Process and apparatus for preparing a crown portion to be fixed on a tooth

• US 4,411,626 A
• Filed: 01/09/1981
• Issued: 10/25/1983
• Est. Priority Date: 01/31/1980
• Status: Expired due to Fees

• Current Assignee: Becker Dental-Labor GmbH
• Original Assignee: Becker Dental-Labor GmbH
• Inventors: Becker, Gunter, Weiden, Horst
• Primary Examiner(s): Peshock, Robert
• Application Number:
  US06/223,685
• Time in Patent Office: 1,019 Days
• Field of Search: 433/223, 433/76
• US Class Current: 433/223
• CPC Class Codes: A61C 13/0004 Computer-assisted sizing or machining of dental prostheses
• CPC Class Codes: A61C 19/04 Measuring instruments specially adapted for dentistry A61C5/44 takes precedence; testing vitality of teeth A61B5/0534; radiation diagnosis specially adapted for dentistry A61B6/51
• CPC Class Codes: A61C 5/77 Methods or devices for making crowns
• CPC Class Codes: G05B 19/4207 in which a model is traced or scanned and corresponding data recorded
• CPC Class Codes: G16H 20/40 relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture

Abstract

An apparatus and process for use in preparing a crown portion to be affixed on a tooth stump is described. A model of the tooth stump is clamped to remain immobile and scanned with a scanning head attached to a numerically controlled processing machine. Data from the scanning head indicative of the contour of the tooth stump is stored in a computer memory. From this data a contour for a casting model used to make a crown portion is calculated and stored in the computer memory. Molding material, such as wax, is placed on the tooth stump and a contour tool attached to the numerically controlled processing machine processes the molding material to produce the casting model using the calculated data. The casting model may then be used to produce a crown portion which may be further finished with a contour tool coupled to the numerically controlled processing machine using the calculated data from the computer memory.

Claims

1. In a process for preparing a dental crown portion to be secured to a tooth stump in which a model is made of the tooth stump, molding material is applied to the model and has its outer contour formed by removal of material, said molding material being thereafter removed from the model and used as a casting model for the dental crown portion, the steps of:

scanning with a scanning head for conversion into geometrical data at least part of the contour of the tooth stump;

supplying the geometrical data to a computer memory coupled to the scanning head;

calculating, from the geometrical data, the contour for the casting model, taking into account an allowance for material on the outer surface of the tooth stump and storing said data in the computer memory; and

,

guiding, according to the calculated contour for the casting model, a contour tool coupled to the computer memory along the molding material that has been applied to the model of the tooth stump whereby a casting model for a dental crown portion is formed.

2. The steps of claim 1, including the additional steps of;

placing the dental crown portion produced from the casting model on the tooth stump model; and

guiding a contour tool coupled to the computer memory on said casting model in accordance with the calculated contour of the casting model, reduced a slight measure in order to super-finish said dental crown portion.

3. An apparatus for use in preparing a dental crown portion to be secured to a tooth stump, said apparatus using a numerically controlled processing machine and comprising:

a clamping device on said processing machine for a model of a group of teeth containing a tooth stump or for a model of a tooth stump;

a scanning head on said processing machine for generating position data;

a guiding means on said processing machine for guiding the scanning head along said model;

a computer memory connected to said scanning head for storing position data generated when the scanning head is guided along the model; and

a contour tool on said processing machine controlled by said memory and movable relative to said model.

4. An apparatus according to claim 3 wherein the scanning head has a contact sensor which only allows the storage of position data in the computer memory when the scanning head contacts another object.

5. Apparatus for the preparation on a blank of a copy from an original object comprising:

a numerically controlled processing machine having a scanner for generating position data of the surface of the original object;

an electronic control device having a memory for storing said position data; and

a processing tool connected to said electronic control device and guided along a blank in accordance with the stored position data to reproduce the surface of the original object.

6. A process for producing from molding material on a tooth stump model a casting model for a dental crown, said casting model having a specified minimum thickness over all parts of the tooth stump model comprising:

fixedly mounting the tooth stump model relative to a numerically controlled processing machine;

scanning at least part of the surface of the tooth stump model to acquire data characteristic of the surface contour of the tooth stump model with a scanning head on said processing machine;

storing said data in a computer memory coupled to said machine;

applying a molding material to the tooth stump model; and

moving a contouring device on said processing machine to form a casting model from said molding material using said stored data from said computer memory to control said contouring device.

7. A process for producing a finished dental crown for insertion onto a tooth stump wherein a casting model has been produced according to claim 6 and said casting model has been used to produce the dental crown, comprising:

placing the dental crown on the tooth stump model; and

milling, with a contouring device on said processing machine, said dental crown, said contouring device being controlled by said stored data from said computer memory according to the measure used to form the casting model reduced in size a small amount, whereby rough sites and casting defects are removed from the surface of said dental crown.

8. A process for smoothing the outer surface of a dental crown, said dental crown produced from a casting model in which data characteristic of the surface of the tooth stump on which the dental crown is to be placed has been stored in a computer memory and used to control a contouring device on a numerically controlled processing machine in order to form the casting model from molding material applied to a model of the tooth stump, comprising:

placing the crown portion on the model of the tooth stump; and

milling, with a contouring device on said processing machine, said dental crown, said contouring device being controlled by stored data from said computer memory in order to mill the dental crown according to the measure used to form the casting model, reduced in size a small amount.

9. An apparatus for use in producing a casting model or a dental crown portion for a tooth stump for which a tooth stump model has been made comprising:

means for generating data indicative of the contour of the surface of the tooth stump model;

computer means coupled to said means for generating data for storing said generated data and for calculating from said stored data the outer contour of a dental crown or a casting model;

a contouring device movable relative to said tooth stump model; and

means coupled to said contouring device for moving said contouring device relative to the tooth stump model, said means coupled to and cooperating with said computer means so that material placed on said tooth stump model is formed by said contouring device according to said calculated outer contour into a dental crown or casting model.

10. An apparatus as in claim 9 wherein said means for generating data indicative of the contour of the surface of the tooth stump model comprises:

a contact sensor; and

position transmitting means for transmitting the position of said contact sensor to said computer means when said contact sensor is placed in contact with said tooth stump model.