Abstract: The invention relates to cast parts which contain at least 87 wt. % silicon nitride and up to 13 wt. % of an additive combination comprised of Al2O3 and Y2O3. The initial composition of the mass formulation starts with Y2O3/Al2O3 ratios of less than 1.1, preferably with Y2O3 Al2O3 ratios of 0.2 to 1.09. 1% to 20% of the Y2O3 portion can thus be substituted by an additional element group of IVb of the periodic table or by the oxide thereof. The cast parts can comprise up to 1.0 wt. % HfO2 and/or ZrO2. Said cast parts preferably have a thickness >98% of the theoretic thickness. At room temperature, the bending strength of the inventive cast parts amounts to ≧1100 MPa and amounts to ≧850 MPa at 1000° C. The inventive cast parts correspond to the formula Si6-zAlzOzN8-z. The degree of substitution z thus amounts to 0.20 to 0.60, preferably from 0.22 to 0.54, especially from 0.3 to 0.35.

Abstract: A hip joint prosthesis has an external metal shell, an internal socket insert in which a ball head can rotate. The ball head is joined to a metal prosthesis shaft of the femoral shaft component and the movement of the prosthesis shaft is limited by abutting against the margin of the socket insert. A soft, biocompatible cushioning element is applied to the socket insert on the circumferential surface of the prosthesis shaft.

Abstract: External electrodes on piezoceramic multilayer actuators, composed of a layer of a basic metallization applied to the ceramic material of the surface of a actuator, to which metallization there is joined by means of a joining layer a reinforcing layer to which a connecting wire is soldered, wherein the layer of basic metallization is structured by discontinuities or recesses.

Abstract: Joint prostheses which have one joint partner configured as a socket and the other joint partner configured as a ball head generally consist of two components. The socket is comprised of a metallic outer cup in which an insertion cup made of ceramic material or of a biocompatible plastic is inserted. The shaft has a peg, the so-called cone, on which a ball head is placed. The press fit connection, especially so-called conical pressing, is used as a connection technique between the respective components. Stress can result in a relative movement between the components, thus leading to a wear-related loosening of the connection thereof. In order to solve this problem, the invention provides that, from the prosthetic components (2, 3), the component (3) made of ceramic or plastic fitted with a covering (6), said covering being made of a biocompatible metal or of a biocompatible metal alloy, on the pressing surface (7) thereof via which said component (3) is connected to the metal component (2).

Abstract: During operation, large tensile stresses act on the insulating region under the base metallization with external electrodes on piezoceramic multilayer actuators. Since this insulating region forms a homogeneous unit together with the base metallization and the interconnecting layer, this fails when the tensile strength of the weakest element is exceeded and cracks develop. The cracks running unchecked through the insulating region are very critical, since they reduce the insulation distance and seriously increase the probability of actuator failure due to flashovers. According to the invention it is therefore proposed that, in the inactive region (14), the surface (10) of the multilayer actuator (1) has a pattern (18) that is produced by erosions (19) interrupting the surface (10), and that the base metallization (11) is deposited exclusively on the surface (10) left by the pattern (18).

Abstract: The invention relates to a reversible cutting plate made from ceramic material for chucking in a cutting tool for machining cast materials, with each corner of the reversible cutting plate (9) having a minor cutting edge (5a, 5b, 5c, 5d) and a major cutting edge (4a, 4b, 4c, 4d). In order to remove cast-material shavings from the cutting edge, it is proposed that the corners of the reversible cutting plate (9) be ground, pressed or injected into approximately ¼ of the diagonal plane (D) and form a triangular face (3) and the triangular face (3) have at least one incline.

Abstract: Joint prostheses, in which one joint partner is formed as a socket and the other joint partner is formed as a spherical head which is rotatably mounted in the socket, are known in particular as shoulder-joint and hip-joint prostheses. The force-fit connection, in particular conical jamming, is also used here as the connecting technique between metallic or ceramic spherical heads and the cone. A coupling element (6) is inserted between the cone (5) and the spherical head (3) of the force-fit connection (1). The elasticity and damping properties of the coupling element (6) can be predetermined by its porosity and the structure of its surface.

Abstract: Conventional modular sockets for ball joint prostheses usually consist of a metal socket housing and a skid-type shell inserted in the housing. Ceramic skid-type shells are usually press-fitted in the socket housing. The socket housing may become stiff, thereby causing a migration of the generic sockets. If the skid-type shell is inserted improperly, material may chip off at the edge of the skid-type shell. Due to the various designs of sockets, skid-type shells with different outer diameter have to be made available for every gliding surface diameter. The invention provides for a ceramic skid-type shell (2) that is rigidly inserted into a biocompatible metal ring (5). Said ring (5) is provided with at least three radially outwards extending fixing elements (6). Said fixing elements (6) engage with respective recesses (8) in the socket housing (7). The ring (5) is spaced apart from the socket housing (7) by a gap (14).

Abstract: A protective cap for prosthetic joints having one element in the form of a ball head, especially in the case of hip end-prosthetic joints, protects the ball head when it is positioned and fixed on the cone of the shank by the surgeon by hand. A crown is arranged on the pole of the protective cap. The crown is in the form of a plate for, the shape of the plate and its extent relative to the protective cap being such that it is possible to grip behind the plate on the side that faces the protective cap.

Abstract: The invention relates to cast parts which contain at least 87 wt. % silicon nitride and up to 13 wt. % of an additive combination comprised of Al2O3 and Y2O3. The initial composition of the mass formulation starts with Y2O3/Al2O3 ratios of less than 1.1, preferably with Y2O3 Al2O3 ratios of 0.2 to 1.09. 1% to 20% of the Y2O3 portion can thus be substituted by an additional element of the group IVb of the periodic table or by the oxide thereof. The cast parts can comprise up to 1.0 wt. % HfO2 and/or ZrO2. Said cast parts preferably have a thickness >98% of the theoretic thickness. At room temperature, the bending strength of the inventive cast parts amounts to ≧1100 MPa and amounts to ≧850 MPa at 1000° C. The inventive cast parts correspond to the formula Si6−zAlzOzN8−z. The degree of substitution z thus amounts to 0.20 to 0.60, preferably from 0.22 to 0.54, especially from 0.3 to 0.35.

Abstract: A method tests a ceramic socket insert of a hip joint endoprosthesis in which, in use, a spherical head articulates against a functional inner surface of a ceramic socket insert which is anchored in a pelvic bone by means of a socket housing. The method includes providing the ceramic socket insert in a holding arrangement, applying a predetermined pressing force to a predetermined sub-area of the functional inner surface of the ceramic socket insert, and applying a supporting force to a sub-area of an outer surface of the ceramic socket insert to counteract the pressing force. The predetermined sub-area of the functional inner surface symmetrically surrounds a pole of the inner surface of a ceramic socket insert. The predetermined force is such that stresses generated in the ceramic socket insert are higher than stresses generated in the case of a physiological load.

Abstract: The well known slip casting process for the production of ceramic green parts, in which hardening is achieved by water removal with porous molds, is characterized by disadvantages in terms of strength, shrinkage during drying and problems with cracking during drying. The present invention avoids these disadvantages and produces ceramic green parts by changing the surface potential of powder particles in the slip instead of by removing water. Further more the coagulation strength is increased by adding polymers or extremely fine divided colloidal particles.

Abstract: An instrument for manipulating, detachably holding and placing an insert portion of a joint socket prosthesis into an outer shell of a said prosthesis. The instrument includes a handle and a holding tool. The holding tool includes two or more grasping claws which extend radially from the longitudinal axis of the handle over the insert, and serve to engage the insert to the holding tool. The handle is elongated and slideably positioned within a longitudinal bore or hole in the holding tool and typically includes a plunger. The insert is released when an operator causes the handle to slide within the holding tool towards the insert with sufficient force to disengage the insert from the grasping claws.

Abstract: The invention relates to a sintered shaped body comprising a matrix material that contains an aluminum oxide/chromium oxide mixed crystal and an additional mixed crystal selected from at least one mixed crystal according to one of the general formulas La0.9Al11.76−xCrxO19, Me1Al11−xCrxO17, Me2Al12−xCrxO19, Me2′Al12−xCrxO19 and/or Me3Al11−xCrxO18, wherein Me1 stands for an alkali metal, Me2 represents an alkaline earth metal, Me2′ stands for cadmium, lead or mercury and Me3 represents a rare earth metal and x has a value ranging from 0.0007 to 0.045.

Abstract: Prostheses with artificial joints have only a few metallic and ceramic materials whose compatibility with human or animal tissue has been established. These materials, however, cannot be combined with one another in any manner if a friction pairing occurs as a result, for example, in the case of artificial joints. With artificial joints, joint partners are required to have good mechanical properties as well as tribological properties. According to the invention, a sintered material is thus provided which is comprised of zircon oxide with an addition of 0.1 to 40 wt. % aluminum oxide. This sintered material enables an artificial joint of a prosthesis whose other ceramic materials are comprised of aluminum oxide or zircon oxide with the given proportions of aluminum oxide to be assembled with joint partners.

Abstract: A knee-joint prosthesis comprising a tibial component fixed to the proximal tibia, a femoral component fixed to the distal femur, the femoral component having condylar bearing sections which cooperate in an articulated manner with tibial bearing sections of said tibial component, and an anterior plate section of said femoral component which touches the patella or a patella component fixed to the patella.

Abstract: A hip-joint socket of a hip-joint endoprosthesis is provided, in which the bearing shell of the socket that mounts the ball head of the shaft is made of a ceramic material. The bearing shell (2) of the hip-joint socket (1; 11), in the region of its surface (4) with which it is inserted into the hip bone, is covered with a coating (5; 15) that is made of a biocompatible metal or a biocompatible metal alloy.

Abstract: A knee-joint endoprosthesis includes a metallic femoral part (2) anchored in the femur that articulates with a tibial part anchored in the tibia bone, the articulating surface of the femoral part (2) being a ceramic structural member (3) that is connected to the femoral part (2) in a mechanically stable manner. The attachment of the ceramic structural member (3) to the femoral part (2), can be accomplished by using a conical clamping device, by use of a fixing screw, by shrinking, soldering or welding it on, or by vapor deposition or spray application.

Abstract: A monolithic multi-layer actuator includes a sintered stack of thin films of piezoceramic material with metallic internal electrodes which lead out of the stack (2) in alternate directions and are connected electrically in parallel by way of external electrodes, with the external electrodes on the contact sides of the stack consisting of an applied basic metallisation and being connected to electrical connection elements preferably by way of soldering. In order to avoid failures of the actuator during dynamic loads it is suggested that an electroconductive electrode which is structured to be three-dimensional in structure be arranged between the basic metal lining and the connection elements, which electrode is connected to the basic metallisation by way of partial contact points and is constructed to be expandable between the contact points.

Abstract: The well known slip casting process for the production of ceramic green parts, in which hardening is achieved by water removal with porous molds, is characterized by disadvantages in terms of strength, shrinkage during drying and problems with cracking during drying. The present invention avoids these disadvantages and produces ceramic green parts by changing the surface potential of powder particles in the slip instead of by removing water. Further more the coagulation strength is increased by adding polymers or extremely fine divided colloidal particles.