WO2004082512A1

WO2004082512A1 - Method for the production of a dental moulded part

Info

Publication number: WO2004082512A1
Application number: PCT/EP2004/003022
Authority: WO
Inventors: Anton Bodenmiller
Original assignee: Kaltenbach & Voigt Gmbh & Co. Kg
Priority date: 2003-03-20
Filing date: 2004-03-22
Publication date: 2004-09-30
Also published as: JP2006520229A; EP1603482A1; CA2519538A1; US20070034347A1; DE102004013939A1

Abstract

The invention relates to a method for the production of a dental moulded part wherein a mould (10) is formed with a cavity (11), the shape of which substantially corresponding to the shape of a model (2) of the moulded part and wherein a cast part (20) is formed by filling the cavity (11) of the mould with a hardenable material and is hardened. The model (2) is provided with an offset (2a, 2b, 2c) which is taken into account when the mould (2) is formed. Once that cast part (20) has hardened, it is abrasively machined in order to form the dental moulded part.

Description

Process for the production of a dental molding

The present invention relates to a method for producing a dental molded part according to the preamble of claim 1 and claim 20. In particular, the present invention relates to a method for producing molded parts made of precious metal or non-ferrous metal alloys that are difficult to machine.

In dental technology, prosthetic restorations are made from a wide variety of materials, depending on the indication-aesthetic demands, health consciousness and financial strength of the patients. Due to new manufacturing technologies such as laser welding, electroplating and, last but not least, the advance of dental CAD / CAM systems, in addition to the classic precious metal casting alloys, new biocompatible materials in the form of semi-finished products such as titanium, glass ceramics, high-performance ceramics or plastics can be used today.

The proportion of classic precious metal cast alloys is still very high when producing fixed or combined (so-called attachment) dentures. This is because the precious metal alloys have proven themselves to be very reliable in the patient's mouth for decades, are tolerant of design and design errors and, last but not least, are highly biocompatible. Another advantage of the precious metal alloys is that a proven range of tried-and-tested and easily processable veneering ceramics is available for these molded parts.

However, these advantages are offset in the manufacture of precious metal dentures with dental CAD / CAM systems by the high maintenance costs for the required semi-finished products and the considerable costs for the separation of the machined precious metal, whereby it must be taken into account that the degree of machining is currently above 90% lies. Accordingly, most attempts to manufacture precious metal dentures by means of CAD / CAM systems in dental or practice laboratories have failed for cost reasons. When manufacturing dental prosthetic parts from non-ferrous metal (non-ferrous metal) semi-finished alloy products with the help of CAD / CAM systems, the focus is on the problem of the difficult machinability of the Co-Cr-Mo bonding alloys. The savings in using the inexpensive non-precious alloys are offset by the high wear and tear of expensive milling tools and the long machining times, which lead to high machine hour costs.

One solution to circumventing the aforementioned problems in the manufacture of dentures from precious metal or non-precious metal alloys is so-called laser sintering. Such systems, however, require an enormous investment in the amount of several hundred thousand euros, which a dental or practice laboratory generally cannot provide. In addition, there are physical limits to the accuracy of layer-by-layer construction of the parts, so that long, complex, mechanical and manual reworking is required. The production of the fine metal powders required for the sintering process is also technologically very complex and, particularly in the case of precious metals, is not economical. In addition, the dental technician must externally base his prosthetic work, i.e. outsourced to external workshops so that there are waiting times and the dental technician loses a significant part of his financial production chain.

A method for producing dental moldings from precious metal alloys, which at least partially uses the advantages of a CAD / CAM system, is known from US Pat. No. 5,224,049. Here, after a model of the molded part to be formed has been created, the mold whose structure comes closest to the molded part to be produced is selected from a series of predetermined casting molds (so-called molds). If there are still deviations from the molded part to be created, the mold is machined until the cavity corresponds to the molded part to be formed. Then it is filled with a hardenable material, for example a precious metal alloy.

The method known from US Pat. No. 5,224,049 thus reduces the effort required to produce a dental molded part, but it has been shown that this method has certain limits with regard to its accuracy. In particular, more complicated surface structures of the dental molded part can only be realized with difficulty with the required accuracy.

The present invention is accordingly based on the object of specifying a possibility of including dental molded parts with more complicated structures in a way that is as rationalized as possible. In particular, it should be possible to use the advantages of CAD / CAM technology as extensively as possible.

The object is achieved by a method for producing a dental molding according to claim 1 and by a method according to claim 20. The subclaims relate to advantageous developments of the method according to the invention.

According to the present invention, the method for producing a dental advantage essentially consists of the following four steps: a) creating a model of the molded part to be formed, b) creating a mold with a cavity, the shape of which essentially corresponds to the shape of the model, c ) Creating a casting by filling the mold cavity with a durable material and d) allowing the casting to harden.

According to a first idea according to the invention, the model created in step a) is provided with an offset which is taken into account when the mold is created, and after the casting has hardened, it is machined to finally create the dental mold. The thickness of the offset can depend both on the shape of the molded part to be produced and on the hardenable material, and the offset can partially or completely cover the model.

The present invention combines or supplements the advantages of classic CAD / CAM technology with classic casting technology in a modified form and in this way enables highly precise, partially automated and economical production of dental prosthetic work from precious metal or Co-Cr-Mo Alloys in the dental or practice laboratory. In comparison to the method known from US Pat. No. 5,224,049, the manufacture of the mold is simplified, since the use of the offset makes it possible to compensate for more complex structures in the surface of the molded part to be produced, so that the mold can be worked out relatively quickly and easily. Compared to the known method, processing of the hardening cast part is then still necessary, but there is the advantage that the desired molded part can ultimately be produced with a very high degree of precision. In addition, according to the inventive method, more complicated surface structures for the Molding are created that would otherwise be difficult or impossible to achieve.

In order to be able to take full advantage of CAD / CAM systems, it is provided according to a particularly preferred variant of the method according to the invention that the mold is produced by fully automatic machining, in particular by milling, turning, drilling and or grinding at least one mold blank. Here _. , a removal program that takes the desired contours of the mold into account specifies control commands for an ablating machine, the program in particular also being created on the basis of a three-dimensional CAD reconstruction of the model provided with the offset. Furthermore, it can be provided that when the mold is created, at least one gating channel is simultaneously machined into the blank, through which the curable material is then subsequently filled.

According to a second idea of the present invention, it is provided that after the casting has hardened, it is left unbuilt for final processing, i.e. inserted together with the mold in a tool holder and processed there. This is preferably the same ablating machine that was previously used to create the mold. In this case, since an exact reprositioning of the cast-off part into the machine tool is made possible, a high degree of accuracy is ensured during the final machining of the cast part.

A particular advantage of this second inventive concept is that the mold material can simultaneously serve as a milling or grinding support or holding material, so that the processing of very thin and fragile castings is made possible. After the mold material has been partially milled away, it can then be provided that the casting is back-bedded with another supporting material and then the rest of the casting is machined occlusally.

Overall, the present invention thus creates the possibility of creating dental moldings from precious metal or non-precious metal alloys in a very effective manner, while at the same time ensuring the highest possible accuracy in the production of the molding.

The invention will be explained in more detail below with reference to the accompanying drawing. Show: 1 to 10 the various steps of a preferred exemplary embodiment of the method according to the invention and FIG. 11 a tabular overview of the method steps of a classic method for producing a dental casting and the method according to the invention.

The method according to the invention for producing dental foam parts represents a significant advance in comparison to the classic method for producing gold castings, since many of the work steps which are usually to be carried out can now be carried out automatically or by machine. To clarify the advantages according to the invention, the classic method for producing a single gold cap is briefly summarized below.

After finishing the preparatory operations, a film cap is first deep-drawn, which is then adapted to the previously processed tooth stump. After isolating the tooth stump, the film cap is fixed and then a wax model of the crown to be made is created. This wax model is now varnished and then the casting is prepared, for which the muffle is first prepared, an investment paste is made and the model of the wax crown is finely embedded. After completing the embedding, the muffle is waxed and preheated and finally poured out with the liquid precious metal alloy. After the casting has hardened, it is divested, the casting blank is cleaned and the casting channel is separated.

The cast piece created in this way can then be worked out with a handpiece until it takes on the shape of the desired crown cap. This cap is then blasted and cleaned for surface treatment. After cleaning the tooth stump, the cap can then be put on in the final operation.

The previously known method is summarized in a table in FIG. 11. As can be seen from the above summary, a large part of the tasks involved in the classic process must be carried out manually, with some of the work steps taking a long time. In particular, modeling the crown in wax and working out the cast part with the handpiece take up a relatively large amount of time. In contrast, the manufacturing process can be significantly accelerated and automated with the aid of the present invention, as will be explained below.

The beginning of the process according to the invention corresponds to the classic manufacturing process, i.e. in the course of the preparatory operations, the tooth is first machined and then, with appropriate checking of the working documents and the models, preparation margins, etc., the tooth stump shown in FIG. Positive model, made of the same. The stump 1 produced by classic impressions and the like is then optically measured three-dimensionally and inserted for this purpose into a corresponding measuring device, as is generally known from CAD / CAM systems.

As soon as the data regarding the three-dimensional structure of the tooth stump is completely available, an automatic surface return can then take place under PC control, which ultimately leads to the construction of the crown cap. With the help of classic CAD-3D technologies, the crown cap is largely automatically generated on the so-called NURBS (Non Uniform Rational B-Sρlines) surface, i.e. on the die geometry described with the aid of a mathematically complex method, and - if necessary - manually light corrected. This results in a three-dimensional model in digital form of the cap provided with the reference number 2 in FIG. 2, the structure of which corresponds exactly to the molded part to be produced.

An essential step of the method according to the first idea according to the invention is shown in FIG. 3, in which the cap 2 is provided with an offset 2a, that is to say an additional layer applied to the cavity and / or occlusal side, as part of the three-dimensional modeling or CAD reconstruction becomes. This offset 2a can depend on the one hand on the structure of the molded part to be produced and on the other hand on the type of material and is typically in the range of approximately 0.5 mm. It can partially or completely cover the model 2.

According to the representation in FIG. 4, this offset 2a can then be additionally modeled, that is to say provided with additional layers 2b and 2c, so that overall there is an offset shape, generally provided with the reference number 3, which roughly corresponds to the shape of the molded part to be produced, however - partially or on all sides - is surrounded by an additional layer. The additional modeling of offset 2a can be used in particular to make it relatively simple To form surface structure for the offset mold 3, whereby the subsequent manufacture of the mold for carrying out the casting process is facilitated.

In a next step, a mold should then be created, as shown in FIG. 5 and provided with the reference numeral 10, the mold 10 being intended to have a cavity 11 which provides the structure of the offset, which may have been modified Molding corresponds.

The mold is produced fully automatically in accordance with the exemplary embodiment shown, an NC program for producing the mold being generated first with the aid of a CAM module and taking into account the model geometry. The CAM module automatically generates the shape division and the appropriate milling program to form the cavity 11.

The manufacture of the mold is shown in FIGS. 6a and 6b, with a first mold blank 12 consisting of a suitable material 13 first being inserted into a clamping bridge of an ablating machine, for example a milling, turning, drilling or grinding machine, and with the aid of a corresponding one Tool 5 is machined to form the lower outer surface 14 of the cavity. A second mold blank 15 shown in FIG. 6b is in turn processed with the aid of the tool 5 in such a way that the upper boundary surface 17 of the cavity results. Depending on the geometry of the mold, one or two mold blanks are thus machined, preferably milled with 5 axes, so that finally in the assembled state, a cavity is formed, the structure of which corresponds to offset shape 3 shown in FIG. 4. While the milling process is being carried out, an NC program for later machining of the cast part can be generated automatically, which is necessary to obtain the desired crown cap geometry with a suitable cavity and the desired occlusal side.

It is important that during the machining of the ingot blanks 12 and 15, corresponding sprue channels 21 - shown in FIG. 7 - can already be provided, which will later be used to fill the cavity 11 with the liquid alloy. As soon as the mold or the mold halves have been processed accordingly, they can be removed from the clamping bridge and - if there are two mold blanks - put together and inserted into the casting machine.

The mold thus formed is then poured out with the noble metal or the Co-Cr-Mo alloy, with the special, millable mold material preheating before casting in accordance with the previously known Procedure is no longer required. As soon as the resulting cast part has hardened sufficiently, the mold 10 consisting of the two halves 12 and 15 can then be reinserted into the clamping bridge 19 of the milling machine (FIG. 7), with the greatest possible accuracy due to the exact repositioning possibilities later processing is enabled.

The final machining of the cast part 20 is now carried out with the help of a

, abrasive tool 6, according to the representation in Fig. 8, the cast part 20 is first machined from the top until finally a surface 25 is formed which corresponds in its dimensions and in its structure to the desired crown cap. In the machining cycles "finishing" and "fine finishing", the offset is removed with the least loss of material, thus creating the dimensionally accurate cavity. It is essential that the outside of the cast part 20 is supported by the remaining mold material 13 or 16, so that even very fine cast parts can be machined without the risk that they will be damaged, in particular break out.

Before a final machining of the occlusal side, the cavity side is then embedded again with an embedding material 22, for example an appropriate milling wax or plastic, and is thus supported, so that the cast part 20 is securely stored and supported even during the final machining process shown in FIG. 10. In this process, the occlusal side is then milled until finally this side also has a surface structure 26 which corresponds to the desired crown structure.

After the milling process has been completed, the machined cast part 20 is removed from the machine and detached from the embedding wax or plastic, which e.g. can be done by heating with a hot air dryer. In rare cases, a final minor correction using a dental motor handpiece is required to rework the inside of the cavity.

The resulting crown cap is then blasted briefly on the inside and outside of the veneer surface in a blasting device, whereupon the cap can be put on after cleaning the tooth stump and the surgeries removed, and subsequent operations can be carried out.

The workflow described illustrates that, in contrast to the classic dental casting process, the main activities of the dental technician are based on the Relocate CAD / CAM workstation as well as on the CNC-controlled - preferably five-axis - milling machine. The majority of the time-consuming manual work is thus eliminated, as is also shown by the comparison in the table in FIG. 11. It becomes clear that a large number of work steps are transferred to the PC or the machine and, in particular, can also run automatically. The remaining manual tasks, however, are mostly such that they can be carried out very quickly.

Another advantage is that the millable mold is in front. the casting does not have to be preheated for a long time in a controlled thermal process as has been customary up to now and has to be converted into the casting device in the glowing state. Since the mold material is also easy to mill or grind without major tool wear, it can also serve as a holder for the casting in the clamping bridge after casting the mold. The advantage here is not only that the cast part is supported during the final machining. At the same time, it is ensured that extremely precise reprositioning is made possible. Because of these advantages, a very thin offset can be used and expensive precious metal can be saved. When using Co-Cr-Mo alloys, on the other hand, the low cutting volume reduces tool wear, which in turn enables cost-covering production.

Claims

Expectations

1. A method for producing a dental molded part with the following steps: a) creating a model (2) of the molded part to be formed, b) creating a mold (10) with a cavity (11), the shape of which essentially corresponds to the shape of the model (2 ) corresponds to, c) creating a casting (20) by filling the mold cavity (11). with a hardenable material and d) allowing the cast part (20) to harden, characterized in that the model (2) created in step a) is provided with an offset (2a, 2b, 2c) which is used when the mold (2) is created is taken into account, and that after hardening of the cast part (20) this is machined to create the dental molded part.

2. The method according to claim 1, characterized in that at least one cavity side of the model (2) is completely provided with an offset (2a, 2b, 2c).

3. The method according to claim 1, characterized in that at least one occlusal side of the model (2) is completely provided with an offset (2a, 2b, 2c).

4. The method according to claim 1, characterized in that the entire surface of the model (2) is provided with an offset (2a, 2b, 2c).

5. The method according to any one of the preceding claims, characterized in that the thickness of the offset (2a, 2b, 2c) depends on the shape of the molded part to be created.

6. The method according to any one of the preceding claims, characterized in that the thickness of the offset (2a, 2b, 2c) depends on the curable material.

7. The method according to any one of the preceding claims, characterized in that the model (2) of the molded part to be formed is created on the basis of an optical measurement of a tooth stump (1) on which the molded part is to be arranged.

8. The method according to claim 7, characterized in that the model (2) with the offset (2a, 2b, 2c) is created by means of a three-dimensional CAD reconstruction, the data obtained during the optical measurement of the tooth stump (1) being taken into account ,

9. The method according to any one of the preceding claims, characterized in that the mold (10) is created by machining at least one mold blank (12, 15) with an ablating machine.

10. The method according to claim 9, characterized in that the processing of the at least one mold blank (12, 15) is carried out fully automatically, in particular by milling, turning, drilling and or grinding.

11. The method according to claim 10, characterized in that a removal program which takes into account the desired contours of the mold (10) and of the mold cavity (11) contains control commands for the removing machine.

12. The method according to claim 8 and claim 10, that the removal program is created on the basis of the three-dimensional CAD reconstruction of the model (2) provided with the offset (2a, 2b, 2c).

13. The method according to any one of claims 9 to 12, characterized in that when creating the mold (10) at least one sprue (21) is simultaneously machined into the mold blank (12, 15).

14. The method according to any one of the preceding claims, characterized in that after the casting (20) has hardened, it is inserted into a tool holder of an ablating machine together with the mold (10).

15. The method according to any one of claims 9 to 13 and claim 14, characterized in that the same machine is used to process the ingot blank (12, 15) and the casting (20), wherein. the mold is repositioned in the tool holder.

16. The method according to claim 14 or 15, characterized in that during the machining of the casting (20) the mold material (13, 16) serves as a support or holding material.

17. The method according to claim 16, characterized in that the processing of the casting (20) takes place in at least two steps, in each of which certain areas of the casting (20) are processed, the previously processed areas of the casting (20) again an investment material (22), in particular a milling wax or a plastic.

18. The method according to any one of claims 14 to 17, characterized in that the machining of the cast part (20) is carried out fully automatically, in particular by milling, turning, drilling and / or grinding.

19. The method according to claim 18, characterized in that an ablation program taking into account the contours of the cast part (20) and of the molded part to be created contains control commands for the ablating machine.

20. A method for producing a dental molding with the following steps: a) creating a model (2) of the molding to be formed, b) creating a mold (10) with a cavity (11), the shape of which essentially corresponds to the shape of the model (2 ) corresponds to, c) creating a casting (20) by filling the mold cavity (11) with a curable material and d) Allowing the cast part (20) to harden, characterized in that after the cast part (20) has hardened, it is machined to produce the dental molded part, the cast part (20) being embedded together with the mold (10) in one for this purpose Tool holder of an ablating machine is used.

21. The method according to claim 20, characterized in that during the machining of the casting (20) the mold material (13, 16) serves as a support or holding material.

22. The method according to claim 21, characterized in that the processing of the casting (20) takes place in at least two steps, in each of which certain areas of the casting (20) are processed, the previously processed areas of the casting (20) again an investment material (22), in particular a milling wax or a plastic.

23. The method according to any one of claims 20 to 22, characterized in that the machining of the cast part (20) is carried out fully automatically, in particular by milling, turning, drilling and / or grinding.

24. The method according to any one of the preceding claims, characterized in that the molded part is formed from a noble metal alloy.

25. The method according to any one of claims 1 to 23, characterized in that the molded part is formed from a non-ferrous metal alloy, in particular from a Co-Cr-Mo alloy.