DENTAL DIVESTMENT METHOD AND MUFFLE

Abstract

The invention relates to a dental divestment method in which dental restoration parts are divested from a cured muffle by sandblasting. In the production of the muffle molded part or moldings (20) or protrusions (58) are realized in or at the casting mold by means of a casting compound (21), said molded part or moldings or protrusions consisting of a burn-out material. They are removed after curing. The indentations produced in this way are configured as predetermined breaking points for the muffle.

Claims

1. A dental divestment method for divestment of one or more dental restoration parts comprising divesting the one or more dental restoration parts from a cured muffle by parting or blasting, wherein, in the production of the muffle (10), before the muffle is cast by a casting compound (21), one or more molded parts (20) or protrusions (58) are realized in or at a casting mold wherein the one or more molded parts (20) or protrusions (58) are fabricated of a removable material, wherein the one or more molded parts (20) or protrusions (58) are removed after the muffle (10) has cured, and wherein indentations or mold cavities produced from the one or more molded parts or protrusions are configured and/or used as one or more predetermined breaking points for the muffle (10) during divestment.

2. The dental divestment method as claimed in claim 1, wherein the one or more dental restoration part is removed by sandblasting, wherein the removable material is a burn-out material, and wherein the one or more molded parts (20) or protrusions (58) are removed by a burn-out process.

3. A dental divestment method for divestment of one or more dental restoration parts comprising divesting the one or more dental restoration parts from a cured muffle by parting or blasting, wherein, in the production of the muffle (10), before the muffle is cast by a casting compound (21), one or more molded parts (20) or protrusions (58) are realized in or at the casting mold, wherein one or more molded parts (20) or protrusions (58) are fabricated of a material which differs from the casting compound (21), and wherein the one or more molded parts (20) or protrusions (58) are configured and/or used as one or more predetermined breaking points for the muffle (10) during divestment.

4. The dental divestment method as claimed in claim 3, wherein the one or more dental restoration parts is removed by sandblasting, wherein the one or more molded parts (20) or protrusions (58) is not removed by a burn-out process.

5. The dental divestment method as claimed in claim 1, wherein a mark is configured at the muffle by the one or more molded parts (20), said mark extending radially outside the one or more dental restoration parts (16) and at a point outside of which the muffle material is removed quickly by rough blasting.

6. The dental divestment method as claimed in claim 1, wherein the muffle (10) is broken into at least two parts using the one or more predetermined breaking points after the muffle is cooled to a processing temperature and only the muffle core (60) of the muffle (10) comprising the one or more dental restoration parts (16) is blasted.

7. The dental divestment method as claimed in claim 1, wherein a plurality of rib-shaped radial apertures (22) extend from an imaginary ring surface outside of the one or more dental restoration parts (16) to the outside, wherein both the ring surface and the cavities or the boundaries between the one or more molded parts (20) and the casting compound (21) are configured as one or more predetermined breaking points, and wherein pieces surrounding the apertures extending radially are removed after the muffle (10) is cured.

8. The dental divestment method as claimed in claim 1, wherein a heat-resistant cutting tool is used with which the muffle (10) is cut in a hot state along one or more indentations which act as the one or more predetermined breaking points, and wherein a part of the muffle (10) comprising the one or more dental restoration parts (16) is further cooled and/or blasted.

9. The dental divestment method as claimed in claim 8, wherein the heat-resistant cutting tool comprises a sandblaster.

10. The dental divestment method as claimed in claim 1, wherein a fastening device and/or support struts are mounted to a muffle mold, a muffle bottom or a muffle lid (46) non-positively, positively or frictionally before the casting compound (21) is cast.

11. The dental divestment method as claimed in claim 1, wherein the one or more molded parts (20) is produced in a prefabricated manner by injection molding or by 3D printing, and wherein the one or more dental restoration parts (16) and the one or more molded parts are produced to match one another.

12. A dental muffle comprising a dental restoration part invested in a casting compound (21), wherein the casting compound comprises one or more predetermined breaking points spaced apart from the dental restoration part (16), wherein the one or more predetermined breaking points are formed by (i) one or more molded parts or protrusions fabricated of a material which is different from the casting compound (21) and not removable by a burn-out process, or (ii) indentations or mold cavities which are configured from one or more molded parts or protrusions which are removable by the burn-out process.

13. The muffle as claimed in claim 12, wherein the muffle (10) is cylindrical and wherein the one or more predetermined breaking points is/are arranged outside a height of the invested dental restoration part (16) when viewed along a cylinder axis of the muffle.

14. The muffle as claimed in claim 12, wherein the one or more molded parts (20) or protrusions (58) preparing a predetermined breaking point is part of a horizontal molded part (20) having apertures (22), wherein the one or more molded parts (20) extend transversely through the muffle (10).

15. The muffle as claimed in claim 12, wherein the one or more molded parts comprise a disc, which the disc or protrusion (58) extends substantially planar, in a direction of the diameter of the muffle (10), through the muffle.

16. The muffle as claimed in claim 12, wherein support struts are anchored to the one or more molded parts (20) or extend away from the one or more molded parts (20) in one piece, wherein the support struts are mounted on a muffle bottom.

17. The muffle as claimed in claim 15, wherein the apertures of the disc occupy at least 10% and no greater than 90% of the disc or between 20% and 80% of the disc or between 30% and 70% of the disc.

18. The muffle as claimed in claim 12, wherein at least one fastening element for one or more molded parts (20) is configured in one piece with the one or more molded parts (20), wherein the at least one fastening element supports the one or more molded parts on a muffle mold or a muffle lid (46).

19. A method for producing dental articles comprising shaping a model of a desired dental article using a removable material, inserting the model into a muffle, inserting one or more molded parts or protrusions, fabricated of a removable material, in the muffle above and/or below the model, inserting casting material into the muffle and curing the casting material, removing the removable material, wherein molds for the desired dental article are produced from the model, wherein indentations or cavities are produced from the one or more molded parts or protrusions, wherein the indentations or mold cavities produced are configured and/or used as one or more predetermined breaking points for the muffle during divestment.

20. A method for producing dental articles comprising shaping a model of a desired dental article using a removable material, inserting the model into a muffle, inserting one or more molded parts or protrusions, fabricated of a heat-resistant material, in the muffle above and/or below the model, inserting casting material into the muffle and curing the casting material, removing the removable material, wherein molds for the desired dental article are produced from the model, wherein the one or more molded parts or protrusions are configured and/or used as one or more predetermined breaking points for the muffle during divestment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Further advantages, details and features may be taken from the following description of several exemplary embodiments of the invention in conjunction with the drawings, in which:

[0066] FIG. 1 shows a perspective illustration of an inventive dental muffle for use in an inventive dental divestment method in a first embodiment;

[0067] FIG. 1a shows a top view of a possible embodiment of a molded part or molding for use with the dental divestment method according to the invention;

[0068] FIG. 1b shows a further embodiment of a molded part or molding for use with the inventive divestment method;

[0069] FIG. 2 shows a schematic illustration of an inventive dental muffle in a side view in a further embodiment;

[0070] FIG. 3 shows a schematic illustration of an inventive dental muffle in a side view in a further embodiment;

[0071] FIG. 4 shows a schematic illustration of an inventive dental muffle in a side view in a further embodiment;

[0072] FIG. 5 shows a schematic illustration of an inventive dental muffle in a side view in a further embodiment;

[0073] FIG. 6 shows a schematic illustration of an inventive dental muffle in a side view in a further embodiment;

[0074] FIG. 7 shows a schematic illustration of an inventive dental muffle in a side view in a further embodiment;

[0075] FIG. 8 shows a schematic illustration of a part of the dental muffle in the second embodiment; and

[0076] FIG. 9 shows a schematic illustration of the same part of the muffle but in the first embodiment.

DETAILED DESCRIPTION

[0077] A dental muffle 10 is illustrated in dashed lines in FIG. 1. In FIG. 1 the muffle 10 is illustrated in the press position in which its actual bottom side is at the top. In the initial position, that is to say in the casting position, the muffle 10 is upside down as opposed to the illustration according to FIG. 1.

[0078] In a way known per se, a press channel 12 illustrated in dashed lines is provided which is connected with mold cavities or molded parts or moldings for dental restoration parts 16 via sprue channels 14.

[0079] The dental restoration parts 16 extend annularly radially outside of the press channel 12, in the position of the muffle 10 according to FIG. 1 obliquely below the press channel 12.

[0080] According to the invention, a molded part or molding 20 is provided which is inserted into the muffle 10 before the investment material or casting compound 21 solidifies. In the exemplary embodiment illustrated, the molded part or molding 20 is substantially disc-shaped wherein it comprises a plurality of apertures 22 in any case.

[0081] The apertures 22 extend radially outside of a mandrel aperture 24. The aperture serves to receive the muffle mandrel 36 (see e.g. FIG. 2) and is sized such that it is spaced apart considerably from the muffle mandrel 36.

[0082] In this respect, the molded part or molding 20 is like a circular ring-shaped disc with apertures 22.

[0083] The molded part or molding 20 extends substantially at half the height of the muffle 10.

[0084] The positioning of height is realized in the illustrated exemplary embodiment by feet 26 which are supported on a muffle bottom 32 illustrated in FIG. 3.

[0085] The length of the feet 26 is selected such that the circular disc 20 is located just below (in the illustration according to FIG. 1 just above) the dental restoration parts 16.

[0086] The molded part or molding 20 extends out to the lateral surface 30 of the muffle 10.

[0087] After the muffle 10 has cured, the muffle 10 is burnt out, that is to say that all enclosed regions made of wax are melted out and removed. Accordingly, this also holds true for the molded part or molding 20. As a result of this configuration, a slit 62 whose thickness corresponds to the thickness of the molded part or molding 20 extends in the lateral surface 30 of the cured muffle 10. This spot serves as a predetermined breaking point for parting the muffle 10.

[0088] The slit 62 is circular and circumferential, however it does not lead to the muffle 10 being separated in two parts. Rather, it is still made of one piece as the investment material 21 of the muffle 10 also extends through the apertures 22.

[0089] In this respect, the apertures 22 have the dual function of enabling inflow into the lower part of the muffle 10 during casting of the casting compound 21 on the one hand, and of allowing for cohesion of the muffle 10 after the casting process.

[0090] From FIG. 1a, an exemplary embodiment of a molded part or molding 20 of this kind is apparent in the top view. A plurality of apertures 22 is provided. This also includes a central aperture 23.

[0091] The molded part or molding 20 according to FIG. 1a is intended for being deposited or inserted above the dental restoration parts 16. At this position, the press channel 12 and the associated muffle mandrel 36 do not exist anymore such that the central aperture 23 may be smaller than the muffle mandrel.

[0092] From FIG. 1b, a molded part or molding 20 is apparent which may be arranged at the position according to FIG. 1. Here, too, a plurality of apertures 22 are provided wherein a mandrel aperture 24 has a diameter which is considerably larger than the muffle mandrel 36.

[0093] An embodiment of an inventive dental muffle 10 during the investment process is apparent from FIG. 2. A molded part or molding 20 extends in the region of the press channel 12, i.e. below the dental restoration parts 16. A further molded part or molding 20 extends above the dental restoration parts 16 and may be configured according to FIG. 1a for instance.

[0094] The muffle 10 rests on a muffle bottom 32. It is connected in a liquid-tight manner with a muffle ring 34. A muffle mandrel 36 extends from the muffle bottom 32 towards the top. Muffle mandrel 36 and muffle bottom 32 are integral with one another in a way known per se and consist of e.g. silicone.

[0095] From the muffle bottom 32 the muffle mandrel 36 protrudes centrally to the top along the axis 40 of the muffle 10 and extends approximately up to half the height of the muffle 10 or slightly beyond. A sprue base may be waxed on its upper side 42 in a way known per se. Alternatively, sprue channels 44 and 47 extend from the muffle mandrel 36 obliquely radially towards the outside and the top. On the other end of the sprue channels 44 and 47, dental restoration parts 16 are arranged, or else initially corresponding wax molded parts to form the dental restoration parts 16.

[0096] To produce the cast muffle 10, the muffle bottom 32 is initially positioned and provided with the muffle ring 34. The arrangement of dental restoration parts 16 or else their wax models is located on the muffle mandrel 36.

[0097] The molded part or molding 20 is now pulled over the dental restoration parts 16 and placed on the feet 26 such that it extends in a disc-shaped manner slightly below the dental restoration parts 16.

[0098] For this purpose, it is required that the mandrel aperture 24 apparent from FIG. 2b has a sufficient size to fit outside of the dental restoration parts 16.

[0099] Alternatively, the molded part or molding 20 may also be placed on the muffle bottom 32 before the dental restoration parts 16 are waxed thereon.

[0100] The muffle 10 illustrated herein comprises a muffle lid 46 which fits on the muffle ring 34. The muffle lid 46 comprises a filling opening 48 via which it is possible to fill the interior of the muffle ring 34 with the liquid investment material 21.

[0101] There, a second molded part or molding 20 which is also disc-shaped is also mounted in a suspended manner. This upper molded part or molding 20 terminates slightly above the dental restoration parts 16.

[0102] Alternatively, it is also possible that the upper molded part or molding 20 is supported with additional feet 26 on the molded part or molding 20 below the dental restoration parts 16.

[0103] When the muffle lid 46 comprises no filling opening 48, it is still possible to provide the upper molded part or molding 20 in a suspended manner. In that case, the muffle 10 is filled and the lid with the suspended molded part or molding 20 is placed thereupon, while the investment material 21 is still liquid.

[0104] In any case, the upper molded part or molding 20 also comprises apertures 22 and for instance corresponds to the configuration according to FIG. 1a.

[0105] Further possible modifications of the inventive molded part or moldings 20, i.e. of the upper molded part or molding 20 and the lower molded part or molding 20, are apparent from FIGS. 3 to 7.

[0106] FIG. 3 shows a support arrangement 50 for the lower molded part or molding 20 instead of the feet 26, said support arrangement 50 leaning centrally against the muffle mandrel 36 and extending therefrom laterally radially towards the outside and obliquely towards the top to determine the position of height of the lower molded part or molding 20.

[0107] FIG. 4 shows a configuration in which the muffle lid 46 carries both the upper molded part or molding 20 and the lower molded part or molding 20. For this purpose, cross members 52 which fix the distance between the lower and the upper molded part or molding are provided instead of feet 26.

[0108] In this configuration, the central mandrel aperture 24 should be so large in any case that it may be pulled over the arrangement of the dental restoration parts 16.

[0109] FIG. 5 shows an arrangement of additional molded parts or moldings 54 and 56. The molded part or molding 54 extends like a circular wall radially within the muffle ring 36. It comprises numerous apertures.

[0110] The molded part or molding 56 extends radially within the molded part or molding 54 and between the dental restoration parts 16 and the lower molded part or molding 20.

[0111] In the embodiment illustrated herein, the lower molded part or molding 20 is additionally supported on protrusions 58. The protrusions 58 extend radially towards the inside at the muffle ring 36.

[0112] While in case of the embodiments of the muffle 10 according to FIGS. 2 to 4 the muffle 10 is initially parted along the lower molded part or molding 20 and then along the upper molded part or molding 20 which each form predetermined breaking points after burning out, a further separation is possible in the embodiment according to FIG. 5.

[0113] Here, too, the predetermined breaking points along the molded part or moldings 20 and 54 are initially utilized again. However, the remaining central part of the muffle 10 may be separated further by also splitting off radial outer parts of the muffle 10 along the slits 62 or predetermined breaking points corresponding to part 54.

[0114] There, too, ribs may extend between the molded part or molding 54 and the muffle ring 36 radially towards the outside such that the corresponding parts may be separated more easily in the manner of pieces of a cake.

[0115] Additionally, further separation of the now remaining muffle core may be performed along the predetermined breaking point corresponding to the molded part or molding 56. Thus, only one muffle core piece 60 remains which is markedly compact and extends only slightly outside of the dental restoration parts 16.

[0116] As all the molded part or moldings comprise apertures 22 respectively, the pressure existing thereat is still supported by the muffle material up to the lateral surface 30 of the muffle 10 such that muffle breakages or muffle cracks must not be feared.

[0117] In the embodiment according to FIG. 6, the lower molded part or molding 20 is supported by hanging struts 52 at the upper edge of the muffle ring 36.

[0118] In the embodiment according to FIG. 7, the upper molded part or molding 20 is realized in the manner as already mentioned, while the lower molded part or molding 20 is slid in through a slit 62 in the muffle ring 36 laterally at the desired height. It is to be understood that in this solution the mandrel aperture 24 is open laterally in a U-shaped manner. If desired, this embodiment allows for a comparatively small mandrel recess as the lower molded part or molding 20 is slid in when the dental restoration parts 16 are already in situ.

[0119] The molded part or molding 20 is supported in the slit 62 in the ring 36 wherein it is to be understood that sealing measures may be taken against leaking investment material 21 if necessary.

[0120] The dental divestment method, referred to as second embodiment further above in the description, is to be described below.

[0121] In contrast to the configuration according to claim 1 which is referred to as the first embodiment herein, the material of the molded part or moldings 20 or protrusions 58 may not be removed by boiling out or burning out in this configuration. When the wax-like material in the mold cavities for the dental restoration parts 16 is removed, the material of the molded part or moldings remains in the muffle 10.

[0122] The configuration of the molded part or moldings 20 or protrusions 58 may correspond to the configuration according to FIGS. 1 to 7 and may thus be provided in any desired manner to provide for the desired predetermined breaking point 70.

[0123] Technical basis for realizing the predetermined breaking point 70 by means of the non-removable molded part or moldings is the boundary layer or boundary 66 and 68 thereof towards the casting compound 21 of the muffle.

[0124] The molded part or moldings 20 of this second embodiment are also invested in the casting compound 21. The phosphatic casting compound 21 tends to penetrate into porous or rough surfaces and to produce a secure connection.

[0125] This tendency is counteracted inventively in that the molded part or moldings 20 or protrusions 58 are smooth and thus have a very low surface roughness of less than R.sub.a=2 m.

[0126] Additionally, the materials of the molded part or moldings 20 on the one hand and of the casting compound 21 on the other hand are dispersed against each other, i.e. they do not mix with one another even when heat-treated.

[0127] The microgap existing at the boundary 66 and 68 in this respect is sufficient to form the desired predetermined breaking point 70. If a breaking force is applied thereto, the muffle 10 splits up at the boundary 66 and 68 from the molded part or molding 20. This may be realized e.g. by a breaking process but also by means of a cutting tool such as a chisel which is applied on the outside at the boundary 66 and 68.

[0128] It is to be understood that a disc-shaped molded part or molding 20 has two boundaries 66 and 68, or possibly additional boundaries 66 and 68 of which one points upwards and the other points downwards. Both boundaries 66 and 68 may be provided as predetermined breaking points 70, wherein it is sufficient basically to keep one of the boundaries 66 and 68 smooth and to realize it as a predetermined breaking point 70 accordingly.

[0129] A possible configuration of a part of a corresponding muffle 10 according to this second embodiment is illustrated in FIG. 8. The molded part or molding 20 extends in a disc-shaped manner of which a radial outer region is illustrated. Apertures 22 are provided radially further to the inside but are not illustrated herein.

[0130] In the embodiment according to FIG. 8, i.e. the embodiment referred to as second embodiment, the molded part or molding 20 is comparatively thick. It may be fabricated of materials such as, but not limited to, certain silicates, zirconia, alumina, ceramics, glass-ceramics and the like, which have a considerably higher thermal capacity than the phosphate-bonded investment material and which are preferably not removable during the burn-out process.

[0131] This fact may be utilized specially according to the invention:

[0132] During the first cooling process of the hot muffle 10, the muffle 10 initially becomes comparatively cold at the lateral surface 30 of the muffle 10, and then cools both the casting compound 21 and the molded part or molding 20. While doing so, however, the casting compound 21 cools more quickly than the molded part or molding 20, due to its lower thermal capacity. It is assumed, for instance, that the casting compound 21 has a temperature which has dropped to 600 C., while the molded part or molding 20 further radially towards the inside still has a temperature of 900 C.

[0133] In this state, the volume of the molded part or molding 20 is larger compared to that of the molded part or molding compound than when the parts have the same temperature. Thus, axial pressure is exerted along the cylinder axis 64 of sleeve 10 at the location of molded part or molding 20, as it were, from the inside. The casting compound 21 is brittle and therefore breaks at the location of the molded part or molding 20.

[0134] However, it is also possible to work with comparatively thin molded part or moldings 20 made of a heat-resistant material, and to still realize a predetermined breaking point 70. In this embodiment, the thickness may correspond to that of the slit 62 from FIG. 9, for instance.

[0135] In this instance, the axial force is not sufficient for splitting the muffle 10 due to the greater expansion of the molded part or molding 20, since the temperatures are angled across the interfaces 66 and 68 due to the heat conduction of the molded part or molding 20.

[0136] In this embodiment, the smoothness of the molded part or molding 20 at the boundaries 66 and 68 towards the muffle material 21 is effective. There is a microgap thereat which does not offer any cohesion against axial forces.

[0137] This may be utilized by applying a cutting tool for instance at the predetermined breaking point 70 corresponding to the radial outer end of the boundary 68 and thus splitting the muffle 10 at this position.

[0138] It is also possible to round the molded part or molding 20 thereat, i.e. for instance at the lower boundary 68, in a slightly convex manner. Then, the casting compound 21 forms a circumferential tongue-like protrusion 72 towards the top which can be easily removed with a knife or screwdriver, for example, in order to be able to attach the cutting tool more easily.

[0139] It is to be understood that here both boundaries 66 and 68 are available as predetermined breaking points 70. If a bending force is applied to the muffle 10 without further ado, the muffle 10 will break at the position at which the casting compound 21 which extends through the apertures 22 not illustrated comprises the lower cohesion.

[0140] Compared to the embodiment referred to as second embodiment herein, the realization of a predetermined breaking point 70 in the embodiment referred to as first embodiment herein is illustrated in FIG. 9. The slit 62 was produced by a removed molded part or molding 20.

[0141] The predetermined breaking point 70 is clearly visible as slit 62. Here, a cutting tool may be applied, or a bending force or a torsional moment is exerted on the muffle 10 to break the casting compound 21 extending through the apertures 22 at this position which ensures for cohesion.