Method of manufacture of dental prostheses and auxiliary elements

Dental prostheses, such as crowns, bridges, inlays, consist regularly of complex moldings, which mostly take into account on the one hand the spatial configuration of preserved tooth parts (tooth stumps), lost whole teeth or parts of the jaw, and on the other hand the spatial situation with respect to neighboring and / or antagonistic teeth have to. According to the prior art, such dentures are produced in complex processes. The most widespread is the production of the required moldings - mostly made of precious metal - or non-noble metal alloys as well as pure metals - in a multi-stage molding and casting process. However, the data-controlled milling of such shaped bodies from the full material has also become known, which inevitably results in considerable waste, which has to be reworked in a complex manner or causes high costs.

Out <patcit id="pcit0001" dnum="FR22754704"><text>FR 22 754 704</text></patcit> A method for producing a dental implant is known, in which an impression of the bone cavity of an extracted tooth is taken, this impression is recorded digitally and subsequently a polymer is hardened in layers from the digitally recorded data by means of a stereolithographic method which contains zirconium oxide particles. The hardened plastic blank is subsequently burned out in a heat treatment process, so that a ceramic particle framework remains and this is sintered in a further heat treatment process in order to harden the tooth root implant. The method has the disadvantage that a complex manufacturing technique is used and for which a complete burnout of the plastic material cannot be achieved. The products that can be achieved with this process have a residual porosity that does not allow their use in the heavy-duty tooth contact area, because the strength of the porous ceramic is not sufficient for this.

Out <patcit id="pcit0002" dnum="US4863538A"><text>US 4,863,538</text></patcit> A selective laser sintering method is known in which a powder, which comprises plastic, metal, ceramic or polymer substance, is cured with a laser. The disadvantage of this method is that it is not possible to produce sufficiently dense and thus sufficiently resilient products, and extensive mechanical post-processing and thermal post-treatment are required to achieve the tight tolerances and strengths required in the dental implant area.

The aim of the invention is to show another, more advantageous way of producing moldings of this type. For this purpose, it uses another method, namely for the production of complex tools or components known as "rapid prototyping", in which the shaped bodies are built up layer by layer from a sinterable powder by successively giving each layer of the powder an energy which leads to local sintering is exposed to a laser beam, the guidance of the laser beam over the respective powder layer being subject to control by data, which represent the configuration of the shaped body in this layer. The energy supply causes the powder constituents concerned to melt on the surface and form a firm bond with one another. Due to the narrow focus of the laser beam - with high density - the energy supply can be configured very precisely and accordingly controlled accordingly by the stored spatial data of the desired shaped body.

The invention further provides that the powder consists of a biocompatible material with different grain sizes between 0 and 50 microns. In contrast to the previous application of the laser sintering process for technical applications, this is intended to ensure that the shaped body intended for dental purposes is compatible with human tissue (cf.<i>Hoffmann ax helmet,</i> Lexicon of dentistry, 6./11. Ed., P. 97 and<i>Newbie,</i> Biocompatibility of dental alloys). The grain size curve ensures a particularly dense sintering with the advantage of high pressure resistance of the molded body and less formation of cavities which would be susceptible to the formation of bacterial cultures; it also defines the size and accuracy of the restoration.

However, it is also possible to carry out the precise local compacting of the powdery starting material in another way, be it by means of a different type of energy supply. In general, however, optically focusable electromagnetic radiation will be preferable to other measures - such as corpuscular radiation to be carried out in a vacuum - for the energy transmission.

Due to its certain roughness, the sintered surface of the molded article produced according to the invention is particularly well suited for the frequently desired veneering by means of ceramic or other materials, as is the case, for example, with crowns or bridges. Furthermore, as a result of the fact that it is possible to exert an influence on the file which effects the control, it is possible to make corrections to the configuration of the shaped body, which may appear desirable for a wide variety of reasons (compared to the scanned result).

Preferably the powder consists of an alloy with substantially equal proportions of the alloying constituents in each powder grain. This represents a great advantage over the conventional production of dental moldings from molten alloys, because there is no risk of the alloy components separating in the melt and / or the cast moldings. In addition, the production of semi-finished products from certain alloys, which can be used particularly advantageously for dental purposes, requires complicated and costly process measures, such as suction casting, while pulverizing such alloys is considerably less expensive. However, while a melt produced from such powder (for the subsequent production of cast moldings) is in turn subject to the risk of segregation and thus inhomogeneity, a molded body sintered according to the invention maintains its uniform distribution of the alloy components.

A metal powder of the following composition has proven itself for use in the method according to the invention, without the method being restricted to this:<ul id="ul0001" list-style="none"><li>Ni61, 4Cr22, 9MO8, 8Nb3, 9Fe2, 5MnO, 4TiO, 1</li></ul>