Patent Abstract:
A method for producing dental restoration components includes filling a retort cylinder of a retort system with a forming mass, the retort cylinder being at least partially encircled by a charging body, and hardening the forming mass. After the hardening of the forming mass, the retort cylinder and the charging body are removed from the forming mass, thereby leaving behind a retort. Thereafter, with the assistance of a press blank apparatus, a press blank having an outer contour substantially corresponding to the outer contour of the charging body is pressed into the retort.

Full Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a method for producing dental restoration components, a retort system, and a press blank, all especially for use in connection with dental ovens.  
         BACKGROUND OF THE INVENTION  
         [0002]    Retort ovens have been known for a long time such as, for example, as is disclosed in DE-OS 198 44 136. In retort ovens of this type, a wax model of a dental restoration is embedded in a cast bed in order to produce a negative form. The retort is then heated and warmed so that the model composed of wax melts and there remains the temperature resistant negative form or mold in readiness for the introduction thereinto of a to-be-pressed ceramic mass.  
           [0003]    Dental restoration can demand decidedly different forms and volumes. Correspondingly, at the same time several wax models are frequently made ready in a single batch—that is, several wax models are poured within a single retort—and, correspondingly, several ceramic restoration pieces are produced via pressing. The pressing is performed with ceramic mass which is introduced via a feed-in channel and formed into the form mass by a press stamp during simultaneous heating of the negative form.  
           [0004]    The mass can be introduced in a pre-pressed condition, in a powder-type condition, or even in a fluid condition, whereby the pre-pressed form body is typically designated as a blank.  
           [0005]    Instead of blanks, powder-formed ceramic masses can also be deployed. The use of blanks has, on the one hand, the advantage that an exact or precisely measured amount of ceramic material is deployed so that the operation of the stamp for exerting pressure in the press oven can be exactly specified and can be corrected with a corresponding material offset.  
           [0006]    The dental restoration component to be produced can require significantly different amounts of ceramic—either in the form of ceramic powder or in the form of ceramic blanks.  
           [0007]    In order to competently handle these requirements, the length of the ceramic blank can be adapted to the requirements, within certain limits. The ceramic blank is introduced into the channel which remains as the negative form of the retort cylinder. In order to achieve a press result of high quality, the ceramic blank must practically be comprised of the same diameter as that of the retort cylinder.  
           [0008]    One can, indeed, increase the length of the retort cylinder and, consequently, increase the possible length of the ceramic blank. However, in connection with an overly long length, there arises a comparatively large friction during the press process. This is unfavorable from, for example, the perspective of the adhesion/sliding friction conditions during the press process, which have only been studied to a limited degree and in connection with which there occur pressure oscillations in the hollow space in which the dental restoration is configured.  
           [0009]    In order to competently handle various sizes of dental restorations, it has heretofore typically been the practice to maintain a plurality of different retort cylinders in readiness so that, in connection with larger dental restorations of large diameter, larger diameter versions of the retort cylinder can be deployed.  
           [0010]    However, maintaining in readiness an inventory of several retort systems of various sizes is a relatively large effort, simply from the point of view of requiring a correspondingly large inventory.  
           [0011]    In order to avoid this, it has frequently been the case that an average-sized configuration of a retort system or a retort arrangement is deployed and then several restoration components are stuck outwardly from wax on the growth surface via corresponding support arms, so that the mass is, in total, somewhat enlarged and the blank can be better exploited.  
           [0012]    However, imperfect accommodation to the required dental restoration configurations leads to considerable material loss, since, in the case of an only partially pressed blank, the blank must, for all practical purposes, be thrown away.  
           [0013]    If, on the other hand, in connection with a desired large material mass, a blank of an overly long length is deployed such that it extends out of the channel of the corresponding retort cylinder, the danger exists that the blank will tip, leading to an unstable press process.  
         SUMMARY OF THE INVENTION  
         [0014]    In contrast to the above-noted shortcomings, the present invention provides a solution to the challenge of providing a retort system, which is an improvement from the point of view of ease of manual manipulation and cost.  
           [0015]    In connection with the solution of the present invention, a single retort system can by itself, surprisingly, handle a wider range of ceramic amounts, which are designated for dental restoration models. Via the inventive charging body, a markedly large dental restoration can be created with the same retort system.  
           [0016]    In this connection, a correspondingly thicker charging body, which, preferably, encircles the retort cylinder in an annular manner, is deployed. Due to the enlarged thickness, the thus-deployed ceramic blank can, at the same time, be longer without giving rise to a fear that a downgrade in stability will occur.  
           [0017]    To this extent, a mass increase to the third power can be realized via the diameter enlargement made possible by the invention so that, as well, a significantly greater mass amount can be achieved with a comparatively thin charging body.  
           [0018]    Preferably, the retort cylinder, and the charging body which encircles it, have a round configuration. There then occurs, in connection with the pressing of the ceramic blank, a centralized loading impact on the ceramic blank so that no tipping force is thereby introduced on the blank.  
           [0019]    In accordance with the present invention, the charging body can melt, preferably together with the model mass. In this connection, the charging body, as well as the model, can be comprised of wax and can be disposed together with the melted wax of the model in the hollow space of the retort.  
           [0020]    In accordance with the present invention, it is particularly advantageous if the charging body comprises a smooth outer surface. Due to the smooth outer surface, it is ensured that an overly strong friction between the hardened form mass and the ceramic blank does not occur, thereby permitting the greatest possible disturbance-free slide friction during the press process.  
           [0021]    In accordance with the present invention, it is especially favorable in this connection that the inner top surface of the retort—that is, the outer circumference of the press channel—typically has small wax remnants still remaining thereon. Such wax remnants operate, surprisingly, as lubrication means without, however, forming debris on the dental restoration.  
           [0022]    In this connection, it is particularly advantageous that the growth channels, which correspond to the support arms in connection with the wax model securement on the growth surfaces, are configured centrally—that is, clearly within the tube-shaped charging body, so that the outer regions of the ceramic blank do not project into the growth channels or, at the least, do not project into the growth channels at the end of the press process and, in any event, do not project so far as to reach the dental restoration.  
           [0023]    It is to be understood that the lubrication effect of the wax remnants endures only so long as the temperature in the retort is not at least substantially over the vaporization temperature of the model mass—that is, this effect lasts during the preparation and pre-heating of the retort oven for the respective actual press process.  
           [0024]    In a further particularly favorable configuration, it is provided that the charging body extends over the retort cylinder.  
           [0025]    In this configuration, a somewhat longer blank can be deployed as well without engendering any tipping danger.  
           [0026]    In furtherance of this purpose, the charging body is disposed on the retort cylinder before the growth on the growth base has begun.  
           [0027]    It is to be understood that not only a tube-shaped charging body is contemplated in connection with the term “charging body”. In addition, for example, a charging body comprised of several rings axially and/or radially combined with one another can be deployed. It is to be understood that the radial diameter of the charging body can be adapted in any suitable desired manner to the requirements.  
           [0028]    The deployment of the inventive charging body or bodies does not rule out the provision, in a conventional manner, of a growth surface, having a blind bore, which can serve as the growth base. If the charging body extends outwardly over this surface, the surface can, in furtherance of this purpose, comprise a corresponding through bore.  
           [0029]    Any suitable desired coding system can be deployed to differentiate the various charging bodies from one another. For example, different charging bodies can be differently colored.  
           [0030]    If the outer form of the charging body deviates from an annular form, the possibility then also exists that the ceramic blank will be friction-free but, also, that the ceramic blank will be even more securely supported on its side. For example, a six-sided form can be selected in order to achieve the desired outer bracing.  
           [0031]    Further advantages, features and details are set forth in the following description of several embodiments of the present invention taken in connection with the figures of the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    [0032]FIG. 1 is a front elevational view, in partial section, of a first embodiment of the inventive retort system;  
         [0033]    [0033]FIG. 2 is a front elevational view, in partial section, of the combination of a retort base and a retort cylinder for the embodiment shown in FIG. 1;  
         [0034]    [0034]FIG. 3 is a front elevational view, in partial section, of a modified combination of a retort base and a retort cylinder for the embodiment shown in FIGS. 1 and 2;  
         [0035]    [0035]FIG. 4 is a front elevational view, in partial section, of a further modified combination of a retort base and a retort cylinder;  
         [0036]    [0036]FIGS. 5, 6,  7 , and  8  are plan views of respective various embodiments of an inventive charging body; and  
         [0037]    [0037]FIG. 9 is a front elevational view, in section, of a press form created in connection with the inventive method.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0038]    [0038]FIG. 1 shows a first embodiment of the inventive retort system  10  which comprises a retort base  12  from which a retort cylinder  14  extends downwardly, as viewed in the position shown in FIG. 1.  
         [0039]    In accordance with the present invention, the side of the retort cylinder  14  is encircled by a charging body  16 , whereby, in the illustrated embodiment shown in FIG. 1, the charging body  16  is annularly shaped and has a wall thickness of approximately one-half the radius of the retort cylinder.  
         [0040]    The retort cylinder  14  comprises a growth surface  18  on its lower region on the end face thereof turned away from the retort base  12 . At least one support arm comprised of wax is mounted on the growth surface  18 , whereby, in the illustrated embodiment, two support arms  20  and  22  are configured. Wax models  24  and  26  are provided somewhat centrally in the retort system  10  on the other ends of the support arms  20  and  22 , the wax models corresponding in their form to the dental restorations.  
         [0041]    In the operational condition shown in FIG. 1, the retort system has already been filled with a forming mass  28  which completely encloses the retort cylinder, the support arms, and the wax models without the presence of any included air.  
         [0042]    To effect the filling of the retort system  10 , the retort system comprises a retort cover  30  which—as is also the case with the retort base  12 —is removable and is in the form of a cylindrical retort form  32 , which can be, for example, comprised of a piece of a plastic pipe or can be formed of cardboard. The orientation of the retort system  10  is, in this connection, turned around so that the retort base  12  and the retort cylinder  14  assume the positions shown in FIG. 2. In this operational condition with the retort form  32  removed, the charging body  16  is, initially, inserted or twisted on.  
         [0043]    The growth surface  18  comprises, in a conventional manner, a blind hole recess or receptacle  34  which is configured for the receipt of a growth plug or stopper in order that the support arm can be anchored in an improved manner to the growth surface  18 . In the illustrated embodiment, the wax models  24  and  26  extend sufficiently outwardly so as to render impossible an insertion of the charging body  16  on the grown out models. It is to be understood that this situation can be remedied, if the models comprise a reduced total outer diameter.  
         [0044]    Following the conclusion of the wax working, the retort form  32 , which can also be formed of cardboard, is inserted onto an indentation  42  of the retort base  12 . Thereafter, the forming mass  28  is carefully introduced. The forming mass hardens into a form mass and is heat resistant with respect to the temperatures which are required for the sintering of ceramic—that is, for example, up to 1100 C.  
         [0045]    The retort cover  30 , which, in any event, comprises an indentation whose configuration corresponds to that of the indentation  42 , is then put on so that the retort system  10  can be manually manipulated as desired.  
         [0046]    In connection with the preparation of the press, the retort system  10  is then preferably disposed in the position shown in FIG. 2 and the retort base  12 , together with the retort cylinder  14  as well as the retort cover  30  and, additionally, the retort form  32 , is removed. The forming mass  28  is thereafter somewhat pre-heated so that the charging body  16 , the support arms  20  and  22 , and, as well, the wax models  24  and  26 , melt and exit downwardly. In this condition, the presence of some wax remnants remaining as a fluid film on the walls of the form does not cause any disruption or disturbance.  
         [0047]    The forming mass  28  is then again rotated so that it is in the position shown in FIG. 1. In this position, a ceramic blank is introduced which has an outer diameter corresponding to that of the charging body  16 . The ceramic blank can have a height/width relation of approximately one to one so that it encloses a significant volume and is suitable for the filling up of large hollow spaces which correspond to that of the wax models  24  and  26  and the support arms  20  and  22 . The ceramic blank is, together with the forming mass  28 , further heated, whereby the remaining wax remnants are vaporized.  
         [0048]    It is important that the wax be handled so as to be residue-free. In this connection, the method of the invention is described, for example, with respect to wax deployed as the material for the charging body  16 . It is to be understood, that in lieu of this, other suitable different materials can be deployed which are residue-free—that is, primarily organic materials.  
         [0049]    In the embodiment shown in FIG. 2, the charging body  16  is configured as a cylindrical tube which extends over the entire length of the retort cylinder  14 —that is, the charging body extends up to the growth surface  18 .  
         [0050]    It is to be understood that, in lieu of this, other embodiments are possible.  
         [0051]    Thus, in the embodiment shown in FIG. 3, a somewhat enlarged charging body  16  is provided which extends outwardly of the retort cylinder  14  and covers the retort cylinder  14  on its topside (or on its underside in the position shown in FIG. 1). The wall thickness of the charging body  16  on its back surface and on its cylindrical wall are dimensioned the same in this embodiment.  
         [0052]    In order that access to the blind hole receptacle  34  is possible, in this configuration, a through receptacle  44  is provided which is aligned with the blind hole receptacle  34  and is securable in the support arms  20  and  22 .  
         [0053]    A modified embodiment with a multiple component charging body  16  can be seen in FIG. 4. In this configuration, there is provided a spacer body  46 —in the example, a spacer ring  46 —which is disposed on the retort base  12  and is releasably inserted on the retort cylinder  14 . The spacer body  46  can, together with the retort cylinder  14  and the retort base  12 , be removed so that it is not lost if a pre-heating process is to be undertaken.  
         [0054]    In this embodiment, in lieu of the pot-shaped charging body  16  as shown in FIG. 3, a ring-shaped charging body  16  can be provided as well. The charging body  16  extends outwardly over the growth surface  18 , whereby the ring space between the through receptacle  44  and the charging body  16  is filled via a charging disk  48  which, in correspondence with the required profile, can be configured as a lost or not lost (vaporizable or non-vaporizable) disk.  
         [0055]    It is to be understood that, in lieu of the ring-shaped charging body illustrated herein, other suitable desired forms can be deployed for the charging body.  
         [0056]    FIGS.  5 - 8  show different embodiments with the same inner configuration having, however, differing outer forms.  
         [0057]    [0057]FIG. 5 shows an annular-shaped outer form, FIG. 6 shows an eight-sided outer form, FIG. 7 shows a form comprised of a spherically rounded rhombus, and FIG. 8 shows a right angled-shape with rounded-off corners. Suitable desired forms of the blank can be used, whereby it can be advantageous to permit the blank outer form to deviate from the charging body outer form in order to make possible a reduced contact surface.  
         [0058]    [0058]FIG. 9 shows the configuration of the forming mass  28  which serves as the press form, as soon as the retort base and the retort cylinder are removed and the mass formed of wax has melted. Channels  48  are provided to extend outwardly in lieu of the support arms, and the locations at which the wax models  24  and  26  are configured are provided as hollow spaces  50 . The area of the charging body  16  is open so that the ceramic blank can be inserted therein.  
         [0059]    It is possible that the charging body  16  as well as the spacer ring  46  and the charging disk  48  can be provided with corresponding coding such as, for example, color coding and/or corresponding text. In this connection, each size can be characterized by a respective color coding so that different sizes can be easily recognized.  
         [0060]    The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.

Technology Classification (CPC): 8