WO1997030654A1

WO1997030654A1 - Implantable tooth replacement, abutment therefor and process for making abutments

Info

Publication number: WO1997030654A1
Application number: PCT/EP1997/000871
Authority: WO
Inventors: Arnold Wohlwend
Original assignee: Arnold Wohlwend
Priority date: 1996-02-22
Filing date: 1997-02-23
Publication date: 1997-08-28
Also published as: AU1794597A

Abstract

An implantable tooth replacement consists of an implant (27) which can be secured in a jawbone, an abutment (9) made of a ceramic material which can be secured to the implant (27) by a securing screw (29), a tooth prosthesis, e.g. a crown or bridge, and a securing means for fixing said abutment to said tooth prosthesis. The ceramic material has a fracture toughness KIC of at least 6 MPa.m1/2 and a flexural strength of at least 700 or 800 MPa and consists at least to the extent of 90 wt.% of zirconium oxide.

Description

IMPL _A NETABLE DENTAL REPLACEMENT, ABUTMENT THEREFOR AND METHOD FOR

MAKING ABUTMENTS

The present invention relates to an implantable

Dentures according to the preamble of claim 1, an abutment for such an implant system, and method for producing an abutment.

Dental prosthesis systems used today, hereinafter referred to as implant systems, essentially consist of two parts: the implant itself, which is surgically inserted into the upper or lower jaw under the gums, in particular screwed in, there for 3 -6 months to achieve healing (osseointegration); and the so-called abutment, which connects the so-called implant shoulder to the artificial tooth crown attached to the abutment. After the healing phase of the implant, the gums are opened surgically to screw the abutment onto the implant. The crown is then attached to the abutment either by screwing or gluing ^* :. Today, both implants and abutments made of titanium are used most frequently, and for reasons of biocompatibility and the possible osseointegration, titanium has in any case established itself as the implant material. The dark color of the titanium implant - because the implant is surrounded by opaque bones - is not perceived as a nuisance, in contrast to that of a titanium abutment. This results in discoloration of the gingiva (gums), making it difficult to match the color to the remaining teeth, and the implant head generally has a different diameter from the natural tooth.

The implant shoulder and the tooth root to be imitated at the level of their gingival passage have different cross-sections in dimension and shape. If, for example, a missing, upper, central incisor is replaced by a single tooth implant, the circular, one Implant shoulder having a diameter of approximately four millimeters may be transferred to a more triangular, larger cross-sectional shape at the gingival passage point.

Various solutions have been proposed to at least partially address these difficulties. For example, prefabricated titanium butments are arranged so that titanium components can be placed sufficiently far below the Gmgiva. However, this definitely complicates the cementing process because the crown edges, due to the arcade-shaped course of the gum, particularly on the proximal surfaces, come to lie massively subgmgival (under the gums), and excess cement may only be possible by opening the Gums can be removed more easily.

Another solution is the grinding of a conventional abutment made of pure titanium, with the dental technician individually preparing the titanium abutment so that the preparation limit is adjusted to the arcade-shaped course of the gum. This makes it possible to achieve a uniform subgmgival crown edge course of approximately 1.0 to 1.5 mm depth, which significantly facilitates the subsequent removal of residual cement after the crown has been finally cemented. A crown framework made of a high-gold alloy is poured over this customized titanium abutment and then veneered with ceramic. This procedure facilitates the definitive cementation, but it requires the correct implant position, since the necessary corrections to achieve an optimal, general aesthetic are only possible to a limited extent. In the case of a thin gingiva, however, there is a risk of metallic shimmering through.

"Correct implant position" means positioning the implant at the location of a tooth root. Positioning the implant "incorrectly" will be an option or should be preferred if, for example, the bone punch is firmer next to the tooth root to be imitated or if there is more space available.

Another option is the use of abutments made of aluminum oxide. For example, US Pat. No. 5,125,839 describes the use of a densely sintered, high-purity aluminum oxide ceramic (over 99.5% Al 2 O 3). The material pure titanium is thus replaced by ceramic, and in the case of a thin gingiva there is no longer any danger of metallic shimmering through.

Such aluminum oxide abutments are generally manufactured in such a way that aluminum oxide powder is pressed into shape under pressure and thus compacted. Porosities in the compacted mass are inevitable, and due to the resulting brittleness of the compacted mass, minimum and also maximum wall thicknesses are essential in order to ensure the stability of the essentially hollow cylindrical abutment. Incorrectly placed implants, however, require an asymmetrical wall thickness shape of the abutment to compensate for the position of the implant that is decentred with respect to the tooth root to be imitated. Alumina abutments are therefore only needed for a few, optimally placed implants: they can be used. It is also not certain whether

Abutments made of aluminum oxide can withstand the considerable forces that occur when biting and chewing.

The abutment is fastened to the implant implanted - in particular screwed - in the jawbone via the fastening screw, a hexagon socket or octagon socket opening being generally provided in the abutment, so that there is a counterhold when the fastening screw is tightened. For this purpose, a hollow pin with a corresponding hexagon or octagonal shape is inserted into this opening, the hollow pin receiving the screwdriver. While tightening the fastening screw (force of more than 30 N), this hollow pin serves as a rotation lock, so that Implant is not moved out of the bone when the abutment is screwed on. This hexagon socket or octagon opening, with its inside diameter that goes beyond the screwdriver required to insert the screwdriver, means that the outside diameter of the abutment has to be larger in order to achieve a sufficient minimum wall thickness that ensures stability.

Since aluminum oxide is X-ray translucent, it is difficult to check the fit in the patient's mouth. Like all ceramic materials, aluminum oxide is difficult to grind, which makes the post-processing necessary, especially if the positioning is incorrect.

The object of the present invention is to overcome the above-mentioned problems inherent in the prior art, which is made possible by an implant system in which the characterizing features of claim 1 are realized or by an abutment with the characterizing features of the application. Proverb 6, as well as by methods for producing an abutment for such an implant system, in which the characterizing features of claims 8, 16 or 18 are realized.

Further advantageous or alternative designs are described in the characterizing features of the dependent claims.

The invention is described below purely by way of example with reference to drawings. Show it:

Fιg.1 an elevation of an implant system with crown in

Jaw; 2 shows an abutment for correctly placed implants in plan and elevation;

3 shows an elevation of a prefabricated abutment for

Inclusion of a crown; 4a, 4b and 4c different abutment shapes; 5a and 5b representations of implants and matching abutments with specially designed contact surfaces; 6a-6f a schematic representation of a possible production method for an abutment according to the invention; 7 shows an abutment with an attached clamping device; 8 abutments fixed to a natural tooth via a splint; 9 shows a milling machine when creating the outer shape of an abutment; Fig.10 em example of an automatic production of a

Abutments in a copy milling machine; 11 shows a schematic illustration of a computer-assisted production of an abutment;

12 shows an elevation of a work stump and a presintered abutment with an inner ring; 13 a prefabricated abutment with a prefabricated, attached crown part; 14 shows a prefabricated plastic sleeve for creating a plastic model abutment; and FIGS. 15a to 15d show a schematic illustration of a computer-assisted production of external abutment forms.

An implant system is shown in FIG. 1, wherein an implant 27 made of titanium, if appropriate, is introduced into a jawbone 26 - screwed in if necessary. An abutment 9 is connected to the implant 27 via a fastening screw 29, which is screwed into the implant 27 through an opening 30 m provided in the abutment with an internally threaded screw opening 31. The abutment 9 is seated on the upper locking surface of the implant 27, the so-called implant shoulder 32. The abutment 9 is essentially hollow-cylindrical in shape, with a web-like projection 33 in the interior of the opening 30 serving as a stop for the head of the fastening screw 29. The abutment 9 is in the region adjacent to the implant shoulder 32 ground in a ter-shaped manner, as a result of which implant misalignments can be corrected and the transition from the round cross-sectional shape to the more triangular of the natural tooth can be formed. The abutment 9 is prepared on the buccai and incisal side in accordance with the evaluated crown shape, and the crown 11 is placed on it.

To ensure the long-term success of an implant-borne crown or bridge reconstruction, a ceramic abutment with the highest possible strength and toughness values is required - as already explained in the introduction. For a ceramic material, zirconium partially stabilized with yttrium oxide (tetragonally stabilized zirconium oxide) not only has a high bending strength value between 900 and 1300 Pa and a low Young's modulus of elasticity of approx. 200 kPa, but also what is particularly important , a high toughness value with a fracture toughness of approx. 9-10 MPa * m ^1/2 . The high value of the fracture toughness can be explained by the ability of the tetragonal (TZP) or partially (PSZ) stabilized zirconium oxide, which itself can repair faulty, superficial defects through a volume-increasing phase transformation in stress areas (eg crack tips) can. The metastable tetragonal phase of the zirconium oxide m is converted into the thermodynamically stable monoclear phase. This effect can be achieved through the

Use of a high-purity zirconium oxide powder, to which alkaline earth oxides, such as MgO and CaO, and / or rare earth oxides, such as Y2O3, are admixed, which enable the tetragonal or cubic phase to be stabilized at room temperature.

The zirconium oxide thus far exceeds the key figures for the mechanical strength of the high-purity, densely sintered aluminum oxide, which has a bending strength in the range of 500-600 Pa, and one with 3-4.5 MPa / m ^1/2 only half as much great fracture toughness achieved. The excellent physical properties for the zirconium oxide ceramic allow the abutment to be ground individually, regardless of the minimum dimensions, which allows the production of aesthetically high-quality reconstructions on single tooth implants. Clinical manufacture is facilitated by grinding the abutments in the dental laboratory.

Instead of the zirconium oxide ceramic described above, other biocompatible ceramics or alloys can be used whose bending strength values are above 700 MPa and whose fracture toughness is at least 6 MPa-m / ² . Alloys of Al2O3 ~ ZrO2 can thus be used, strength values of 1000 MPa being achievable, for example, with a proportion of 15 vol% ZrO2. Siss ^ or TiC or fiber-reinforced ceramics, such as SiC fiber, SiC whiskers, Al 2 O 3 SiC fibers, can also be provided. The materials listed here are purely exemplary; what is essential are the physical properties suitable for these materials, which are given by the lower limits listed above. It goes without saying that materials with higher fracture toughness or fracture toughness values have a positive influence on the resistance and thus the service life of the implant system, but on the other hand their use due to the difficult processability may have been - and this has been the case up to now set the limit - makes it problematic.

In the context of the invention, "oxide ceramic" or "zirconium oxide" is to be understood below as meaning any ceramic or ceramic combination having the above properties and having the required physical properties.

The poor grindability of oxide ceramics is indeed to be regarded as a disadvantage if the preparation of ceramic spacer sleeves is carried out directly in the patient's mouth, since this is extremely tedious both for the patient and for the dentist. The treatment time for the preparation an oxide ceramic abutment requires 2-3 times the time compared to the preparation of a natural tooth. However, in the laboratory, for example, the use of diamond sintered discs for coarse preparation can be done quickly and precisely. The poor grindability of the Zrθ2 abutment can also be completely compensated for by the use of an inter-sintered abutment type (see below). Such abutments can also be ideally processed in the laboratory by the dental technician. If, for example, an imprint of the relative implant position is taken immediately after the implant has been placed, there is sufficient time during the healing phase of the implants to prepare these Zrθ2 abutments in the laboratory and to sinter them so that when the abutment is screwed on (unscrewing the abutment on the implant) an individual and therefore optimal provisional restoration can be attached immediately to the fixtures or the ZrO2 abutments.

It has proven to be advantageous not to fix the crown 11 attached to the abutment 9 with a composite, glass ionomer or phosphate cement that is common today, but with a binder that is elastic over the entire service life. The cements known to be used are rigid and transmit the large forces which occur when biting the occlusal surface directly to the ceramic abutment 9 and via the implant 27 to the jaw bone 26. In the natural teeth there is one between the bone and the tooth Buffer zone (Desmodont), which in most cases prevents tooth chipping. Although the use of a Teflon ring between the implant and the abutment has become known, this can lead to the screw connection between the abutment and the implant being loosened. To ensure the success of the implant system, it is advantageous to provide such a buffer zone between the implant and the crown or bridge restoration. According to the invention, the joint 28 is designed as an elastic intermediate layer. The hard composite, glass ionomer or phosphate cement is, for example, by a cement on silicone or composite Base replaced, which contain soft plastic fillers instead of glass fillers. Cements based on composites with elastic polymeric materials as additives or with reversible thermoplastic constituents are also suitable for this. Such a cement is elastic and dampens

Impacts that could otherwise cause the abutment to break and thus the loss of the implant system. Instead of such an elastic cement or, if necessary, also in addition to it, the surface of the prepared abutment can be covered with a plastic jacket, which becomes effective as a damping intermediate layer between the abutment and the crown part. The joint 28 serves as a buffer zone. The provision of such a joint, which acts as a buffer zone and which, for example, has such a cement and / or comprises a plastic layer covering the abutment, proves to be advantageous not only for the implant system according to the invention.

Due to their excellent physical properties, zirconium oxide abutments also lend themselves to complex implant situations, since problems are not to be expected either with extremely thin, a few tenths of a millimeter or with thick side walls, and fractures or abrasion neither during dental processing nor during fixation of the abutment to the implant.

In order to be able to cover every implant situation, even with incorrectly placed implants, and despite the difficulty in grinding oxide ceramic abutments, the dental technician is provided with various pre-made abutment shapes (FIGS. 2, 3, 4a, 4b and 4c) ), which reduce grinding work to a minimum and make it possible to solve every implant situation in a rational manner. Correctly operated diagnostics simplify the correct selection of the appropriate abutment shape. Abutment forms, as shown in FIGS. 2 and 3, are indicated if the implant is set correctly and only minimal preparations are necessary. Depending on requirements, a roughly pre-shaped abutment 9a with milled side surfaces 5 or a more complex spatial relationship, ie larger and wider interdental spaces, adapted abutment 9b can be used. Abutment forms 9c, 9d and 9f, as shown in Fig.4a, 4b and 4c, can be used if the implant is not correctly placed. Aesthetic grinding corrections are possible, because not only the abutment body, the side walls of which are substantially thicker than, for example, the abutments of FIGS. 2 and 3, but also the abutment neck can be modified and prepared in any shape as required become. This form of abutment has also been developed for the indication in the molar area. This is particularly clear from FIG. 4c, the left part of FIG. 4c representing an asymmetrical basic shape for an abutment 9f, in which - in order to compensate for the incorrect, decentered positioning of the implant 27 - a particularly large and also one particularly small wall thickness is realized. This makes it possible - as the right part of FIG. 4c shows - to still correctly place the prosthetic reconstruction 11.

In order to facilitate the process of regrinding and re-preparation of the zirconium oxide abutment, inter-sintered and / or abutment forms, similar to those shown in FIGS. 4a and 4b, are provided, which are only after after the clinical trial to be sintered into high-quality zirconium material This shape is also advantageous for the direct veneering of the abutment, because it enables correct ceramic support.

This solves the problem of the difficult machinability of zirconium oxide with the

counter the extraoral prepaxation using diamond grinders and / or the selection of already prefabricated, finished or inter-sintered abutment forms. For the first time, the use of zirconium oxide allows shaping for abutments, which until now could only be produced from metals such as titanium, but not from brittle, less resilient Al 2 O 3 ceramics. 5a shows an example of an implant 27a-abutment 9e combination, the abutment 9e having a sharp-edged termination on the contact surface with the implant 27a. If such an abutment were to be formed from aluminum oxide, even if it was presintered and re-sintered in a work pack (as described in more detail below), aluminum oxide would have to have a relatively low fracture toughness unfavorable breaking behavior can be expected.

5b shows a special shape of the contact surface 43 of an abutment 9g. In this case, 43 projections 44 are provided on this contact surface, which are pressed against the implant shoulder 32 when the fastening screw 29 is tightened and - since the material of the implant, for example titanium, is softer than the material of the abutment 9g according to the invention - engage in it . This achieves an excellent seal between the abutment and the implant. Bacterial flow due to leaks is prevented, which could otherwise lead to inflammation and would jeopardize the success of the implant system. These projections 44 can be annular, for example, and can be arranged concentrically around the opening 30, with slightly rounded edges, thus representing a type of labyrinth seal.

Due to the different shapes of the ceramic abutments, different requirements can be met. In this way, the contouring can be correctly adjusted to natural teeth, with which buccal gingival retraction can be avoided. The cross-sectional situation of the tooth root and tooth neck area at the gingival passage point can be designed correctly. An incorrect implant position or longitudinal axis can be improved. The subgingival preparation tion limit can be properly designed taking into account the arcade-shaped Gmgiva course in the approximal area.

A possibility of producing a zirconium oxide abutment is described purely schematically on the basis of FIGS. 6a to 6f: zirconium oxide powder cannot be pressed directly into a mold, as in the production of aluminum oxide ceramic, since, as already mentioned, this shown, would require extremely high pressures. In addition, zirconium oxide produced in this way would not be biocompatible. Zirconium oxide powder or chips are pressed isostatically onto a mandrel (not shown), so that an enlarged tube shape 34 is created (FIG. 6a). The enlargement results from the fact that during the subsequent sintering process the material shrinks by a certain amount. This tube shape 34 is shortened to the desired length in the so-called "green", not sintered, state and bevelled on two sides, approximately in a wedge shape (FIG. 6b). A depression 35 is then formed on the side facing the implant (FIG. 6c), which is formed into a hexagon socket using a special instrument 41 (FIG. 6d), preferably with an ultrasound device (other forms of engagement are also possible) , which comes into engagement with a corresponding external hexagon 36 on the implant shoulder (see FIGS. 1 and 5) and fixes the relative position of the abutment on the implant. Such a special instrument 41 can be seen from FIG. 6d, which has a ring-shaped projection 41b in the form of an external hexagon on a rod-shaped part 41a provided for alignment in the opening 30 '. If this device is now subjected to longitudinal ultrasonic vibrations while it is held within the opening 30 'of the tube shape 34, since the ceramic material can be easily machined at this stage, a precise hexagon socket shape is produced. The opening 30 'is widened from above with a spiral drill, the web-like projection 33 being obtained at the same time (FIG. 6e). Chips, for example with a length of 2/10 mm, are milled away from a zirconium oxide ceramic compact (not shown) that has been compacted, for example, at room temperature at approximately 2000 bar. Powder material with grain sizes between, for example, 30 to 500 μm can also be used.

The enlarged abutment form 9 'obtained in accordance with the work steps described above with reference to FIGS. 6a to 6e and the chips are now presintered, for zirconium oxide ceramic at approximately 1180 ° C. If necessary, abutment mold 9 'and chips can also be worked out from a pre-sintered press.

The processing of ceramics in the so-called green stage, i.e. in the non-pre-sintered state, as well as the processing in the semi-sintered (pre-sintered) state, has the advantage over the methods that mill the desired shapes directly from the finished sintered work block that fewer micro cracks are incorporated into the surface when processing the ceramic and that the naturally high tool wear, which is given when processing the high-strength materials, is reduced.

The chips are then mixed with water to form a thick paste and embedded around the abutment mold 9 '(the so-called work pack 36). The water added to the chips or the powder grains can contain different admixtures, for example the addition of about 1% acetic acid facilitates the handling of the pulp, resulting in a thixotropic behavior. The stability or compactness of the mixture is increased by adding alcohols, for example. The type and amount of the admixtures will therefore have to be provided depending on the desired or required property. A thin layer of lacquer of 10 to 50 μm, applied to the inside and outside of the abutment mold 9 ¹ , closes the pores on the surface and serves as a release agent for the work pack 36. sintering, which is carried out for zirconium oxide at a temperature of approximately 1500 ° C., and with the abutment mold 9 'and working pack 36 shrink to the same, defined extent, the lacquer burns without residue, with a minimal gap between the abutment mold 9' and the work pack 36 results, so that the latter can be easily removed from the abutment form 9 'or - in particular also due to the porous consistency - can be emitted. The sintering process can be controlled precisely using such a work pack 36, since the change in the external dimensions allows the shrinking process to be controlled directly.

FIG. 7 shows the procedure for fixing the abutment 9 on the implant. In the case of the zirconium oxide ceramic abutment according to the invention, there is no need to attach an internal hexagon as a rotation lock. In order to prevent the implant in the bone from moving when the abutment 9 is fixed when the fastening screw 29 is screwed in, which is inserted through the opening 30 in the abutment 9 (FIG. 1), the counter-torque to be applied is here, for example, via a Clamping device 3 (for example an artery clamp) is constructed. This clamping device 3 grips the abutment 9 on two opposite outer surfaces and holds it in place while the fastening screw 29 is being screwed in. The zirconium oxide ceramic used is stable enough to be able to withstand these forces, which will generally not be the case for aluminum oxide ceramic abutments. In this way it is possible to reduce the central opening 30 of the abutment to a minimum, since only the space for the screw head and screwdriver is required. The resulting wall thickness is available for free preparation of the abutment or the overall diameter of an abutment can be reduced.

Fig. 8 shows another possibility to build up the counter torque required when fixing abutments. For this purpose, a splint 7 can be provided, which connects an abutment 9 with a natural tooth 8, or several abutments 9 and bonded to one another or in combination with natural teeth. This rail 7, which serves as a rotation lock, is provisionally cemented onto the natural tooth 8 and the abutment (s) 9 to be fixed, an occlusal opening 10 being provided for receiving the screwdriver.

FIG. 9 shows a possibility of making the dental prosthetic reconstruction work even more efficient by including the Cad-Cam technology in the work procedure. For this purpose, one or more inner shapes of prefabricated dental prosthetic reconstructions, such as crown or bridge elements, stored in the computer are transferred to the outer surfaces of abutments 9 fastened to an implant model using a computer-assisted milling machine. This always ensures a uniform outer shape of the abutments, and prefabricated crown parts 11 (FIG. 1) can be used without further adjustment, since the respective inner surface fits exactly on the corresponding abutment surface. These crown parts 11, which are made of plastic or ceramic, can still be ground in a corrective manner and the color matched to the neighboring teeth.

The Cad-Cam technology can also be included in the workflow to copy an abutment form made of plastic. This means that the prepreparation of a plastic abutment is first carried out in the mouth or on the model. For this purpose, for example, prefabricated plastic sleeves 50, as shown in FIG. 14, can be shaped in the mouth or on the model by applying self-hardening plastic to the desired abutment outer shape. In order to avoid twisting of the plastic sleeve 50 during this process, the inside of the plastic sleeve 50 can be provided with a corresponding contact surface, for example an incorporated metal pad 50a. This model is then applied to the ceramic material in the pre-sintered state by means of a copy milling system, with a necessary enlargement factor adapted to the respective sintering process. transfer microabutment, which is sintered after grinding. The inter-sintered and different forms of the ZrO 2 abutment are particularly suitable for this.

The abutment can be enlarged, for example, in various ways, as shown in FIGS. 10 and 11:

An automatic, mechanical possibility of producing abutments is shown in FIG. In this case, a plastic model 13 of an abutment and a ceramic abutment blank 14 are clamped on the brackets 16 of a copy milling system with clamping screws 15 and fixed in the mutual position by means of a connecting piece 17. The zirconium oxide abutment can be copied in the finished or intermediate sintered state. If the abutment is to be ground in the sintered state, an enlargement 18 must also be provided. By using a diamond disc 19 or other, correspondingly abrasive grinding instruments and by abundant water cooling when grinding the

Abutments make it possible to grind even a sintered oxide ceramic in adequate time - and then without enlargement. The feed motor 20 moves the holder with the clamped abutment relatively slowly at approximately 20 revolutions per minute. Between the feed motor 20 and the holder 16 with the clamped plastic model 13 of an abutment there is a screw thread 21 which slowly moves the holders with the abutments forward. In contrast to the feed motor 20, the drive motor 22 for the diamond disk 19 must have a high speed, as is ensured, for example, in the case of air turbines. The mechanical scanning device 24 is guided over the surface of the plastic model 13 via a shaft 23 guided with ball bearings, and the abutment is correspondingly ground out of the ceramic blank 14 on the opposite side. 11 shows a computer-aided variant in which the scanning of the plastic abutment 13 and the milling out of the ceramic abutment are carried out in successive steps. The scanning device 12 can comprise, for example, laser optics or also a mechanical scanning probe. The measured data are stored (represented schematically by 37). After the scanning device 12 has been replaced by a drilling unit 38 and the plastic model 13 has been replaced by a ceramic block 39 or by a pre-sintered or pre-sintered abutment, the ceramic abutment is milled out of the latter in a computer-controlled manner.

15a to 15d show a further possibility of modeling the abutment shape with computer support. The external shape of the teeth, which - as described above - were created in wax or plastic as a model, is recorded, stored and processed by software in accordance with the process described with reference to FIG. 11, so that a reduced shape 51 of this type is displayed on the screen scanned outer shape 51a can be created and this is available in the form of data. Other, predetermined abutment external shapes that may be present in the memory library can also be used for this. These data then form the basis for processing the uncut, rough-ground abutment raw molds 52 of different diameters, which are applied to implant analogs on a working model, whereby - if they are pre-sintered abutments - the corresponding shrinkage factor must be taken into account. 15c shows the abutments 53 that have already been ground, the cut is indicated by dots. Then, in order to create the crowns or the bridge prosthetic reconstruction (FIG. 15d), the tooth form 54 - corresponding to the stored data - and the tooth form 54a can be appropriately modeled according to the data of the outer shape of the abutment.

12 shows a pre-sintered or also in the green stage abutment 9 'with a working stump 40, which one Has corresponding upper contact surfaces. Since the different internal dimensions of the abutment, depending on the type of implant, must also have the necessary enlargement in order to be able to compensate for the shrinkage given in the subsequent sintering process, the enlarged, lower opening is advantageously made of plastic by using an intermediate piece 24. For the sintering process, this enlarged abutment 9 'is now placed on the stump 40, which in turn is not subjected to any significant size change during the heat treatment, the abutment 9' will shrink to the desired size, the intermediate piece 24 burns in the process resistance-free.

13 shows a prefabricated abutment 9 made of zirconium oxide with a prefabricated crown part 11 'made of plastic or

Ceramic that is ground to the shape of a crown and the color is adapted to the neighboring teeth. If the implant situation is correct, these abutments are also suitable for permanent restoration. But this implant-crown combination is also ideal as a temporary restoration for the so-called abutment connection (cutting open the gums and screwing the abutment) because the patient can be treated with optimal gaps with the best materials on the same day.

A possible procedure for producing an implant-supported bridge or crown is described below:

A precise impression of the implant position is a prerequisite for the perfect fit of the superstructure in the mouth. The manufacture of a gum mask on the Mcdell is essential so that the gingival parts of the abutment can be designed correctly. The zirconium oxide abutment is then prepared in the dental laboratory according to one of the methods described above. The abutment is adapted to the gingiva. In the laboratory, a rough preparation takes place under water cooling, which in practice with the filling wax-up try-in can be corrected. Diamond discs are used for the rough preparation and coarse-grained, conical diamond grinders are used for the fine preparation. By delegating the abutment preparation to the dental laboratory, not only is valuable clinical stool time saved, but the dental technician also enjoys a better overview of the individual grinding of the abutment on his working model in order to achieve optimal gingival aesthetics. The dentist is then only responsible for the aesthetic fine adjustment of the cervical abutment part, unless one of the methods described above (Cad-Cam, copy milling) is used to maintain the shape.

A separate try-in of the filling wax-up with the abutment is necessary because the abutment height, cervical boundary, correct position of the exit point and the aesthetics can be checked. A correction of the abutment in the patient's mouth by re-preparation may be appropriate. Only in the mouth of the patient is it possible to determine the definitive shape of the abutment in connection with the soft parts.

It is sensible to use all-ceramic crowns.

For the cementing procedure of the crowns or bridges on the abutment, depending on the cementing concept, this is prepared either by silicating or by sandblasting the abutment surface. The abutment is then removed using a

The screw is fixed under a torque of 31 Ncm, the gold screw head m: t gutta-percha is closed, the abutment surface is cleaned, dried and silanized, and the crown or bridge is prepared for the further cementation steps.

The abutment shows good compatibility with the common porcelain systems. It should be noted that the heat expansion coefficient of the Keramikverblendmasse entspre ^¬ sponding base ceramic is tuned. Zirconia has a coefficient of thermal expansion of 9.5-70.5 (10 ^-6 -. ° K ^~ ^ In the rule, the thermal expansion coefficient of the veneering ceramic ^¬ a factor of about 1x10 ^"6 ° κ ^-'1 should be smaller than that of the Abutmentmaterials. In special cases it is possible by ^¬ from each abutment is directly ent to blind, whereby a screw-caused removable reconstruction.

Claims

PATENT CLAIMS

1. Implantable dentures, consisting of an implant (27) which can be fastened in a jawbone, an abutment (9) made of a ceramic material, which can be connected to the implant (27) via a fastening screw (29), a dental prosthetic reconstruction tion, such as a dental crown or dental bridge, and a fastening means for connecting said abutment to said dental prosthetic reconstruction, characterized in that said ceramic material has a fracture toughness KJ _Q of at least 6 MPa * m ^1/2 and a bending ¬ has a strength of at least 700 MPa or 800 MPa.

2. Dentures according to claim 1, characterized in that the ceramic material consists essentially, that is at least 90% by weight, of zirconium oxide.

3. Dentures according to claim 2, characterized in that the ceramic material contains between 0 and 10% by weight of a rare earth oxide and / or an alkaline earth oxide.

4. Dental prosthesis according to claim 3, characterized in that calcium and / or magnesium oxide are provided as rare earth oxide yttrium oxide, or as Erdaika lioxide.

5. Dental prosthesis according to one of the preceding claims, characterized in that the dental prosthetic reconstruction, such as a crown (11), with the abutment (9) via a plastic sheath covering the abutment (9) and / or via an elastic . Fastening means, in particular a cement based on silicone or on a composite basis.

6. Abutment for a denture according to one of the preceding claims, characterized in that the loading said ceramic material has a fracture toughness KJ _Q of at least 6 MPa * m ^1/2 and a flexural strength of at least 700 MPa or at least 800 MPa and preferably essentially, that is at least 90% by weight, consists of zirconium oxide, wherein in particular between 0 to 10% by weight of a rare earth oxide and / or an alkaline earth oxide are contained and optionally yttrium oxide is provided as a rare earth oxide and calcium and / or magnesium oxide is provided as an alkaline earth oxide.

7. Abutment according to claim 6, characterized in that the contact surface (43) of the abutment (9) with a corresponding surface provided on the implant (27) - the implant shoulder (32) - has a counter surface, preferably concentrically arranged, annular, pre- has jumps (44) for engagement in the implant shoulder (32).

8. A method for producing an abutment made of a ceramic material for a denture according to one of claims 1 to 4 or for an abutment (9) according to claim 6 or 7, wherein a specific, by the predetermined implant situation and / or the implant ( 27) predetermined, three-dimensional contour of the abutment (9) is determined, according to which, in a step which is referred to as pretreatment, a predetermined by the shrinkage of the ceramic material which occurs during post-treatment - in particular during sintering Enlargement factor enlarged, three-dimensional abutment shape (9 ') is produced, which abutment shape (9 ¹ ) is subjected to the aftertreatment, shrinking to a size corresponding to the abutment (9) to be produced, characterized in that - one by the specified magnification factor and the three-dimensional outer and, if necessary, also inner contour of the abutment form (9 ') corresponding work pack (36) is produced from a material, which has approximately the same shrinkage factor as the ceramic material,

- The work pack (36) for post-treatment is packed at least from the outside around the abutment form (9 '), in particular completely enveloping it, whereby the abutment form (9 ¹ ) is stabilized during the post-treatment, and

- The work pack (36) is separated from the abutment form (9 ') after the aftertreatment.

9. The method according to claim 8, characterized in that zirconium oxide is used as the material for the ceramic abutment (9) and, if appropriate, also as the material for the working pack (36).

10. The method according to claim 8 or 9, characterized gekennzeich¬ net that the pretreatment comprises compacting on the Grün¬ stage of the ceramic material and / or a presintering, in particular at a temperature between 1000 and 1300 ° C.

11. The method according to any one of claims 8 to 10, characterized ge indicates that the material for the working pack (36) consists of compacted and / or - in particular at a temperature between 1000 and 1300 ° C - pre-sintered oxide ceramic.

12. The method according to claim 11, characterized in that the compacted and / or pre-sintered material for the working pack (36) is brought in powder or chip form.

13. The method according to any one of claims 8 L -: S 12, characterized in that before the abutment form (9 ') is introduced into the working pack (36), the abutment form (9') on its outside, optionally also on its inside surface te, is coated with a thin layer of a release agent, the work pack (36) - after if necessary Introducing the abutment form (9 ') into the same - m block form.

14. The method according to any one of claims 8 to 13, character- ized in that the aftertreatment includes post-sintering at a sintering temperature corresponding to the ceramic material - for zirconium oxide at about 1500 ° C.

15. The method according to any one of claims 8 to 14, wherein the pretreatment comprises the following steps:

- The ceramic material is pressed isostatically under pressure in the green state, a tube shape (34) provided with a continuous opening (30 '), a so-called green body, being formed; - The tubular shape (34) is chamfered on one side at two ends;

- The through opening (30 ') is machined in the area of the bevel in such a way that a cylindrical widening occurs; - The extension is processed in this way, especially with

With the aid of ultrasound that a shape is created that fixes the positioning of the abutment (9) on the implant (27), in particular an internal hexagon shape (35);

- In the continuous opening (30 ¹ ), a counterpart, in particular a web-like projection (33), is incorporated for the fastening screw (29); thus obtaining an abutment form (9 ') to be subjected to the aftertreatment.

16. Process for making a ceramic

Material existing abutments for a tooth replacement according to one of claims 1 to 4 or for em abutment (9) according to claim 6 or 7, wherein emo bes' immte, predetermined by the predetermined implant situation and / or the implant (27) predetermined, three-dimensional contour of Abutments (9) determined, then a model, in particular a plastic model (13), created, which together with a ceramic blank (14) on holders (16) of a copying Milling system spanned and - if necessary via a connecting piece (17) - fixed in position to it, on the one hand a first scanning device (24) being guided over the surface of the plastic model (13) and on the other hand the ceramic blank (14) accordingly - in particular by means of a Diamond disc (19) - is ground, with a feed motor (20) possibly moving the holders (16) with the plastic model (13) or the ceramic blank (14) via a screw thread (21) at approximately 20 revolutions per minute.

17. The method according to claim 16 as a pretreatment in one of the methods according to one of claims 8 to 14, wherein the grinding of the ceramic blank (14) is carried out with the enlargement factor determined by the subsequent treatment.

18. A method for producing an abutment made of a ceramic material for a denture according to one of claims 1 to 4 or for an abutment (9) according to claim 6 or 7, wherein a specific, by the predetermined implant situation and / or the implant ( 27) predetermined, three-dimensional contour of the abutment (9) is determined, then a model, in particular a plastic model (13), is created, the shape of which - in particular computer-controlled - scanning and, if necessary, processing device via an - optionally removable - second scanning device (12) is read in and stored in data form, whereupon - if necessary after exchanging the model for a ceramic block (39) or a basic ceramic abutment shape and the scanning device (12) against a drilling unit (38) - a corresponding shape from the ceramic block (39) or όus from the basic ceramic abutmet shape.

19. The method according to claim 18 as pretreatment in one of the methods according to any one of claims 8 to 14, wherein the working out of the mold from the ceramic block (39) with the magnification factor determined by the subsequent treatment.

20. The method according to any one of claims 16 to 19, characterized in that the first and the second scanning device (12, 24) is a mechanical probe.

21. The method according to any one of claims 16 to 19, characterized in that the first and the second scanning device (12, 24) consists of laser optics with evaluation unit.