Process and Device for Manufacturing a Dental Restoration

Abstract

Methods for manufacturing a dental restoration for a patient and dental ceramics production devices are disclosed. A dental restoration may be designed based on a scan of the patient's mouth, using a CAD software module. The software module may produce conveyor channels for a positive model based on the dimensions of a muffle in relation to the size and shape of the positive model. The conveyor channels may extend at an angle of between 0° and 130° away from an axis of the pressing channel, the axis being located essentially along an isotherm inside the muffle. A docking site may be selected based on a position with the greatest wall thickness of the positive model. The present disclosure allows the creation of a high-quality dental restoration in a very efficient fashion, in particular when lithium disilicate is used as the dental ceramics material.

What is claimed is: 
     
         1 . A method for manufacturing a dental restoration for a patient comprising:
 designing a dental restoration based on a scan of the patient's mouth, using a CAD software module;   producing a positive model of the dental restoration using a material that is removable from a mold without leaving a residue;   producing, using the CAD software module, at least one conveyor channel for the positive model based on the dimensions of a muffle in relation to the size and shape of the positive model, wherein the conveyor channel is determined by defining a space within the muffle for arrangement of the dental restoration;   removing the positive model using the muffle, wherein the muffle has a pressing channel which is connected via a conveyor channel with a cavity for the dental restoration corresponding to the positive model;   inserting a blank of dental material into the pressing channel; and   heating and applying pressure to the blank such that the blank is deformed and dental material for shaping the dental restoration flows through the conveyor channel and fills the cavity;   wherein the conveyor channel extends at an angle of between 0° and 130° away from an axis of the pressing channel, the axis being located essentially along an isotherm inside the muffle; and   wherein a docking site is selected based on a position with the greatest wall thickness of the positive model, and the CAD software module positions the positive model in relation to the conveyor channel to elongate the axis of the conveyor channel and that the length of a virtual axis through the positive model is maximized.   
     
     
         2 . The method of  claim 1 , wherein the CAD software module determines, based on the shape of the positive model, starting from the position with the greatest wall thickness of the positive model, a primary flow direction for the dental material in which the cross-section of the flow in a pre-determined distance from the thickest position is greatest, and that the maximized virtual axis through the positive model deviates in the primary flow direction. 
     
     
         3 . The method of  claim 1 , wherein the arrangement of the dental restoration within the muffle are determined by the CAD software module in such a fashion that the greatest longitudinal extension of the dental restoration essentially extends along an isotherm. 
     
     
         4 . The method of  claim 1 , wherein that if a plurality of dental restorations are manufactured at the same time, the plurality of dental restorations are positioned essentially along the envelope curve of a cone or taper and equally spread around the pressing channel which essentially terminates at the peak of the cone or taper. 
     
     
         5 . The method of  claim 1 , wherein the conveyor channel is provided with radii and/or constant transitions in the direction towards the pressing channel, and in the direction towards the dental restoration. 
     
     
         6 . The method of  claim 1 , wherein the conveyor channel determines the alignment of the dental restoration, and an alignment of the dental restoration is determined such that a penetration length of the conveyor channel through the dental restoration is maximized. 
     
     
         7 . The method of  claim 1 , wherein the dental restoration is formed as a crown or a bridge and the basal area of the crown extends in elongation of a pressing channel axis with an open side away from the pressing channel. 
     
     
         8 . The method of  claim 5 , wherein the dental restoration is formed as a prefacette or a veneer and the basal area of the prefacette or the veneer extends such that it points radially outwards in relation to a pressing channel axis. 
     
     
         9 . The method of  claim 1 , wherein an alignment of the dental restoration with respect to the conveyor channel axis is selected such that the elongation of the conveyor channel axis through the dental restoration extends through the center of mass of the dental restoration when the conveyor channel axis is positioned at the thickest position of the dental restoration. 
     
     
         10 . The method of  claim 1 , where the CAD software module connects the conveyor channel, in relation to the outside surfaces of the dental restoration, in an eccentric or off-center fashion. 
     
     
         11 . The method of  claim 1 , wherein the length of the conveyor channel is determined by the CAD software module depending on the size and the weight of the dental restoration. 
     
     
         12 . The method of  claim 1 , wherein if a number of dental restorations are arranged in one muffle, the CAD software module determines the conveyor channels to the dental restorations such that the dental restorations are arranged at regular intervals within an isothermal corridor such that the arrangement of dental restorations approximates a taper or cone. 
     
     
         13 . The method of  claim 1 , wherein the CAD software module accesses a conveyor channel library which indicates different profile designs, lengths, docking points and angles of conveyor channels based on sizes and types of dental restorations, and that the CAD software module, based on these values, determines or suggests the conveyor channels with regards to their lengths, their diameters, and their angles. 
     
     
         14 . The method of  claim 1 , wherein the virtual inside is dependent on the size of the muffle and releases a placing space of the dental restoration within the muffle such that the dental restoration keeps a distance from the muffle of at least 2 mm with respect to the outside wall of the muffle and the height of the virtual inside space is lower in a radially inwardly direction than in a radially outwardly direction. 
     
     
         15 . The method of  claim 1 , wherein the positive model is manufactured by a milling process and a milling blank is formed as a cylinder with a cylinder height corresponding to the virtual space of between 15 mm and 50 mm. 
     
     
         16 . The method of  claim 1 , wherein at least one conveyor channel is formed as a dummy channel without an associated dental restoration. 
     
     
         17 . The method of  claim 1 , wherein the length and thickness of each conveyor channel relative to the other conveyor channels is selected such that it is adapted to the volume of its associated dental restoration. 
     
     
         18 . A dental ceramics production device comprising:
 a CAD/CAM device for providing a pressing mold for manufacturing a dental ceramics; and   a CAD software module executed by the CAD/CAM device, the CAD software module configured to:
 determine the shape of a dental restoration, based on a scanning result of a mouth of a patient; 
 determine the configuration of the dental restoration using an expendable muffle; 
 determine the arrangement of an angle and dimensions of a conveyor channel between a central pressing channel and a cavity for shaping the dental restoration inside a virtual inside space within the muffle; and 
 determine the work angle of the dental restoration in relation to a conveyor channel axis of the associated conveyor channel at a docking site of the dental restoration at the conveyor channel, the docking site positioned at the thickest position of the dental restoration, such that an elongation of the conveyor channel axis extends through the largest possible length of the dental restoration starting from the thickest position, in particular based on a pre-set library of shapes of dental restorations and/or conveyor channels. 
   
     
     
         19 . The device of  claim 18 , wherein the docking site of the dental restoration at the conveyor channel is selected by the CAD software module at the position at which a ball with the largest possible diameter fits into the dental restoration, wherein an elongation of the axis of the conveyor channel extends in particular essentially through the center of this ball. 
     
     
         20 . The device of  claim 18 , wherein each dental restoration is determined by the CAD software module in the virtual space with regards to its arrangement and alignment such that it has a marginal distance both from the outside wall of the muffle and from the neighboring dental restoration which does not exceed a pre-determined value. 
     
     
         21 . The device of  claim 18 , wherein the docking site of the dental restoration at the conveyor channel in a vertical projection in relation to the muffle is selected in such a fashion that a narrow position of the dental restoration is arranged radially inwards and a wider position further outside radially. 
     
     
         22 . The device of  claim 18 , wherein the conveyor channel and/or the dental restoration is provided with a code or an identification at a basal or a covered position, which facilitates the association with the order concerned and/or the patient concerned. 
     
     
         23 . The device of  claim 18 , wherein the dental restoration is provided with a constant and layer-by-layer construction which is suitable for stereolithography, in particular with an envelope curve whose slope is always larger than or equal to zero over its entire extension from docking site of the dental restoration in the lateral view or observed in the direction of the pressing channel axis. 
     
     
         24 . The device of  claim 18 , wherein the CAD/CAM device uses as the zero position of the virtual inside space the front surface of the pressing channel and polymerizes a conveyor channel base directly to that front surface away from which the conveyors channels extend.