Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2002-01-31
2004-07-20
Picard, Leo (Department: 2121)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S118000, C433S213000
Reexamination Certificate
active
06766217
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of manufacturing a dental prosthesis by utilizing a CAD/CAM device. Also, the present invention relates to a method and device for placing an object so that an objective surface of the object does not overhang when a surface shape of the object is measured.
THE BACKGROUND ART
An attempt has been made to introduce a method of manufacturing a dental prosthesis by using the technique of CAD/CAM into the field of dentistry. In order to obtain a prosthetic shape from the oral cavity, a means for obtaining the prosthetic shape by taking an impression model is effective although it is apparently complicated because it is a method, as a usually adopted dental technical means, by which a precise shape of a dental prosthesis is obtained in a short period of time.
On the other hand, the calculating capacity of a computer has been enhanced and further the price has been reduced, the techniques of CAD/CAM have come into wide use, and manufacturing a dental prosthesis by utilizing the combination of the technique of CAD/CAM has come into practical use.
In this connection, in the case where a dental prosthesis for a small decayed portion of a tooth such as an inlay is manufactured, it is possible to directly mold the decayed portion of the tooth and take it out as a model. However, since the shape of such a dental prosthesis is indefinite, even if the small decayed portion is molded and taken out as a model, it is necessary to mark a contact margin portion coming into contact with a tooth and also it is necessary to mark a portion which becomes a surface of the tooth. Since the dental prosthesis concerned is very small and its shape is indefinite, it is complicated to directly measure the surface of the dental prosthesis.
As a method of making a three-dimensional measurement of an object, there are provided a laser beam method, a contact method, a gray scale method, a moire method and so forth. However, when the measurement is made in one direction, if the object has an overhang portion, it is impossible to measure a portion shaded by the overhang portion. In this case, the overhang portion means a portion which protrudes in a direction perpendicular to the measuring direction.
In order to obtain information which cannot be obtained from the portion shaded by the overhang portion, there is provided a method in which multiple axes are manually or automatically controlled. However, actually, the adjusting axes, ranges and units are limited. Therefore, it is necessary to place the object at a position and also it is necessary to place the object in a direction so that the object can be measured under the above conditions. This important work must be manually conducted, which is complicated and difficult.
In the case of using a measurement device, the degree of freedom of which is high, the accuracy is usually low. In the case of using a measurement device, both the accuracy and the degree of freedom of which are high, the cost is increased.
In the case where an object is measured in one direction, it is necessary to place the object so that an overhang portion cannot be created. In this case, the overhang portion means a portion located at the rear of a protruding portion in a direction perpendicular to the measuring direction. However, in the case of an object, the shape of which is horizontal with respect to the measuring direction, or the shape of which is oblique and is close to the horizontal shape, it is difficult to manually place the object so that the overhang portion cannot be created. It can be considered that even if the overhang portion is created, it is impossible to discriminate the overhang portion from other portions and a measurement is executed as it is.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of manufacturing a dental prosthesis capable of providing a dental prosthesis, the shape of which is indefinite, with high accuracy.
It is another object of the present invention to provide a method of placing an object for measurement and a measuring device capable of accurately measuring an object to be measured which may have an overhang portion.
In order to accomplish the above object, the present invention provides a method of obtaining shape measuring data of a dental prosthesis while consideration is given to machining the dental prosthesis by CAD/CAM.
That is, first, data of a natural tooth having a decayed portion are obtained from an impression model. After that, a temporary filler is charged into this impression model, and data of the entire tooth after prosthetic treatment are obtained. Then, these two sets of data are differentially synthesized in the same coordinate space so as to obtain a shape of the dental prosthesis.
According to this method, the calculation of a difference can be executed while attaching an importance to one of three directions, and the amount of calculation can be reduced. That is, the surface after the completion of prosthetic treatment is smooth in many cases. In this case, it is possible that the surface is assumed to be on a plane formed by axes of X and Y. On the other hand, data of the decayed portion may be assumed to be data in the direction of Z-axis. Therefore, it is possible to concentrate the calculation upon one coordinate in the three dimensional coordinates.
Further, since the data are based on the surface data of the tooth which has been subjected to dental prosthetic treatment, the margin line and the surface portion of the tooth can be easily recognized.
Due to the foregoing, when the dental prosthesis is machined, a position of the connector for connecting the machining device with the machining block can be automatically grasped, and a space in which adhesive is coated can be easily formed.
When the connector is mounted on the surface, the dental prosthesis and the natural tooth can be connected to each other without being affected by the connector. The remnants produced when the connecting rib and the dental prosthesis are separated from each other after the completion of machining can be easily cut off and adjusted.
The present invention provides a method of forming data used when a dental prosthesis, the shape of which is indefinite, such as an inlay is measured and the dental prosthesis concerned is machined. On the assumption that the data are formed, an organized decayed tooth portion, into which a dental prosthesis is introduced, is formed.
A model of a shape of a decayed tooth portion is made of plaster by a conventional method.
Data of a surface shape of the model are obtained.
Concerning the means for obtaining the surface shape data, there are provided a means for obtaining digital data by contact scanning on the surface conducted by a contact probe, an optical means in which laser beams are used, and a means for obtaining digital data by using ultrasonic waves or photographs. In order to obtain highly accurate surface shape data, it is preferable to adopt a means in which the contact probe is used.
A decayed portion of the decayed tooth portion model is prosthetically treated, and a tooth shape model having a surface after the completion of prosthetic treatment is obtained.
Surface data of the tooth shape model are obtained by the above method.
Measuring a tooth model of a predetermined size stably as described above is easier than directly measuring an indefinite dental prosthesis shape.
Three dimensional coordinates are set on the basis of the surface data concerned. Alternatively, the surface data are converted onto the common three dimensional coordinates.
In this connection, the surface data are not necessarily provided with a flatness property in a portion to be prosthetically treated. Further, it is not necessary for the surface data to have a flatness property in a portion to be prosthetically treated.
The decayed tooth shape portion model is converted into three dimensional data so that the model can be matched with the surface data from the positional viewpoint. In this case, a portion which changes from a
Christie Parker & Hale LLP
Jarrett Ryan
Kabushiki Kaisya Advance
Picard Leo
LandOfFree
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