Production of replacement teeth from a three-dimensionally determined and digitised positive model

• US 20040158342A1
• Filed: 12/19/2003
• Published: 08/12/2004
• Est. Priority Date: 07/13/2001
• Status: Active Grant

• Current Assignee: Degudent GmbH
• Original Assignee: Degudent GmbH
• Inventors: Volki, Lothar, Fecher, Stefan, Wolf, Dietrich, Pest, Andrea
• Granted Patent: US 6,970,760 B2
• Time in Patent Office: Days
• US Class Current: 700/98
• CPC Class Codes: A61C 13/0004 Computer-assisted sizing or machining of dental prostheses
• CPC Class Codes: A61C 5/77 Methods or devices for making crowns

Abstract

The invention relates to a method for the production of replacement teeth (5) from a three-dimensionally determined and digitised model, whereby for improved handling, cost and quality of the thus produced replacement tooth (5) a method comprising the following steps is disclosed: inputting the data for the digitised model, treating the inner surface (9) of the surface model with a given offset value to generate a cement gap (7, 8) between the tooth replacement (5) to be and tooth stump (1, 2) and calculation of a programme for machining the blank or a mould by means of a machine tool.

Claims

1. A method for the production of a dental prosthesis (5) to be fastened to a tooth stump (1;

2) consisting of a three-dimensionally mapped and digitized positive model which comprises the following steps;

inputting the data of the digitized positive model;

machining the inner surface (9) of the positive model with a preset offset value to form a gap (7, 8) between a future dental prosthesis and tooth stump (1, 2), and

calculating a program for processing a blank by a machine tool for producing the dental prosthesis.

characterized in that

as material for the dental prosthesis (5) one is employed which has, in normal use of the prosthesis, a maximum tensile stress occurring which corresponds to about 0.1-0.7 times the tensile strength of the material used.

2. A method according to claim 1,

characterized in

that the dental prosthesis is prepared in such a way that the maximum tensile stress in the dental prosthesis corresponds to ≦

0.5 times, in particular 0.2-0.5 times the tensile strength of the material used.

3. A method according to claim 1,

further characterized by the following procedural steps:

calculation of the wall thickness of the data model by comparing the data of the inner surface (9) of the positive model with the outer surface (12) of the positive model and comparison of the value of the wall thickness with a wall thickness minimum value, correcting the data of the outer side (12) of the positive model that that at least the wall thickness minimum value is obtained and/or a warning is issued.

4. A method according to claim 3,

characterized in

that the wall thickness minimum value is at least about 0.05 mm, preferably about 0.05 mm-1.0 mm, in particular 0.1 mm-0.8 mm.

5. A method according to claim 4,

characterized in

that the wall thickness minimum value is at least 0.3 mm.

6. A method according to at least one of the preceding claims,

further characterized by the following step:

calculation of the material cross-section in bridge elements in the area (13, 14) between two posts formed by the tooth stumps (1, 2), comparison of the cross-section with a minimum value, correction of the data of the outer side (12) of the positive model so that at least the minimum value is obtained and/or a warning is issued.

7. A method according to claim 6,

characterized in

that the minimum value of the cross-section is at least about 2 mm², preferably about 2 mm²-7 mm².

8. A method according to claim 7,

characterized in

that the minimum value of the cross-section is at least 7 mm².

9. A method according to claim 1,

characterized in

that the offset value is preset dependent on the axis.

10. A method according to at least one of the preceding claims,

characterized in

that the offset value is up to 150 μ

m.

11. A method according to at least one of the preceding claims,

characterized in

that the offset value on the periphery of the cavity is about ≦

5 μ

m, preferably about ≦

2.8 μ

m, in particular ≦

1.5 μ

m.

12. A method according to at least one of the preceding claims,

further characterized by the following step:

conduction of a plausibility test of the data with reference to the data of adjacent areas of the positive model and, optionally, issuance of a warning.

13. A method according to at least one of the preceding claims,

further characterized by the following step:

replacement of missing, preferably individual, data points or non-plausible data points by interpolated values with reference to the data of adjacent areas of the positive model.

14. A method according to at least one of the preceding claims,

further characterized by the following step:

conduction of a test of the data of the inner surface (9) of the positive model for undercuts with reference to the data of adjacent areas and, optionally, issuance of a warning.

15. A method according to at least one of the preceding claims,

further characterized by the following step:

smoothing the outer and/or surface (12) of the data model by means of a smoothing function.

16. A method according to at least one of the preceding claims,

further characterized by the following step:

calculation of the radii of the inner surface of the surface model, comparison of the values of the radii with a minimum radius, correction of the data of the inner surface of the positive model so that the cavity is enlarged until at least the minimum radius is obtained and/or a warning issued.

17. A method according to at least one of the preceding claims,

further characterized by the following step:

machining the positive model with a preset offset value to adapt it to the tool contour during the subsequent processing.

18. A method according to at least one of the preceding claims,

further characterized by the following step:

processing the data of the positive model with an enlargement factor to compensate shrinkage or swelling of the material for the dental prosthesis during production.

19. A method according to at least one of the preceding claims,

characterized in

that the enlargement factor is anisotropic and/or non-linear over the surface model.

20. A method according to at least one of the preceding claims,

characterized in

that the enlargement factor over the surface model is determined by a three-dimensional transfer function f(x, y, z) .

21. A method according to at least one of the preceding claims,

characterized in

that the three-dimensional transfer function f(x, y, z) is determined by the three-dimensional density distribution F(x, y, z) of a ceramic blank.

22. A method according to at least one of the preceding claims,

characterized by

reading from a data carrier the transfer function f(x, y, z) or density distribution F(x, y, z) allocated to a blank to be processed.

23. A method according to at least one of the preceding claims,

characterized in

that the data carrier is a bar code label, a transponder label or a data bank which can be accessed via identification means applied to or supplied with the blank.

24. A method according to at least one of the preceding claims,

further characterized by the following step:

comparison of the radii of the outer and/or inner surfaces of the positive model with a minimum radius of at least about 0.1 mm, preferably about 0.2 mm, in particular 0.3 mm,

correction of the data of the outer and/or inner surface of the positive model to the minimum radius and/or issuance of a warning.