WO2004073541A2

WO2004073541A2 - Dental implant comprising a base body and implant post and corresponding base body and implant post

Info

Publication number: WO2004073541A2
Application number: PCT/EP2004/001605
Authority: WO
Inventors: Ralf Schröder
Original assignee: Schroeder Ralf
Priority date: 2003-02-21
Filing date: 2004-02-19
Publication date: 2004-09-02
Also published as: EP1626670A2; WO2004073541A3

Abstract

The invention relates to a dental implant (1) for a fixed dental prosthesis, comprising an essentially cylindrical base body (2) that can be implanted in the jaw bone, whereby an implant post (4) can be inserted into the internal bore (3) of the base body, said bore being open at the coronal end. The invention also relates to a corresponding base body and a corresponding implant post. Said implant post (4) has an essentially cylindrical base body section (5), which can be introduced into the internal bore (3) and has a external contour (6), to which a contour of the internal bore (3), (internal bore contour (7)) is adapted. The invention is characterised in that the external contour (6) of the base body section comprises an anti-rotation device (10) that is devoid of edges, said device engaging with the correspondingly configured internal bore contour (7) in a positive fit and/or over its entire surface.

Description

Dental implant with base body and implant post as well as base body and implant post for a dental implant

description

The invention relates to a tooth implant for a fixed tooth replacement with an essentially cylindrical base body that can be implanted in the jaw bone and in whose inner bore, which is open at its coronal end, an implant post can be inserted. The invention relates in the same way to the base body, the implant post and the combination of the base body and the implant post.

Dental implants with a base body and implant posts are known in the prior art. A dental implant is known from DE 4224785 C2, in which the fastening head can be firmly connected to the base body by a screwing movement of the fastening head while simultaneously rotating the implant post. From DE 197 18 175 A1 a cone-shaped implant is known in which a stable anchoring of the implant structure with little damage to the patient's bone tissue is to be achieved by a special shaping of the inner bore of the base body for receiving the implant post.

A dental implant under the name "SwissPlus" is known from the company SulzerMedica, in which a stable anchoring of the implant structure is also to be achieved by a special shaping of the inner bore of the base body for receiving the implant post and a corresponding shaping of the implant post. This dental implant has an implant post which has a cone at its lower end facing the base body.This cone is intended to engage a corresponding contour in the inner bore of the base body.Under this contour, the inner bore in the base body continues in the form of a thread which engages in this thread a screw which is rotatably held in the cone of the implant post In the assembled state of the implant post, loosening of the implant post is essentially avoided by the cone of the implant post being in frictional engagement with the corresponding contour of the base body In order to improve the security of rotation, the product "SwissPlus" already provides that a hexagon contour is provided at about half the height of the cone surface, which is intended for engagement with a hexagon socket in the base body. If correct Adjusted implant post and tightened screw prevents undesired rotation of the implant post and the associated implant structure.

Another alternative for preventing undesirable rotation possibilities of the implant structure has become known with a product from the Altatec company under the name "CAMLOG". In this implant, the implant post has grooves in its section which can be inserted into the inner bore of the base body and which are in corresponding recesses in the Intervene in the contour of the inner bore, which also prevents rotation of the implant post when it is correctly adjusted. The implant post is fixed in the base body with a screw that runs through the entire length of the implant post, in that the screw has a thread in the section that extends through the implant post which interacts with a corresponding threaded section in the inner bore of the base body.

The previously known implementations for preventing undesirable possibilities of rotation of the implant post are not yet quite optimal in that e.g. on the one hand an adaptation of the base body, in particular an at least piecewise expansion of the base body is required. This is disadvantageous because a correspondingly larger hole in the jawbone of the patient has to be provided for introducing such a basic body with an enlarged cross-sectional area. This leads to greater damage to the patient's bone tissue. On the other hand, the absorption of forces acting perpendicular to the axis of rotation of the implant post is not optimal because of the unfavorable relationship between the section held in the base body and the section extending above the base body with the implant structure.

The object of the present invention is therefore to provide a dental implant or a base body and an implant post of such a dental implant, with which the above-mentioned. Disadvantages are avoided, which can thus be anchored in the jaw bone without unnecessary damage to the patient's bone tissue and in which an undesired rotation of the implant post is reliably avoided.

This object is achieved with a dental implant with the features of claims 1, 2 or 3. For this purpose, according to claim 1, in the case of a dental implant for a fixed dental prosthesis with an implantable in the jawbone, generally substantial cylindrical base body, in the inner bore of which an implant post can be inserted at its coronal end, the implant post showing an at least essentially cylindrical base body portion provided for insertion into the inner bore with an outer body portion outer contour, and wherein the contour of the inner bore - inner bore contour - on the base body portion is matched outer contour, it is provided that the base body section outer contour has an edge-free; "Seamless" rotation lock with at least one round tooth and each having an adjoining convex tooth base, which comes into engagement with the correspondingly designed inner bore contour in particular in a form-fitting and / or in particular full-surface manner.

The special engagement of the outer contour of the base body section in the inner bore contour enables a significant reduction in the "rotational play" compared to known types of engagement. For example, when using a hexagon, which is provided for engagement in a correspondingly designed hexagon socket, there is a manufacturing tolerance of 0.02 an unavoidable rotatability (rotational play) in the order of 4.5 °. With a hexagon socket, a contour known under the brand name "Torx", the rotational play is still approximately 2.2 °. The edge-free rotation lock according to the invention creates even more favorable conditions and there is a rotational play of less than 1 °. This rotational play can also be reduced even further in the rotation lock according to the invention if, according to a preferred embodiment, a cone is provided in the connection to the base body section. A cone inserted into a cone holder is known to cause self-locking against undesired rotation. That a combination of rotation lock and cone can reduce the rotational play to almost zero.

The fact that the inner bore contour and the base body section outer contour of the implant post include a rotation lock prevents undesired twisting of the implant post with the crown attached to it. The fact that the rotation lock is free of edges results in particularly favorable conditions with regard to the stress on the material. In particular, if titanium is used as the material for the base body and / or the implant post, it has been found that in the area of known tooth implants with rotation lock, always existing edges in the area of the anti-rotation device can have undesirable notch effects, ie the material tends to crack in the area of the edges, which negatively affects the integrity of the base body.

If the rotation lock on the outer body section contour comes into positive engagement and / or over its entire surface with a corresponding rotation lock receptacle in the inner bore contour, this results in a particularly favorable power transmission. This favorable force transmission makes it possible to minimize the wall thickness, in particular to minimize the corner dimension of the implant post in the area of the base body section, in particular in the area of securing the base body section against rotation. A minimum wall thickness is often specified for the implant post in the area of the base body section. In the case of an anti-rotation contour with edges, e.g. a hexagon, the minimum wall thickness must be in the area of the sides of the hexagon. In the area of the edges, the wall thickness is then considerably greater than the minimum wall thickness (corner dimension). For its part, the base body must have the minimum wall thickness specified for it precisely in the region of the edges. In the case of a rotational securing contour with edges, one either has the option of increasing the cross section of the base body or of reducing the size of an inner bore penetrating the implant post. Both are undesirable and are avoided with the present invention. The edge dimension in the area of the round tooth results from the edge-free rotation securing contour formed from a sequence of round teeth and round tooth base. However, this is considerably less than the corner dimension of a hexagon or octagon. It is therefore neither necessary to increase the diameter of the base body nor to reduce the diameter of the implant post inner bore. In fact, the diameter of the implant post inner bore could even be slightly increased, which on the one hand facilitates the handling of the implant post and the attachment of a crown, but on the other hand also makes it possible to provide the same inside diameter of the implant post inner bore for different sizes for all sizes, including the smallest embodiment , so that all implants can be used with the same tool and the same screws to attach the respective crowns.

The minimized wall thickness means that the wall thickness or the outer diameter of the base body can also be minimized. This further advantageously leads to the fact that the damage to the bone tissue of the patient when the base body is implanted in the jawbone can also be minimized or that an implantation of the dental implant is still possible even if the jawbone is damaged.

The invention is also based on an implant post (claims 15, 16 and 17) and a base body for use in the above. Dental implant (claims 31, 32 and 33) solved. With regard to the implant post for a dental implant with an essentially cylindrical base body that can be implanted in the jaw bone, in whose inner bore open at its coronal end the implant post can be inserted, the implant post having an at least essentially cylindrical base body section provided for insertion into the inner bore 15 has a basic body section outer contour, it is provided according to claim 15 that the basic body section outer contour comprises an in particular edge-free rotation lock with at least one round tooth and in each case an adjoining convex tooth base. With regard to the base body for a dental implant with a substantially cylindrical shape, in the inner bore of which an implant post can be inserted at its coronal end, the inner bore comprising a threaded portion and an implant post portion and wherein the implant post portion has a contour — inner bore contour — is provided according to claim 31 that the inner bore contour comprises an in particular edge-free rotation lock with at least one round tooth receptacle and in each case an adjacent convex tooth receptacle.

The invention is based on the knowledge that rotation locks on a tooth implant are essential for a permanently satisfactory treatment success. In known solutions, however, the existing rotation lock leads to an increase in the outer diameter of the base body. Such an enlarged base body on the one hand results in additional damage to the patient's jawbone, while on the other hand, particularly in the case of previously damaged jawbones, it is sometimes not even possible to implant such an enlarged base body. Finally, in another embodiment of a dental implant with rotation lock, the rotation lock is provided in the area of the coronal end of the inner bore in the base body. The implant post therefore only extends a short distance into the inner bore of the base body. This is unfavorable in terms of the implant post perpendicular to its axis of rotation, which coincides with an axis of rotation of a screw fixing the implant post in the base body. In order to overcome this disadvantage, the invention provides that the implant post has an at least essentially cylindrical, elongated base body section. This basic body section lies with its outer body section outer contour against the inner bore contour. Due to the length of the base body section, there is a lever which is able to effectively absorb the above-mentioned loads on the implant post perpendicular to its axis of rotation.

Advantageous embodiments of the invention are the subject of the dependent claims.

A particularly favorable transmission of force both with regard to the rotation lock and with regard to loads on the implant post perpendicular to its axis of rotation results if the base body section outer contour comprises a rotation lock extending over the entire height of the cylindrical section of the base body section.

A particularly favorable force transmission, in particular with regard to the rotation lock, results when the outer body section outer contour comprises a rotation lock extending over the entire circumference of the base body section.

Advantageously, both versions of the anti-rotation device can be combined, so that there is an outer contour of the main body section, which includes the entire height of the cylindrical section of the main body section and the entire circumference of the cylindrical section of the main body section.

A particularly efficient implementation of an edge-free rotation lock is obtained if the rotation lock comprises at least one round tooth, in particular six or eight round teeth distributed symmetrically over the circumference of the outer body section outer contour and a tooth base delimiting the or each round tooth on both sides, the or each round tooth and the or every tooth base and every transition between a circular tooth and the adjacent tooth base is edge-free. The outer contour of the anti-rotation device is thus perpendicular to the axis of rotation of the implant post in the area of the base body section revolving wavy line. If the rotation lock only comprises a round tooth and the tooth base delimiting it on both sides, the contour in the projection is characterized by a section of the otherwise resulting wavy line. The rotation lock or a section of the rotation lock with a round tooth and an adjacent tooth base can also be described in that the round tooth and tooth base have opposite radii.

In order to also be able to attach the crown to the implant post in such a way that undesired rotation of the crown on the implant post is prevented, it is further advantageously provided that the implant post has a crown-side rotation lock on its crown-side end. The crown-side rotation lock corresponding to the rotation lock of the base body section is particularly favorable. The implant post can then be produced along its entire height in one working process.

If the implant post has a cone between the crown-side end and the base body section, which is provided for insertion into a corresponding section of the central bore of the base body - cone receptacle, this cone facilitated the insertion of the implant post into the central bore of the base body. Together with the essentially cylindrical base body, which can also be understood as a "shaft", this results in a "cone shaft". The cone itself is particularly easy to produce if it has a surface that is free from rotation. In the case of the cone, the rotation lock can be avoided because the rotation lock contour of the base body section of the implant post ensures adequate rotation lock. In the case of a cone, if the cone surface is inclined below 8 °, it is self-locking, i.e. preventing undesired rotation.

If the cone has ribs symmetrically distributed along its circumference, which extend parallel to the axis of rotation of the implant post and are intended for engagement in corresponding recesses in the cone receptacle, it is advantageous with the ribs and the depressions to pre-adjust the implant post with respect to its rotation for correct engagement achieved the rotation lock of the base body section in the corresponding rotation lock receptacle in the base body. This is particularly useful if the rotation lock on the base section does not long the full height of the base body section, so that it is possible that the ribs and depressions of the cone engage with each other rather than the rotation lock with the rotation lock retainer.

If the depth of the recesses in the cone receptacle decreases along the height of the cone receptacle from the smallest inside diameter and the height of the ribs also decreases from the smallest diameter of the cone, in particular to the same extent, there is an advantageous possibility when inserting the implant post in the inner bore of the base body first ensures a correct adjustment of the implant post caused by the cone and, when inserted further into the inner bore, by the engagement of the ribs in the corresponding recesses, to ensure the correct rotation of the implant post.

If the implant post itself has a central bore in which a screw is held or into which a screw can be inserted, the screw being provided for fixing the implant post in the base body and the central bore of the implant post having a thread for fixing the crown has particularly favorable conditions with regard to the assembly of the entire implant are achieved. The implant post inserted into the base body is fixed by the screw that can be inserted into the implant post or that is held in the implant post. In the fixed state, the screw releases a thread provided in the crown-side end of the center hole of the implant post. A screw for fixing the crown to the implant post can engage in this thread.

It will be apparent to those skilled in the art from this description of the invention that there are numerous modifications to the invention, but which still fall within the basic concept of the invention. So it is z. B. possible, as already described above, to provide a cone on the implant post with its own rotation lock (ribs and corresponding recess in a cone receptacle in the base body). This rotation lock can be combined with the rotation lock in the base body section of the implant post. Likewise, it is also possible, in the case of a cone with a rotation lock, to dispense with the rotation lock on the base body section or to make the rotation lock on the base body section smaller. This change in the dimension of the rotation lock in the base body section can affect the position and the height of the anti-rotation device along the base body section and an arc length of the anti-rotation device along the circumference of the base body section. Additionally or alternatively, it is possible that such a dimensioning also relates to the height and the number of the individual round teeth. Furthermore, it is possible that the base body section itself is conical, wherein either the rotation lock follows such a conical base body section, ie the height of the individual circular teeth remains constant along the entire height of the conical base body section, or the height of the individual round teeth is proportional to the reduction in circumference of the cone increases.

A preferred exemplary embodiment of the invention is explained in more detail below with reference to the drawing.

Show in it

1 shows a dental implant with a base body and an implant post,

2a-2e the implant post,

3a-3d the base body,

4a-4d the tooth implant with a base body and an implant post in the assembled state,

5a-5d a first alternative embodiment of the base body,

6a-6d a second alternative embodiment of the base body,

7a-7d a third alternative embodiment of the base body,

8a-8d a fourth alternative embodiment of the base body, F Fiigg .. 9 9 a special embodiment of the implant post and

Fig. 10 different rotation locks in comparison.

1 shows a tooth implant 1 with an upper part of a base body 2 that can be implanted in a jawbone (not shown) with an inner bore 3 and an implant post 4 that can be inserted into this inner bore. The implant post 4 has an essentially cylindrical base body section 5 with a base body section outer contour 6 on. A contour of the inner bore 3 - inner bore contour 7 - is matched to the base body section outer contour 6. The base body 2 points to it Outside a thread 8 with which the base body 2 is securely held in the jaw bone in the healed state.

2a to 2d show different views of the implant post 4. FIG. 2e shows a section through the implant post 4. The base body section 5 of the implant post 4, i.e. the section of the implant post 4 that can be inserted into the base body 2 is essentially cylindrical and continues at its upper end in the form of a cone 9. The outer contour of the cylindrical section of the base body section 5 has an edge-free rotation lock 10 as the base body section outer contour 6. The rotation lock 10 can be seen particularly well in the illustration according to FIG. 2 c, which shows the implant post from its end seen in the inner bore 3 of the base body 2, that is to say in the top view of the base body section 5. It can be seen from the illustration that the outer body section contour 6 and the rotation lock 10 formed thereby are edge-free. The basic body section outer contour 6 namely comprises a number of circular teeth 11 distributed symmetrically over the circumference of the cylindrical basic body section 5 and a tooth base 12 between each round tooth. In the example shown, the basic body section outer contour 6 comprises eight round teeth 11 and correspondingly eight tooth bases 12. Each round tooth 11 and each tooth base 12 and each transition between a circular tooth 11 and the adjacent tooth base 12 is edge-free. The edge freedom of round tooth 11 and tooth base 12 can, as far as this is not already apparent from the figure, best be explained using an example. The outer contour of the round tooth 11 corresponds to a symmetrical wave (wave crest). The outer contour of the tooth base corresponds to an equally symmetrical, counter-rotating shaft (trough). The transition between "wave crest" and "wave trough" is now carried out in such a way that there is a continuous (edge-free) transition. The contour can be described mathematically starting from a first circular tooth 11 via the adjacent tooth base 12 to the next circular tooth 11 in that the slope of a tangent guided along the contour has no discontinuities.

The cone 9 has side surfaces with a slope of seven to nine degrees. The cone 9 is thus useful for holding the implant post 4 inserted into the inner bore 3 of the base body 2. At its crown-side end 13, that is to say the end of the implant post 4 opposite the base body section 5, it has a crown-side rotation lock 14. The crown-side rotation lock 14 is designed in the same way as the rotation lock 10 of the base body section 5 and is therefore also edge-free. The crown-side end 13 ends in a cone 15, which makes it easier to hold and fix a crown (not shown). In a section through the implant post 4 according to FIG. 2e, it can be seen that the implant post also has an inner bore — implant post inner bore 16. The implant post inner bore 16 has an internal thread 17 at the crown-side end 13 of the implant post 4. This is provided for engagement with a screw (not shown) which fixes the crown at the crown-side end 13 of the implant post 4. Below the internal thread 17, the implant post inner bore 16 is provided for receiving a cylinder head screw (likewise not shown). The cylinder head screw is inserted into the implant post inner bore 16 from the crown-side end 13 of the implant post 4 and, when the implant post 4 is inserted into the base body 2 and fixed there by tightening the cylinder head screw, releases the internal thread 17.

3a, 3b and 3c show the base body 2 from different views. 3a shows the base body 2 seen from the side. It can be seen that the base body 2 is essentially cylindrical in shape. The base body 2 is widened at its coronal end. The upper end of the coronal end has, in particular, a chamfer which enables the jaw mucosa to be placed against the base body 2 in a favorable manner. The base body 2 is rounded at its other end. The base body 2 is introduced into a hole in the jaw bone (not shown) in a manner known per se. The base body 2 is held in this bore by means of its thread 8. 3b shows a view from diagonally above into the inner bore 3 of the base body 2. The inner bore contour 7 is visible, which is matched to the anti-rotation contour 10 of the base body section 5 of the implant post 4. The inner bore contour 7 is therefore itself free of edges. The basic body section outer contour 6 or the rotation lock 10 of the implant post comes into engagement with the inner bore contour 7 in a form-fitting and / or in particular full-surface manner when the implant post 4 is inserted into the inner bore 3. On the one hand, this enables particularly favorable conditions for power transmission, on the other hand, with the same manufacturing accuracy in comparison z. B. with a rotation lock with a hexagon, which is held in an internal hexagon, reduced by more than half the unavoidable rotatability of the Implant post 4 reached. 3c shows a view from above into the inner bore 3 of the base body 2. It can be seen that the inner bore contour 7 is also distributed symmetrically over the circumference of the inner bore 3. FIG. 3d shows a section through the base body 2. The inner bore 3 comprises a threaded section 20 and an implant post section 21. The implant post section 21 continues in the area of the coronal end of the base body 2 in the form of a cone receptacle 22.

4a, 4b and 4c show the complete implant 1 with base body 2 and implant post 4 from different views. 4a shows the implant 1 in a side view. FIG. 4b shows the implant 1 in a side view from above and FIG. 4c shows the implant 1 in a top view. 4d shows a sectional view of the implant 1 with the base body 2 and implant post 4. In the sectional view it can be seen that a screw 23 is guided in the implant post inner bore 16, the screw provided at the lower end in the threaded section 20 of the inner bore 3 engages in the base body 2. In order to be able to insert the screw 23 along the thread 17 into the implant post inner bore 16 of the implant post 4, it is provided that the head of the screw 23 has an external thread which is matched to the thread 17 of the implant post inner bore 16. The screw 23 can thus be turned through the thread 17 and, after passing the thread 17, is freely movable in the otherwise thread-free implant post inner bore 16. In the state fixed by the screw 23, the base body section 5 lies with the cylindrical part of the base body section 5 having the rotation lock 10 and the cone 9 adjoining it in the implant post section 21 of the base body 2.

5a, 5b, 5c and 5d show an alternative embodiment of the base body 2. The alternative embodiment relates to the design of the inner bore 3, which is only in the view of the base body obliquely from above according to FIG. 5b and in the sectional view of the base body 5d is visible. According to the embodiment, the implant post section 21 has an inner-bore contour 7 which is in particular edge-free and which differs from the inner-bore contour 7 described so far in that the inner-bore contour 7 corresponding to the outer body section contour 6 has circular tooth receptacles and tooth base receptacles, their height or depth, in particular the height of the tooth base receptacle, along the depth of the inner bore tion 3 increases. The implant post 4 (not shown in this embodiment) accordingly has in its base body section 5 a base body section outer contour 6 placed thereon, the height of the round teeth at the lower end of the implant post 4 being the lowest and increasing steadily in the direction of the cone 9. The base body section 5 thus has a conical envelope contour. The slope of the lateral surface of such a conical envelope contour is in the range from one to five degrees, in particular in the range from 1.0 ° to 1.5 °. This configuration results in an even better retention of the implant post 4 in the base body.

6a, 6b, 6c and 6d show a further embodiment of the base body 2 starting from a basic shape, as shown in FIGS. 3a to 3d. The embodiment relates to the fact that in the implant post section 21 of the inner bore 3, an internal thread 24 is introduced into the “round ribs” of the inner bore contour 7, which interact with the tooth base 12 of the base body section 5 of the implant post 4. The internal thread 24 can only be seen in FIGS. 6b and 6d, that is to say in the view of the base body 2 obliquely from above with a view into the internal bore 3 and in the sectional view. The internal thread 24 in the implant post section 21 of the inner bore 3 also enables screws with a corresponding thread to be introduced into the implant post section 21 (not shown). The base body 2 can be used even more versatile in this embodiment, because it is therefore suitable on the one hand for receiving an implant post 4 (as described above) but also for receiving screws and thus for the immediate fixation of corresponding crowns (not shown).

FIGS. 7a, 7b, 7c and 7d show a further embodiment of the base body 2. The embodiment which is only visible in FIGS. 7b and 7d essentially corresponds to the embodiment which is already in connection with FIGS. 6b and 6d was explained, ie the inner bore contour 7 has a thread 24 in the ribs bulging into the inner bore 3. 5b or 5d, the ribs of the inner bore contour are designed such that the height of the ribs decreases with increasing depth of the inner bore 3. 6a to 6d is thus a base body 2 according to FIGS. 3a to 3d, that is to say with a cylindrical implant post section 21, the inner bore contour 7 having a thread 24. Analogously, the configuration according to FIGS. 7a to 7d is a basic Body 2 according to FIGS. 5a to 5d, that is to say a conical implant post section 21, the inner bore contour 7 again having a thread 24.

8a, 8b, 8c and 8d show a further configuration of the base body 2. According to this configuration, the base body 2 has in its inner bore 3 a cone receptacle 22 with channels 25 running parallel to the axis of the base body 2. The implant post section 21 is shortened and, in the exemplary embodiment shown, only comprises the threaded section 20. Of course, an implant post section can also be arranged between the cone receptacle 22 and the threaded section 20 in accordance with the embodiments described above. The grooves 25 of the cone receptacle 22 are provided for cooperation with corresponding elevations on the lateral surface of the cone 9 of the implant post 4 (not shown). The troughs 25 of the cone receptacle 22 interact with a correspondingly shaped cone 9 in such a way that rotation is secured. The troughs 25 and also the elevations on the cone 9 can, like the inner bore contour 7 or the base body section outer contour 6, be formed without edges.

The implant post 4 can have a chamfer at its end opposite the crown-side end 13, such as, for. B. shown in Fig. 1, so that the insertion into the inner bore 3 of the base body 2 is facilitated. This is particularly useful if the base body 2 at its coronal end no expansion and z. B. also has no cone receptacle 22.

Another aspect of the invention relates to an embodiment of the implant post as shown in FIG. 9. The implant post 4 has slots 30 distributed uniformly over its circumference. These slots extend from the crown-side end 13 of the implant post 4 over approximately two thirds to three quarters of the height of the implant post 4. At the lower end, the slots 30 run into an elongated hole 31. The slots 30 and also the elongated holes 31 penetrate the wall of the implant post 4 completely, ie they extend from the outside into the implant post inner bore 16, so that movable tongues 32 are formed within the scope of the mobility of the material of the implant post 4. The implant post 4 thus functions overall as a "collet". In order for the tongues 32 to be pressed together to receive a crown 33, it is necessary for the implant post to be in its base body section 5 is slightly conical and / or that the cone 9 for the cone receptacle 22 is not exactly true to size. Only then is it possible that when the implant post 4 is inserted into the inner bore 3 of the base body 2, the tongues 32 are pressed together at the crown-side end 13 of the implant post and thereby fix a crown 33 inserted into the implant post inner bore 16. The crown 33 in this case has an implant post contour 34 which essentially corresponds to the basic body section outer contour 6 of the implant post. I.e. the implant post connection contour 34 is formed without edges with a number of round teeth evenly distributed over the circumference of the implant post connection contour 34. Accordingly, the implant post 4 has at its crown-side end a crown receptacle 35, which is designed to form a form-fit connection to the implant post connection contour 34 and essentially corresponds to the inner bore contour 7.

10 shows the rotation lock 10 in comparison with other conventional rotation locks, namely a hexagon 40, a so-called hexagon socket 41, a modified hexagon socket, that is to say a hexagon socket-like contour with more or less than six circular teeth, which is referred to below as the "multipoint socket" 42 , and a star-shaped rotation lock 43.

The rotation lock 10 according to the invention is characterized by an alternating sequence of round teeth 11 and round tooth bases 12, that is to say an alternating sequence of convex surfaces (round tooth 10) and concave surfaces (tooth base 11). A circle can be fitted into each round tooth 11 and each tooth base 12. The radii of such circles are considered below. The radius R _A of the circle fitted in the round tooth 11 is always larger than the radius R 1 of the circle fitted in the tooth base 12. The quotient of both radii (R | / R _A ) is therefore always less than one (Ri / R _A <1). Rotation locks 10 with a quotient of the two radii (R | / R _A ) in the range from 0.2 to 0.6 have proven successful. A rotation lock 10 is shown with a quotient of the two radii (R | / R _A ) in the order of magnitude of 0.38. With somewhat increased manufacturing effort, rotation locks with a quotient of the two radii (R | / R _A ) in the range from 0.2 to 0.9 can also be produced particularly advantageously.

Furthermore, an outer circle with a radius D _A can be drawn around the rotation lock 10 in such a way that all vertices of the round teeth 11 lie on the outer circle. Accordingly, an inner circle with a radius D | such in the ro tion assurance 10 are drawn in that all inward vertices of the tooth bases 12 lie on the inner circle. The difference between radius D _{A of} the outer circle and radius D, of the inner circle is very small. The quotient of the radius R _{A of} the circle fitted into a circular tooth 11 and the difference between the radius D _{A of} the outer circle and the radius Di of the inner circle is always greater than 10 (“ten”) - (R _A / [D _A - D ,]> 10). The difference (D _A - D,) between radius D _{A of} the outer circle and radius D | of the inner circle, the smaller the quotient of the two radii (R | / R _A ) - in the range from 0.2 to 0.6 or in the range from 0.2 to 0.9. As the difference (D _A - D |) becomes smaller and the denominator of the quotient (R _A / [D _A - Di]) becomes smaller, the quotient itself becomes larger.

These conditions do not exist with other rotation locks, such as the hexagon 40 shown or the hexagon socket 41. The hexagon 40 can - analogous to the rotation lock 10 - with an outer circle with a radius D _A , in which all the corner points of the hexagon 40 lie on the outer circle, and an inner circle fitted in the hexagon 40 with the radius D |, with all the centers between two adjacent corner points each lie on the inner circle. The difference between the radius D _{A of} the outer circle and the radius D, of the inner circle is greater for the hexagon 40 than for the rotation lock 10. The same applies to the hexagon socket 41, the modified multipurpose socket 42 and the star-shaped rotation lock 43, each with a corresponding outer and inner circle the radii D _A and D |.

With the hexagon socket 41 there is also the fact that a circle with the radius R _A can be assigned to each circular tooth. The radius Di of the inner circle can be assigned to the convex surface between two round teeth. The radius R _{A of} the round tooth is always considerably smaller than the radius Di which can be assigned to the convex surface between two round teeth. The quotient of these two radii (D ₍ / R _A ) is therefore always greater than one (D | / R _A 1). This represents an important difference to the corresponding quotient (R | / R _A ) in the rotation lock 10 according to the invention. Furthermore, in the case of the hexagon socket 41, there is also the ratio between the radius R _{A of} the round tooth and the difference between the radius D _{A of} the outer circle and Radius Di of the inner circle is less favorable than in the case of the rotation lock 10 according to the invention, if the center of the circle assigned to the round tooth of the hexagon socket 41 is just on the inner radius, the radius R _A corresponds exactly to the difference between the radius D _{A of} the outer circle and the radius Di of the inner circle (R _A / [D _A - Di] = 1). Even if the center point of the circle assigned to the round tooth lies within the inner circle, the quotient (R _A / [D _A - Di]) remains less than ten in the case of sensible configurations of a hexagon socket - (R _A / [D _A - Di] <10) , If the center of the circle assigned to the round tooth lies outside the inner circle, that is the difference between the radius D _{A of} the outer circle and the radius D | of the inner circle becomes larger, the value of the quotient (R _A / [D _A - D,]) becomes even less than two - (R _A / [D _A - Di] <2). For the hexagon socket 41, the quotient (R _A / [D _A - D |]) is therefore always less than ten, often even less than two - (R _A / [D _A - Di] <10). This is another important difference from the rotation lock 10 according to the invention, in which the corresponding quotient (R _A / [D _A - D ₍ ]) is always greater than ten - (R _A / [D _A - Di]> 10). The same applies to the inner polygon 42. Here too, the value of the quotient (R _A / [D _A - D |]) is always less than ten.

In addition, with the rotation lock 10 according to the invention, convex surfaces, namely the circular tooth 11, and concave surfaces, that is to say the respectively adjacent tooth base 12, alternate. In the hexagon socket 41, on the other hand, there are only convex surfaces, the convex circular tooth and the likewise convex surface between two adjacent circular teeth. In other words, this can also be expressed as follows: With the rotation lock 10 according to the invention, a "change in direction" of the radii of the round tooth and tooth base takes place. There is no such change of direction in the hexagon socket 41. In the rotation lock 10 according to the invention, the radii of the round tooth and tooth base run tangentially into one another. In the case of the hexagon socket 41, however, there is no such tangential transition.

An important difference between the rotation lock 10 according to the invention and a hexagon socket 41 or an inner multi-round 42 is that in the rotation lock 10 according to the invention the apex of the concave tooth base 12 lies on the inner circle, that is to say the circle with the radius D. Even if you wanted to understand the area between two round teeth in the hexagon socket 41 as "tooth base", it was only a convex and not a concave surface. If you wanted to further understand the transition between a round tooth and the convex surface between two round teeth in the hexagon socket as a "tooth base", it was not an edge-free surface. If you look at that in this area Wanted to eliminate the edge, there would be an edge-free, concave surface, as with the inner polygon 42, whose apex does not lie on the inner circle.

Based on the above description, it is clear to the person skilled in the art that the advantages of the rotation lock 10 according to the invention are, on the one hand, on the edge freedom of the rotation lock contour 10 and, on the other hand, on the small difference between the radius R _{A of} the outer circle and the radius Ri of the inner circle and the alternating sequence of convex and concave surfaces. The freedom from edges of the rotation lock 10 is based on the tangential transition of the radii of the round tooth 11 and tooth base 12. Of course, in each round tooth 11 and / or each tooth base 12, for example in the area of the respective apex, or also in the area of the transition between round tooth 11 and tooth base 12 a trough or the like, for example parallel to the longitudinal extent of the round tooth 11 / tooth base 12 are introduced. If such a channel has edges, the rotation lock 10 is no longer free of edges. Thus, when we speak of an edge-free rotation lock 10, we mean an "edge-free envelope contour" of the rotation lock, whereby the envelope contour only captures those contours, ie circular tooth 11 and tooth base 12, of the rotation lock 10 that prevent the implant post 4 from rotating in the base body 2 to avoid undesired rotation contribute.

Another advantage of the anti-rotation device 10 according to the invention is that the area effective as anti-rotation device, ie the area that absorbs the force exerted during the attempt to rotate the inserted implant post 4 (anti-rotation device), is greatest compared to all other anti-rotation devices , In the rotation lock 10 according to the invention, the surface under consideration covers a circular tooth 11 and half of the adjacent tooth base 12. Of this surface, 50% is effective as an anti-rotation lock. The hexagon 40 has the most unfavorable anti-rotation lock. In fact, only the extreme corners of the hexagon take up 40 force. In the case of the hexagon socket 41, the surface under consideration covers the round tooth and half of the two adjacent convex surfaces. Only half of this area is effective, as only about 18% (one "half" of the round tooth) as an anti-rotation device. On the basis of analogous relationships, only approximately 15% of the area under consideration (namely again a "half" of the round tooth) is effective as an anti-rotation device in the case of the inner multirundle 42. Only for the star-shaped rotation lock 43 are more favorable values. The area under consideration includes a tooth (the "point" of the star) and each half of the adjacent tooth base. Approximately 46% of this area is effective as an anti-rotation device. The effective area could be increased if the thickness of the teeth were reduced until the circles with the radius R | cut on the outer circle with the radius D _A , however this only increases the area for the force absorption, sufficient material to actually absorb the force is then no longer available.

Furthermore, both the value of a quotient (D _A / [D _A - D,]) and the value of a quotient (I _A / [D _A - D,]) are most favorable for the rotation lock 10 according to the invention. I _A denotes the outer radius of the base body 2 of the implant.

For the relationships shown, the following values result from the above. quotient:

((DD _AA // [[DD _AA - DD ,,]])) (l _A / [D _A - D,])

rotation lock

"According to the invention" (10) 11.5 24.0

Hexagon (40) 7.45 14.75

Hexagon socket (41) 8.0 16.0 I Internal nominal length ((4422)) 5 5, .22 9.6

"Star" (43) 4.5 8.0

This comparison is even more favorable in favor of the anti-rotation device 10 according to the invention if the same remaining wall thickness, ie the difference between I _A and D _A , is used. As a result, it can be ascertained that with the anti-rotation device 10 according to the invention, a maximum size of the inner bore 3, which is important for fixing the actual implant, can be achieved and that the effective area of the anti-rotation device is maximum.

Another tabular comparison relates to the different radii under consideration as previously explained:

rotation lock

"According to the invention" (10) 2.64 0.91

Hexagon (40) is omitted 0.86

Hexagon socket (41) does not apply to 0.86

Internal polygon (42) 0.5 0.8

0.77

"Star" (43) is omitted

18.02.2004 / 7526

LIST OF REFERENCE NUMBERS

1 dental implant 29

2 base body 30 slot

3 inner bore 31 slot

4 implant posts 32 tongue

5 main body section 33 crown

6 basic body section outer contour 34 implant post contour

7 inner bore contour 35 crown admission

8 threads

9 cone 40 hexagon

10 rotation lock, 41 hexagon socket

Anti-rotation contour 42 inner polygon

11 round tooth 43 star-shaped

12 Tooth bottom rotation lock

13 crown end

14 anti-rotation lock on the crown

15 cone

16 implant post inner bore

17 internal thread

18

19

20 thread section

21 implant post section

22 cone holder

23 screw

24 internal threads

25 channels

26

27

28

Claims

0 / SRD-12-W0 02/18/2004 / 7526 patent claims

1 . Dental implant (1) for a fixed denture with an implantable in the jawbone, essentially cylindrical base body (2), in its open at the coronal end inner bore (3) an implant post (4) can be used, the implant post (4) one Introducing into the inner bore (3) provided, at least substantially cylindrical base body section (5) with a base body section outer contour (6) and wherein a contour of the inner bore (3) - inner bore contour (7) - is matched to the base body section outer contour (6), characterized in that the basic body portion outer contour (6) comprises an in particular edge-free rotation lock (10) with at least one round tooth (11) and in each case with a convex tooth base (12) adjoining it on both sides, which with the correspondingly designed inner bore contour (7) in particular in a positive and / or especially over the entire surface.

2. Dental implant (1) for a fixed dental prosthesis with an essentially cylindrical base body (2) that can be implanted in the jawbone, in the inner bore (3) of which is open at its coronal end, an implant post (4) can be inserted, the implant post ( 4) has an at least substantially cylindrical main body section (5) provided for insertion into the inner bore (3) with an outer contour (6) of the main body section and wherein a contour of the inner bore (3) - inner bore contour (7) - is matched to the outer body contour (6) characterized in that the basic body section outer contour (6) has an in particular edge-free rotation lock (10) with at least one round tooth (11) and in each case a concave tooth base (12) adjoining it on both sides, the circular tooth (11) having a circle with a radius R _A and a circle with a radius Ri can be assigned to the tooth base, a quotient of the two radii (Ri / R _A ) is in the range from 0.2 to 0.6, in particular in the range from 0.2 to 0.9, which comes into engagement with the correspondingly designed inner bore contour (7) in particular in a form-fitting manner and / or in particular over the entire surface.

3. Dental implant (1) for a fixed dental prosthesis with an essentially cylindrical base body (2) which can be implanted in the jawbone and in whose inner bore (3) which is open at its coronal end, an implant post (4) can be inserted, the implant post (4) has an at least substantially cylindrical main body section (5) provided for insertion into the inner bore (3) with an outer body section outer contour (6) and wherein a contour of the inner bore (3) - inner bore contour (7) - is matched to the outer body section outer contour (6) characterized in that the basic body section outer contour (6) comprises an in particular edge-free rotation lock (10) which comes into engagement with the correspondingly designed inner bore contour (7) in particular in a form-fitting and / or in particular full-area manner and with the implant post (4) between one crown-side end (13) and the base body portion (5) e has a cone (9) which is provided for insertion into a corresponding section of the inner bore (3) of the base body (2) - cone receptacle (22).

4. Dental implant according to claim 1, 2 or 3, wherein the rotation lock (10) extends over the entire height of the cylindrical portion of the base body portion (5).

5. Dental implant according to claim 1, 2 or 3, wherein the rotation lock (10) extends over the entire circumference of the cylindrical portion of the base body portion (5).

6. Dental implant according to one of claims 1 to 5, wherein the rotation lock (10) at least one round tooth (11), in particular six or eight round teeth (11) distributed symmetrically over the circumference of the outer body portion outer contour (6), and one or each round tooth ( 11) comprises a tooth base (12) delimiting on both sides, the or each circular tooth (11) and the or each tooth base (12) and each transition between a circular tooth (11) and the adjacent tooth base (12) being edge-free.

7. Dental implant according to one of the preceding claims, wherein the implant post (4) at its crown-side end (13) has a crown-side rotation lock (14).

8. Dental implant according to claim 7, wherein the crown-side rotation lock (13) is designed in accordance with the rotation lock (10) of the base body section (5).

9. Dental implant according to claim 7 or 8, wherein the implant post (4) between the crown-side end (13) and base body section (5) has a cone (9) which for insertion into a corresponding section of the inner bore (3) of the base body (2) - Cone seat (22) - is provided.

10. Dental implant according to claim 9, wherein the cone (9) has a rotation-free surface.

11. Dental implant according to claim 9, wherein the cone (9) along its circumference symmetrically distributed ribs which extend parallel to the axis of rotation of the implant post (4) and are provided for engagement with corresponding recesses - grooves (25) - the cone receptacle (22) are.

12. Dental implant according to claim 11, wherein the depth of the grooves (25) along the height of the cone receptacle (22) from the smallest inner diameter of the cone receptacle (22) decreases and the height of the ribs correspondingly from the smallest diameter of the cone (9) seen also, especially to the same extent, decreases.

13. Dental implant according to one of the preceding claims, wherein the implant post (4) has an implant post inner bore (16) in which a screw (23) is held or into which a screw (23) can be inserted, the screw (23) for fixing of the implant post (4) is provided in the base body (2) and the implant post inner bore (16) has a thread on the crown-side end (13) for fixing a crown.

14. Dental implant according to one of claims 6 to 13, wherein the height of the or each round tooth (11) from the crown-side end (13) of the implant post decreases, the height of the round tooth (11) being reduced in particular in that the round tooth is conical , in particular at an angle of 1.0 ° to 1.5 °, is ground off.

15. Dental implant according to one of claims 6 to 14, wherein the inner bore contour (7) corresponding to the or each tooth base (12) comprises a convex tooth base receptacle and wherein the height of the or each tooth base receptacle increases from the coronal end of the base body (2), the height of the base of the tooth increases in particular because the base of the tooth is ground conically, in particular at an angle of 1.0 ° to 1.5 °.

16. Implant post (4) for a dental implant with a substantially cylindrical base body (2) which can be impregnated into the jawbone and in whose open inner bore (3) at its coronal end the implant post (4) can be inserted, the implant post (4) being one for insertion into the inner bore (3) provided at least substantially cylindrical base body section (5) with a base body section outer contour (6), characterized in that the base body section outer contour (6) has an in particular edge-free rotation lock (10) with at least one round tooth (11) and in each case an adjoining convex tooth base (12).

17. Implant post (4) for a dental implant with an essentially cylindrical base body that can be implanted in the jawbone, (2), in the inner bore (3) of which is open at its coronal end, the implant post (4) can be inserted, the implant post (4) has an at least substantially cylindrical base body section (5) provided for insertion into the inner bore (3) with a base body section outer contour (6), characterized in that the base body section outer contour (6) has an in particular edge-free rotation lock (10) with at least one Round tooth (11) and in each case an adjoining concave tooth base (12), the circle tooth (11) being able to be assigned a circle with a radius R _A and the tooth base a circle with a radius Ri, a quotient of the two radii (R ₍ / R _A ) is in the range from 0.2 to 0.6, in particular in the range from 0.2 to 0.9, which corresponds to the correspondingly designed inner bore ur (7) in particular comes into positive engagement and / or in particular over the entire surface.

18. implant post (4) for a dental implant with an implantable in the jawbone, essentially cylindrical base body (2), in the open at its coronal end inner bore (3) of the implant post (4) can be used, wherein the implant post (4) has an at least substantially cylindrical base body section (5), which is provided for insertion into the inner bore (3) and has a base body section outer contour (6), characterized in that the base body section outer contour (6) has an in particular edge-free rotation lock ( 10) and that the implant post (4) has a cone (9) between a crown-side end (13) and the base body section (5).

19. Implant post according to one of claims 16, 17 or 18, wherein the base body section outer contour (6) comprises a rotation lock (10) extending over the entire height of the cylindrical section of the base body section (5).

20. Implant post according to one of claims 16, 17 or 18, wherein the base body section outer contour (6) comprises a rotation lock (10) extending over the entire circumference of the base body section (5).

21. Implant post according to one of claims 16 to 20, wherein the rotation lock (10) has at least one round tooth (11), in particular six or eight round teeth (11) distributed symmetrically over the circumference of the outer body section outer contour (10), and one or each round tooth ( 11) comprises a tooth base (12) delimiting on both sides, the or each circular tooth (11) and the or each tooth base (12) and each transition between a circular tooth (11) and the adjacent tooth base (12) being edge-free.

22. Implant post according to one of claims 16 to 21, wherein the implant post (4) has at its crown-side end (13) a crown-side rotation lock (14).

23. The implant post according to claim 22, wherein the crown-side rotation lock (14) corresponds to the rotation lock (10) of the base body section (5).

24. The implant post according to claim 22 or 23, wherein the implant post (4) between the crown-side end (13) and base body section (5) has a cone (9) which for insertion into a corresponding section of the inner bore (3) of the Basic body (2) - cone holder (22) - is provided.

25. The implant post according to claim 24, wherein the cone (9) has a surface that is free from rotation.

26. The implant post according to claim 24, wherein the cone (9) has symmetrically distributed ribs along its circumference, which extend parallel to the axis of rotation of the implant post (4) and are provided for engagement with corresponding depressions - grooves (25) - of the cone receptacle (22) are.

27. The implant post according to claim 26, wherein the depth of the grooves (25) decreases along the height of the cone receptacle (22) from the smallest inside diameter of the cone receptacle (22), and the height of the ribs accordingly from the smallest diameter of the cone (9) seen also, especially to the same extent, decreases.

28. Implant post according to one of claims 16 to 27, wherein the implant post (4) has an implant post inner bore (16) in which a screw (23) is held or into which a screw (23) can be inserted, the screw (23) is provided for fixing the implant post (4) in the base body (2) and the inside of the implant post (16) of the end (13) on the crown side has an internal thread (24) for fixing a crown.

29. Implant post according to one of claims 21 to 28, wherein the height of the or each round tooth (11) from the crown-side end (13) of the implant post (4) decreases, the height of the round tooth (11) being reduced in particular by the fact that the round tooth is ground conically, in particular at an angle of 1.0 ° to 1.5 °.

30. Implant post according to one of claims 16 to 29, with slots (30) which run parallel to the longitudinal extent of the implant post (4) and are distributed symmetrically over the circumference of the implant post (4), as a result of which a tongue (32) between two adjacent slots (30) is formed and the at least two tongues (32) of the implant post (4) are provided for holding a crown (33).

31. Implant post according to claim 30, with a base body section 5, in particular a cone 9, which is slightly enlarged in relation to an implant post section (21) or a cone receptacle (22) of a base body (2) for receiving the implant post (4), so that by inserting the implant post (4) into the base body (2), it is possible to compress the tongues (22) in the direction of a central axis of the implant post (4).

32. Base body (2) for a dental implant with an essentially cylindrical shape, in the inner bore (3) of which is open at its coronal end, an implant post

(4) can be used, the inner bore (3) comprising a threaded section (20) and an implant post section (21) and the implant post section (21) having a contour - inner bore contour (7) -, characterized in that the inner bore contour (7) includes, in particular, an edge-free rotation lock with at least one concave circular tooth holder and in each case one convex tooth base holder adjoining it on both sides.

33. Basic body (2) for a dental implant with an essentially cylindrical shape, in the inner bore (3) of which an implant post (4) can be inserted at its coronal end, the inner bore (3) having a threaded section (20) and an implant post section (21 ) and wherein the implant post section (21) has a contour - inner bore contour (7) -, characterized in that the inner bore contour (7) comprises an in particular edge-free rotation lock with at least one concave circular tooth holder and in each case a convex tooth base holder adjoining it on both sides, the round tooth holder a circle with a radius R _A and the base of the tooth a circle with a radius R | can be assigned, a quotient of the two radii (R, / R _A ) being in the range from 0.2 to 0.6, in particular in the range from 0.2 to 0.9.

34. Basic body (2) for a dental implant with a substantially cylindrical shape, in the inner bore (3) of which an implant post (4) can be inserted at its coronal end, the inner bore (3) having a threaded section (20) and an implant post section (21 ) and wherein the implant post section (21) has a contour - inner bore contour (7) -, characterized in that the internal Nine bore contour (7) comprises an in particular edge-free rotation lock and that the inner bore (3) has a cone receptacle (22) at its open (coronal) end.

35. Base body according to claim 32, 33 or 34, wherein the inner bore contour (7) comprises an anti-rotation device extending over the entire height of the innervant post section (21).

36. Basic body according to claim 32, 33 or 34, wherein the inner bore contour (7) comprises a rotation lock extending over the entire inner circumference of the inner bore (3) in the region of the implant post section (21).

37. Basic body according to one of claims 32 to 36, wherein the rotation lock of the inner bore contour (7) at least one round tooth receptacle, in particular six or eight circular tooth receptacles distributed symmetrically over the inner circumference of the inner bore (3) in the region of the implant post section (21), and one or each round-tooth receptacle comprises elevation delimiting on both sides, the or each round-tooth receptacle and the or each elevation and each transition between a round-tooth receptacle and the adjacent elevation being edge-free.

38. Base body according to one of claims 32 to 37, wherein the inner bore (3) has a cone receptacle (22) at its open (coronal) end.

39. Base body according to claim 38, wherein the cone receptacle (22) has a non-rotationally secure surface.

40. Base body according to claim 38, wherein the cone receptacle (22) along its circumference symmetrically distributed depressions - grooves (25) - which extend parallel to the longitudinal extension of the inner bore (3).

41. Base body according to claim 40, wherein the depth of the grooves (25) along the height of the cone receptacle (22) decreases from the smallest inside diameter of the cone receptacle (22).

42. Base body according to one of claims 37 to 41, wherein the depth of the or each circular tooth receptacle decreases from the open end of the inner bore (3).

43. Base body according to one of claims 37 to 42, wherein an internal thread (24) is introduced into the or each elevation of the rotation lock of the inner bore contour (7).

44. Base body according to one of claims 32 to 43, wherein the height of the or each tooth base receptacle increases from the coronal end of the base body (2), the height of the tooth base receptacle increasing in particular because the tooth base receptacle conical, in particular at an angle of 1 , 0 ° to 1, 5 °, is ground.