Ceramic or composite blank

Description

The fabrication of dental prostheses by means of CAD/CAM (computer-aided design/computer-aided manufacturing) processes has increasingly widespread use. There are a series of processes using computer-aided design/computer-aided manufacturing of dental prostheses, e.g. the milling of ceramic blanks according to 3D data sets (EP 904 743, DE 198 38 238 A1, DE 101 07 451A1, CEREC® system by Sirona Dental Systems, PROCERA® system from Degussa, LAVA® system manufactured by 3M Espe). Instead of ceramic blanks, millable composite blocks (consisting of polymer(s) and inorganic and/or organic fillers) can also be used as blanks.

In these milling processes, usually a rotatable blank is clamped into a machine tool for processing the blank by removing material (EP 160 797 B1). For this purpose, the blanks are provided with an integrated holder that enables the clamping. Such holders are described in e.g. DE 44 36 231 A1, WO 0245614, EP 455 854 B1 or EP 982 009 A2. The holders are generally discarded after use, thus wasting the ceramic or composite materials that are relatively expensive and also require complex manufacturing processes; this results in higher costs.

The process that has now been developed provides a surprisingly simple solution to this problem.

The invention concerns ceramic or composite blanks with at least one magnetic or magnetizable part mounted on it sideways. This part corresponds to the contours of at least one magnet in the clamping chuck of the machine. For the magnetic or magnetizable part and the magnet of the clamping chuck usually a flat form fit will suffice. However, this can also be a structured fit that provides additional footing. Preferably two opposite recesses are provided on the blank, into which e.g. an iron part or a steel part is inserted such that it fits accurately. The part only needs to be fixed in such a way that it does not get lost during use. Once it is clamped, it is retained in its position by pressure. For the purpose of clamping, the milling machine has a magnetic device, usually a plate on which the metal part of the blank is mounted.

FIG. 1 is a sketch of a cylindrical blank 1; wherein the magnetic part 2 is arranged in the clamping axis. FIG. 2 illustrates a similar blank with a structured part 2.