Abstract:
A mold for embedding casts in an embedding compound for producing molds for dental workpieces, such as crowns and bridges, which has a mold cavity which can be filled with the embedding compound, which holds at least one cast and which is closed by a cylindrical peripheral wall and by a bottom part. The peripheral wall is formed by a blank of a transparent or translucent flat elastic material.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a mold for embedding casts in an embedding compound for producing molds for dental workpieces, such as crowns and bridges. 
     Dental workpieces, for the purposes of the invention, are defined as crowns and bridges. An embedding mold for producing a casting mold for these types of dental workpieces is known (DE 85 19 112). 
     The object of the invention is to provide an embedding mold which compared to the known embedding mold provides improvement and simplification of handling while maintaining precision with respect to the resulting molds. 
     SUMMARY OF THE INVENTION 
     In the mold as described by the invention, a wall of an open blank of film is produced from transparent, preferably crystal-clear or essentially crystal-clear plastic. This film is rolled together into a wall which surrounds the mold cavity with overlapping of the film ends. The film ends are held together and the film is supported by the outer sleeve. 
     After completing the mold, i.e. after curing of the embedding compound, preferably before final curing, the wall can be removed especially easily and quickly by simple lifting of the sleeve and by unwinding the blank which forms the wall. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     The invention is detailed below using the following figures: 
     FIG. 1 shows in a simplified representation and in a side view an embedding mold as claimed in the invention; 
     FIG. 2 shows the mold from FIG. 1 in a lengthwise section; 
     FIG. 3 shows the bottom part in an individual representation; 
     FIG. 4 shows an overhead view of the bottom part of the embedding mold of FIGS. 1 and 2; 
     FIG. 5 shows in a representation similar to FIG. 4 another embodiment of the mold as claimed in the invention; and 
     FIG. 6 shows the embodiment of FIG. 5 in a simplified side view. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embedding mold  1  shown in FIGS. 1-4 contain a bottom part  2  which is produced in the shape of a round disk from hard rubber or another elastic material. In the middle area, the bottom part  2  has a projection  3  which is shaped like a truncated cone, which is rounded on the top, and which is made concentric to one axis of symmetry, or the center axis S of the bottom part  2 . On the side which has the projection  3 , the bottom part  2  has a ring-shaped gradation  4  which symmetrically surrounds the axis of symmetry, radially offset to the outside, relative to the projection  3 . The gradation forms a circular cylindrical surface  4 ′ which concentrically surrounds the axis of symmetry S and a subsequent annular surface  4 ″ which lies in one plane perpendicular to the axis of symmetry S, underneath the top of the bottom part  2  which has the projection  3 . On the gradation  4 , the bottom part  2  is produced in one piece with a peripheral sealing lip  5  which concentrically surrounds the axis of symmetry S and which in the representation chosen for FIG. 3, i.e. the bottom part  2  removed from the other elements of the embedding mold, protects over the surface  4 ′. The sealing lip  5 , in this embodiment, is repeatedly interrupted or indented at  6 . 
     The embedding mold  1  has a circular cylindrical wall  7  which is attached to the bottom part  2  and concentrically surrounds the axis of symmetry S and which is produced from an open blank  7 ′ of transparent or translucent film, from a plastic material which ensures a certain strength or stiffness for the wall  7 . As is indicated in FIG. 4, the blank  7 ′ is rolled together into the wall  7  such that the two ends of the blank overlap at  8  without the ends of the blank being interconnected, so that an increase of the diameter of the interior space of the embedding mold  1  is possible without the wall  7  counteracting one such increase in diameter with a significant opposing force. 
     The wall  7  has its lower edge resting on the surface  4 ″ and in the area of the lower edge, has its inner surface lying against the surface  4 ′ and also against the sealing lip  5  so that a tight seal is achieved. By means of the notches  6  the sealing lip  5  can follow a change of the inside diameter of the embedding mold almost without force. An outer sleeve is labelled  9 ; it surrounds the wall  7  at least on one part of the height of the embedding mold  1  and is produced from a harder plastic material. The sleeve  9  is continuously slotted, at a position so that the sleeve  9  on the two ends  9 ′, which are formed by the slot  10 , can be opened or bent away from one another elastically such that the sleeve  9  can be mounted and dismounted on or from the wall  7 . The sleeve  9  in its mounted state holds the wall  7  together. 
     To simplify handing of the sleeve  9 , it is provided on its ends  9 ′ with one recess  11  which forms a gripping surface. Furthermore, the sleeve  9  is provided with various recesses or windows  12  through which, with the embedding mold  1  completely assembled, the interior of the embedding mold also remains visible from the side, through the film which forms the wall  7 . 
     In the conventional manner, the cast  13  of a crown or bridge is attached to the conical projection  3  via a bridge-like element  14  which is produced from the casting compound (wax) and later forms the casting channel when casting the crown or bridge. 
     The embedding mold is used, such that after assembling the mold and placing the respective cast  13  in the interior of the embedding mold, the embedding compound is placed in the embedding mold from the open top, and this insertion can be observed not only from the top, but also laterally through the window-shaped openings  11  and  12 . In particular, it can be observed or ensured that the embedding compound flows optimally into the cavity of the cast  13  without air inclusions remaining here. 
     As FIGS. 1 and 2 show, the wall  7  projects over the top edge of the sleeve  9 . This makes it easy to check the fill level of the embedding mold with the embedding compound, especially to prevent too much embedding mass from being placed in the embedding mold  1  and thus flowing over the top edge; this would make it difficult to open the embedding mold after curing of the embedding masses. 
     As is recognized, the embedding compounds used are made such that during curing, but especially when a certain solid state has been achieved during curing, the compounds expand in order to compensate for the shrinkage of the metal-cast crown or bridge which is caused by cooling, by increasing the size of the mold cavity formed by the respective cast  13  in the embedding compound. Even small forces or constraints can disrupt this expansion process, for example, such that when the expansion process is limited or restricted by the wall  7 , the expansion process is intensified in the direction of the axis of symmetry S, by which the crown or bridge produced then has overly large dimensions in this axial direction, while in the axial directions which run perpendicularly thereto the dimensions are below the desired value. 
     It has been found that the above described formation of the peripheral wall and also the division of the sealing lip  5  keep the forces or constraints opposing the expansion of the embedding compound so small that radially to the axis of symmetry S the desired dimensions are maintained with high precision for the mold cavity formed by the cast  13 . 
     Important components of the embedding mold  1  are the cylindrical peripheral wall  7  which is produced by the blank  7 ′ of transparent plastic, the sleeve  9  which supports this peripheral wall, and the bottom part  2  with the self-supporting sealing lip which has been repeatedly notched at  6 . 
     FIGS. 5 and 6 show another possible embodiment in which the wall  7   a  which surrounds the mold cavity is produced from transparent material. The material is chosen such that the wall  7   a  already has the necessary strength. The wall  7   a  is in turn made such that the pertinent blank  7   a ′ overlaps itself so that when the embedding compound expands, the inside diameter of the mold internal cavity can be increased without the wall  7   a  becoming loose due to the divergence of the blank  7   a ′. Due to the self-supporting and repeatedly indented sealing lip  5  it also yields in this embodiment, when the embedding compound expands, so that unwanted deformations in the mold which has been produced in the dental workpiece are effectively prevented. 
     In FIG. 6, a display is labelled  15 ; and is provided on the blank  7   a  and responds to the temperature of the embedding compound during setting. This display  15  is formed, for example, by a liquid crystal temperature display which in the embodiments shown has three fields  15   1 ,  15   2 , and  15   3  which each are activated at different temperatures and then appear in different colors. For example, field  15   1  is red at low temperature, meaning that the embedding mold must still be kept closed, field  15   2  is yellow at a somewhat higher temperature, meaning that the embedding mold should be opened as soon as possible, and field  15   3  is green, meaning that at this point the embedding mold should be opened immediately. 
     The display  15  prevents uncontrolled expansion of the embedding compound by too early opening of the embedding mold and thus by too early release; this expansion leads to cracks in the embedding compound or in the mold which has been produced. In FIG. 6, two velcro closures are labelled  16 ; they are used to interconnect the overlapping ends in the area of the overlap  8  without the desired elasticity of the wall  7   a  being lost. 
     The invention was described above using various embodiments. It goes without saying that changes and modifications are possible without in this way departing from the inventive idea underlying the invention. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference number list 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1, 1a 
                 embedding mold 
               
               
                   
                 2 
                 bottom part 
               
               
                   
                 3 
                 projection 
               
               
                   
                 4 
                 gradation 
               
               
                   
                 4′, 4″ 
                 surface 
               
               
                   
                 5 
                 sealing lip 
               
               
                   
                 6 
                 indent 
               
               
                   
                 7, 7a 
                 wall 
               
               
                   
                 7′, 7a′ 
                 blank of transparent material 
               
               
                   
                 8 
                 overlap 
               
               
                   
                 9 
                 sleeve 
               
               
                   
                 9′ 
                 end 
               
               
                   
                 10 
                 slot 
               
               
                   
                 11, 12 
                 recess 
               
               
                   
                 13 
                 cast 
               
               
                   
                 14 
                 bridge-like section 
               
               
                   
                 15 
                 temperature display 
               
               
                   
                 15 1 , 15 2 , 15 3   
                 field 
               
               
                   
                 16 
                 velcro closure