Method of manufacture of dental prostheses and auxiliary elements

Dentures such as crowns, bridges, inlays and. Like., Regularly consists of complex moldings which usually one hand receive the spatial configuration retarded tooth parts (stumps), lost whole teeth or parts of the jaw and on the other hand, the spatial situation with respect to adjacent and / or must consider antagonistic teeth individually. According to the prior art of such dentures manufactured in expensive processes. spread well most is the production of the required molding - mostly from precious or non-precious metal alloys and pure metals - in a multistage molding and casting processes. but became famous also the data-driven milling such moldings from the solid material, which inevitably have a major drop has the consequence that must be reprocessed or consuming, high cost.

From FR 22754704 a method for manufacturing a dental implant is known, in which an imprint of the bone cavity of an extracted teeth is taken, this print is recorded digitally and is then cured as following from the digitally recorded data layer, a polymer by means of a sterevlithographischen method which zirconium oxide contains. The cured plastic blank is subsequently burned in a heat treatment process, so that a ceramic framework particles remains and this is sintered in a further heat treatment process to harden the tooth root implant. The method has the disadvantage that a complicated manufacturing technique is used and at which a complete combustion of the plastic material can not be obtained. The advantages attainable with this process products exhibit porosity which permit not use in heavy-duty Zahnaufbereich, since the strength of the porous ceramic is not sufficient for this purpose.

From US 4,863,538 a selective laser sintering technique is known in which a powder, which includes plastic, metal, ceramic or polymer material is cured using a laser. The disadvantage of this method is that no sufficiently dense and thus sufficiently loadable products can be produced and to the extensive mechanical post-processing and thermal post-treatments are required to achieve the required tight tolerances in the tooth implant area and strength.

Object of the invention is to show a different, more advantageous way of producing such moldings (and especially required in implantology dental auxiliary parts). It makes use of to an otherwise, namely for the manufacture of complex tools or components under the name "rapid prototyping" become known method in which the molding of a sinterable powder layer by layer by successively each layer of the powder a leading to local sintering energy a laser beam is exposed, wherein the guide of the laser beam over the respective powder layer is subject to control by data which represent the configuration of the molded body in this layer. By the power supply to each affected powder ingredients are melted superficially and go together form a stable bond. Due to the close focusing the laser beam can be - with high density - configure the power supply very accurate and hence control in accordance with the stored spatial data of the desired molded article.

The invention further provides that the powder consists of a biocompatible material of varying particle size between 0 and 50 microns. Unlike the previous application of the laser-sintering process for technical applications is to ensure in this way that the particular for dental purposes moldings with compatible human tissue (see FIG.<i>Hoffmann-Axthelm,</i> Dictionary of Dentistry, 6./11. Ed., P 97 and<i>Reuling,</i> Biocompatibility of dental alloys). The grain size curve ensures a particularly dense sintering with the advantage of high pressure resistance of the molding and less formation of voids, which would be susceptible to the formation of bacterial cultures; it also establishes the size and fit of the restoration.

However, it is also possible to perform the precise local compacting the powdery raw material in other ways, either through other types of power supply, or - in the case of plastics as a raw material - by localized polymerization control. In general, however, an optically focusable electromagnetic radiation other measures - such as, to be made in a vacuum corpuscular - be preferable for the energy transfer.

The sintered surface of the molding according to the invention is due to their certain roughness particularly well suited for the often desired veneering by means of ceramic or other materials, as is the case for example with crowns or bridges. Further, it is not difficult due to the possible influence on the - the control effecting - file possible to make corrections to the configuration of the molding that may be desirable for various reasons (compared to the sampled result).

Preferably, the powder consists of an alloy with substantially equal amounts of the alloy constituents in each powder grain. This constitutes a great advantage over the conventional production of dental moldings from molten alloys because there is no risk of separation of the alloy constituents in the melt and / or the cast shape body consists. Moreover, the manufacture of semi-finished products from certain alloys which are particularly advantageously used for dental purposes, complicated and expensive process steps, such as the Saugguß while pulverizing such alloys is much less complex. While but a melt prepared from such powders (for subsequent manufacture of cast moldings), in turn, is subject to the risk of separation, and thus inhomogeneity, retains an inventively sintered molded body at its uniform distribution of the alloy components.

a metal powder of the following composition has proved for use in the present process without the method being limited thereto:<ul><li>Ni61, 4Cr22, 9M08, 8Nb3, 9Fe2, 5Mn0,4Ti0,1</li></ul>