EP2429442A1

EP2429442A1 - Guided dental implant positioning system

Info

Publication number: EP2429442A1
Application number: EP09787717A
Authority: EP
Inventors: Gian Luigi Telara
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-29
Filing date: 2009-04-29
Publication date: 2012-03-21
Also published as: WO2010125593A1

Abstract

The present invention concerns a guided dental implant positioning system, of the kind making use of a surgical guide (10) provided with one or more holes or sleeves (11) in correspondence of the implants insertion points and for controlling the orientation of insertion of the implants, comprising means for simultaneously controlling the position, the final insertion depth, the insertion axis direction and the rotation angle around said axis of each implant, through the setting up of the rotation angle around its own axis of each implant at the beginning of its insertion into the osteotomic seat. The invention also concerns means for simultaneously controlling the depth and axis direction of realisation of osteotomic seats.

Description

GUIDED DENTAL IMPLANT POSITIONING SYSTEM

The present invention concerns a guided dental implant positioning system. The invention regards the field of odontology and in particular the sector relating to the so called guided implantology.

It is known that it is possible to recover dental elements gone lost through the insertion into the jawbone (upper and/or lower) of so called implants, structures having a cylindrical or conical shape (if the end, called dental apex, is smaller than the so called implant abutment, i.e. the portion of the implant protruding towards the osseus crest) provided with thread, so that they can be screwed into the bone, suitably prepared by means of the preparation of a suitable seat called osteotomic seat. At present, said implants are made of titanium or alloys of said material. In the design of a dental prosthesys with implant mounting, the so called implant prostheses, it is necessary to consider, as far as the design of the implant mounting is concerned, the number and position of the implants within the dental arch, and further the insertion depth, the insertion axis and, given a reference point along the perimeter of the implant platform, the position of the latter with respect to the dental arch (or to an external reference point, positioned with respect to the oral cavity), or after all the rotational angle of the implants around their own axis.

At present, there are significant difficulties for inserting implants in a precise matter and assuring at the same time insertion depth, axis and rotation.

Moreover, such difficulties increase if it is needed to insert more than one implant into the oral cavity, since the error that can be considered as possible for one implant has to be added to the possible error for the other implants.

From the above said it is easily understood that it is in practice impossible to work in a precise manner and overcome these difficulties without the help of suitable means and methods, on the development of which have been concentrating the research during the last years. In particular, different methods were developed, allowing inserting implants in a predictable manner, and allowing, once the final position of the implants is known, having the prosthesys ready before the surgical operation for the insertion of the same implants. All of these different methos undergo under the name of guided implantology, since they allow the guided insertion of the implant into the bone.

In particular, the bone must be preliminarily prepared in a guided manner by means of milling cutters, guided by a surgical guide suitably designed, provided with guide holes named guide cylindres or sleeves; in this way is prepared the seat into the bone (osteotomic seat) wherein the implant will be positioned. Also the implant is in turn inserted into the osteotomic seat by means of a guide (ideally the same used for the preparation of the bone, since, as it can be understood, fewer passages imply a better final result), through which the implant itself is passed together with a further component, called mounter, or a extension that is necessary since the implant, in itself, goes completely under the level of the guide and the gingiva, that is some millimetres under the sleeve and so its sliding while screwing could not be controlled all along its insertion.

Nevertheless, none of the solution already known can assure at the same time the respect of all the parameters that must be taken into consideration in order to correctly perform the insertion of the implant, or the insertion depth with respect to the level of the osseus crest, the direction of the insertion axis and at last the rotation angle around the insertion axis.

In fact, every change in one of these parameters implies modifications of the others.

Moreover, a further difficulty is due to the possibility of a lateral shift or deviation with respect to the programmed centre (in odontological terms when indicating the direction of the lateral shift reference is made to the teeth with respect to the rima oris, the lips, and the teeth close to the throat, more on the back, respectively with the terms mesial and distal deviation, whereas as lateral deviation is intended a deviation towards the cheek, or lingual, towards the interior of the oral cavity) due to the difference in diameter between osteotomic milling cutters and respective guides and, in the step of insertion of the implant, also between the implant and the respective guide.

As far as the rotation around its axis and the depth is concerned, since the implants are provided with a thread through which they are engaged in a seat prepared into the bone, it is easy to understand that in order to make a point of the circumference of the implant correspond with a reference position on the osseus crest it can be necessary to engage the implant until it is slightly above the crest or slightly under the crest: thus the point of arrival is not predictable without losing the depth value. This happens because the initial point of engagement of the implant into the bone can not be guaranteed: if it could, then it would also be predictable the point of arrival.

Moreover, in order to correctly position the implants into the upper and lower jawbones, implants are generally inserted not vertically, but with a converging direction in the upper arch and diverging direction in the lower arch.

Since the insertion of the implants is not vertical, as already disclosed, every differences in the insertion depth of the implants necessarily imply also a difference in the distance of the implants and in particular, they will be closer in the upper arch and farer in the lower arch while increasing the insertion depth.

Such movements in horizontal direction are always present, even when, for reasons of osseus resorption, implants must be inserted in an incorrect manner from a prosthetical point of view, with various directions, according to the type and degree of osseus resorption. Since the emerging cone realised above the implant abutment must have an insertion axis that can be suitable for every possible abutments of an arch in order to allow the insertion of a prosthesys (conception of parallelism of the traditional prosthetic odontoiatry, both with respect to the points of contact of teeth that are close to a bridge to be inserted, and with respect to other abutments), a different depth will imply, with respect to an abutment already prepared, a different emerging profile from the gingival level, with a decrease or an increase of the distance of the abutments.

Moreover, needs of prosthetic nature deriving from traditional prosthetic odontoiatry (applied to natural teeth), the abutment is never realised perfectly conical: the spaces to be left free at disposition of the future bridge must have values that are as precise as possible in order to house metal and ceramic, spaces that, if not precise, bring to deformations during welding with subsequent inaccuracies in the final product. An incorrect insertion of the implant with reference to any of these parameters implies a variation of the position and orientation of the abutment, with consequences of inaccuracy further worse due to the directionality of the abutment.

This applies to all different kinds of connection between implant and abutment and in particular to shaped mortise joints, amongst which hexagonal mortise joints are the most common, with an hexagonal tenon emerging from the body of the implant (defined "external hexagons"), all provided with a pehmetral flat platform allowing for the exclusion of the hexagon as a joint, keeping together different parts only by means of a connection screw between the abutment and the implant abutment, but in particular for hexagonal mortise joints where the hexagon is realised as a hollow within the implant body (defined "internal hexagons"), wherein the hexagon can be excluded, but the connection is weakened, since the release of the forces from the abutment to the platform along the walls of the countersink of the implant body, can imply an easier break of the upper part of the platform, due to the weight of the lateral load, or the component towards the external of the masticatory pressure. Further, the same happens also for telescopic and conometric internal connections, with interference of the conical tenon, realised on the abutment, inserted into the conical mortise of the implant body, with different conical angle, because even if these connections allows for any orientation of the abutment, in practice they can not guarantee an error free orientation. At last, the same kind of problem occurs for connections resulting from a mix of conometric and mortise joint connections, so that once the hexagon was found, it must be engaged with the mortise of the implant (the joining between the metals of the implant and the abutment is such that it is also defined "cold weld").

On top of the abutment are the applied dental prostheses and it is an obvious consequence of the correct positioning of the abutment and the implant below, also the possibility of realising an optimal prosthesys. Recently, preliminary planning of the position fo the implants and the methods of insertion of the implants into the bone also benefit by the developments of computer assisted virtual modelling, possibly also with the aid of digital scanning of photographic or radiologic images of the insertion area. Merely for illustrative purposes, one of this modelling methods is disclosed according to European patent N. EP 0 756 735 in the name of the Belgian company Materialise. Starting from the analisys of an image of the intervention area, by means of these modelling methods it is possible to simulate the position of the implants and consequently realise a surgical guide (surgical guide), or a structure, generally made of a resin, reproducing the shape of the intervention area, so that it can be applied on it and provided with one or more passing through holes, having reinforced walls thanks to metal cylinders, forming the guides for the orientation of milling cutters that will prepare the osteotomic seat wherein the implants will be positioned, and further for the orientation of the implants during their insertion. Surgical guides can be realised to have an osseus support (to be applied in direct contact with the bone in the intervention area, previously deprived of the above gingiva through the opening of a strip), or to have a dental or mucous support (in the last case with some lack of precision due to the resilience of the gingiva acting as a support). Anyway, the technique currently in use provides for the use of screws or pins for fixing the guide to the bone in order to offer a stable working base. Some of these systems of modelling allow for simulating also the teeth surrounding the area of the intervention, both in the portion below the gingiva, and in particular in the emerging portion, also allowing for the realisation of a model in plaster of the intervention area and of the prosthesys. If, on one hand, these modelling techniques surely allowed for improving the determination of optimal values of essential parameters for a correct insertion of the implant (insertion depth with respect to osseus crest level, insertion axis direction and rotation angle around the insertion axis), none could overcome the problem of assuring at the same time the respect of all of these parameters, and also of avoiding the possibility of a lateral shift.

Also the so called passive systems, i.e. those depriving the surgeon of the possibility to decide how to milling cut the bone, and also the position of the implants, if on one hand allow for obtaining a correct implant axis and a correct depth, on the other hand allow for controlling the rotation of the implant a discapito of the depth, because they provide for making the implant go further in its screwing path into the bone, until reaching the correct rotation angle. Moreover, such systems also do not prevent the possibility of a lateral shift with respect to the desired position. In view of the above, it becomes evident the need for a guided dental implant positioning system suitable to guarantee at the same time the respect of the position of the implant (with respect to the possibility of a deviation or lateral shift), of the insertion depth with respect to the osseus crest level, of the insertion axis direction and of the rotation angle around the insertion axis.

In this framework is proposed the solution according to the present invention, with the aim of providing a new guided dental implant positioning system of a passive kind, able to control at the same time the position, depth and insertion axis, and also the exact initial point and conditions of implant screwing into the bone, and, as a consequence also the point and conditions at the end of the screwing and the rotation angle around its own axis.

Thus, it is the object of the present invention that of providing a dental implants positioning system allowing for overcoming the drawbacks of the solutions according to the prior art and obtaining the technical results previously described. Further purpose of the invention is that said system can be realised with substantially low costs, or with a very low cost increase with respect to the systems of the passive kind available at present, both as far as production costs and managing costs is concerned.

Not least purpose of the invention is to realise a dental implants positioning system being substantially simple, safe and reliable.

It is therefore a specific object of the present invention a guided dental implant positioning system, of the kind making use of a surgical guide provided with one or more holes or guides in correspondence of the implants insertion points and for controlling the orientation of insertion of the implants, comprising means for simultaneously controlling the position of insertion, the final depth of insertion, the insertion axis direction and the rotation angle around said axis of each implant by setting up the rotation angle around its own axis of each implant at the beginning of its insertion into the osteotomic seat. In particular, according to the invention, said means for setting up the rotation angle around its own axis of the implant at the beginning of its insertion into the osteotomic seat comprise a threaded portion made integral with the surgical guide and a correspondent threaded portion made integral to the implant, said threaded portions being screwed according to a set number of screwing positions, the final screwing position being defined by a counterboring, the pitch of said threaded portions being identical to the pitch of the implant. Preferably, according to the present invention, said threaded portion made integral with the surgical guide is realised on the internal surface of a countersleeve movably inserted into a sleeve of the surgical guide without possibility of rotating and said corresponding threaded portion made integral to the implant is realised on the lateral surface of a mounter, a first end of which is engaged without possibility of rotating to said implant and a second end of which is engaged without possibility of rotating to screwing guiding means, chosen amongst screwing manual guiding means, such as a manual ratchet, and screwing motor guiding means, such as a surgical micromotor.

Alternativamente, always according to the present invention, said threaded portion made integral with the surgical guide can be realised on a cylindrical element made integral to or movably engaged without the possibility of rotating to the surgical guide around a sleeve and said corresponding threaded portion made integral to the implant can be realised on the internal lateral surface of a hollow cylindrical element, provided with an axial portion the extremity of which is movably engaged without possibility of rotating to a mounter in its turn movably engaged without possibility of rotating to the implant, said hollow cylindrical element being engaged without possibility of rotating to screwing guiding means, chosen amongst screwing manual guiding means, such as a manual ratchet, and screwing motor guiding means, such as a surgical micromotor.

Moreover, according to the present invention, said guided dental implant positioning system can comprise means for simultaneously controlling the position, depth and axis direction of realisation of osteotomic seats.

Always according to the invention, said means for simultaneously controlling the depth and axis direction of realisation of osteotomic seats can comprise one extension provided with depth reference notches or an extension for each desired depth, each extension comprising a portion thin enough to be inserted into the sleeve of the guide and a portion large enough to constitute a battente on the surface of the guide. At last, according to the present invention, said guided dental implant positioning system can comprise further means for controlling the position and rotation angle around its own axis, simultaneously with controlling the depth and axis direction of realisation of osteotomic seats con tapping.

The present invention will now be disclosed, for illustrative, non limitative purposes, according to one preferred embodiment, with reference in particular to the enclosed drawings, wherein:

- figure 1 shows a surgical guide for implantology,

- figure 2 shows a perspective view of a first embodiment of the guided dental implant positioning system according to the present invention, - figure 3 shows a sectional view of the guided dental implant positioning system of figure 2, in use,

- figure 4 shows a sectional view of a second embodiment of the guided dental implant positioning system according to the present invention, - figure 5 shows a perspective view of the guided dental implant positioning system of figure 4, and

- figure 6 shows a sectional view of an extension for osteotomy and a milling cutter for osteotomy according to the present invention.

Making reference to the figures, it is possible to comprise that the basis of the guided dental implant positioning system of the present invention is constituted by having modified guide systems at present on the market in order to make them suitable for use not only for preparing the osteotomic seat, but also for positioning the implant. In pratice, the guided dental implant positioning system of the present invention could be used together with any available software programme for producing a guide with a cylinder for the preparation of of the osteotomic seat, with modification always falling within the scope of the present invention.

In particular, figure 1 shows a surgical guide 10, provided with sleeves 11 for the orientation of milling cutters for the preparation of the osteotomic seat where implants will be positioned, and also for the orientation of implants insertion.

The guide 10 can be used with suitable modifications to guarantee at the same time the respect of all the parameters of correct insertion of an implant, i.e. position, insertion depth, insertion axis and rotation angle of each implant with respect to its own axis.

The solution of the problem of insertion depth can be easily solved by realising some stops, by means of counterborings on the sleeves 11. Moreover, if the axis is correct, the so called torque, i.e. the displacement with tendency to rotation of the implant occurring in case there is not a correspondence of the position of platform and abutment when the screw providing for the engagement between these elements is tightened, does not occur.

However, the counterboring must be realised, as will be shown in the following, in order to guarantee at the same time also the respect of the rotational angle of the implant around its axis.

The need to control the position and insertion axis is assured by modifying the sleeves so that no room is left between the sleeve and the mounter used for the implant.

As far as the respect of the correct position of the rotational angle of the implant around its own axis is concerned, it can be obtained by modifying the sleeves 11 with a threaded system that, engaging with a correspondent thread realised on the mounter, allows for guiding the implant in depth, thus also assuring the the perfect control of the insertion axis. In particular, in order to assure the implant final rotation position, it is necessary to fix a priori the screwing starting point of the mounter. The solution therefore is the realisation of a mounter provided with the same thread of the implant, engaging with a counterthread realised on the sleeve in a set engagement position and as a consequence mathematically setting the point of arrival.

According to a first embodiment of the present invention, shown with reference to figure 2, it is provided for modifying the sleeves to allow correspondent countersleeves 12 to be inserted by slipping within the sleeves. In particular, modified sleeves 13 and countersleeve 12 can be provided with a telescopic mortise joint system that can be unthreaded in vertical direction, as that shown, having one or more protrusions 14 on the external surface of the countersleeve 12 engaging with corresponding grooves 15 of the internal surface of the sleeve 13. In particular, this configuration allows for reproducing at the level of the mortise joint between the sleeve 13 and the countersleeve 12 the six faces of the hexagon mortise joint between the implant and the abutment. Grooves 15 can also be realised as slots through the thickness of the wall of the sleeve 13, to allow the protrusions 14 of the countersleeve 12 to be in contact with the material of the structure of the guide 10, thus decreasing stress on the sleeve 13 and consequently lowering the possibility of its disengagement, result that can also be obtained through alternative systems, for example providing the sleeve 13 with tongues clasping like hooks or a simple post to the structure of the guide 10.

The engagement between the protrusions 14 of the countersleeve 12 and the grooves 15 of the sleeve 13 acts as an antirotational system and must be able to avoid the unthreading of the countersleeve during the insertion of the implant, and at the same time also allow disengagement once the implant is inserted. This result can be obtained for example by means of a bayonet coupling or similar. Moreover, grooves 15 does not interest all the length of the sleeve 13, thus forming a stop to the movement of the countersleeve 12, that must have a set final position.

The internal surface of the countersleeve 12 is threaded to allow screwing engagement with a mounter 30 (shown with reference to figure 3), also threaded, and the pitch of the thread of the mounter 30 must correspond to that of the implant 31 , in order not to cause vertical stripping, due to a smaller or bigger shelving of the implant into the bone 32. It is not necessary that the shape of the thread is exactly the same, but the pitch must be. Moreover, the thread must be such to allow starting the screwing in a set position. This result can be obtained for example extending the thread beyond the base facing the oral cavity of the countersleeve 12, as if it was a toungue 33. Similarly, it is possible to realise a thread extending as a toungue on the mounter 30. The threaded mounter 30 has a set length, and its point of arrival is determined by the vertical stop consequent to the filling of the thread in its last turn. The insertion depth of the implant can therefore be managed by realising different countersleeves 12 having different length. Moreover, the height of the countersleeve 12 must be such to overcome the height of the sleeve, so to allow not only for controlling the depth of the implant, but also in order to ease the removal after insertion of the implant. Such feature can be important for implants with a double or triple thread.

The implant 31 diametre must be smaller than that of the mounter 30, since the implant 31 must be free to move within the sleeves without contacting the walls of the countersleeves 12. Differently, the implant 31 and mounter 30 should have a continuous thread, and the scraping of the implant 31 against the walls of the countersleeve 12 could damage the thread. In pratice, couples of countersleeves and mounters with different diameters must be realised, each for guiding implants having a smaller diametre. Only one big sleeve diametre would be theoretically possible, but the possible number of implants that can be inserted in a portion of bone would be limited.

Such embodiment of the present invention can be realised by a dental laboratory, or, through CAD-CAM methods with the aid of a design software programme, starting from the setting up of the position of the implant in its final position and calculating as a consequence, by reverse engineering the unscrewing of the implant along the insertion axis with respect to the pitch of the thread, the initial engagement position of the thread of the mounter with the thread of the countersleeve.

The countersleeve could also be realised as an extension of the sleeve, to be inserted into the surgical guide with a pin kind mechanism or other or be made integral to the guide, provided that the consequent increase of the working length necessary to the system is compatible with the possibility of opening the mouth of the patient.

In implant systems providing for the preliminary tapping of the bone subsequent to the passage of the osteotomic milling cutters and before the insertion of the implant, it must be provided for a system analogous to the one just disclosed also for the tapper milling cutter.

Actually, according to the present invention, the mounter is sort of an extension of the implant, with which a driver of common use can be engaged, if necessary suitably modified to obtain a correct threading, or the same components generally contained in surgical kit can be used and in particular manual drivers with their ratchet, or surgical spindles, not needing any modification. The driver can be easily engaged with the mounter and equally easily removed (as already happens in common implant surgical kits). However it is essential that the engagement of the driver with the mounter happens according to a preset position.

By modifying the sleeve through a spiral path in its part coming in contact with the driver, or at the side of the oral cavity, at the end of each complete turn of 360 degree it has a different depth of the profile, forming a vertical step. As a consequence, if the driver is engaged with the mounter in a precisely set position, the point of arrival will necessarily be always in only one possible position. Obviously, the driver must be a little larger than the sleeve so that in its last turn it will come in contact with the sleeve, until its stop. Conveniently, therefore, the driver can be modified by applying a sleeve to it, engaged by means of a vertical groove acting as an antirotational mechanism and an horizontal groove, to avoid the vertical shift of the sleeve in resin with respect to the driver. This embodiment of the positioning system of the present invention allows for a very simple disassembly of the system, being sufficient to remove the countersleeve 12 in vertical direction. In this phase, the countersleeve 12 being higher than the sleeve 13 ease the taking of the countersleeve and therefore its removal. During its removal, the countersleeve 12 also trails the mounter still engaged with it. Obviously, before going on with removal, it will be necessary to unscrew the screw keeping together implant and mounter (such screw being a feature that the solution of the present invention has in common with the solutions of the prior art). According to an alternative of this embodiment, it is possible to realise threaded sleeves, without any need of countersleeves. Such an alternative is easier to be realised (a countersleeve not being necessary) but has a limited functionality. This alternative can be conveniently used in cases wherein it is not requested for providing for antirotational mechanisms in the engagement between implant and abutment, for which it is essential only the respect of the correct value of position, depth and insertion axis. The unthreading of a guided dental implant positioning system as that according to said alternative is possible only in case of implants that are all parallel to one another, or also in case of disparallel implants, provided they are deprived of antirotational mechanisms that could form back drafts during removal, subject to separation of the mounters and relative implants and subsequent removal of the surgical guide together with all the mounters.

In an alternative embodiment, shown with reference to figure 4 - 5, the guided dental implant positioning system of the present invention can be realised also through a hollow cylindrical element, having the sape of a threaded cap, called driver-cap 40, its thread having a pitch exactly corresponding to that of the thread of the implant 46, to which it is linked by means of a mounter 44 of the prior art, on which it operates by means of an axial portion 51 the extremity of which is shaped so to engage through a shaped mortise joint with the mounter 44. The driver-cap 40 is screwed around a cylindrical element 41 with external thread, similar to a bottle neck, made integral with the surgical guide 42, in correspondence of the sleeve 43.

According to this embodiment, the insertion of the implant 46 respecting the insertion position, axis and depth, and the final rotational angle around its own axis is guaranteed by screwing the driver-cap 40 around the cylindrical threaded element 41 ; as a consequence, the dimensions of each sleeve 43 and corresponding mounters 44 does not have any importance and sleeves 43 and mounters 44 identical to those of the prior art can also be used. The function of the sleeves 43 is still essential only for the guided passage of osteotomic milling cutters.

The bottle neck of the cylindrical element 41 can be realised to be movably engaged to the surgical guide 42, for example by means of pins 45 engaging with a corresponding seat realised on the guide, or can be made integral with the guide 42. in case of movable engagement, in order to avoid the unthreading of the cylindrical element during the insertion of the implant removable fixing must be present.

Implant systems providing for a preliminary tapping of the bone 47 subsequent to the passage of the osteotomic milling cutters and before the insertion of the implant 46, a driver-cap must be provided also for the milling cutter tapper.

Obviously, the pitch of the thread of the driver-cap 40 must correspond to that of the implant 46, in order not to create vertical strippings during the insertion. In particular, it is not necessary that the form of the thread is exactly the same, but the pitch must be. To guarantee at the same time screwing depth and controlling the rotation angle of the implant around its own axis, it is possible to give at the last turn of the driver-cap 40 a helicoidal screwing following the thread, so that, amongst the turns, a vertical step 48 forming a counterboring ( figure 5). A corresponding step 49 can be realised on the cylindrical element 41 , so to make the screwing corsa of the driver-cap 40 always end at the same point.

Anyway, in order to ream the depth and insertion of any implant according to specific needs, for example in consideration of different thickness of the gingiva 50, suitable reducer can be realised, for example caps open on top, screwing around the cylindrical element 41 until they come into contact with the plane of the guide 42 and their portion towards the oral cavity being shaped so to stop the descent of the driver-cap 40 at a desired height.

Once the complete screwing of the driver-cap 40 and therefore insertion of the implant 46 is obtained, the problem arises of how to unscrew the driver-cap 40 without displacing the implant 46 below.

In case the cylindrical element 41 is not integral with the surgical guide 42, but simply movably engaged to the surgical guide 42, for example through pins 45 or through a system using tongues or equivalent means, housed in a corresponding seat of the guide 42, it is sufficient to lift the system comprising the driver-cap 40 and the cylindrical element 41 screwed with it, and they will respectively unthread from the mounter 44 and guide 42. Subsequently it will possible remove the mounter 44 from the implant 46, as in prior art.

In case the cylindrical element 41 is made integral to the surgical guide 42, the driver-cap 40 can be designed so that the threaded portion of the cap 40 and the axial portion 51 guiding the mounter 44 during the insertion of the implant 46 are respectively movably engaged, for example through a precision mortise joint system, such as in particular splines that can be easily disengaged, so that disengagement of the axial portion 51 and mounter 44 and therefore of the latter and the implant 46, can be obtained independently from the lifting of the surgical guide 42 (and the cylindrical elements 41 and threaded portions of the driver-caps together with it) from its support (bone, tooth or gingiva).

The dimensions of the cylindrical element 41 , in particular its diametre, can be only one, thus adapting to different diametres of implants 46 and sleeves 43, the sole limit being the distance between two adjacent cylindrical elements 41 on the same surgical guide 42, which must be sufficient to allow for screwing the corresponding driver-caps.

An alternative to the cap system, not shown in the figures, provides for realising an internally threaded cap, screwed with a correspondent thread realised on a countersleeve of a sleeve- countersleeve system similar to that of the first embodiment of the present invention. In particular, the countersleeve according to this further embodiment is not threaded internally but externally on its portion coming out of the sleeve, acting as a guide for the cap. A limit of application of this alternative is nevertheless posed by the possibility of mouth opening, or by the more or less rear position of the implant into the oral cavity. With reference to figure 6, is shown what the guided dental implant positioning system according to the present invention implies with respect to the preparation of the osteotomic osseus seat, or how instruments for the preparation of the osteotomic osseus seat can be conveniently modified to become more functional.

In particular, the figure shows how, in order to control the maximum insertion depth of the milling cutter 60, it is possible to make use of an extension or extender 61 similar to those of the prior art, but provided with notches identifying the different depths. As shown according to the figure, a part of the extension 61 surrounds the upper portion of the milling cutter 60.

Obviously it is also possible to realise a different extension 61 for each depth, supporting all the osteotomic milling cutters 60 that must follow to one another until the use of the final osteotomic milling cutter for the desired depth of the osteotomic seat.

The extension 61 is divided into two portions having different diametres, a first smaller portion 62 that can be inserted into the sleeve 64 of the guide 65 and a second bigger part 63 forming a stop to the insertion depth when coming in contact with the surface of the sleeve 65. This extension 61 can be used with all the osteotomic milling cutters of standard osteotomic kits.

If for example the implant system provides for implants having different length and diameter, for which a series of differently sized milling cutters must be used, with one extension 61 for each implant length it is possible to satisfy every needs mounting each extension 61 with all the milling cutters 60 in sequence from the smaller to the bigger diameter until using the right diameter for the specific implant.

With reference to the available space within the oral cavity of the patient, since in order to perform osteotomy it is necessary to use a surgical micromotor, the total length of the instruments could be a limiting feature in case it is necessary to realise deep osteotomic seats (longer milling cutters must be used in this case) in the rear part of the oral cavity. In order to solve also this problem, since it is desirable that the milling cutter metts the bone being guided since the beginning, it is preferable for an osteotomy of a certain depth not to use immediately the osteotomic milling cutter with the right extension for such depth, because otherwise the first part of the osteotomic milling cutter 60 will freely enter into the bone, since in its first part there is not any engagement of the extension 61 with the sleeve 65. In order to guide the milling cutter 60 also in the first part is then necessary using an extension enveloping a bigger portion of the milling cutter 60 to realise a first osteotomic part ending at a lower depth, and after the same milling cutter 60 is used with an extension enveloping a shorter portion, so that the osteotomy will be guided, in the part not guided by the extension, by the same osteotomy prepared by the extension previously used. In its deeper part, where the bone is not yet prepared, the osteotomy course is guided by the engagement of the smaller portion 62 of the extension with the sleeve 64 of the guide 65.

It is possible to preliminarily foresee also the use of a mucosal punch (or a hollow cylindrical bistoury with cutting edge) mounted on the extension 61. The length of the spindle supporting the mucosal punch must be such as it protrudes from the extension 61 of a length (3 mm) sufficient to cut the gingiva 66, without damaging the plane of the bone 67 below. In such a way it is possible to round cut the gingiva, which is subsequently removed by a manual bistoury, in a guided manner.

According to an alternative of the present invention, it is possible to use a kit comprising modified milling cutters, that can be mounted directly on the surgical micromotor, so that a portion of the same milling cutters forms an enlargement that can engage with the sleeve 64 of the guide 65 and a further portion forms a counterboring surface against the surface towards the oral cavity of the guide 65. For every diameter as many milling cutters will be necessary as the possible implant length. Moreover, since the sleeve is larger then the osteotomic seat, it is necessary to use all the shorter milling cutter before that having the final length, in order to guarantee the control over the insertion axis during the realisation of the osteotomic seat. The starting hole made by the shorter milling cutter will act as a guide for the longer milling cutter in its first part, that will continue its course in depth guided by the portion of the milling cutter engaging with the sleeve.

An alternative solution to the sequencial passage of milling cutters having the same diameter, and an increasing length, is the introduction in the osteotomic system of a counter-sleeve, similar to that shown with reference to figures 2 and 3, but provided with a smooth surface, allowing to make the engagement portion longer. The advantages of the guided dental implant positioning system according to the present invention with respect to the already known positioning systems appear to be evident, and in particular with respect to the closest systems, i.e. those of the passive kind. In particular, the guided dental implant positioning system according to the present invention allows for reducing to a minimum the expenses for achieving a guided implantology with passive systems, not bound neither to a specific implant system nor to a specific modelling software programme and not involving important technical difficulties to be realised, such as, for example, the need to buy a specific software programme and a specific mounting kit for every different kind of implant at present on trade (with different mounters depending on the kind of implant). By mapping the bone, which is an outpatient technique, it is possible to obtain a plaster model where the part interested by the implants insertion seats shows the available osseus volume and consequently the method can also be managed by a dentist's surgery and an associated laboratory.

Further, the guided dental implant positioning system of the present invention allows for mechanically controlling the position of the implant and consequently that of its mortise joint system as far as all the parameters (depth, insertion axis and position of the shaped mortise joint) is concerned.

Moreover, the guided dental implant positioning system of the present invention has the advantage of allowing for the management of the guide and the prebuilt prosthesys by means of both possibilities at present most common: that providing for the realisation in a laboratory of the implant and the prosthesys and that providing for the use of software using CAD-CAM techniques.

At last, according to the present invention it is not important that the sleeve corresponds as much as possible to the diameter of the implant (and to that of the mounter substantially identical), as needed according to the prior art, because the guided insertion system is transferred to the threaded engagement between the mounter and the countersleeve, or between the driver-cap and the cylindrical element, both guided from the starting of the engagement (set) until the precise end of insertion.

This implies that for the insertion of the implant the sleeve can have a medium diameter, suitable for small and medium implants, but also a bigger sleeve can be provided, useful during the milling cutting of the bone.

Moreover, it will no more be necessary to realise as many mounters as the available number of implants diameters, but it will be sufficient to have only one mounter for different implants, also those having a smaller diametre, a bigger mounter being necessary only for the insertion of implants having a big diametre.

Further, since it is needed only one guide, it is also possible to design a series of three screws (called fixing screws) making the guide integral to the bone (regardless the support of the guide), in such a way avoiding any error due to possibly different positioning of the guides in sequence according to the prior art.

The present invention was described for illustrative, but not limitative purposes, according to its preferred embodiments, but it must be understood that any variation and/or modification can be made by the skilled in the art without escaping from its scope of protection, as defined in the enclosed claims.

Claims

1) Guided dental implant positioning system, of the kind making use of a surgical guide (10) provided with one or more holes or sleeves (11) in correspondence of the implants insertion points and for controlling the orientation of insertion of the implants, characterised in that it comprises means for simultaneously controlling the insertion position, the final insertion depth, the insertion axis direction and the rotation angle around said axis of each implant.

2) Guided dental implant positioning system according to claim 1 , characterised in that said means for simultaneously controlling the insertion position, the final insertion depth, the insertion axis direction and the rotation angle around said axis of each implant comprise means for setting up the rotation angle around its own axis of each implant at the beginning of its insertion into the osteotomic seat. 3) Guided dental implant positioning system according to claim

2, characterised in that said means for setting up the rotation angle around its own axis of the implant at the beginning of its insertion into the osteotomic seat comprise a threaded portion made integral to the surgical guide and a correspondent threaded portion made integral to the implant, said threaded portions being screwed according to a set number of screwing positions, the final screwing position being defined by a counterboring.

4) Guided dental implant positioning system according to claim

3, characterised in that the pitch of said threaded portions is identical to the pitch of the implant.

5) Guided dental implant positioning system according to claim 3 or 4, characterised in that said threaded portion made integral with the surgical guide is realised on the internal surface of a countersleeve (12) movably inserted into a sleeve of the surgical guide without possibility of rotating and said corresponding threaded portion made integral to the implant is realised on the lateral surface of a mounter (30), a first end of which is engaged without possibility of rotating to said implant (31) and a second end of which is engaged without possibility of rotating to screwing guiding means. 6) Guided dental implant positioning system according to claim

5, characterised in that said screwing guiding means are chosen amongst screwing manual guiding means, such as a manual ratchet, and screwing motor guiding means, such as a surgical micromotor.

7) Guided dental implant positioning system according to claim 3 or 4, characterised in that said threaded portion made integral with the surgical guide is realised on a cylindrical element (41) made integral to or movably engaged without the possibility of rotating to the surgical guide (42) around a sleeve (43) and said corresponding threaded portion made integral to the implant is realised on the internal lateral surface of a hollow cylindrical element (40), provided with an axial portion (51) the extremity of which is movably engaged without possibility of rotating to a mounter (44) in its turn movably engaged without possibility of rotating to the implant (46), said hollow cylindrical element (40) being engaged without possibility of rotating to screwing guiding means.

8) Guided dental implant positioning system according to claim 7, characterised in that said screwing guiding means are chosen amongst screwing manual guiding means, such as a manual ratchet, and screwing motor guiding means, such as a surgical micromotor.

9) Guided dental implant positioning system according to any of the previous claims, characterised in that it compriseas means for simultaneously controlling the depth and axis direction of realisation of osteotomic seats.

10) Guided dental implant positioning system according to claim 9, characterised in that said means for simultaneously controlling the depth and axis direction of realisation of osteotomic seats comprise an extension provided with depth reference notches.

11) Guided dental implant positioning system according to claim 9, characterised in that said means for simultaneously controlling the depth and axis direction of realisation of osteotomic seats comprise an extension (61) for each desired depth, each extension (61) comprising a portion (62) small enough to be inserted into the sleeve (64) of the guide (65) and a portion (63) large enough to for a counterboring on the surface of the guide (65).

12) Guided dental implant positioning system according to claim 9, 10 or 11 , characterised in that it further comprises means for controlling the position and rotation angle around its own axis, simultaneously with controlling the depth and axis direction of realisation of osteotomic seats with tapping.