Abstract:
A system for creating a data record describing a dental prosthesis part, wherein the system comprises means with which a data record can be created, comprising: Entries regarding a plurality of elements that describe the surface or the shape of a dental prosthesis part, wherein for each entry one, two or more attributes are listed. The invention further relates to a corresponding system for producing a dental prosthesis part with a data record, corresponding methods and a corresponding data record.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention refers to a system for creating a data record describing a dental prosthesis part, a system for the production of a dental prosthesis part, associated methods as well as a data record. 
       BACKGROUND 
       [0002]    For the production of dental prosthesis parts by means of CAD/CAM methods it is known to create a model of a dental prosthesis part on a computer, the shape of this dental prosthesis part being stored in a data record. By means of such a data record, a dental prosthesis part can be manufactured in automated form. 
         [0003]    These data records describe the desired shape of the dental prosthesis part so that this desired shape can be produced by the respective production methods. 
         [0004]    However, it is desirable for special dental prosthesis parts and for some production methods that besides the information concerning the shape other information is also usable. 
       SUMMARY OF THE INVENTION 
       [0005]    According to one embodiment of the invention, a system is provided for creating a data record having entries with respect to a plurality of elements, wherein these elements describe the shape or the surface of a dental prosthesis part. The elements can for instance be points or surface elements of the surface or also volume elements. For each such entry also one, two or more attributes are listed. Besides such entries with elements for which attributes are listed it is also possible that the data record comprises entries with respect to a plurality of elements for which, however, attributes are not listed. However, respective attributes can also be listed for all elements of the data record. 
         [0006]    The system preferably comprises hardware and/or software components for designing a dental prosthesis part. For this purpose, a scanner can also be provided that can scan a model of a remaining tooth portion or a remaining tooth portion itself so that by this a data record is provided on the basis of which a data record describing the dental prosthesis part can be designed. 
         [0007]    Furthermore, the system preferably comprises hardware and software components by means of which a plurality of elements can jointly be selected and certain attributes can jointly be associated to these elements. It is also possible that the allocation of attributes takes place in an automated manner in that a model is for instance automatically analyzed as to certain portions, and respective attributes are set automatically. Attributes can also be set manually in that when designing the dental prosthesis part in a computer-assisted manner respective portions of the dental prosthesis part are produced or provided with the respective attributes. Elements can also be selected for instance by means of a mouse or another operating device, and one or several attributes can then be allocated to these elements by respective instructions. For this purpose an area can be marked or selected in the visually shown model of the dental prosthesis part by a respective input device. The input could also be made by a selection of elements by means of certain criteria. The selection can also be made in a tabular illustration of the data record. 
         [0008]    The attributes can for instance define a product accuracy, a material or the color for an element. 
         [0009]    A system for producing a dental prosthesis part can for instance be a laser sintering device, however it can also be another device, such as generally a rapid prototyping device. Such a system can read-in a data record, wherein information concerning the attributes are also read in. Such attributes can be processed for controlling the production process. The system can for instance react with one or several predetermined actions on one or several attributes. 
         [0010]    Preferably, attribute values are associated to other geometric elements, such as lines, wherein these geometric elements are used in the production process. Such other geometric elements can for instance be produced by a transfer of the shape defined by the surface elements to another geometric illustration required for production. 
         [0011]    The data record is characterized in that not only a plurality of elements are entered that describe the surface or shape of the dental prosthesis part, but also by the fact that an attribute is listed for each element. 
         [0012]    For instance more than 1,000, 5,000 or 10,000 entries can exist that describe elements. Attribute values are set for each such element. 
         [0013]    Thus, entries can also exist in which no attributes are set. These can also be more than 1,000, 5,000 or 10,000 entries. 
         [0014]    The data record can exist in the form of an stl format, a wmf format or any other format for storing a three-dimensional shape. Stl or wmf formats are detected by commercially available rapid prototyping devices. 
         [0015]    The attributes are preferably stored in 2 bytes. The data to the elements in an entry can preferably occupy 48 bytes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Preferred embodiments of the invention are explained by means of the enclosed Figures: 
           [0017]      FIG. 1  is a graphical illustration of one example of a model of a dental prosthesis part composed of surface elements with attributes; 
           [0018]      FIG. 2  is a schematic illustration of a section through a dental prosthesis part; 
           [0019]      FIGS. 3   a  and  3   b  are schematic illustrations of the surface of a dental prosthesis part for use in a laser sintering process; 
           [0020]      FIGS. 4   a  and  4   b  further illustrate schematically various surface elements of a dental prosthesis part during a production process; and 
           [0021]      FIG. 5  is a schematic illustration of a system for generating a data recording and a system for producing a dental prosthesis part. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  shows a section of the surface of the model of a dental prosthesis part. The model is composed of a plurality of triangular surface elements. Adjoining surface elements have a common side  6  and the corners of the triangles carry reference numeral  7 . 
         [0023]    With a network of such surface elements any three-dimensional shape can be approximated or shown. 
         [0024]    For storing this model, the data of the individual triangular surface elements is stored. This data for instance comprises the X, Y and Z coordinates of the three corner points. These are for surface element  2  e.g. points P 1 , P 2  and P 3 . 
         [0025]    Furthermore, a normal vector N with its X, Y and Z component is stored for this surface element. This normal vector can be standardized to 1. The normal vector usually serves for defining an orientation of the surface element, e.g. to distinguish the inner from the outer side of the surface. 
         [0026]    If each of the X, Y, Z coordinates of the three corner points as well as the X, Y, Z component of the normal vector N is stored with 4 bytes each, a total of 48 bytes are required for this purpose. This part of the data of an entry in a data record is shown in  FIG. 1  under reference numeral  46 . 
         [0027]    Particularly, the STL data formal shall be listed in the following: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 &lt;STL file&gt; 
                 := &lt;name&gt;&lt;facet number&gt;&lt;facet 1&gt;&lt;facet 2&gt; . . . &lt;facet n&gt; 
               
               
                 &lt;name&gt; 
                 := 80 bytes long file name; filled by blanks 
               
               
                 &lt;facet 
                 := 4 bytes integer 
               
               
                 number&gt; 
               
               
                 &lt;facet&gt; 
                 := &lt;normal&gt;&lt;corner 1&gt;&lt;corner 2&gt;&lt;corner 3&gt;&lt;stuff bytes&gt; 
               
               
                 &lt;normal&gt; 
                 := Nx, Ny, Nz; standardized to 1, 32 bit floating point 
               
               
                   
                 numbers each 
               
               
                 &lt;corner&gt; 
                 := X, Y, Z; 32 bits floating point numbers each 
               
               
                 &lt;stuff bytes&gt; 
                 := 2 stuff bytes 
               
               
                   
               
             
          
         
       
     
         [0028]    The file is therefore substantially composed of facets (triangular surface elements), wherein each facet has 50 bytes of memory space available, from which 48 bytes are used for data of the normal and the corner points and 2 bytes are not used. In these two bytes attribute values can be stored and this for each individual facet. 
         [0029]    Different attributes A 1 , A 2  can be set for the surface elements  2  to  5 . This is shown in  FIG. 1  by a cross hatching of the surface elements  2  and  3 , which corresponds to attribute A 1  and furthermore, the surface elements  2 ,  4  and  5  are shown in dotted form, which corresponds to the attribute A 2 . 
         [0030]    As can be seen in  FIG. 1 , surface elements can comprise no attribute (in  FIG. 1  in the upper half), they can have one of the two attributes A 1  or A 2 , or also both attributes. More than two attributes A 1 , A 1  can also be provided. 
         [0031]    Each attribute can be stored in its own byte. However, a plurality of attributes can also be stored in one byte or several attributes can be distributed to several bytes, as for instance 3 or 4 attributes to two bytes. 
         [0032]    The attributes for an entry in a data record are indicated in  FIG. 1  by reference numeral  47 . The entire entry carries reference numeral  45 . 
         [0033]    Such an entry  45  is provided for each surface element  2  to  5 . 
         [0034]    If none of the attributes is to be set for a surface element, the data field provided for this purpose remains empty (e.g. filled by zeros). 
         [0035]      FIG. 2  shows a section through a dental prosthesis part  10 . It has an outer side  11  and an inner side  13 . On the lower end of the inner side  13  a section  12  is shown for which for instance an extremely high production accuracy is desired, since this portion finishes the inner portion  13  when setting the dental prosthesis part onto a remaining tooth. The area  12  is for instance designated as a preparation line. 
         [0036]      FIG. 3  shows two examples on how different product accuracies can be set in the laser sintering process. During laser sintering the workpieces usually have a step-like profile, which results from the layer-type application and solidification of the material to be sintered. These steps  17  are shown in  FIG. 3   a . Furthermore, a surface element  15 ′ with the normal is shown in  FIG. 3   a , as it could be situated in a respective data record. 
         [0037]    As can be seen, the surface  16  formed by the steps differs from the shape determined by the surface element  15 ′. To reduce these deviations it is for instance possible to carry out the laser sintering process with thinner material applications so that smaller steps  18  result, as shown in  FIG. 3   b . In the area of the surface element  15 ″ the deviation of the real shape from the desired shape is significantly smaller than in  FIG. 3   a.    
         [0038]    By use of the attributes, the production process during laser sintering can for instance be modified in that depending on the desired production accuracy differently high steps are generated or differently thick material applications take place that are subsequently solidified by laser sintering. 
         [0039]    As shown in  FIG. 3 , sections along the triangles are required in the production process, wherein the sections can extend e.g. horizontally. The attributes associated to the surface elements can be processed in various ways. This shall be explained by  FIG. 4 . 
         [0040]      FIG. 4   a  shows a section along a plane of the production process. The dental prosthesis part has an outer surface  29  and an inner surface  30  whose sections form straight line pieces with the drawing layer. The straight line pieces collide on the corner points  25 ,  26 ,  27 ,  28 . The corner points  25  to  28  result from the section of a plane  20  with the triangular surface elements, as shown in  FIG. 4   b.    
         [0041]    The attribute(s) of the surface element  21  can be associated to the line piece between the corner points  25  and  26 . The attribute(s) of the surface element  22  can be associated to the line piece between the corner points  26  and  27 , and the attribute(s) of the surface element  23  can be associated for the corner points  27  and  28 , etc. 
         [0042]    An attribute can also be associated to the corner points themselves. On the one hand it is conceivable that two overlapping corner points are provided instead of one corner point, wherein each corner point is associated to one line each. The attribute of the associated line is associated to each of these corner points. If, however, a corner point between two line pieces is associated to the two line pieces, either one of the two attributes can be selected, wherein respective predefined rules can be used, or a mean value can be formed, if the type of attribute values makes this possible. 
         [0043]    Since the outer side  29  and the inner side  30  are defined by different surface elements, different attributes can be used in the same plane for the outer side and for the inner side. 
         [0044]    A computer system  40  is shown in  FIG. 5  on the left side for producing a data record defining a dental prosthesis part. The model of such a dental prosthesis part is shown on the screen by reference numeral  44 . The model  44  can be processed or generated by means of the keypad and the mouse or other input means. The system  40  can generate a data record from the model that can directly be used by the system  40  for producing a dental prosthesis part or that can also be sent (e.g. via an internet connection). 
         [0045]    The system  40  further preferably comprises a scanner  42  by means of which a remaining tooth portion can be scanned. The data obtained thereby can serve as a basis for a model  44  of a dental prosthesis part. 
         [0046]    The data record  43  comprises various entries  45 , wherein each entry comprises a portion  46  that defines elements defining the surface or shape of a dental prosthesis part, as well as a part  47  that defines the attributes for such elements. 
         [0047]    On the right-hand side of  FIG. 5  a system for producing a dental prosthesis part is schematically shown. A laser sintering device is shown, in which a laser beam  49  is focused to a focus  50  and locally heats there, which leads to a solidification of the shapeless material located there. The material can for instance be liquid, powdery or granular and can be modified locally in structure by the laser and can thereby be solidified. 
         [0048]    The focus  50  is located on the material surface  52 , wherein further material  51  is applied onto this surface  52  in a layered manner and is there locally solidified by the laser beam  49 . For this purpose the laser beam  49  or also a receiving trough  53  can be displaceable in all three spatial directions (see reference numeral  54 ). The laser beam  49  can also be movable along the surface  52  and the trough can be movable in a direction perpendicular thereto or vice versa. 
         [0049]    By controlling the relative arrangement of the laser  49  with respect to the trough  53 , parts shaped in any manner can be laser-sintered. 
         [0050]    The material  51  used can for instance be gold dust or possibly a sinterable ceramic material. 
         [0051]    A controller  48  is provided to control the relative arrangement of the laser  49  and the trough  53 . This controller can read-in a data record  43 , wherein during read-in the attribute data  47  is also used for producing the dental prosthesis parts. This relative control between the laser and the trough  53  can be influenced by the attributes. 
         [0052]    The consideration of the attribute data can for instance lead to the fact that, as shown in  FIG. 3   b , a higher production accuracy is achieved for certain surface elements  15 ″ than for other regions.