WO2012085039A1

WO2012085039A1 - Dental implant and dental implant kit

Info

Publication number: WO2012085039A1
Application number: PCT/EP2011/073523
Authority: WO
Inventors: Steffen Kuehne; Ulrich Mundwiler
Original assignee: Straumann Holding Ag
Priority date: 2010-12-23
Filing date: 2011-12-21
Publication date: 2012-06-28

Abstract

The invention relates to a dental implant system, comprising a dental implant for insertion in the jaw bone of a patient and a secondary component for connection to the implant. The implant (1) comprising an elongated body having a longitudinal axis (2) and a coronal implant head (8) with a bore (10) which has a coronal truncated cone portion (16) extending radially around the longitudinal axis and an anti-rotation means (5) radially limited by an annularly closed line (20) varying between a major radius (a) and a minor radius (b) of the truncated cone portion (16), such that the anti-rotation means consists of a plurality of anti-rotation recesses (18) located at least partially within the truncated cone portion. Alternatively the anti-rotation means may be located in a cylindrical portion of the bore such that each recess has the same length and axial location. The secondary component (25) comprises an attachment portion (29) for insertion into the bore of the implant which has a longitudinal axis which in use is co-axial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means (28) radially limited by an annularly closed line varying between a maximum radius and a minimum radius, such that the anti-rotation means of the secondary component consists of a plurality of anti-rotation protrusions which can engage with but do not match any of the anti-rotation recesses of the implant.

Description

Dental implant and dental implant kit

Description

The invention relates to a dental implant for insertion into the jaw bone of a patient and to a secondary component for attachment to this implant.

A dental implant system is known from EP 1 139 906 Bl . A dental implant for insertion into the jaw bone of a patient is provided with an internal bore having anti-rotation recesses. These anti-rotation recesses are for engagement by a driving tool when the dental implant is screwed into the jaw bone as well as for engagement by an abutment, when the abutment is mounted to the implanted dental implant by means of a particular screw. The anti-rotation recesses are radially outlined by an octagon, thus each recess has a triangular cross section with two planar outside surfaces. Both the driving tool and abutment have corresponding anti-rotation protrusions such that these protrusions can fully engage the anti-rotation recesses of the implant.

The high torque applied to the anti -rotation recesses during insertion of the implant can lead to distortion or deformation of these recesses. According to standard implant systems such as the one outlined above, the abutment is shaped to match the anti-rotation recesses of the implant, and hence any distortion of these recesses can affect the fit between implant and abutment, In particular, distortion of the recesses can lead to increased rotational play between the abutment and implant, which is highly undesirable.

One system designed to overcome this problem is disclosed in WO2005/06781 1. This system provides an implant having an anti-rotation means comprised of two differently profiled sets of recesses. One of these sets is used to engage a driving tool and the other set engages the abutment. This ensures that the recesses intended for engagement with the abutment are undamaged by use of the driving tool. EP1419746 discloses a similar system in which the two different sets of anti- rotation recesses are axially displaced from one another within the implant bore.

These systems therefore both provide independent sets of recesses with different functions and thus prevent deformation of the abutment-engaging recesses during fixation of the implant. However, the provision of additional recesses decreases the volume of the implant and therefore weakens this. Further, extra machining is required to produce these recesses.

It is therefore an object of at least a preferred embodiment of the present invention to overcome the above problems and to improve the said conventional dental implant so that the effect of any damage to the anti-rotation recesses on the connection between the implant and abutment is limited. It is a further object of at least a preferred embodiment of the present invention to prevent or reduce damage to the anti-rotation recesses by the driving tool.

According to one aspect the present invention provides a dental implant system comprising a dental implant for insertion into the jaw bone of a patient and a secondary component for connection to said implant. The implant comprises an elongated body having a longitudinal axis and a bore extending from the coronal end of the implant along the longitudinal axis. The bore comprises a coronal truncated cone portion and an anti-rotation means radially limited by an annularly closed line varying between a major radius (a) and a minor radius (b) of the truncated cone portion, such that the anti-rotation means consists of a plurality of anti-rotation recesses located at least partially within the truncated cone portion. The secondary component comprises an attachment portion for insertion into the bore of the implant which has a longitudinal axis that, in use, is coaxial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means radially limited by an annularly closed line varying between a maximum radius and a minimum radius, such that the anti-rotation means of the secondary component consists of a plurality of anti-rotation protrusions which can engage with but do not match any of the anti-rotation recesses of the implant.

Viewed from another aspect the present invention provides a dental implant system comprising a dental implant for insertion into the jaw bone of a patient and a secondary component for connection to said implant. The implant comprises an elongated body having a longitudinal axis and a bore extending from the coronal end of the implant along the longitudinal axis. The bore comprises a cylindrical portion within which an anti-rotation means is radially limited by an annularly closed line varying between a major radius (a) and a minor radius (b), such that the anti-rotation means consists of a plurality of anti-rotation recesses which are equal in length and axial location. The secondaiy component comprises an attachment portion for insertion into the bore of the implant which has a longitudinal axis that, in use, is coaxial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means radially limited by an annularly closed line varying between a maximum radius and a minimum radius, such that the anti-rotation means of the secondary component consists of a plurality of anti-rotation protrusions which can engage with but do not match any of the anti-rotation recesses of the implant. By "secondary component" it is meant one of numerous components which in use are mounted to the implant, In particular, the secondary component can be a dental abutment, which in use acts a support for a dental prosthesis. This prosthesis can be cemented, screwed, directly veneered or otherwise attached to the abutment. Other secondary components include, for example, healing caps and impression posts, which are attached to the implant on a temporary basis.

According to the present invention, the anti-rotation means of the secondary component is shaped to engage with the anti-rotation means of the implant without precisely fitting any of the anti-rotation recesses. In other words the anti-rotation means of the secondary component is radially limited by an annularly closed line which partially corresponds to but is not identical to the annularly closed line which defines the anti-rotation recesses of the implant. This enables the anti- rotation means of the secondary component to engage with some portions of the anti-rotation recesses of the implant, i.e. at those areas at which the lines

correspond, but not with others, i.e. at those areas at which the lines do not correspond. One preferred way to achieve this is by creating implant anti-rotation means and secondary component anti-rotation means defined by annularly closed lines of different shapes. By this it is meant that the anti-rotation means differ from one another more than simply through an adjustment in dimensions.

Therefore, if the implant comprises, say, triangular anti-rotation recesses the secondary component anti-rotation protrusions will not be smaller proportioned triangles but will have a different shape, for example, rectangular protrusions that can extend partially into the triangular recesses.

The dental implant system of the present invention thus allows for sections of the anti-rotation recesses to be distorted without having any effect on the connection between the implant and secondary component. However, unlike existing systems, this result is achieved without requiring the addition of an extra dedicated set of anti-rotation recesses. Instead, the existing anti-rotation means of the implant and/or the secondary component are adjusted such that the anti-rotation protrusions of the secondary component no longer exactly match any of the anti- rotation recesses of the implant. The present invention therefore enables a single set of anti-rotation recesses to be used for both insertion and anti-rotation security whilst preventing any deformation of the recesses caused during insertion from affecting the fit of the secondary component.

The single set of recesses can be located either in a conical section of the implant, in which case the annularly closed line will vary between a major and minor radius of the conical portion, or it may be located in a cylindrical section of the implant bore, in which case the recesses will all have the same axial start and end points.

When it is stated that the anti-rotation recesses are located at least partially within the truncated cone portion it is meant that the recesses can extend axially beyond the cone portion. However, as the annularly closed line defining the recesses varies between a major and minor radius of the cone, the recesses will be fully radially contained within the cone. Preferably, in accordance with this aspect of the invention, the anti-rotation recesses are located entirely within the truncated cone, i.e. they do not extend apically of this. In other words, the anti-rotation recesses of the implant extend both radially and axially between the major radius and minor radius. This helps to create a more compact bore and facilitates the manufacturing process as less material must be removed from the implant bore.

The anti-rotation means of the secondary component of the present invention is radially limited by an annularly closed line varying between a maximum radius and a minimum radius. In some embodiments the maximum and minimum radii could be equivalent to the major and minor radii respectively, such that the anti- rotation protrusions extend to the radial extremities of the anti-rotation recesses, In accordance with the present invention however, in such circumstances the protrusions would not fill the recesses and thus areas of the side walls of the recesses would remain untouched by the protrusions and thus free for exclusive contact with the insertion tool.

Preferably the anti-rotation means are designed such that, in use, the protrusions do not contact the areas of the anti-rotation recesses that are subject to the greatest forces during insertion. To this end, it is preferred that the maximum radius of the anti-rotation means of the secondary component is less than the major radius but greater than the minor radius of the anti-rotation means of the implant. In this way, the radially outer parts of the recesses are not contacted by the secondary component. It is these areas that will normally be subjected to the greatest torque during use of the insertion tool and hence these are the areas most likely to be distorted. By creating a secondary component which does not contact these areas of the recesses any deformation in this area will not affect the fit between implant and secondary component and the radially outer sections of the recesses can be used exclusively for torque transfer between the implant and driving tool. The radial depth of the anti-rotation recesses is given by the difference between the major and minor radii. Preferably the maximum radius of the anti-rotation means of the secondary component is less than the sum of the minor radius plus half the radial depth of the anti-rotation recesses. In other words the anti-rotation protrusions are sized such that they do not extend into the radially outer half of the recesses. This enables this outer area to be used exclusively for torque transfer. More preferably the anti-rotation protrusions are sized such that they extend no more than a quarter of the way into the recesses, i.e., the maximum radius is less than or equal to the sum of the minor radius plus a quarter of the radial depth.

As the attachment portion must fit within the implant, the minimum radius of the secondary component anti-rotation means is less than or equal to the minor radius of the anti-rotation means of the implant. Preferably the minimum radius of the anti-rotation means of the secondary component is equal to the minor radius of the anti-rotation means of the implant. In this way the gaps between the implant and secondary component are minimised and further the strength of the secondary component is increased by maximising its volume,

The skilled man will appreciate that the anti-rotation means of the implant and secondary component can be designed to have many alternative shapes that enable these means to be brought into partial contact such that the protrusions engage with the recesses without matching any of these.

According to a preferred embodiment the annuiarly closed line of the anti-rotation means of either the secondary component or implant is at least partially curved and the annuiarly closed line of the anti-rotation means of the other component is at least partially straight such that, when the secondary component is inserted into the implant, areas of curved anti-rotation means are aligned with areas of straight anti-rotation means.

This is an advantageous way of providing the necessary discrepancies between the implant and secondary component.

Either the implant or secondary component can be provided with the partially rounded anti-rotation means. For example, the anti-rotation recesses of the implant may be straight walled and the anti-rotation protrusions formed by the anti-rotation means of the secondary component may be rounded at their radially outer ends such that these do not extend to the tips of the recesses.

However, the inventors of the present invention have noticed that conventional dental implants suffer from a particular problem. That is, when the dental implant is screwed into the jaw bone of a patient, there is some tendency that a phenomena occurs which is called cold welding or contact welding, whereby some small portions of the planar surfaces of the dental implant and of a matching bit tool which is used as a driving tool may strongly adhere to each other. After that, the bit tool has to be removed by applying some force, whereby the surfaces of the anti-rotation recesses may be damaged. Subsequently, it may be difficult to insert the abutment or other secondary component into the dental implant, and/or the inserted abutment may have a bad snug fit in the dental implant.

Cold welding does not normally occur between metals on earth because they have very fine layers of oxidized metal due to the atmosphere. However, under certain circumstances, the fine layers of oxidized metal may be damaged by local strong surface pressure and friction, such as occurs when an octagonal bit tool is put into an octagonal socket and heavily turned. Circumstances that facilitate cold welding are that the contacting metals are similar to each other, that the surfaces of the contacting metals are very smooth, that at least one of the contacting metals is a galvanic surface, and that the metal oxide has mechanical properties different to those of the parent metal. In particular, if the metal oxide is harder than the parent metal, surface deformations and friction may crack the oxide film, whereupon some exposed areas of the parent metals have opportunity to develop powerful molecular connections to each other.

The inventors of the present invention have recognized that the said circumstances apply when the said conventional dental implant made from titanium or a titanium alloy is contacted by a driving tool made of stainless steel and/or a titanium alloy, in particular when the driving tool is not held precisely axially with the dental implant. Therefore, preferably, the anti-rotation means of the implant is radially limited by an annularly closed line varying between a major radius and a minor radius, wherein the line is at least partially curved so as to form rounded anti-rotation recesses. Preferably the anti-rotation means is fully rounded, such that the radially outer boundary is formed by a continuous line with no angles or jumps. In alternative embodiments however, while the anti-rotation recesses can be fully rounded, the joining portion between the recesses may be straight. For example, the apical end of the conical portion or the geometric base of the cylindrical portion may be non-circular.

When a correspondingly shaped driving tool is inserted into the curved anti- rotation recesses and is turned against the stationary dental implant, the contact surfaces there between are substantially larger than those in case of the said conventional dental implant, where the contact surfaces are more or less in line form. In particular, according to the invention, the contact surfaces are two- dimensional, while in the said state of the art the contact surfaces are rather one- dimensional. Thus the rotational forces are distributed over a much larger surface, the surface pressure is much less, and cold welding is prevented.

This is considered inventive in its own right and therefore, viewed from a further aspect, the present invention provides a dental implant system comprising a dental implant for insertion into the jaw bone of a patient and a secondary component for connection to said implant. The implant comprises an elongated body having a longitudinal axis and a bore extending from the coronal end of the implant along the longitudinal axis. The bore comprises an anti-rotation means radially limited by an at least partially curved annularly closed line varying between a major radius ( ) and a minor radius (b), such that the anti-rotation means consists of a plurality of rounded anti-rotation recesses. The secondary component comprises an attachment portion for insertion into the bore of the implant which has a longitudinal axis that, in use, is coaxial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means radially limited by an annularly closed line varying between a maximum radius and a minimum radius, such that the anti-rotation means of the secondary component consists of a plurality of anti-rotation protrusions which can engage with but do not match any of the anti-rotation recesses of the implant.

This aspect of the present invention preferably comprises a single set of anti- rotation recesses, namely, the recesses are equal in length and axial location and are located in a cylindrical portion of the bore, or they are radially contained in a truncated cone portion of the bore having a major radius a and a minor radius b. Other preferred features of this aspect of the invention are the same as described throughout this specification in relation to the other aspects of the invention. In particular, it is preferred that the protrusions of the anti-rotation means of the secondary component are at least partially straight sided in order create the necessary discrepancies between the two anti-rotation means.

A further advantage of the curving of the anti-rotation recesses is that insertion of the bit tool is facilitated. Insertion of the tool, and of the secondary component, is even more facilitated by the provision of a truncated cone portion at the coronal end the bore.

According to a preferred embodiment of the invention, the anti-rotation means of the implant is radially limited by an annularly closed continuous wave line undulating between a major radius and a minor radius. The term continuous as used herein is to be understood in the mathematical sense, i.e. without any angles or jumps. The terms wave line and undulations as used herein denotes a kind of sine curves or combinations of sine curves. According to this preferred embodiment of the invention therefore, the radially external limitation of the anti-rotation recesses is totally rounded or curved without any edges.

Preferably the major radius and the minor radius differ by between approximately 5 and 10%, more preferably between 8 and 10%.

A preferred secondary component for use with curved recesses has an anti rotation means which is radially defined by an annularly closed line having linear sections, these sections being arranged to align, in use, with the curved recesses of the implant. Preferably the anti-rotation means of the secondary component is polygonal in shape. In this way, the curved recesses of the implant can only partially contact the secondary component.

In one particularly preferred embodiment therefore the anti-rotation means of the implant is defined by a continuous undulating line and the anti-rotation means of the secondary component is polygonal.

The polygon may be any shape, such as, for example a cross or star shape.

Preferably however the anti-rotation means of the abutment forms a regular polygon, for example a square, pentagon, hexagon or octagon. The vertices of the polygon form the maximum radius of the anti-rotation means and may, in certain embodiments, be rounded or beveled. In accordance with a preferred embodiment of the present invention these vertices are dimensioned to be smaller than the anti- rotation recesses of the implant such that the outer edges of the vertices can not, in use, contact the radial extremities of the recesses. When the implant bore comprises, at its coronal end, a truncated cone portion, the attachment portion of the secondary component preferably further comprises, coronal of the anti-rotation means, a truncated cone portion complementary to that of the implant. When the secondary component is inserted into the implant these complementary conical portions create a good frictional seal, which prevents the incursion of bacteria into the bore.

In accordance with conventional dental terminology, "apical" refers to the direction towards the bone and "coronal" to the direction towards the teeth.

Therefore the apical part of a component is the part which, in use, is directed towards the jaw bone and the coronal part is that which is directed towards the oral cavity.

The lines which radially define the anti-rotation means of the implant and secondary component vary between the major and minor radius and maximum and minimum radii respectively. These variations may result in recesses being formed which do not extend to the maximum or minimum radius, however in accordance with the present invention none of these recesses are completely matched by any of the anti-rotation protrusions of the secondary component.

In a preferred embodiment, the annularly closed lines which radially define the anti-rotation means of the implant and secondary component alternate between the major and minor radius and maximum and minimum radii respectively. This requires that in between each maximum/major radius peak, there is a

minimum/minor radius low and vice versa with no intermediate peaks or lows. The effect of this is that, although the anti-rotation recesses can have different shapes, these must begin at the minor radius and extend to the major radius.

Similarly the protrusions of the secondaiy component all begin at the minimum radius and extend to the maximum radius. In a further preferred embodiment the annularly closed lines which define the anti-rotation means alternate smoothly, such that there are no intermediate inflections or discontinuities (such as changes in curvature, angle etc) between the major/maximum peak and the minor/minimum low. This creates a simple shape for the anti-rotation means and improves force distribution.

In one embodiment the anti-rotation contour of the implant may be uniformly shaped, such that identical recesses are spaced at regular intervals about the longitudinal axis of the implant. In such an embodiment therefore the secondary component can be designed with similarly spaced protrusions such that a

protrusion partly extends into each recess.

However, in a particularly preferred embodiment the recesses are arranged pairwise equidistantly around the longitudinal axis, with the angular distance between the peaks of each pair of recesses being less than and preferably

approximately half of the angular distance between the peaks of neighbouring recesses of two neighboured pairs. The paired recesses are thus adjacent to each other and more closely spaced to each other than to neighbouring recesses. This creates a plurality of "camel back" double recesses evenly spaced about the longitudinal axis of the implant. One means of designing this configuration is to start with a number of uniformly shaped recesses evenly spaced around the longitudinal axis and then to "flip" every second recess such that this becomes the mirror image of its neighbouring recesses. When the maximum radial extent (peak) of the recess is off centre, this will result in the peaks of the recesses being paired together.

In this embodiment preferably the anti-rotation means of the secondary component comprises an even sided regular polygon, the polygon and recesses being shaped such that the sides of the polygon have a length greater than the minimum distance between the peaks of each pair of recesses. Thus, when the secondaiy component and implant according to this embodiment are connected together, every alternate side of the polygon is in alignment with a double peak and every other side is in alignment with an intermediate portion of the implant anti-rotation means.

This configuration has been found to be particularly beneficial as only half of the polygon sides align with the double peaks, whereas the other half of the polygon sides are in much closer contact with the implant. Therefore, this embodiment provides areas of non-contact between the anti rotation means of the implant and secondary component while still providing sufficient contact to limit rotational play between the implant and secondary component. In some embodiments the recesses of each pair may be joined by a line segment and/or neighbouring pairs of recesses may be joined by a line segment. This enables a better engagement with the polygonal sides of the secondary component.

The most preferred and advantageous embodiments of the inventive dental implant system are characterized by one or more of the following features; the recesses are arranged pairwise equidistantly around the longitudinal axis; the angular distance between the peaks of each pair of recesses is substantially smaller than and preferably approximately half of the angular distance between neighboured peaks of two neighboured pairs; the recesses are rounded; the anti-rotation means of the secondary component is a polygon; the number of the recesses is eight; and the dental implant is of titanium or a titanium alloy or ceramics.

Preferably the anti rotation recesses begin at a location axially removed from the coronal end of the implant. This results in the anti-rotation recesses beginning within the bore. This is particularly important in the present invention as the abutment does not exactly match the anti-rotation recesses of the implant.

Therefore, if these recesses began at the coronal end of the implant, the gaps between the implant and abutment would allow bacteria to enter the implant bore. The coronal end of the bore is preferably tapered or conical in shape however alternatively this could be cylindrical. In either case the secondary component preferably comprises, coronal of the anti-rotation means, a complementary

(tapered, conical or cylindrical) portion that matches the coronal end of the bore. This enables a gapless connection to be formed between the coronal end of the implant and the secondary component.

As discussed above, the provision of an implant and secondary component in accordance with the present invention enables sections of a single set of anti- rotation recesses, preferably the radially outer sections, to engage exclusively with a driving tool. Therefore the system of the present invention preferably further comprises a tool for inserting the dental implant into the bone, comprising a tool tip which is profiled to at least partially engage with the same anti-rotation recesses as the anti-rotation means of the secondary component Preferably the tool tip is shaped to come into exclusive engagement with at least the radially outer sections and more preferably at least the radially outer quarter, most preferably the radially outer half of the anti-rotation recesses. In other words, the tool tip is preferably shaped such that it extends further into the anti-rotation recesses than the anti-rotation protrusions of the secondary component, such that it engages with the anti-rotation recesses at more radially outer areas than the secondary component anti-rotation protrusions. Thus the "exclusive" nature of the contact between the tool tip and outer areas of the implant recesses refers specifically to the system of implant, secondary component and tool.

Preferably the engagement is a form fit engagement, namely, the contour of the tool tip matches, as far as possible taking into consideration manufacturing tolerances, the contour of the anti-rotation recesses in the areas where these components are to engage. The tool can be designed such that it does not fully engage the anti-rotation means of the implant. Thus, in one preferred embodiment the tool tip is designed to contact the same anti-rotation recesses as the anti- rotation protrusions but in different areas. In this way certain sections, preferably the outermost sections, of the anti rotation recesses will be engaged exclusively by the driving tool and other sections, preferably the radially inner sections of the anti-rotation recesses, will be engaged exclusively by the secondary component.

However, in an alternative preferred embodiment the tool tip is profiled to come into engagement with the implant anti-rotation means along the full radial depth of the implant anti-rotation recesses. In such embodiments some areas of the recesses will be engaged by both the tool tip and the secondaiy component.

In a preferred embodiment the tool tip is profiled to come into form fit

engagement with all of the implant anti-rotation means. This ensures a

distribution of forces and reduces the risk of deformation.

Preferably, the cross-sectional area of the tool tip is constant over a given length of its longitudinal axis in order to facilitate manufacturing of the tool, and the tool may have a necking which represents a breaking point.

Preferably the secondary component is an abutment for supporting a dental prosthesis.

The combination of a secondary component and an insertion tool which both engage the same anti-rotation recesses but in contrasting manners is considered inventive in its own right and therefore, viewed from a further aspect, the present invention provides a dental implant system comprising a dental implant for insertion into the jaw bone of a patient, the implant comprising an elongated body having a longitudinal axis and a bore extending from the coronal end of the implant along the longitudinal axis, said bore comprising anti-rotation means radially limited by an annularly closed line varying between a major radius and a minor radius, such that the anti-rotation means consists of a plurality of anti- rotation recesses located within the bore. The system further comprises a tool for inserting the implant into a jaw bone, the tool comprising a distal end for insertion into the implant bore, which has a longitudinal axis that, in use, is co-axial with the longitudinal axis of the of the implant, said distal end comprising torque transfer means radially limited by an annularly closed line varying between a maximum radius and a minimum radius such that the torque transfer means comprises a plurality of torque transmission protrusions which can engage the anti-rotation recesses of the implant. The system further comprises a secondary component for connection to said implant, comprising an attachment portion for insertion into the bore of the implant which has a longitudinal axis that, in use, is co-axial with the longitudinal axis of the of the implant, the attachment portion comprising anti-rotation means radially limited by an annularly closed line varying between a maximum radius and a minimum radius such that the anti-rotation means comprises a plurality of anti-rotation protrusions which can engage with the anti-rotation recesses of the implant, wherein the torque transmission protrusions engage with the same implant anti-rotation recesses as the secondary component anti-rotation protrusions, the torque transmission protrusions however being shaped such that they engage the anti-rotation recesses at more radially outer areas of the recesses than the anti-rotation protrusions of the secondary component.

In this way, as discussed above, a single set of recesses can be used both to transmit torque to the implant and prevent rotation of a secondary component, while at the same time any distortion suffered by the recesses during torque transfer has a minimised effect on the fit of the anti-rotation means of the implant and secondary component. This is because the anti-rotation means of the secondary component and torque transfer means of the insertion tool, while both shaped to engage with the anti-rotation means of the implant, have different cross- sectional profiles to one another. In particular the maximum radius of the torque transmission protrusions is greater than that of the anti-rotation protrusions, such that the torque transfer means engages with the anti-rotation recesses of the implant at more radially outer areas than the secondary component. These radially outer parts of the recesses will be subject to higher torque, and are therefore more likely to deform during use of the tool. As the secondary component is not shaped to contact these areas of the implant recesses any deformation at these radially outer areas does not affect the fit of the secondary component within the implant.

The implant, secondary component and insertion tool of this aspect of the invention can have any or all of the preferred features listed above in relation to the previous aspects. In particular, the implant anti-rotation means may comprise curved recesses while the secondary component anti-rotation means comprises a generally polygonal cross-section. In such embodiments it is preferred that the torque transmission protrusions of the tool are curved such that these conform to at least the radially outer quarter, more preferably at least the radially outer half of the recesses of the implant. More generally, it is preferred that the maximum radius of the torque transfer means is approximately equal to the major radius of the anti-rotation recesses such that torque transmission can occur at the radially outermost part of the recesses. In such systems, the maximum radius of the anti- rotation protrusions is less than the maximum radius of the torque transmission protrusions and thus the major radius of the implant anti-rotation recesses.

Preferably the maximum radius of the anti-rotation protrusions is less than the sum of the minor radius plus half the radial depth of the recesses. In all embodiments the maximum radius of the anti-rotation protrusions is greater than the minor radius of the implant recesses so that engagement can occur. In one preferred embodiment the anti-rotation recesses are uniformly shaped and spaced about the longitudinal axis. Also or alternatively the annularly closed line defining the implant anti-rotation means may preferably alternate between the major and minor radii, more preferably smoothly alternate.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a top view from a coronal end of a dental implant;

Fig. 2 shows a partial longitudinal section of the dental implant of Fig. 1 ;

Fig. 3 shows a scaled down perspective view of the dental implant of Figs. 1 and 2;

Fig. 4 shows a perspective view of a dental abutment for use with the implant of Figs. 1 to 3;

Fig. 5 shows a cross section through the aligned anti-rotation means of the implant of Fig. 1 and abutment of Fig. 4;

Figs. 6-8 show alternative anti-rotation means according to the present invention;

Fig. 9 shows a top view from the implant side end of a tool for insertion of the dental implant of Figs. 1 to 3 into the bone of a patient;

Fig. 10 shows a lateral view of the tool of Fig. 9; Fig. 1 1 shows a scaled down perspective view of the tool of Figs. 9 and 10;

Fig. 12 shows the implant anti-rotation means of Fig. 7 in combination with a cross-section of a suitable torque transfer means; and

Fig, 13 shows the implant anti-rotation means of Fig. 8 in combination with a cross-section of a suitable torque transfer means.

As shown in Figs. 1 to 3, a dental implant 1 for insertion into the jaw bone of a patient has a substantially axially-symmetric elongated body extending along a longitudinal axis 2 and consisting of titanium or a titanium alloy. An apical part 4 of the dental implant 1 which is to be located inside the bone may have external threads 6. A coronal implant part 8 on the other end of the dental implant 1 has an axial bore 10 which is a blind hole extending along the longitudinal axis 2. The axial bore 10 has an apical threaded portion 12 with internal threads 14 and a coronal truncated cone portion 16. The inner surface of the coronal truncated cone portion 16 tapers inwards towards the apical end from the coronal end of the implant.

in the truncated cone portion 16 of the bore there is formed an anti-rotation means 5 comprising a plurality of anti-rotation recesses 18 which extend axially and radially between a major radius a and a minor radius b of the truncated cone portion 16.

Shortly stated, the anti-rotation recesses 18 are formed by projecting an annularly closed continuous wave line 20, which undulates and smoothly alternates radially between the major radius a and the minor radius b, along the longitudinal axis 2 into the truncated cone portion 16, and by removing any material inside the projected annulaiiy closed continuous wave line 20. Accordingly, the anti-rotation recesses 18 can be fabricated by a milling tool, whose cutting edge is moved along the whole annul arly closed wave line 20, for example by moving the milling tool 360° around the longitudinal axis 2 while simultaneously displacing the tool radilally to follow wave line 20. Many other well known manufacturing methods can however also be used to create the anti-rotation recesses.

In more detail, the anti-rotation recesses 18 are radially outwardly limited by the annularly closed continuous wave line 20 undulating radially between the major radius a and the minor radius b of the truncated cone portion 16, as seen in Fig, 1. As seen in Fig. 2, the anti-rotation recesses 18 extend in the axial direction from a substantially ring-shaped bottom area 22, which is radially outwardly limited by the annularly closed continuous wave line 20, up to a top wave line 24. The top wave line 24 is the intersection of the axial projection of the wave line 20 with the inner surface of the truncated cone portion 16. The top wave line 24 undulates in the direction of the longitudinal axis 2 with an amplitude c. In accordance with the slight conicity of the truncated cone portion 16, the amplitude c of the the top wave line 24 in the axial direction is a multiple of the amplitude (a-b) of the wave line 20 in the radial direction.

As seen best in Fig. 1, the annularly closed continuous wave line 20 forms eight recesses 18, The recesses 18 are arranged pairwise equidistantly about the longitudinal axis 2. The angular distance with respect to the longitudinal axis 2 between the peaks 19 of each pair of recesses 18 is about 30°, and the angular distance between neighbored peaks 19 of two neighbored pairs of recesses 18 is about 60°. As, in this embodiment, the wave line 20 alternates between the major radius a and minor radius b, each peak 19 has major radius a.

It is seen that each pair of closely adjacent recesses 18 forms a so-called "camelback" double recess, and that four "camelbacks" are arranged with angular distances of 90° around the longitudinal axis 2.

Such an annularly closed continuous wave line 20 with alternating angular distances is obtainable by some mathematical combination of different annularly closed sine curves.

Although in this embodiment the anti-rotation means 5 is formed in a truncated cone portion 16 it is also possible for the same annularly closed line 20 to define the same anti-rotation recesses 18 within a cylindrical portion of the bore. In such cases, the whole of each recess will have the same start and end axial locations. In other words, there will be no top wave line 24 which undulates in the longitudinal direction,

Fig 4 shows an abutment 25 for use with the implant 1 of Figs. 1 to 3. It comprises an attachment portion 29 for insertion into the bore 10 and an occlusal portion 21 which in use extends coronally from the implant into the oral cavity of the patient. This portion can this be used to support a dental prosthesis.

The attachment portion 29 comprises anti-rotation means 28 shaped for partial engagement with the anti-rotation means 5 of the implant 1. The anti-rotation means 28 is radially limited by an annularly closed line that smoothly alternates between a maximum and minimum radius to form an octagon.

The attachment portion 29 further comprises, coronally of the anti-rotation means 28, a truncated cone portion 27 which is complementary in shape to the surface of the truncated cone portion 16 of the dental implant 1. These complmentary cone portions 27, 16 come into frictional surface contact when the abutment 25 is mounted onto the dental implant 1.

When the abutment 25 is connected to the implant 1, the anti-rotation means 28 of the abutment 25 is axially aligned with the anti-rotation means 5 of the implant 1, but the non identical shapes of these components means that the octagon does not completely match any of the anti-rotation recesses 18. A cross section through the aligned anti-rotation means 28, 5 is shown in Fig 5, however the gap between abutment and implant anti-rotation means is exaggerated for clarity..

In this figure it can be clearly seen that the radially outer sections of the recesses 18 do not engage with the anti-rotation means 28 of the abutment. Instead, as the maximum radius A of the octagon is less than major radius a, the walls of the octagon only contact the radially inner surfaces of the anti-rotation means 5.

The contact between the implant 1 and abutment 25 is enough to prevent relative rotation between the two components but also leaves areas of the anti-rotation recesses 18 free for exclusive engagement by a driving tool. Any resulting deformation of these areas will not affect the fit or rotational play between the implant 1 and abutment 25.

The camelback pairing of the anti-rotation recesses 18 results in the peaks 19 of each pair aligning with a single side of the octagon, i.e the length of one side of the octagon is greater than the length between each peak 19 of the camelback pair This leaves alternate sides of the octagon free to engage with sections of the anti- rotation means 5 having a smaller radius and thus provides a closer contact between the implant and abutment.

Although the above described embodiment is particularly preferred, many alternative combinations of anti-rotation means are possible. Some other possible designs are shown schematically in Figs. 6 to 8.

Fig. 6 shows a combination very similar to that of Fig. 5, however, in contrast to the implant of Fig. 1 the anti-rotation means 65 of the implant 61 comprises straight sided sections 62 joining each pair of camel backs. This provides a closer fit to the abutment 25 in these areas.

Fig. 7 shows an alternative configuration in which the anti-rotation means 75 of the implant 71 comprises four rounded recesses 78 arranged at angles of 90° to each other. The abutment 95 comprises a cross-shaped polygonal anti-rotation means 98 wherein each arm has a smaller maximum length than the major radius of the anti-rotation recesses 78. Therefore, although the anti-rotation means 98 of the abutment 95 engages the anti-rotation means 75 of the implant 71 to prevent relative rotation of these components, the outermost sections of the anti-rotation recesses 78 are not contacted by the abutment and hence any distortion of these sections does not interfere with the implant/abutment connection.

Fig. 8 shows an alternative embodiment in which the anti-rotation means 85 of the implant 81 is formed by straight line segments and the abutment anti-rotation means 108 is radially limited by a partially curved closed line.

In each of these embodiments the anti-rotation means of the abutment is shaped such that it engages the implant in a non-rotational manner but does not

completely fill any of the anti-rotation recesses of the implant. This enables sections of the anti-rotation recesses to be used exclusively for engagement with a driving tool. The anti-rotation recesses shown in Figs 6-8 could be formed either in a truncated cone portion of the implant or in a cylindrical portion. Figs. 9 to 11 show an elongate bit tool 35 which can be used for insertion of the dental implant of Fig. 1 to 3 into the jaw bone of a patient. An implant side tip 26 of the tool is shaped to come in form fit with the radially outer sections of recesses 18 of the dental implant. In particular, the implant side tip 26 has eight torque transmission projections 38 each extending longitudinally at the outer

circumference the implant side tip 26. These projections 38 are radially limited by an annulaiiy closed line and form torque transfer means 36. With respect to a longitudinal axis 30 of the tool and its implant side tip 26, the projections 38 have a similar cross section to and are arranged in the same angular pattern as the recesses 18 with respect to the longitudinal axis 2 of the dental implant 1. In particular the maximum radius of the projections 18 is substantially equal to the major radius a of the implant recesses 18. Therefore, the tool tip 26 engages with a large area of the implant recesses 18, including the radially outermost areas of these. This is in contrast to the anti-rotation means 28 of abutment 25, which only engages the radially inner most areas of the recesses 18. In this way, any distortion caused to the radially outer areas of recesses 18 during use of the tool 35 will not have any affect on the fit of the abutment 25. Further, it can be seen from a comparison of Figs. 1 and 9 that the minimum radius of the projections 38 is less than the minor radius b of the recesses 18, such that the tool tip 26 does not contact the radially innermost areas of the implant anti-rotation means 5, enabling these areas to be exclusively engaged by the abutment 25.

When the tool tip 26 is inserted axially into the coronal truncated cone portion 16 of the bore 10 (cf. Fig. 2) of the dental implant, the eight projections 38 engage with the recesses 18. When the tool tip 26 is fitted within the recesses 18, it does not contact the surface of the truncated cone portion 16 of the dental implant. Thus, the surface of the truncated cone portion 16 would not be damaged by the tool tip 26. This tool can also be used with an implant in which the anti-rotation recesses are formed in a cylindrical portion of the bore.

At a driving side end of the tool, there is formed a standard hexagon 32 for engagement by a standard driving tool which is driven manually in order to screw the dental implant into the bone. In an alternative embodiment however the driving side end may be configured for attachment to an automated driving tool, such as a dental hand piece.

Between the implant side tip 26 and the driving side end of the tool, the tool has a radial necking 34 or reduction in its cross section which forms a breaking point in order to prevent overturning when the dental implant is screwed into the bone.

Figs. 12 and 13 show further possible cross-sections for torque transfer means in accordance with the present invention. Fig. 12 shows the anti-rotation means 75 of implant 71 of Fig. 7, with the corresponding anti-rotation means 98 of the abutment 95 shown in dashed lines. The cross-section of the torque transfer means 126 has a greater maximum radius than the maximum radius of the abutment anti-rotation means 98 and matches, as far as practically possible in view of manufacturing tolerance limits, the shape of the radially outermost areas of the anti-rotation recesses 78. For clarity Figs. 12 and 13 show a slight gap between the implant anti-rotation means and torque transfer means at areas where these two components are said to "match". This is simply to enable the viewer to clearly see both parts and in practice, the contours of the components will, in these areas, be as closely dimensioned as possible within tolerance limits. Therefore the tool engages the recesses 78 at locations where the maximum torque can occur. The torque transfer means 126 is shaped such that it does not contact the implant anti- rotation means 75 at its radially innermost areas. It is these areas which will be contacted by the abutment anti-rotation means 95. The shape of the torque transfer means 126 therefore ensures that any damage suffered by the implant anti- rotation means 75 during insertion will not affect the fit of the abutment to the implant.

Fig. 13 shows the implant anti-rotation means 85 of Fig. 8, again with the abutment anti-rotation means 108 shown in dotted lines. Here the tool torque transfer means 136 exactly matches, as far as practically possible in view of manufacturing tolerance limits, the anti-rotation means 85 of the implant 81.

Although both the abutment and tool therefore engage the same area of the implant anti-rotation means 85, the torque transfer means 136 also engages the radially outer areas of the implant anti-rotation means 85, where the greatest torque will be experienced. Thus, any distortion is likely to occur in these areas rather than at the radially inner areas of the anti-rotation means 85, where the abutment contacts the anti-rotation means. Thus, this embodiment also prevents or reduces damage to the implant during insertion from affecting the fit of the abutment.

The above described embodiments are for illustrative purposes only and the skilled man will realize that many alternative arrangements are possible which fall within the scope of the claims. For example, the implant and/or abutment may be made of a ceramic material. The abutment could also be any other secondary component for attachment to the implant. Instead of contacting the whole of the recesses, the bit tool may only contact certain areas of these recesses, in particular the radially outer parts of the recesses. Embodiments in which the anti-rotation protrusions extend to the peaks of the recesses are also possible, wherein the protrusions do not entirely contact the side walls of the recesses.

Claims

1. A dental implant system, comprising a dental implant for insertion into the jaw bone of a patient and a dental secondary component for connection to said implant,

said implant (1) comprising an elongated body having a longitudinal axis (2) and a bore (10) extending from the coronal end of the implant along the longitudinal axis, said bore comprising a coronal truncated cone portion (16) and an anti-rotation means (5) radially limited by an annularly closed line (20) varying between a major radius (a) and a minor radius (b) of the truncated cone portion (16), such that the anti-rotation means consists of a plurality of anti-rotation recesses (18) located at least partially within the truncated cone portion,

said secondary component (25) comprising an attachment portion (29) for insertion into the bore of the implant which has a longitudinal axis that, in use, is co-axial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means (28) radially limited by an annularly closed line varying between a maximum radius and a minimum radius, such that the anti- rotation means of the secondary component consists of a plurality of anti-rotation protrusions which can engage with but do not match any of the anti-rotation recesses of the implant.

2. A dental implant system as claimed in claim 1 wherein the anti-rotation recesses (18) are located entirely within the truncated cone portion (16).

3. A dental implant system comprising a dental implant (1) for insertion into the jaw bone of a patient and a secondary component (25) for connection to said implant, said implant comprising an elongated body having a longitudinal axis (2) and a bore (10) extending from the coronal end of the implant along the longitudinal axis, said bore comprising a cylindrical portion within which an anti-rotation means (5) is radially limited by an annularly closed line (20) varying between a major radius ( ) and a minor radius (b), such that the anti- rotation means consists of a plurality of anti-rotation recesses (18) which are equal in length and axial location,

said secondary component (25) comprising an attachment portion (29) for insertion into the bore of the implant which has a longitudinal axis that, in use, is coaxial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means (28) radially limited by an annularly closed line varying between a maximum radius and a minimum radius, such that the anti- rotation means of the secondary component consists of a plurality of anti- rotation protrusions which can engage with but do not match any of the anti- rotation recesses of the implant.

4. A dental implant system as claimed in claim 3, where in the bore (10)

further comprises a coronal truncated cone portion (16).

5. A dental implant system as claimed in any preceding claim, wherein the annularly closed line of the anti-rotation means (5, 28) of either the secondary component (25) or implant (1) is at least partially curved and the annularly closed line of the anti-rotation means of the other component is at least partially straight such that, when the secondary component (25) is inserted into the implant (1), areas of curved anti-rotation means are aligned with areas of straight anti-rotation means.

6. A dental implant system as claimed in any preceding claim, wherein the annularly closed line (20) which radially limits the anti-rotation means (5) of the implant (1 ) is at least partially curved so as to form rounded anti- rotation recesses (18).

7. A dental implant system comprising a dental implant (1) for insertion into the jaw bone of a patient and a secondary component (25) for connection to said implant,

said implant comprising an elongated body having a longitudinal axis (2) and a bore (10) extending from the coronal end of the implant along the longitudinal axis (2), said bore comprising an anti-rotation means (5) radially limited by an at least partially curved annularly closed line (20) varying between a major radius (a) and a minor radius (b), such that the anti-rotation means consists of a plurality of rounded anti-rotation recesses (18), said secondaiy component (25) comprises an attachment portion (29) for insertion into the bore of the implant which has a longitudinal axis that, in use, is coaxial with the longitudinal axis of the implant, the attachment portion comprising anti-rotation means (28) radially limited by an annularly closed line vaiying between a maximum radius and a minimum radius, such that the anti- rotation means of the secondary component consists of a plurality of anti- rotation protrusions which can engage with but do not match any of the anti- rotation recesses of the implant.

8. A dental implant system as claimed in any preceding claim, wherein the maximum radius (A) is less than the major radius (a) but greater than the minor radius (b).

9. A dental implant system as claimed in any preceding claim wherein the anti- rotation protrusions are sized such that they do not extend into the radially outer half of the recesses.

10. A dental implant system as claimed in any preceding claim, wherein the anti-rotation means (5) of the implant (1) is radially limited by an annularly closed continuous wave line (20) undulating between the major radius (a) and the minor radius (b).

1 1.A dental implant system as claimed in any preceding claim wherein the anti- rotation means (28) of the secondary component (25) is polygonal in shape.

12. A dental implant system as claimed in any preceding claim, wherein the anti-rotation means (5) of the implant (1 ) is radially limited by an annularly closed line (20) alternating between the major radius ( ) and the minor radius (b),

13. A dental implant system as claimed in any preceding claim, wherein the anti-rotation means (28) of the secondary component (25) is radially limited by an annularly closed line alternating between the maximum radius and the minimum radius.

14. A dental implant system as claimed in any preceding claim, wherein the peaks of the recesses (18) are arranged pairwise equidistantly around the longitudinal axis (2) such that the angular distance between the peaks of each pair of recesses is less than the angular distance between the peaks of neighbouring recesses of two neighboured pairs.

15. A dental implant system as claimed in claim 14 wherein the anti-rotation means (28) of the secondary component (25) comprises an even sided regular polygon, the polygon and recesses (18) being shaped such that each side of the polygon has a length greater than the length between the peaks of each pair of recesses,

16. A dental implant system as claimed in any preceding claim, further

comprising a tool (35) for inserting the dental implant (1) into the bone, comprising a tool tip (26) which is profiled to at least partially engage with the same anti-rotation recesses (18) as the anti-rotation means of the secondary component (25).

17. A dental implant system as claimed in claim 16, wherein the tool tip is

shaped to come into exclusive engagement with at least the radially outer sections of the anti-rotation recesses.

18. A dental implant system as claimed in claim 16 or 17, wherein the tool tip (26) is profiled to exactly match the anti-rotation means (5) of the implant (1 ).

19. A dental implant system comprising a dental implant for insertion into the jaw bone of a patient, the implant comprising

an elongated body having a longitudinal axis and

a bore extending from the coronal end of the implant along the longitudinal axis, said bore comprising anti-rotation means radially limited by an annularly closed line varying between a major radius and a minor radius, such that the anti-rotation means consists of a plurality of anti-rotation recesses located within the bore, the system further comprising a tool for inserting the implant into the jaw bone, the tool comprising

a distal end for insertion into the implant bore, which has a longitudinal axis that, in use, is co-axial with the longitudinal axis of the of the implant, said distal end comprising torque transfer means radially limited by an annularly closed line varying between a maximum radius and a minimum radius such that the torque transfer means comprises a plurality of torque transmission

protrusions which can engage the anti-rotation recesses of the implant, the system further comprising a secondary component for connection to said implant, said secondary component comprising

an attachment portion for insertion into the bore of the implant which has a longitudinal axis that, in use, is co-axial with the longitudinal axis of the of the implant, the attachment portion comprising anti-rotation means radially limited by an annularly closed line varying between a maximum radius and a minimum radius such that the anti-rotation means comprises a plurality of anti-rotation protrusions which can engage with the anti-rotation recesses of the implant, wherein the torque transmission protrusions engage with the same implant anti-rotation recesses as the secondary component anti-rotation protrusions, the torque transmission protrusions however being shaped such that they engage the anti-rotation recesses at more radially outer areas of the recesses than the anti-rotation protrusions of the secondary component.

20. A system as claimed in claim 18 comprising any of the features of claims 1 to 18.