DE102008036661A1 - Process for the production of oxidic dental ceramics - Google Patents

Abstract

The invention relates to a method for producing oxidic dental ceramics, comprising the steps of a) providing numerical data of the three-dimensional shape of an oxidic dental ceramic to be produced, b) numerically increasing the dimensions of the three-dimensional shape corresponding to the expected subsequent sintering shrinkage, c) producing a negative mold of dewrgrößerten three-dimensional shape, which is designed such that it consists of at least two parts, d) introducing a feedstock containing an oxide ceramic powder, in the negative mold at a temperature of 60 ° C to 150 ° C, e) removal of a cooled moldings from the negative mold, debinding and final sintering of the debindered molding to a dense oxidic dental ceramic. In this process, no or only a very small loss of material. With this method, very fine crown margins and complex geometries can be produced. A direct coloring of the dental ceramic in basic dental tones is possible by suitable additives in the feedstock. Especially when using the low-pressure injection molding, only a very small amount of equipment is required.

Description

The The invention relates to a process for the production of oxide ceramic Dentures.

The The present invention is in the field of ceramic production Dentures made of oxide ceramics such as alumina or zirconia. This material class stands out over other ceramic ones or glass-ceramic materials due to high strength and good chemical stability.

A disadvantage of the oxide ceramics is their production via a powder technology molding process and subsequent sintering, which has a shrinkage up to the dense ceramics of up to 50 vol.% Result. Only since the establishment of CAD / CAM technologies is it possible to produce dental prostheses from materials of this class in practice by means of a mathematical correction of the dimensions of the desired shape. An overview of the practical use of CAD / CAM systems is the Article fabric for machine assistants, dental dialogue, p. 52, 2005 ,

• – Bei diesem Verfahren wird die herzustellende Form aus einem Rohling aus Oxidkeramik gefräst. Die hierbei eingesetzte Abtragung führt zwangsläufig zu einem Materialverlust, der je nach Materialzusammensetzung und Größe des Zahnersatzes bis zu 90 Vol.% betragen kann. Dieses Material ist verloren, da es bisher nicht aufgearbeitet werden kann.
• – Bei der Bearbeitung des angesinterten Rohlings, die als Weißbearbeitung bezeichnet wird, kommt es insbesondere bei dünnen Kronenrändern zu Ausbrüchen an der Form.
• – Das gesamte Herstellungsverfahren ist apparativ aufwändig.

However, in practice, the following problems arise when using this method:

• - In this process, the mold to be produced is milled from a blank made of oxide ceramics. The erosion used here inevitably leads to a loss of material which, depending on the composition of the material and the size of the denture, can amount to up to 90% by volume. This material is lost because it can not be worked up yet.
• - When machining the sintered blank, which is referred to as white machining, it comes in particular with thin crown edges to breakouts on the mold.
• - The entire manufacturing process is complex in terms of apparatus.

Therefore, there are various efforts to develop new procedures or procedures that are already established in other areas, such as the DE 197 03 177 A1 or off W. Bauer and V. Piotter, Keramische Zeitschrift 56, 2004, 292-297 known powder injection molding or from the DE 103 37 688 B3 or H. von Both, M. Dauscher and J. Haußelt, Keramische Zeitschrift 56, 2004, 298-303 known electrophoretic deposition to adapt to the conditions of dental technology, so that they are characterized in comparison to the CAD / CAM technology by a lower equipment cost and a lower material loss and therefore are particularly cost-effective. However, there always remains the problem of sintering shrinkage, which has been solved in different ways.

Like from the EP 1 324 962 B1 known, the use of shrinkage-free ceramics as thermoplastic compositions has the advantage that this expansion is not required. Disadvantages of this, however, are the lower strengths of such ceramics and the fact that these are multiphase, opaque materials. In addition, the required oxidation reactions lead to longer process times for larger reactions during reaction sintering.

Electrophoretic deposition (EPD) has hitherto been carried out predominantly for the production of infiltration ceramics. In DE 100 499 74 A1 In order to compensate for the sintering shrinkage by means of EPD metallic powders are deposited and then oxidized, whereby here also a subsequent glass infiltration is necessary to close the pores formed. In DE 10 2004 018 136 B3 as in DE 102 32 135 A1 For the production of densely sintered oxide ceramics expanding stump materials are used to compensate for the occurring sintering shrinkage. In principle, with the EPD, due to the process, only uniform layers can be produced; However, no complex geometry, as it represents a dental prosthesis produce, ie it is always a second-consuming manual reworking required.

When Heißgießverfahren be used for shrinkage compensation, as from EP 1 346 702 A1 known, also used expanding models. For the expansion, however, a time-consuming molding process with a subsequent thermal process is required. In addition, the expanded models (so-called copings) are porous and therefore pose difficulties in their handling.

outgoing From this it is the object of the present invention to provide a method for the production of oxidic dental ceramics, which the does not have the disadvantages and limitations mentioned.

Especially it is intended to provide a method which is capable of producing oxidic dental ceramics without material loss or with only very little Material loss possible. This procedure is intended beyond that offer the possibility of complex geometries and very fine Manufacture crown margins.

These The object is achieved by the steps of claim 1. The subclaims describe advantageous embodiments the invention.

The The present invention achieves the stated object with a Process chain, the low-pressure injection molding, hot casting or centrifugal impression as an essential process step. In order to compensate for the sintering shrinkage occurring during sintering, must match the three-dimensional shape or its negative shape be made larger. For this it is necessary that the desired shape of the dental ceramic as numerical Data is available, for which everyone from dentistry or can use the dental technology known methods.

One The method according to the invention therefore comprises the the following process steps a) to e). Under oxidic dental ceramics Both dentures are described in relation to the present invention as well as dental fillings understood.

According to step a) form numerical data of the three-dimensional shape of the desired oxidic dental ceramics, commonly called CAD data present, the starting point for the present production process. The CAD data can here by means of a Abdruckabnahme with subsequent modeling or from an intraoral Data acquisition can be obtained.

Subsequently be according to step b) accordingly the expected later sinter shrinkage the dimensions the three-dimensional shape from step a) numerically enlarged and are then usually available as CAD data.

in the this subsequent step c) is now a Negative shape of the enlarged three-dimensional Mold made. It is crucial that this form is such is designed to consist of two, three, four or more parts consists. The negative mold itself is preferably made of a plastic or silicone.

In In a preferred embodiment, the Negtivform is directly from the enlarged three-dimensional shape produced. In particular, generative processes such as 3D printing are used for this purpose or ablative procedures such as CAD / CAM used.

In an alternative embodiment, first becomes a model the enlarged three-dimensional shape from process step b), preferably made of plastic, wax or a metal exists. Again, in particular Methods such as 3D printing or ablation methods such as CAD / CAM are used. In this model is then in a further step at least copied a negative form, which, as described above, designed in such a way is that it consists of two, three, four or more parts.

Subsequently becomes according to step d) a so-called feedstock, an oxide-ceramic powder, wax and / or paraffin and, if appropriate, contains further additives, in the according to process step c) prepared negative mold consisting of two, three, four or more Shares, introduced. The introduction is preferably carried out by means of Low pressure injection molding at a pressure of 0.01 to 10 MPa, preferably from 0.1 to 2 MPa, and at a temperature of 60 ° C to 150 ° C, preferably from 70 ° C to 120 ° C, more preferably from 80 ° C to 100 ° C. Alternatively, non-pressure casting, hot casting, or centrifugal impression suitable as a method.

After all in step e), the molding is removed from the negative mold removed and thermal, chemical and / or supercritical debind and the debindered molding then to a dense oxidic Dental ceramic sintered.

• – Bei der Verarbeitung der Keramiken entsteht kein oder nur ein sehr geringer Materialverlust.
• – Mit diesem Verfahren lassen sich sehr feine Kronenränder und komplexe Geometrien herstellen.
• – Eine direkte Einfärbung der Zahnkeramik in dentale Grundtöne ist durch geeignete Zusätze im Feedstock möglich.
• – Insbesondere bei Einsatz des Niederdruckspritz- oder Heißgießens entsteht nur ein geringer apparativer Aufwand.

The inventive method has in particular the following advantages:

• - When processing the ceramics no or only a very small loss of material.
• - With this method, very fine crown margins and complex geometries can be produced.
• - A direct coloring of dental ceramic in basic dental tones is possible through suitable additives in the feedstock.
• - Especially when using the low-pressure injection or hot casting arises only a small amount of equipment.

The Invention will be described below with reference to exemplary embodiments explained in more detail.

To determine the form fidelity and the sintering shrinkage was for the two embodiments a simplified, geometrically measurable model of a posterior full crown selected as the archetype.

Embodiment 1

With the dimensions of the original model, a CAD file was generated and milled on this database in a 5-axis milling machine from a plastic blank, an oversized original model. Here, the necessary Abkühlschwindmaß (molding temperature-room temperature) and the Sinterschwindmaß the Al ₂ O ₃ -containing Heißgießmasse of a total of 13.7% were considered from the outset, which corresponds to a linear magnification of 15.9%.

This Original model was using wax wires (diameter 0,5-5 mm) in a special holder later the feed of the mass into an evacuated cavity and thus to ensure a complete filling of the same. The instigated model was so with an addition-curing silicone poured out that finally a two-part negative form originated. The multi-part nature of the silicone mold facilitated final formability of the moldings. The silicone negative mold was after curing and Cleaning to a molding temperature of 100 ° C in one specially manufactured multipart and lockable Pre-heated metal capsule. The linear thermal expansion of the silicone became such in the production of the silicone negative mold takes into account that the silicone negative mold is voltage- and deformation-free in the metal capsule at the corresponding Impression temperature was embedded.

In an evacuable dissolver was 65.0 vol.% Of alumina powder in 35.0 vol.% of a molten thermoplastic binder mixture incorporated. The binder mixture contained a mixture of two paraffins in a ratio of 20% by weight to 70% by weight; of the to 100 wt.% Complementary content formed a dispersing aid.

The rheological behavior of the hot casting composition was characterized by a rheometer using a plate-plate-25 measurement setup. The gap width between the two plates was 0.5 mm; it was measured at a Peltier-controlled temperature of 90 ° C shear stress controlled up to 3000 Pa. The produced hot casting compound had a dynamic viscosity of 6.95 Pa · s at a shear rate of 100 s ^-1 .

For The molding process was the mass in the reservoir filled in an injection system and at a processing temperature of 100 ° C left. The required injection pressure was given by means of a hand lever press on the injection system. The mold filling was carried out under vacuum at an injection pressure of 0.49 MPa for 30 s and a holding pressure of 0.59 MPa for another 30 s.

The specimen thus prepared was removed from the mold after cooling, thermally debinded at a temperature up to 400 ° C and sintered at 1650 ° C for 3 hours. After sintering, the specimen was measured in length and width in each case flat at 5 positions. The measured values obtained were each averaged and the linear shrinkage between prototype and sintered part was calculated. The measured values determined in this way are listed in Table 1. Table 1: Average values of the measured dimensions in length and width and resulting linear shrinkage between the prototype and the sintered component of alumina: Table 1 dimension Measurements of the original form (average) Dimensions of the sintered component (mean value) Linear length change length 13,901 mm 11,997 mm -13.70% width 11.588 mm 9,986 mm -13.82%

According to table 1 were the observed changes in length -13.70% or -13.82%. This is the sintering shrinkage of the original form isotropic for length and width replication. The targeted final dimensions of the sintered ceramic crown were reached.

Embodiment 2:

With the dimensions of the original model, a CAD file was generated and stored on this database in a 5-axis milling machine milled an oversized original model from a plastic blank. Here, the necessary Abkühlschwindmaß (molding temperature-room temperature) and the Sinterschwindmaß the ZrO ₂ -haltigen Heißgießmasse of a total of 21.0% were considered from the outset, which corresponds to a linear magnification of 26.6%.

The Production of the silicone negative mold was carried out as in the exemplary embodiment 1, but the final preheating temperature the silicone mold 70 ° C instead of 100 ° C.

In an evacuable dissolver was 49.4 vol.% Of a yttrium partially stabilized Zirconia (3 mole percent yttria) in a molten state incorporated thermoplastic binder mixture. The binder mixture contained at least 90% by weight of paraffin; of 100% by weight complementary Proportion formed a dispersing aid.

The rheological behavior of the molding composition was characterized in the same manner as in Embodiment 1. The produced hot casting compound had a dynamic viscosity of 13.9 Pa · s at a shear rate of 100 s ^-1 .

Of the Shaping process was as in the embodiment 1.

The specimen thus produced was removed from the mold after cooling, thermally debinded at a temperature up to 400 ° C and sintered at 1450 ° C for 1 hour. After sintering, the specimen was measured in length and width as in Example 1. The measured values obtained were each averaged and the linear shrinkage between prototype and sintered part was calculated. The measured values determined in this way are listed in Table 2. Table 2: Average values of the measured dimensions in length and width and resulting linear shrinkage between the prototype and the sintered component made of partially stabilized zirconium oxide: Table 2 dimension Measurements of the original form (average) Dimensions of the sintered component (mean value) Linear length change length 15.184 mm 12.002 mm 20.96% width 12,666 mm 10.009 mm 20.98%

According to table 2 were the observed changes in length -20.96% or -20.98%. This is the sintering shrinkage of the original form isotropic for length and width replication. The targeted final dimensions of the sintered ceramic crown were reached.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19703177 A1 [0005]
• - DE 10337688 B3 [0005]
• - EP 1324962 B1 [0006]
• - DE 10049974 A1 [0007]
• - DE 102004018136 B3 [0007]
• DE 10232135 A1 [0007]
• EP 1346702 A1 [0008]

Cited non-patent literature

• - Article fabric for machine assistants, dental dialogue, p. 52, 2005 [0003]
• - W. Bauer and V. Piotter, Keramische Zeitschrift 56, 2004, 292-297 [0005]
• H. von Both, M. Dauscher and J. Haußelt, Keramische Zeitschrift 56, 2004, 298-303 [0005]

Claims (8)

Process for the production of oxidic dental ceramics, with the steps a) Providing numerical data of three-dimensional shape of an oxidic dental ceramic to be produced, b) Numerical enlargement of the dimensions of the three-dimensional Shape according to the expected later sintering shrinkage, c) Production of a negative mold of the enlarged three-dimensional shape, which is designed such that it out at least two parts, d) introducing a feedstock, which contains an oxide-ceramic powder in the negative mold at a temperature of 60 ° C to 150 ° C. e) Removal of a cooled mold from the negative mold, debinding and final sintering of the debinded molding a dense oxidic dental ceramic. The method of claim 1, wherein for carrying out of method step c) first a model of the enlarged three-dimensional shape from step b) is produced, into which a negative mold is copied, which is designed in such a way that it consists of at least two parts. The method of claim 1 or 2, wherein the production the enlarged three-dimensional shape or its Negative form according to method step d) by means of generative or abortive proceedings. Method according to one of claims 1 to 3, wherein the introduction of the feedstock according to method step d) in the negative mold by means of low-pressure injection molding at a pressure of 0.01 to 10 MPa and takes place. Method according to one of claims 1 to 4, wherein the introduction of the feedstock in the negative mold according to method step d) at a pressure of 0.1 to 2 MPa and at a temperature of 70 ° C to 120 ° C takes place. The method of claim 5, wherein the introduction of the Feedstocks in the negative mold according to process step d) at a temperature of 80 ° C to 100 ° C. Method according to one of claims 1 to 3, wherein the introduction of the feedstock according to method step d) in the negative mold by means of hot casting or Centrifugal impression takes place. Method according to one of claims 1 to 7, wherein the debindering of the molding according to method step e) takes place thermally, chemically or supercritically.