Ceramic mixture for producing moulded articles, methods for the production thereof, and use thereof
The present invention relates to a ceramic mixture which is suitable for producing moulded articles, preferably dental moulded articles, and to methods for producing the ceramic mixture. The invention also relates to the use of a ceramic mixture for producing moulded articles, preferably dental moulded articles, in particular dental restorations, such as an inlay, onlay, veneer, crown, bracket, bridge, framework, abutment or implant. The invention also relates to methods for producing a moulded article, preferably a dental moulded article comprising applying a ceramic mixture to a carrier or to a positive model, and solidifying the moulded articles thus obtained by gel formation, preferably by means of a standard 3D printer capable of processing paste-like materials. The gel-like moulded article thus obtained can be worked in the gel-like and/or dried state. In a preferred embodiment, the paste-like materials are applied such that the moulded article has an inner layer consisting of a first ceramic material and an outer layer consisting of another ceramic material. The paste can be applied in horizontal layers and/or points and in vertical layers and/or points. The moulded article is preferably a dental moulded article.
1 . A method for producing a moulded article, comprising the following steps:
(a) applying a first ceramic mixture to a carrier or to a positive model, wherein a moulded article is obtained;
(b) solidifying the obtained moulded article by gelation to form a moulded article; and
(c) optionally repeating steps (a) and (b) with a second or further ceramic mixture which has the same composition as the first ceramic mixture or a different one,
wherein each of the ceramic mixtures comprises the following components: an uncoloured and/or a coloured ceramic powder based on ZrO 2 , Al 2 O 3 , zirconia toughed alumina (ZTA), alumina toughed zirconia (ATZ), B 4 C, SiC, or Si 3 N 4 , wherein the ZrO 2 is stabilized, and/or an uncoloured and/or a coloured ceramic granule based on ZrO 2 , Al 2 O 3 , zirconia toughed alumina (ZTA), alumina toughed zirconia (ATZ), B 4 C, SiC, or Si 3 N 4 , wherein the ZrO 2 is stabilized, and/or combinations thereof based on ZrO 2 , Al 2 O 3 , zirconia toughed alumina (ZTA), alumina toughed zirconia (ATZ), B 4 C, SiC, or Si 3 N 4 , wherein ZrO 2 is stabilized;
at least one dispersing agent;
at least one hydrocolloid selected from the group consisting of carubin, gellan gum, hydroxypropyl guar, agarose, carrageenan, alginate, dextran, starch, gum arabic, galactomannans, glucomannan, xanthan, scleroglucan, caseinate, or mixtures thereof; and
at least one solvent.
2 . The method according to claim 1 , wherein in step (b) the solidification of the moulded article by gelation is carried out by adding a metal salt solution, by setting from −50° C. to 120° C. and/or by in situ gelatinization.
3 . The method according to claim 1 , wherein in step (b) the solidification of the obtained moulded article by gelation is started by one or more of the following steps:
(b1) wetting a ceramic mixture according to claim 1 by a syringe and/or by an extruder and/or by atomization and/or by immersing the moulded article in a metal salt solution; or
(b2) going below a specific temperature, wherein the moulded article is cooled to a temperature of less than 35° C.; or
(b3) exceeding a certain temperature, wherein the moulded article is heated to a temperature higher than 35° C.; or
(b4) in situ gelatinization, wherein the moulded article, which contains a calcium salt with low solubility is mixed with an acidifying agent.
4 . The method according to claim 1 , wherein in step (a) a ceramic mixture is applied onto generated positive models by material deposition,
(a1) by a syringe-stamp system and/or by an extruder system; and/or
(a2) wherein a surface of the positive model is additionally provided with a release agent so that the cured moulded article can be removed more easily from the surface of the positive model; and/or
(a3) the application is carried out continuously; and/or
(a4) layers with a thickness from 0.01 mm to 5 mm are applied.
5 . The method according to claim 1 , wherein the obtained moulded article is post-processed in a further step (d) by at least one subtractive process in a green state prior to sintering.
6 . A method for producing a printed dental restoration, comprising the following steps:
(a) printing or milling out the dental restoration from a dimensionally stable material, which is used as a positive model in the subsequent printing process;
(b) modelling an inner dentin core as well as an outer enamel layer based on a scanned tooth via CAD software or by virtual predefined tooth restorations;
(c) separating a moulded tooth restoration into horizontal layers;
(d) preparing path and milling strategies for the application as well as subsequent removal of the printed (ceramic) materials used;
(e) reapplying a release agent described herein to the correspondingly overdimensioned, dimensionally stable dental restoration;
(f) printing a virtually created tooth restoration, which has been separated into horizontal layers, on the previously created overdimensioned, dimensionally stable positive model according to the method described herein;
(g) solidifying the dental restoration by gelation according to to one of the steps (b1), (b2), (b3), or (b4) as defined in claim 3 ;
(h) drying the printed dental restoration;
(i) machining the surface of the printed dental restoration; and
(j) sintering the printed dental restoration.
7 . The method of claim 1 , wherein the first ceramic mixture comprises at least one anti-drying agent, wherein the anti-drying agent comprises ethylene glycol and/or glycerol.