WO2003032861A1 - Method and profiled element for producing a dental prosthesis - Google Patents

Abstract

The invention concerns a method for producing a dental prosthesis which consists in: preparing, in a first step, a profiled ceramic element; then in entirely sintering it. In the next step, the entirely sintered preformed profiled is wrought in order to obtained the final state of the prosthesis. The use of preformed profiled ceramic elements is advantageous since the shaping of the profiled element to obtain its final state consists in eliminating a relatively small amount of ceramic. Thus it is possible to prepare as preformed profiled element, profiled elements entirely sintered with a high degree of hardness.

Description

 Method and molded element for the manufacture of dentures

The invention relates to a method and a molded element for the production of dentures. The dental prosthesis, which is, for example, a crown, a bridge, an inlay or an onlay, consists of ceramic, in particular an oxide ceramic material, such as aluminum oxide, magnesium oxide, zirconium oxide, titanium oxide and / or combinations thereof. Furthermore, the ceramic dental prosthesis can have, for example, small amounts of silicate additives.

Dentures are generally parts such as crowns, bridges, inlays and onlays that are placed on a patient's natural teeth in order to largely restore the natural function of the teeth. Elaborate procedures are required to manufacture dentures that must be extremely precise and therefore only have minimal tolerances. First of all, a dentist has to prepare and extract the part of the bit to be replaced. After that, z. B. made by an impression with conventional methods a model. In the case of ceramic dentures, the manufacture of the dental prosthesis is then usually carried out by copy milling. In this case, the final shape of the denture is reproduced from a cuboid blank made of soft unsintered ceramic by mechanical processing, such as drilling, milling and / or grinding, on the basis of the model created. Blanks used here are described, for example, in DB 196 12 699. After the copy milling, the dentures made of soft ceramic are glass-filtered for hardening. The afterthought Glass infiltration is very time consuming. Furthermore, the subsequent glass infiltration has the disadvantage that an additional high-temperature furnace is required.

Substantially harder and therefore more permanent dentures can be achieved by using fully sintered ceramic. Since strong shrinkage occurs during full sintering of ceramics, it is not possible to fully sinter a denture made from a soft ceramic after reaching the final shape. The degree of shrinkage during full sintering is u. a. depending on the thickness of the dentures and therefore very different. It is therefore not possible to take the shrinkage into account by adding the appropriate material. The narrow tolerances required cannot be achieved here.

For the production of dentures from fully sintered ceramic, it is therefore only possible according to the prior art to completely sinter cuboid blanks prior to processing. Such blanks then have an extremely high hardness. The Vickers hardness of fully sintered ceramics is in the range of 800 - 2500 HV 10. The production of dentures from fully sintered cuboid blanks is extremely time-consuming due to the hardness of the fully sintered ceramics. Of the known blanks, 80% of the blank usually has to be ground away. This requires grinding times of over 10 hours. Since the service life of the processing tools is very short due to the hardness of the fully sintered ceramic, the processing tools must also be changed frequently. This increases the cost of producing the dentures considerably, since the machining of fully sintered ceramics is only possible with expensive tools set with diamonds. The cooling of the end mills is extremely difficult, in particular when producing recesses which are generally produced using end mills. Therefore, only low removal rates are possible. The object of the invention is to provide a method for the production of dentures with which the production of dentures from fully sintered ceramic is economically possible. It is also an object of the invention to provide a shaped element suitable for this.

The object is achieved according to the invention by a method according to claim 1 and by a shaped element according to claim 10.

According to the method according to the invention, in a first step a preformed shaped element made of ceramic is produced. The preformed shaped element is not a cuboidal blank used in accordance with the prior art, but a shaped element which is already preformed in such a way that areas which frequently have to be ground down in order to achieve a final state of the denture are not present. For example, a shaped element preformed according to the invention, from which a crown is to be produced, already has a preformed inner bore into which the remaining healthy part of the tooth is later inserted. A shaped element preformed according to the invention has the advantage that less material has to be removed when the shaped element is subsequently machined to achieve the final state of the denture. Because of this advantage, it is possible to completely sinter the preformed ceramic shaped element produced in a first step in a subsequent step. Only after complete sintering, i.e. H. after the production of a preformed molded element from hard ceramic, the molded element is processed to achieve the final state of the denture.

The shaped element is preferably preformed such that it has a shape approximating the final state of the denture. This has the advantage that, compared to cuboid blanks, only a considerably smaller amount of material has to be removed. The preformed shape of the molded element is preferably approximated to the final state of the denture in such a way that less than 50%, in particular less than 30% and particularly preferably less than 10% of the molded element have to be removed during the processing of the molded element to the final state. In the case of preformed shaped elements whose shape is so close to the final state of the denture, the fully sintered shaped element can be mechanically processed. The required processing times for the preformed shaped elements according to the invention are considerably shorter than for cuboid blanks. As a result, tool costs are also reduced. In particular when machining recesses, which generally have to be done with end mills, the method according to the invention has the advantages that, compared to the prior art, considerably less material has to be removed and thus tools such as end mills with low removal rates can also be used economically.

On the basis of these advantages of the method according to the invention, it is possible to combine dental prosthesis forms occurring in humans and to form a standard shaped element for each group. Such a group includes, for example, similar inlay forms for a molar tooth or frequently occurring forms of crowns for an incisor, etc. In particular, through statistical surveys and / or evaluation of occurring forms of dentures, it is possible to generate standard form elements from which a multitude of different types of dentures are worked out can be. Here, the machining allowance for a standard shaped element is selected such that different individualized denture shapes can be worked out in detail from different machining of the standard shaped element from a single standard shaped element. For example, different inlays for a large number of patients can be worked out from a single standard shaped element for molar tooth inlays, the basic shape of which is similar to one another. It is preferably possible to produce a system from a set of standard shaped elements. Such a set of standard form elements contains, for example, one standard form element for all groups of denture molds. The number of groups of dentures can be varied. With a relatively small number of groups, each standard form element must comprise a relatively large number of individual denture forms. The consequence of this is that more material has to be removed to produce the final state of the denture. By increasing the number of groups, a finer subdivision can take place, so that each standard form element only has to comprise a small number of individual denture forms. This enables a preformed shape of the molded element which is more closely approximated with respect to the final state. The consequence of this is that less material has to be removed when the shaped element is processed. An optimum number of groups can be determined depending on the production costs and in particular the costs for processing the molded element in order to achieve the final state.

A maximum number of ten standard shaped elements is preferably provided in the system for each tooth type, for example for a specific molar tooth. In particular, this number is a maximum of five standard shaped elements per tooth type. For example, a single tooth can be defined as the tooth type. However, further subdivisions are also possible, for example depending on the jaw size and the like.

In a particularly preferred embodiment, a set of shaped elements, for example having a maximum of 30 standard shaped elements, is generated such that with this set of shaped elements, a corresponding standard shaped element in the set of shaped elements in at least 80% of the dental prosthesis forms of a tooth type that occur in the population is included. This is preferably the case for at least 90% and particularly preferably for at least 95% of the population. Includes to reduce costs a set of shaped elements preferably a maximum of 20 and particularly preferably a maximum of 10 standard shaped elements. Here again it must be taken into account that the production costs for the standard shaped elements can be optimized in comparison with the processing costs by the number of standard shaped elements.

The shaped elements according to the invention are preferably produced in a casting process, in particular an injection molding process. With such methods, a molded element preformed according to the invention can be produced from ceramic in a simple manner.

It is also possible to produce the preformed shaped element from a relatively soft solid body. The ceramic solid is produced in particular by mechanical processing, such as grinding, drilling and / or milling. The solid body is preferably pre-sintered into a shaped element before processing. The pre-sintered solid body is relatively soft compared to fully sintered bodies and is therefore easy to machine. The pre-sintering of the full body has the advantage that precise processing is possible. After processing the solid body into a preformed shaped element, it is hardened by full sintering in accordance with the method according to the invention. This is followed by the final processing.

The Vickers hardness of a fully sintered molded element according to the invention is preferably in the range from 1000 to 1400 HV 10 for zinc oxide and in the range from 2000 to 2400 HV 10 for aluminum oxide.

The fully sintered molded element is preferably machined to achieve the final state of the denture by mechanical processing, in particular grinding, drilling and / or milling. Known copying machines can be used for this purpose, for example. It is also possible to use numerically controlled machines that use the image processing Establish the final state of the denture. Here, images of the healthy tooth in which a denture is to be inserted are created and processed using digital image processing.

After processing the preformed shaped element to achieve the final state, post-processing can be carried out. In particular, the ceramic dental prosthesis can be polished. To improve the surface appearance, the dentures can be reworked by so-called tipping. Tipping is a hot isostatic pressing of the denture.

The invention further relates to a molded element for the production of dentures. The shaped element consists of fully sintered ceramic and has a shape approximating the final shape of the denture. The shaped element according to the invention is preferably produced in the method described above and has the corresponding advantages.

The preformed shaped element preferably has a machining allowance to achieve the final state of less than 100%. The result of this is that a maximum of 50% of the entire material of the preformed shaped element must be removed during processing. A machining allowance of less than 50%, in particular less than 30%, is particularly preferred.

As described above, dental prosthesis forms are preferably combined into groups and a standard shaped element is formed for each group. Such standard shaped elements preferably have a recess, so that a thin-walled shaped element is formed. The recess is, for example, a standard shaped element for a crown, the recess into which the healthy residual tooth is inserted. Corresponding preformed recesses can can also be provided, for example, in the case of standard shaped elements for molars for the occlusal surfaces, etc.

Preferred standard shaped elements, which are particularly suitable for crowns, have a truncated pyramid-like outer shape, which is particularly hollow.

In order to be able to clamp the shaped elements according to the invention in a processing machine, such as a copying machine, the shaped elements have a holding attachment. The retaining attachment is preferably connected in one piece to the shaped element. The approach is thus already in the manufacture of the preformed molded element, i. H. for example with injection molding. This has the advantage that the preformed shaped element does not have to be connected to a holding attachment, such as a metal pin or the like. It is therefore also not necessary when connecting the holding attachment to the shaped element to ensure that the position of the holding attachment is defined with respect to the preformed shaped element. This would be extremely difficult, especially in the case of preformed shaped elements with irregular outer contours, and would therefore be time and cost intensive.

The shaped element preferably also has an alignment means for aligning the shaped element in the processing machine. As an alignment means, for example, an extension or a recess can be provided, which interacts with a corresponding counterpart on the processing machine, so that the position of the molding element in the processing machine is always defined. This is very advantageous in particular in the case of shaped elements with complicated outer shapes, since this eliminates the need for an alignment by a user. The alignment means is preferably provided directly on the holding attachment.

The shaped element according to the invention can advantageously be further developed in accordance with the shaped element produced with the aid of the method according to the invention. The invention is explained in more detail below on the basis of preferred exemplary embodiments.

Show it:

Fig. 1 is a schematic sectional view of a first

Embodiment of a standard molded element according to the invention,

Fig. 2 is a schematic plan view of that shown in Fig. 1

Formulas and

3 is a perspective schematic view of a second preferred embodiment of a standard

Form element.

The figures 1 and 2 show a standard shaped element which is particularly suitable for machining a crown. The shaped element shown has an outer contour that is rotationally symmetrical with respect to the axis of rotation 10. This is a truncated cone, the diameter of which decreases from an upper side 12 towards a lower side 14. The outer contour can also be pyramid-shaped. A recess 16 is provided on the top 12. This is arranged asymmetrically to the axis 10. Flanks 18, 20 of the recess 16 have a different angle to the axis 10. As a result, a bottom surface 22 of the recess is arranged offset with respect to the circular opening 24 of the recess (FIG. 2).

A holding projection 26 is also provided on the underside 14 in a rotationally symmetrical manner with respect to the axis 10. The holding projection 26 has a cylindrical outer contour. In the retaining projection 26 there is a perpendicular to the axis 10 arranged recess 28 is provided. This serves as an alignment means in order to be able to align the shaped element held in a processing machine with the aid of the holding attachment 26. The alignment of the molded element can also be done by marking or the like. take place so that the recess 28 and possibly also the retaining projection 26 can be omitted.

The top side 12 of the molded element preferably has an outer diameter of 6-8 mm. The recess 16 has a diameter of preferably 3-5 mm in the area of the top 12 and the bottom surface 22 of the recess 16 has a diameter of 1.5-3 mm. On the underside 14, the shaped element preferably has a diameter of 4.5-6.5 mm. The height of the molded element is preferably 8-10 mm. The depth of the recess 16 is preferably 4-6 mm.

In a further preferred embodiment of the molded element according to the invention, which in principle corresponds to that shown in FIGS. 1 and 2 corresponds to the shaped element shown, the recess 16 is symmetrical to the axis of rotation 10. The recess 16 is thus frustoconical, the bottom surface 22 also being concentric to the axis of rotation 10. In this embodiment, the circles visible in the top view in FIG. 2 are thus concentric. The dimensions of this embodiment of the molded element are preferably also in the ranges specified above.

In particular in the preferred embodiment of a symmetrical frustoconical recess 16, the outer diameter of the upper side 12 is preferably 9-11 mm and the opening 24 of the upper side 12 is preferably 6-8 mm. In this embodiment, the bottom surface 22 is preferably 5-7 mm and the underside 7.5-10 mm. The height of the molded element and the depth of the recess are preferably in the same ranges specified above. A further preferred embodiment (FIG. 3) is also a standard shaped element for producing a crown. This form element is already much closer to the final state of the crown than that in the figures. 1 and 2 standard form element shown. However, the shaped element shown in FIG. 3 is also a fully sintered pre-shaped shaped element that has not yet been processed to produce the final state of the denture. The shaped element is also essentially frustoconical and has a recess 30. On a side surface of the outside of the molded element, webs 32, 34 are provided, whereby the part of the molded element which forms the crown is connected to a plate 36. After machining the upper part of the molded element, ie the crown, it is separated from the webs 32, 34. Such an arrangement of a molded element is advantageous for processing, for example with the aid of a copying machine.

On the underside of the plate 36, a holding projection 38 corresponding to the holding projection shown in FIG. 1 is provided. The holding projection 38 is also cylindrical. A bore 40, which runs perpendicular to the longitudinal direction of the retaining projection 38, is provided in the retaining projection 38 and serves as an alignment means for aligning the molding element in the processing machine.

The entire shaped element shown in FIG. 3 consists of fully sintered ceramic. The shaped element is preferably produced in one piece by injection molding.

Claims

Expectations 1. Procedure for the production of dentures with the steps in the given order: Manufacture of a preformed ceramic molding, Full sintering of the form element and Editing the form element to achieve the final state of the denture. 2. The method of claim 1, wherein the preformed shaped element has a shape approximating the final state of the denture. 3. The method according to claim 1 or 2, wherein the. The molded element is preformed in such a way that less than 50%, preferably less than 30%, particularly preferably less than 10% of the molded element must be removed during processing to the final state. 4. The method according to any one of claims 1-3, in which the shaped element is produced in a casting process, in particular in an injection molding process. 5. The method according to any one of claims 1-4, characterized in that the fully sintered shaped element has a Vickers hardness of at least 800 HV 10, preferably at least 1000 HV 10. 6. The method according to any one of claims 1-5, characterized in that the machining of the molded element is carried out by mechanical processing, in particular grinding, drilling and / or milling. 7. The method according to any one of claims 1-6, characterized in that after the processing of the molded element, a post-processing, in particular a polishing or polishing of the denture takes place. 8. The method according to any one of claims 1-7, in which the production of the molded element is carried out by pre-sintering a full body and subsequent processing of the full body. 9. The method according to claim 8, wherein the processing of the solid body is carried out by mechanical processing, in particular grinding, drilling and / or milling. 10. Shaped element for the production of dentures, consisting of fully sintered ceramic, the shaped element having a shape approximating the final shape of the dentures. 11. Shaped element according to claim 10, characterized in that the shaped element has a machining allowance to achieve the final state of less than 100%, in particular less than 50% and particularly preferably less than 30%. 12. Shaped element according to claim 10 or 11, characterized in that the Vickers hardness of the shaped element is in the range from 1000 to 1400 HV 10. 13. Shaped element according to one of claims 10 - 12, characterized by a recess (16, 30), so that a thin-walled shaped element is formed. 14. Shaped element according to one of claims 10-13, characterized by a truncated pyramid-like outer shape. 15. Shaped element according to claim 13 or 14, characterized in that the recess (16, 30) is arranged asymmetrically to a central axis (10) of the shaped element. 16. Shaped element according to one of claims 10-15, characterized by a holding projection (26, 38) for clamping the shaped element in a processing machine. 17. Shaped element according to claim 16, characterized in that the retaining projection (26, 38) is integrally formed on the shaped element. 18. Shaped element according to one of claims 10-17, characterized in that the shaped element is a casting, in particular an injection molded part. 19. Shaped element according to one of claims 10 - 18, characterized by an alignment means (28, 40) for aligning the shaped element in the processing machine. 20. Shaped element according to claim 19, characterized in that the alignment means (28, 40) is provided on the holding projection (26, 38). 21. Shaped element according to claim 19 or 20, characterized in that the alignment means has a projection and / or a recess (28, 40). 22. System consisting of a set of shaped elements according to one of claims 10-21, in which occurring denture forms are combined into groups and a standard shaped element is formed for each group. 23. System according to claim 22, in which a maximum of 10, in particular a maximum of 5, standard shaped elements are provided for each tooth type. 24. System according to claim 22 or 23, in which a set of shaped elements comprises at least 80, in particular at least 90, particularly preferably at least 95% of the dental prosthesis forms of a tooth type occurring in the population and the set of shaped elements comprises a maximum of 30, preferably a maximum of 20 and particularly preferably has a maximum of 10 standard shaped elements.