cross-section and / or is adapted in terms of their sizing to a tooth-therapeutic clip element.

8. orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to claim 6 or 7, s whose screw head (2) is provided on its side surface with a circumferential fixing groove.

9. orthodontic anchoring screw (1, 1 ^' , 1 ^" ) according to one of claims 1 to 8, which is made as a base material of titanium 0