DE3844151C2 - - Google Patents

Description

The invention is based on a method for manufacturing of a dental-technical prosthetic attachment anchor, ins especially a telescopic or conical crown, from one gold-free alloy using the infusion technique. The The invention further relates to a dental prosthetic attachment anchor made of a gold-free le yaw.

For anchoring removable partial dentures in the mouth are next to brackets, push button mechanisms, or similar special attachments, the so-called attachments anchor used. Such an attachment anchor is common mine consisting of two reversibly interlocking parts built, of which the primary part in the spare crown of the anchor tooth, the secondary part in the removable Dental prosthesis construction is integrated.

In order to ensure the necessary adhesion, the To wear dentures, primary and secondary parts must be included run smoothly with great precision (frictive Principle with parallel wall construction) or on each other keep others stationary (principle of adhesion with conical tub dung). Design-related dead spaces must be avoided hygienic reasons are kept as small as possible.

Attachments are ge in various embodiments manufactures:

• 1. as intracoronal attachments, in which the primary part inside the contour of the anchor crown is taken
• 2. as extracoronal attachments, in which the primary part of the anchor crown is attached externally or as Bridge attachment in a connecting bridge between two Holding teeth is incorporated,
• 3. as a telescopic or double crown, in which an anchor crown in toto forms the primary part: the Anchor tooth is initially not anatomical shaped, circularly milled sleeve (primary telescope) provided, across which then one anatomically shaped outer crown (secondary telescope) is manufactured, which in turn firmly with the removable portion of the prosthesis is connected. With parallel wall milling of the primary crown is a frictional telescopic crown in the narrow Literal sense; with truncated cone milling of the primary sleeve with a so-called cone angle results the adherent conical crown.

Attachments are traditionally cast after indirect casting method from a precious metal, especially gold alloy with a silicone impression of the finished milled  Primary structure produced, which after implementation in a refractory mold the secondary structure by casting allowed to manufacture. This indirect casting technique, the for the relatively low melting gold alloys provides satisfactory results, with increasing Working temperature of the metal, e.g. B. already in use dental palladium alloys, increasingly problematic table and fails when using non-precious metals taler cobalt and nickel-based alloys (NEM) except Random success.

Also ideal for the coefficient of thermal expansion the alloy is set to suit the expansion molding compound will receive a casting result, which by un acceptable tolerances (excessive play or clamping pas solution) is marked. Even if it's through elaborate Reworking succeeds in improving the bed load, In the end, it only becomes one at a few points key fit of primary and secondary part achieved. Disadvantages here are the hygienic be conceivable dead space formation, the premature wear as well as indefinable changes in the original set holding forces.

These disadvantages of the indirect casting method are considered the state of the art through the infusion technique, a direct method of manufacturing the secondary part ver avoided.

In the infusion technique, the primary structure of the Ge slide itself into the mold for the secondary part embedded so that the casting of the secondary part directly on the surface of the primary part takes place. So that primary and the secondary part remain separable, the primary structure against the liquid metal of the secondary casting  be isolated accordingly. The following paths are followed to separate primary and secondary parts in the infusion technique to receive cash:

• - a primary alloy is selected, its working temperature is significantly higher than the working secondary alloy temperature. For example, for that Primary part a cobalt base alloy and for that Secondary part gold selected. This method always brings but the problem of corrosion, especially strengthening of crevice corrosion by acid gradient with itself and should therefore be made from bio logical reasons are not applied,
• - There are oxidic separating layers on the surface che formed of the primary part.
• This can be done in different ways:
  • 1. After the primary part has been glowing for a long time, an autogenous oxide layer is produced (cf. I. Lenz, Die Quintessenz der Zahntechnik, issue 11/1987, pp. 1219-1230). However, the necessary longer annealing near the recrystallization temperature of the primary alloy deteriorates the surface quality. The roughness that occurs can cause micro-wedging of the primary and secondary parts. Above all, however, the auto-gen oxide skin is often hit by secondary metal, which results in the parts being glued. This phenomenon occurs particularly with large attachment areas, so that circularly comprehensive constructions, e.g. B. telescopic and cone crown are not feasible in practical routine.
  • 2. The oxide separating layer is carried out by applying an oxidic insulating compound to the primary part before modeling the secondary part. However, the dried insulation is sensitive to touch and tends to burst. Furthermore, disruptive structures are left behind by application with a brush or spray. Such an application has a different thickness, particularly at the edges. Furthermore, the liquid secondary metal can peel off the insulating compound at rheologically unfavorable points and drag it into the casting. This often results in sticking, particularly in the case of circular attachment areas such as on conical and telescopic crowns. Since the insulating layer must be removed after separation of the castings, the casting is imprecise by a little more than the amount of the layer. Especially cylinder fits are inadequate in their friction or lose them completely in favor of an impermissibly wide clearance fit.
  • 3. The primary part is made from an alloy, which due to its components, eg. B. titanium or aluminum, particularly strongly oxidized and self-insulation when casting (see J. Lindigkeit, Phillip Journal 9-1985, pp. 283-289). Because of the great tendency to oxidize, however, work has to be carried out in a complex vacuum casting system which generally does not have the dental laboratories. In the case of cone and telescopic crowns, the insulating effect of the relatively low titanium and aluminum contents is often insufficient. High titanium contents cause the alloy to be unresponsive to the casting compound and make later metallic connections (soldering, welding) problematic.

The quality of a bed load construction depends on the Precision of the fit of the adhesive or friction Areas. In the known methods for the production of Sliding anchors with a high separability rate can be one adequate temperature-resistant insulation between Primary attachments and secondary attachments only by building one relatively thick separation layer can be achieved. This one Separating layer can be removed after casting must, the fit created in this way becomes imperfect and therefore unsuitable for areas of application where there is a precise fit arrives, such as B. in parallel attachment of Cylinder telescopes.

The invention is therefore based on the object dental prosthetic anchors of any shape Made of a gold-free alloy with a precise fit of Using primary attachments and secondary attachments to create laboratory equipment and materials. These The task is in a process of the type mentioned solved in that in the surface area of the Primary attachment from outside at least one other metal, namely titanium and / or aluminum and / or zirconium brings in.

Preferred embodiments are the subject of the dependent claims.  

The stated task is still solved by a dental prosthetic anchor from one gold free alloy containing titanium and / or Aluminum and / or zirconium of the gold-free alloy of the primary bed load only in the surface area.

In the context of the present invention are among gold-free Alloys understood mouth-proven metal alloys that no gold, but other precious metals, such as B. Palladium and / or ruthenium can contain. To be favoured Known non-precious metal materials are used, especially conventional ones non-precious alloys, such as B. cobalt-chrome Alloys or nickel-chromium alloys.

The two parts of a bedlock anchor are called the primary part and designated secondary part. The primary part is that first made part, what with telescopic and conical crowns usually represents the patrix. The secondary part is that Part that is the second part directly on the primary part is poured. This is the case with telescopic and conical crowns Secondary part the outer crown, the matrix. However, there is Cases, especially with smaller attachments, where you first pour the matrix with the anchor crown. In this case, poses the matrix is the primary part. Then the The male part is poured directly into the female part. In the description and the claims of the present patent application with the primary part (primary attachments, etc.) basically that first marked part,  regardless of whether it serves as a male or female. With a secondary part (secondary attachments, etc.) directly cast on the primary part, regardless of whether it is as a female or male serves.

With flux, as usual, chemical substances referred to, the metal deposition of Ne Promote products or waste materials.

In the method according to the invention, an isolie is therefore used layer within the surface of the Primary part built itself. This has the advantage that no insulation with relevant layer thickness applied becomes. Theoretically, the beneficial effect that To achieve according to the invention, explain as follows: the definitely machined surface of the primary structure is used with titanium and / or aluminum and / or zirconium insulating medium doped, which is in the upper integrated and through its effect as a diffuse sion lock a bonding of primary and secondary casting prevented. The barrier layer, which one after heating the with titanium insulation in primary part Preserves graphite powder and presumably various carbide Containing titanium compounds has proven to be special to us proven kung.

The introduction of titanium and / or aluminum and / or Zirconium in the surface area of the primary attachment producing the barrier layer can preferably after one of the following three procedures:

1. the final machined primary attachment surface is roughened and thus activated. This can e.g. B. with finest micro-corundum powder of no more than 25 µm Grain size at low pressure (e.g. up to 2 bar)  a distance of about 5 to 7 cm so that it is just perceptible to the naked eye. The surface roughness should never be as big as this from Application of oxidic insulating layers is common.

After degreasing with hot steam, mechanical cleaning in an ultrasonic bath (5 minutes, distilled water at 70 ° C) and renewed evaporation, a coat of aqueous titanium hydride slurry (TiH ₂ ) is added, to which about 5% LiF has been added as a flux and adhesive . The order is decomposed after drying in the technical vacuum of a conventional ceramic oven at approx. 900 to 1000 ° C for a few minutes. The furnace should be switched so that the vacuum builds up before the temperature rises. Since oxygen and nitrogen interfere, these residual gases must be removed. Oxygen and nitrogen can be conveniently bound in that titanium chips or the like, e.g. B. a thin titanium wire spiral or a titanium wire braid, which must be blasted before each use, with the workpiece to be machined. It is also advantageous if the atmosphere is hydrogen-containing, which is easily achieved by adding a spatula of pointed TiH ₂ powder in a porcelain bowl to the ceramic oven. The hydrogen bonded in the titanium hydride is released when the need arises, where the coating of titanium hydride pulp in the primary parts breaks down into its elements. The released atomic and thus highly active titanium is stored under these conditions, even below its melting temperature, to a small but sufficient extent in the prepared surface of suitable alloys.

The majority of the titanium hydride burns during Opening the combustion chamber to form titanium oxide or Lithium and oxyacetylene oxides in various forms  a more or less adherent rough layer. This initially adheres to the primary casting oxide layer - unlike conventional methods - in which he Process according to the invention after cooling with a fine abrasive from glass beads completely before the infusion worn without ver ver the actual metal surface last.

During the Ab cooling phase in case of air ingress various oxidation products of the titanium introduced. The after overcast olive-gold to black satin surface considerable isolation from the Secondary casting on. This can be particularly important with regard on the mechanical resilience (hardness) still essential Lich improved if the primary parts in graphite powder embedded in the graphite crucible for about 10 Minutes (e.g. inductive in a high-frequency casting plant ge) are heated to approx. 1000 ° C. The one in the Surface formed carbides or carbide nitrides of titanium and other alloy partners harden the Surface so that after cooling the graphite powder residues before further processing of the primary parts can be rubbed off or brushed off carefully.

After modeling, casting and separating the primary from the The carbides with the finest corundum can be used for secondary parts gently remove powder from the surface, what is a polish with diamond paste on felt wheel can connect. A polish without previous loading action with corundum is also possible, but time-wise more maneuverable. The substance removal is as low as possible to keep. The polish is to be limited to silky sheen ken, high gloss is unnecessary and detrimental in many cases Lich. Therefore, rubber polishers should be applied to the friction and Adhesive surfaces are not used.  

2. The titanium can also pass through in an aluminothermic way Reacting titanium dioxide with the stoichiometric amount of aluminum in the form of the finest aluminum powder in situ to be released. The mixture of titanium dioxide and Aluminum is mixed with water and preferably with flux tel, e.g. B. with the addition of about 5% LiF, moistened and applied as described under 1. The reaction also takes place here in at least the technical vacuum of Ceramic oven, preferably with the addition of titanium wire. A hydrogen atmosphere is not necessary. To The primary parts end as described under 1 above. described, further processed. The reaction residues adhere to the primary parts here somewhat more firmly than with the titanium hydride method.

The TiO ₂ -Al mixture must always be freshly prepared, since it can neither be kept dry nor moist, and must be inactivated in a larger amount of water after use.

3. Another alternative to the production of metallic Ti in the surface area of the primary attachment is the thermal gas phase decomposition of Ti-Haiden. To do this, decompose a Ti (IV) halide, e.g. B. TiJ ₄ , e.g. B. in a low pressure hydrogen atmosphere in the RF induction coil of the melting system. The gaseous Ti that forms is superficially embedded in the gold-free alloy of the primary attachment. Titanium can also be released metallically by decomposing a Ti (II) halide or TiJ ₄ in situ.

Further possibilities of an appropriate formation of the person skilled in the art can readily use metallic Ti Take literature.  

In the methods 1 to 3 described above, when the surface is initially activated and when final overcasting surface substance gen. However, this substance removal is much less ger than in the known methods of the prior art Technology and is basically necessary to e.g. B. Cylinder fits a minimal competitive game lichen. Without such a game, the disassembled Telescopic crown under liquid not at all be pushed because trapped saliva does not could be ousted. Furthermore, one must Error rate in concentricity and parallelism of the laboratory instruments are taken into account. Exceed such errors, however, are the minimum required tolerance the construction, so the infusion construction is mecha wedged inseparably.

Are primary and secondary part, as usual, from Made of the same alloy, both are partners regularly wedged and hardly without mechanical Deformable if it is a cone or deformation Cylinder telescopic crown acts. Intracoronal attachments, where the secondary part is cast in as a male part, are much easier to separate.

With the following theoretical consideration, this could Appearance to be explained: the secondary part heats up Infusion of the primary part almost at its own temperature on, however, in contrast to this one, he still has to Join the phase jump when solidifying and shrink there by essential despite almost the same working temperature stronger than the primary part. Have both alloys the same coefficient of thermal expansion, so ent there is a mechanically practically unsolvable wedge connection  in cases where the infusion is the primary part, as in the Double crown, externally encircled, or other on the one hand a game customization too easy if the Attachment patrix is poured in. Therefore, according to an embodiment of the invention in double crowns secondary outer crown made of an alloy with a ge slightly smaller coefficients of thermal expansion ge poured as the primary inner crown. Has proven particularly successful z. B. the combination of a cobalt-chrome stellite with a coefficient of thermal expansion of 14.7 ppm for the primary crown with one Niobium-stabilized nickel-based alloy with a Thermal expansion coefficient of about 14.5 ppm for the secondary crown. Will the Poured secondary part, so the same alloy how to use primarily as long as it is small dimensioned parts.

The corrosion-chemical activities of cobalt and Nickel alloys in the dental field are so similar that their difference can be neglected and Cor corrosion effects are not caused by this.

Attachments cast on in the manner described made of two different alloys with different Coefficients of thermal expansion are often difficult at first separable. Due to the different thermal expansion coefficient between the primary part and the Se The secondary part can be easily removed if the Ge slide after heating or if you are while cooling the inner crown from the inside, the outer crown heats up. The separation that has occurred can be recognized by this nen that the doors when re-heating together lines of construction through different  Highlight the glow colors of the primary and secondary parts A pneumatic chisel is special for separation suitable. Here the chisel tip is alternating on both sides of the casting cone in the pull-off direction of the Ge put on slide, which is why the castings only after the Separation from their cone should be sawn off.

The present description deals in particular with titanium as another metal that is in the surfaces area of the primary attachment. In the same Aluminum or zircon can also be used bring, these metals from their compounds either in situ on the surface of the primary attachment or be released in the gas phase, the gas shaped metal itself in the surface area of the gold-free Alloy of the primary attachment is stored.

With a gross mismatch between the wall thicknesses or Metal masses when pouring telescope and cone crowns it is to avoid heat build-up in the pri advantageous when you have the refractory one bed mass stump that corresponds to the tooth stump and the Primary parts applied, makes thermally conductive. this will achieved in the sense of the invention that at one beds of the isolated primary parts for pouring them on Interiors are poured out with investment material that approx. 50% of the volume of chrome granules or tungsten granules contains. In individual cases, tungsten can result from its exceptionally good thermal conductivity too strong have a cooling effect (outer crown does not flow out), so that to work with chrome. Care should be taken that Chromium or tungsten not in finely divided powder form is used because the latter with oxygen under the Process conditions reacted to the oxide. The use Leading metals must have a coefficient of thermal expansion  are below that of the investment mixture lie, the melting point must be above that of the Geschiebele Gations are and the oxide formation of the granules Preheating must not lead to deformation of the mold.

Claims (11)

1. A method for producing a dental prosthetic anchor, in particular a telescopic or conical crown made of a gold-free alloy by means of an infusion technique, characterized in that at least one other metal, namely titanium and / or aluminum and / or Brings in zirconium. 2. The method according to claim 1, characterized in that the other metal in the form of a metal compound on the surface of the primary attachment and from it metallic titanium, aluminum in the heat and / or releases zirconium. 3. The method according to claim 2, characterized in that a thermally decomposable metal compound is applied and then to form metallic Titanium, aluminum and / or zirconium thermally decomposed. 4. The method according to claim 2 or 3, characterized in that that in addition to the surface of the Primary bedded flux applies. 5. The method according to claim 2 or 3, characterized in that the primary part with an aqueous Suspesion of titanium hydride (TiH₂) brushed and then in a nitrogen-free reducing atmosphere heated to 900 to 1000 ° C. 6. The method according to any one of claims 1 to 5, characterized in that that the primary part after insertion heated by titanium in graphite powder.   7. The method according to any one of claims 1 to 6, characterized in that that one has the primary attachment or secondary attachment as a patrix made of a gold-free alloy with a larger expansion coefficient than that Expansion coefficient of the gold-free alloy Manufactures die. 8. The method according to claim 7, characterized in that one separates primary and secondary attachments together heated and deterred. 9. The method according to claim 7, characterized in that one cools the inside of the patrix and the The die heats up. 10. The method according to any one of claims 1 to 9, characterized in that the fireproof investment for the stump corresponding to the tooth stump, that of the primary attachment is present, makes it thermally conductive.   11. Dental prosthetic attachment anchor made of a gold-free one Alloy, characterized in that only in the surface area the gold-free alloy of the primary attachment Titanium and / or aluminum and / or zirconium is included.