Holding device for a ceramic blank

• US 20040072121A1
• Filed: 06/03/2003
• Published: 04/15/2004
• Est. Priority Date: 12/07/2000
• Status: Active Grant

• Current Assignee: ETH Zurich
• Original Assignee: ETH Zurich
• Inventors: Gauckler, Ludwig, Kreuder, Peter, Fecher, Stefan, Hoerhold, Heiner, Kocher, Peter, Schaerer, Peter, Luethy, Heinz, Filser, Frank
• Granted Patent: US 7,077,391 B2
• Time in Patent Office: Days
• US Class Current: 433/25
• CPC Class Codes: A61C 13/0003 Making bridge-work, inlays, implants or the like
• CPC Class Codes: A61C 13/0022 Blanks or green, unfinished dental restoration parts
• CPC Class Codes: B23Q 3/084 using adhesive means

Abstract

A holding device (42) comprises a cylindrical or prismatic, porous ceramic blank (10) and means for clamping in a machine tool for processing the blank (10) by removing material, in order to produce a ceramic workpiece (18). A narrow frame (12) is fixed by an adhesive connection over at least part of the periphery of the blank (10), which is held without stresses, in the area of a plane encompassing the longitudinal middle axis (A) of the blank. Said frame (12) only covers a small part of the surface of the blank (10) and can be detached and held in a stable holder (24) with a clamping adapter (34), in such a way that it cannot slide. The entire combination is fixed in the machine tool in such a way as to be resistant to twisting and sliding. The ceramic workpiece (18) emerges continuously from the ceramic blank (10) without predetermination of the advance direction, until holding segments (20) which can then only be freely selected according to number and location have been formed. Said holding segments (20) end on the residual material of the blank in the area of the frame (12) or on the frame (12) itself. The holding device is used especially as a workpiece (18) for producing fully ceramic dental prostheses, particularly crowns or bridges.

Claims

1. Holding device (42) comprising a cylindrically or prismatically formed, porous ceramic blank (10) and means for clamping the holding device in a machine tool for the material-removing machining of the blank (10) to produce a ceramic workpiece (18), characterised in that a narrow frame (12) is fastened in an adhesive bond over at least a part of the periphery of the blank (10) which is held without tension in the region of a plane comprising the longitudinal central axis (A) of the blank (10), the frame (12) covering a small part of the surface of the blank (10) and in turn being held detachably and secured against slipping in a stable holder (24) with a clamping adapter (34), and this combination is fastened non-rotatably and secured against slipping in the machine tool.

2. Holding device (42) according to claim 1, characterised in that the blank (10), perpendicular to the longitudinal central axis (A), is round or polygonal in design, with two parallel side faces, in particular square, rectangular, hexagonal or octagonal.

3. Holding device (42) according to claim 1 or 2, characterised in that the green or sintered-on ceramic blank (10) consists of one or more metal oxides, preferably Al₂O₃, TiO₂, MgO, Y₂O₃ and/or zirconium oxide mixed crystal.

4. Holding device (42) according to any one of claims 1 to 3, characterised in that the frame (12) covers at most 25%, preferably at most 15%, of the surface of the blank (10) to be machined, and/or has a thickness (d) of preferably 1 to 8 mm, in particular 3 to 6 mm.

5. Holding device (42) according to any one of claims 1 to 4, characterised in that the frame (12) has a width (b) of 3 to 10 mm or even up to 20 mm on a longitudinal or narrow side, but is otherwise regularly formed.

6. Holding device (42) according to any one of claims 1 to 5, characterised in that the frame (12) is closed or U-shaped in design with sides extending over substantially the entire length of the blank (10).

7. Holding device (42) according to any one of claims 1 to 5, characterised in that the frame (12) consists of sections adhering to the blank (10) and connected to one another, adjacent to one another or preferably at a slight distance from one another.

8. Holding device (42) according to any one of claims 1 to 7, characterised in that the narrow gap (14) between the frame (12) or its individual parts and the blank (10) is filled with a bonding agent (16), preferably with a glue.

9. Holding device (42) according to any one of claims 1 to 8, characterised in that suitable faces for receiving the holder (24), in particular spheres, pyramids, hemispheres, dovetails and/or roof shapes are formed on the exposed part of the frame (12).

10. Holding device (42) according to any one of claims 1 to 9, characterised in that information which can be read optically or by machine, in particular the shrinkage factor and/or the green density, is provided on the exposed part of the frame (12).

11. Holding device (42) according to any one of claims 1 to 10, characterised in that the frame (12) is held in a mechanically stable holder (24) with a clamping force not acting on the blank (10), and comprises a clamping adapter (34) for the machine tool, in particular a mandrel with a rotation prevention device (36) for insertion or a plate to be flanged-on.

12. Holding device (42) according to claim 11, characterised in that the holder (24) comprises a closed frame with a lower holding part (26) and an upper holding part (30) or two clamping jaws for receiving the frame or parts thereof.

13. Method for the material-removing machining of a blank (10) in a holding device (42) according to any one of claims 1 to 12, characterised in that a preselected workpiece (18) is continuously exposed from the ceramic blank (10) without preselection of the feed direction until only holding webs (20) are formed which are freely selectable according to number and position and which end directly on the residual material of the blank in the region of the frame (12) or on the frame (12).

14. Use of a holding device (42) according to any one of claims 1 to 12 for producing solid ceramic tooth replacement, in particular tooth crowns or tooth bridges, as the workpiece (18).