EP2934370A1

EP2934370A1 - Method and arrangement for veneering crowns and bridges, and firing tray therefor

Info

Publication number: EP2934370A1
Application number: EP13737793.3A
Authority: EP
Inventors: Claudia Petroll
Original assignee: Selection - Dental GmbH
Current assignee: Selection - Dental GmbH
Priority date: 2012-12-20
Filing date: 2013-06-07
Publication date: 2015-10-28
Also published as: DE202012104979U1; WO2014094725A1

Abstract

The invention relates to a method by which crowns and bridges (3) consisting of metallic dental alloys, zirconium and/or ceramic materials are veneered with ceramic compounds in a furnace (1), characterized in that, in order to heat the crowns and bridges (3) in the furnace (1), the crowns and bridges (3) are warmed from the inside by heat-conducting contact. The invention further relates to an arrangement by which crowns and bridges (3) consisting of metallic dental alloys, zirconium and/or ceramic materials are veneered with ceramic compounds, said arrangement having a furnace (1), a firing tray metal plate (2) and at least one holding pin (21) made of metal, wherein the holding pin (21) is provided for holding the crowns and bridges (3) that are to be veneered, characterized in that the firing tray metal plate (2) is planar/closed on its top face, and the holding pin (21) has a foot (22) with a plane underside. The invention further relates to a firing tray metal plate (2) therefor.

Description

DESCRIPTION

Method and arrangement for veneering crowns and bridges as well

Firing tray for it

The invention relates to a method for veneering of dental alloys, zirconium and / or ceramic materials existing crowns and bridges with ceramic materials in a kiln and an arrangement therefor, comprising a kiln and a Brenngutträger- metal plate and at least one retaining pin made of metal, wherein the retaining pin is provided for holding the crowns and bridges to be veneered. Furthermore, the invention relates to a firing tray for it. The metallic dental alloys, zirconium and / or ceramic materials are also hereafter

in summary, called dental materials from which the dental workpieces, especially crowns and bridges are made.

When veneering of dental dental alloys, zirconium and / or ceramic materials existing dentures, such as bridges, with

Ceramic compounds is applied to the dentures scaffold in a suitable way

Ceramic compound applied and placed in a kiln on the for the

Ceramic firing required temperature heated and fired. The quality of the dental prosthesis created in this way is highly dependent on the right choice of materials, the appropriate tools, carefully selected

Process parameters and the experience of the dental technician. With the smallest deviations from the ideal values fatal defects can arise on the dentures, which lead to a high reject rate in the production and to

Complaints from the instructing dentists or patients lead. Typical damage cases are:

poor metal-ceramic composite,

Leap in ceramics (possibly occurring later),

Flaking off ceramic fragments, Formation of bladders, partly open, which are also called "Froschaugen", and

Distortion of the dental work piece (framework), especially with large-span bridges. Previously, the dentures were made entirely of gold. A thin ceramic layer was then fired on this gold-made denture, such as bridges, crowns. The ceramic used had compared to the most used today very fine and uniform

Nano-ceramic a broader particle size distribution, resulting in a coarser and therefore for expelled constituents, such as water vapor, much more permeable mass adjusted.

Metallic dental alloys, zirconium and / or ceramic materials for the production of dental prostheses were then developed as a substitute for gold. At the same time were always finer, with a uniform small grain size

developed (nano-particle) ceramic coatings. Thus, the burning process became more difficult. For the smallest deviations from the optimal process parameters then emerged the above

Claims.

Usually, the crowns and bridges made of dental materials for porcelain veneering are prepared so that they are placed on a firing tray, which is designed in the form of a ceramic honeycomb plate. In this case, plug-in retaining pins are provided in the ceramic honeycomb plate, which are fixed against slipping by insertion into the honeycomb plate and on its upper side, for example, tapered cylindrical shape or hook shape, so that on the prepared crowns and / or bridges can be securely supported. These retaining pins are made of metal or ceramic.

DE 103 25 524 A1 shows a firing tray for dental ceramic dentures made of metal. The support plate has a hole pattern in the correspondingly shaped retaining pins can be inserted for the crowns / bridges to be machined.

DE 1 963 886 U also shows a metallic firing tray, which is equipped with insertion holes for corresponding retaining pins. The retaining pins have so-called support collars, so that the pins occupy a defined depth of penetration into the insertion holes provided in the firing tray.

US Pat. No. 4,184,840 shows a retaining pin for dental ceramic prostheses, which has the shape of a conical mandrel. Again, the retaining pins are inserted in provided in the firing tray holes. No. 3,861,867 A shows a firing tray made of a heat-resistant alloy, with receiving openings, here with therein

cut threads, is equipped. The plug-in or screw-in retaining pins may have different shape, for example, conical shape. For a ceramic coating is on the off the dental material

manufactured crown or bridge, optionally after one

Surface preparation, applied thinly dissolved in a carrier liquid dissolved ceramic material. The thus inserted crown or bridge is placed on the previously aligned holding pins (firing material holders). Then the firing tray is placed in the kiln with the crowns and bridges placed on top of it. This slow heating rates and correspondingly long Rückkühlzeiten are required so that the ceramic material can be burned without damage on the base body formed from the dental material.

The object of the invention is to provide a method and an arrangement of the type described with a kiln and a firing tray for it, with a ceramic facing faster, less prone to damage and thus in always repeatable good quality is possible. This object is achieved by a method according to claim 1.

According to the device, the object is achieved with an arrangement according to claim 6 or a firing tray according to claim 12.

Examinations of a large number of damage cases finally led to the surprising finding that the heating occurring in the kiln to be veneered crown or bridge prevails over that prevailing in the kiln

Thermal radiation causes a drying out of the ceramic material applied with the carrier liquid from the outside to the inside, which leads to errors in the ceramic firing at too fast heating time, too thick order and / or other deviations from the ideal parameters. By heating the crowns and bridges in the kiln via thermally conductive contact from the inside out, in conjunction with the high mass and thus the

Heat absorption capacity of the Brenngutträger-metal plate and subsequent heat conduction over the retaining pins to the dental crown created from the dental material and bridges uniform drying of the ceramic material can be achieved from the inside out.

Contrary to the opinion of the experts, which regards just a warming over heat conduction and an introduction of "unnecessary masses" in the combustion chamber as harmful, can by replacing the light, hardly heat-absorbing and conductive firing material carriers in the form of ceramic

Honeycomb panels now with the massive firing metal plate

trained Brenngutträgern and the heat-conducting heating of the inside of the crowns and bridges surprisingly qualitatively uniform results can be achieved. In this case, faster heating rates and shorter recooling times can be carried out without damage. Due to the

Heating via heat conduction from the inside to the outside does not cause blisters (frog eyes). These frog eyes are likely to occur when drying the ceramic in the previous process whenever the ceramic dries faster from the outside, as the inside evaporates the carrier liquid, in particular the water content. Accordingly, it is believed that the frog eyes hydrothermal vents are those modified by the invention

Heating behavior over the firing tray metal plate from the inside out safely avoided.

Due to the more uniform heating of both the dental material by heat conduction from the Brenngutträger-metal plate on the retaining pins in the crowns or bridges on the one hand and the heating by heat radiation from outside to inside, the resulting during heating and later cooling during cooling material stresses due to different thermal expansion be minimized. Although it has already been tried in the prior art, the thermal expansion coefficient of

To bring dental materials with the coefficient of thermal expansion of the applied ceramic material in a close tolerance range close to each other, however, this theoretical value is of little use, if the two adjacent materials during the firing process, especially during heating or during cooling significantly different

Have temperatures to each other.

On the plane-flat and closed top of the Brenngutträger- metal plate, which has no holes in contrast to the prior art, the retaining pins can be positioned anywhere on the Brenngutträger metal plate by simply setting up. Nevertheless, should be different during the firing process thermal expansions of the

yielding adjacent materials, the erected on the Brenngutträger- metal plate holding pins by simply slipping the

Compensate for thermal expansion differences. This is an excessive stress on the support pins placed dental workpiece (framework) and thus the risk of distortion, for example, on large-span bridges, the subsequent adjustment in the patient or even a

Rebuilding required, avoided.

In contrast, arise in plugged in a known honeycomb plate retaining pins due to the there defined positive association on these held crowns or bridges mechanical stresses that can lead in the worst case to flaking of the fired on the dental alloy ceramic or distortion of the dental workpiece (scaffold), especially in large span bridges. Furthermore, the feet formed with a flat underside of the retaining pins as possible

have large-area, thermally conductive contact. The flat bottom of the downwardly widening base makes with the Brenngutträger metal plate a good, relatively large-area Wärmeleitkontakt ago. At the same time a good stability of the erected on the firing tray metal plate retaining pin is achieved.

If the Brenngutträger-metal plate is an integral part of the kiln, this can be heated by heat conduction in the kiln, but the placement of the Brenngutträger metal plate must be done with the crowns and bridges to be coated on the open kiln. If the Brenngutträger-metal plate is formed actively heated, the heating of the Brenngutträger-metal plate in the kiln, for example, can be supported inductively active, so that the heating time further reduced and provided by heat transfer heat input from the inside can be further increased in the dentures. For example, the Brenngutträger-metal plate is heated electrically in the kiln. Of course, an actively heatable Brenngutträger-metal plate can be made removable from the kiln, for example, if it contains an electric heating wire, which is contacted via electrical contacts during insertion of the Brenngutträger-metal plate in the kiln. If the retaining pin has a mandrel, which is raised when used properly from the firing tray metal plate, for holding the crowns and bridges, a secure and substantially stress-free retention of the dental pieces is achieved. Preferably, the mandrel has a concave tapering towards the top

Truncated cone shape to reliably avoid unwanted distortion of the mandrel in the crown or bridge. The crown or bridge should rest only on the mandrel, but have the largest possible contact surface for good heat conduction.

If the metal or the alloy of the fuel tray metal plate and / or the retaining pins has a density greater than 4.5 kg / dm ³ , preferably greater than 8.0 kg / dm ³ , the firing metal plate is due to heat radiation due to its high mass faster than the ceramic material is heated in the kiln, the heat is dissipated via heat conduction evenly over the retaining pins to the bridge or crown.

At a thickness of 1 to 10 mm, in particular 3 to 5 mm of the Brenngutträger- metal plate introduced into the kiln total mass according to the predetermined density is sufficiently large to absorb thermal energy transmitted by heat radiation and to forward to the crowns or bridges can. However, the fuel tray metal plate does not absorb too much heat when introduced into the kiln, so that the firing process can still be carried out economically. Possibly. The massive firing tray can also be introduced preheated in the kiln. In order to achieve the lowest possible release of ions from the fuel tray metal plate, it consists of a metal alloy with one or more of the following elements cobalt, chromium, molybdenum, manganese, tin, gallium, indium, silicon, tungsten, gold and / or platinum. In particular, the material must be free of arsenic and sulfur. If the firing metal plate and / or the retaining pins with an intermetallic-ceramic glass phase (such

For example, from DE 100 22 259 B4) are coated, it is avoided that the Brenngutträger-metal plate and / or the retaining pins to the dentures and the kiln during firing ion release, bringing the

Ceramic burning result is further improved. Hereinafter, an embodiment of the invention with reference to the

enclosed drawings described in detail.

It shows:

Fig. 1 shows an inventive arrangement in a partially sectioned view and Fig. 2 a firing tray according to the invention in a three-dimensional view.

In Fig. 1, a kiln 1 is shown. The kiln 1 has a

cylindrical combustion chamber 1 1, which is shown in Fig. 1 cut. Around the cylindrical combustion chamber 1 1 heating elements 13 are arranged. Below, the combustion chamber 1 1 has an opening which is closed with a closure plate 12 during the firing process. The closure plate 12 of

Kiln 1 is mounted on a console 15 for the kiln 1 liftable and lowered, as shown by arrow Z. On the closure plate 12 is a

Burning base 14, arranged for example of fireclay, on the one

Firing tray 2 rests, which in turn carries with a ceramic veneer to be provided dental workpieces, namely crowns or bridges 3 with set up on the firing tray 2 retaining pins 21.

FIG. 2 shows, in a three-dimensional view, the firing tray 2 in the form of a flat cuboid firing metal plate 2. The Brenngutträger- metal plate 2 is flat ground at its top and has a

Surface coating 20 of an intermetallic-ceramic glass phase, as known from DE 100 22 259 B4. On this self-contained and flat surface retaining pins 21 are placed. In Fig. 2 are the

For reasons of clarity, only two retaining pins 21 are shown, although of course further retaining pins and thereon a plurality of crowns or bridges 3 (not shown in FIG. 2) can be held.

The retaining pin 21 has a downwardly widening base 22, which is formed flat and level on its underside to a possible good thermal contact with the fuel tray metal plate 2, to achieve a secure footing on this and a displacement on the Brenngutträger metal plate 2. Each retaining pin 21 has a mandrel 23 which rises in approximately cylindrical shape substantially normal from the surface of the Brenngutträger- metal plate 2. The mandrel 23 may also be conical or hook-shaped for special applications. Particularly preferably, the mandrel 23 has a truncated cone shape tapering concavely upward in order to avoid an undesirable distortion of the mandrel 23 in the crown or bridge 3. The crown or bridge 3 is thus only on the mandrel 23. However, for a good heat conduction, the stump of the truncated cone shape has the largest possible support and contact surface. The mandrel 23 is eccentrically on the base 22 substantially normal to the flat surface of the Brenngutträger metal plate 2 above, so that two juxtaposed support pins 21 with their spikes 23 despite the larger feet 22 can be placed as close to each other.

Hereinafter, the operation of the fuel tray metal plate 2 as a firing tray and thereby running burning process will be described.

First, the retaining pins 21 are placed on the Brenngutträger-metal plate 2 in the desired arrangement and placed on it to be veneered dental workpieces, crowns and bridges 3 in a conventional manner. The distances between two or more thorns 23 of the retaining pins 21 can be arbitrarily moved by the simple placement on the flat surface of the Brenngutträger- metal plate 2 without regard to a grid, as in the known ceramic honeycomb panels. When the firing metal plate 2 with its upstanding

Holding pins 21 are coated with the crowns or bridges 3, which are coated in the appropriate form with ceramic masses, the firing tray 2 is centered on the fuel base 14 of the kiln 1 and turned off the

Closure plate 12 of the kiln 1 with the corresponding mechanism in the console 15 in the combustion chamber 1 1 until the closure of Retracted combustion chamber opening. At the same time, the heating elements 13 of the kiln 1 are activated, so that the combustion chamber temperature, for example, with a heating rate of 200 to 250 ° C / min, increases.

The Brenngutträger metal plate 2 takes due to the high density and determined by the plate size and thickness mass prevailing in the kiln 1 heat, especially by radiant heat quickly and gives them on the base 22 of the retaining pins 21 via the mandrel 23 to the resting thereon Crown or bridge 3 by heat conduction on. At the same time, the dental work piece (crown or bridge) from the outside through in the

Combustion chamber 1 1 prevailing heat radiation heated. Nevertheless, it has been shown that the amount of heat coupled via heat conduction from the fuel tray metal plate 2 into the dental workpiece held thereon is greater than the heat quantity supplied externally by heat radiation. Accordingly, the ceramic material spread over the dental workpiece dries from the inside to the outside, so that hydrothermal vents, which become visible in the form of frog eyes, are completely avoided. Likewise, stresses due to different thermal expansion or shrinkage are largely avoided.

Likewise, significantly lower mechanical stresses occur in the formation of the Verblendverbundes between the dental workpiece 3 and the ceramic applied thereto. In addition, thermally generated stresses on the retaining pins 21 can be compensated for by simply slipping the retaining pins 21 on the flat-firing metal plate 2 and thus eliminated. Spalling of ceramic fragments on the dental workpiece 3 thus no longer occur.

Furthermore, it has been shown that when using a solid metal plate as a firing tray 2, the heating and cooling rates can be significantly accelerated without jeopardizing the stability and quality of the ceramic veneer. Accordingly, cooling rates of 100 ° C / min to 250 ° C / min are suitable. This, too, seems to be due to the more uniform and from the inside out Heating on the dental workpiece are. Accordingly, in the

Burning time savings of about 50% compared to conventional methods can be achieved.

Overall, therefore, with the firing tray according to the invention as solid firing metal plate, the incidents occurring in the previous dental technology when firing ceramics on dental workpieces (bridges, crowns) can be virtually completely eliminated. In addition to the clear quality advantages and the high uniform quality, the aesthetic is also convincing

Appearance of the thus created ceramics with a consistent

uniform, shiny surface without missing parts.

LIST OF REFERENCE NUMBERS

kiln

combustion chamber

closing plate

heating element

firing base

console

Firing tray-metal plate

surface coating

retaining pin

stand

mandrel

Dental workpiece, crown, bridge

Lifting or lowering movement

Claims

P A T E N T A N S P R E C H E

Method for blending crowns and bridges (3) comprising ceramic dental alloys, zirconium and / or ceramic materials with ceramic masses in a kiln (1), characterized in that for heating the crowns and bridges (3) in the kiln (1) the crowns and bridges (3) are heated from the inside via heat-conducting contact.

A method according to claim 1, characterized in that in the kiln (1) arranged Brenngutträger-metal plate (2) by the kiln (1) acting radiant heat is heated.

A method according to claim 2, characterized in that the

Firing tray metal plate (2) preheated in the kiln (1) is introduced.

A method according to claim 2, characterized in that the

Firing material metal plate (2) in the kiln (1) is electrically heated.

Method according to one of the preceding claims, characterized in that a firing temperature of 880 to 1000 ° C in the kiln (1) is achieved with a heating rate of 100 to 500 ° C / min.

Arrangement for blending crowns and bridges (3) comprising ceramic dental alloys, zirconium and / or ceramic materials with ceramic masses

a kiln (1) and

a firing metal plate (2) and

at least one retaining pin (21) made of metal,

wherein the retaining pin (21) for holding the crowns to be veneered and Bridges (3) is provided, characterized in that the

Firing material metal plate (2) is designed level on its top and the retaining pin (21) has a base (22) with a flat

Underside has.

Arrangement according to one of claims 6, characterized in that the Brenngutträger-metal plate (2) integral part of

Kiln (1) is.

Arrangement according to one of claims 6 or 7, characterized

characterized in that the Brenngutträger metal plate (2) is formed actively heated.

Arrangement according to one of claims 6 to 8, characterized

characterized in that the retaining pin (21) at

Proper use of the Brenngutträger- metal plate (2) upstanding mandrel (23) for holding the crowns and bridges (3).

10. Arrangement according to claim 9, characterized in that the

Mandrel (23) has a concave tapering towards the top

Has truncated cone shape.

Arrangement according to one of claims 6 to 10, characterized

characterized in that the Brenngutträger-metal plate (2) and / or d retaining pins (21) are coated with an intermetallic-ceramic glass phase.

A firing metal plate (2) for use in an assembly or method according to any one of the preceding claims, characterized in that the metal or alloy is the metal or alloy

Firing tray metal plate (2) has a density greater than 4.5 kg / dm ³ , preferably has greater than 8.0 kg / dm ³ and the Brenngutträger-metal plate (2) is designed plane on its upper side.

13. firing tray (2) according to claim 12, characterized in that the Brenngutträger metal plate (2) has a thickness of 1 to 10 mm, in particular from 3 to 5 mm.

14. firing tray (2) according to claim 12 or 13, characterized

characterized in that the fuel tray metal plate (2) consists of a metal alloy with one or more of the following elements cobalt, chromium, molybdenum, manganese, tin, gallium, indium, silicon, tungsten, gold and / or platinum.

15. firing tray (2) according to claim 12, 13 or 14, characterized

in that the firing material metal plate (2) is coated with an intermetallic-ceramic glass phase.