CA1251306A

CA1251306A - Ceramic intermediate layer for a ceramo-metallic dental reconstruction

Info

Publication number: CA1251306A
Application number: CA000474155A
Authority: CA
Inventors: Michel Heurtaux
Original assignee: Suissor SA
Current assignee: Suissor SA
Priority date: 1984-02-15
Filing date: 1985-02-13
Publication date: 1989-03-21
Also published as: ATE44456T1; ES8601677A1; JPS60191032A; FR2559385B1; DK69485A; ES540353A0; DK69485D0; FR2559385A1; EP0159205B1; EP0159205A1; DE3571391D1

Abstract

PATENT

CERAMIC INTERMEDIATE LAYER FOR A CERAMO-METALLIC DENTAL
RECONSTRUCTION

SUISSOR S.A.

Inventor: Michel HEURTAUX

ABSTRACT
The present invention relates to a ceramic inter-mediate layer of a ceramo-metallic dental reconstruction.
The ceramic intermediate layer according to a preferred embodiment is produced from a mixture containing at least two separate glass frits, namely:
a first glass frit which is fusible and does not devitrify, and a second glass frit which is more refractory and devitrifies partially to leucite. The mixture may be packaged in a suitable dispenser ready for immediate use as a paste by means of a suitable plastizer.

Description

13~, The present invention relates to the -technical field of ceramo-metallic dental reconstructions. More particularly it relates to ceramic glass employed to produce various intermediate layers of dental reconstructions, such as crowns, inlays, bridges, and the like.
This type of dental reconstruction is usually produced from a series of layers of ceramic which is coated on a metal coping deposited, for example, on the stump of a tooth reduced after shaping with the drill.
This series of ceramic layers consists of a basal opacifying layer7 two intermediate layers known by the terms "dentine" and "incisal", and a surface layer, preferably transparent, intended to resemble the gleam of the enamel of the natural tooth.
The subjec-t of the present invention is aimed more particularly at the intermediate ceramic layers, namely the dentine and the incisal.
In the prior art, attempts have been made to obtain a lower baking temperature, namely close to approximately 800C, for these layers of ceramic glass.
In fact, this lowering in the melting point is reflected in a reduction of the hardness of the ceramic glass which, in the present state of the art, generally results in very severe abrasion phenomena in the antagonizing natural teeth.
In accordance with the present invention, -the ceramic intermediate layers are intended to cover -the ceramic basal layer for opacifying the metal coping of a ceramo-metallic dental reconstruction, and are produced u~

from a mixture containing a-t least two separa-te glass frits, namely:
a first glass frit which is -Fusible and does not devitrify 9 and a second glass frit which is more refractory and devitrifies partially to leucite.
Other features and advantages of the present invention will become apparen-t From the reading of the following detailed description of a preferred embodimen-t of the invention.
The glass frits employed results from mixing two separate glasses, one fusible and non-devitrifying, the other slightly more refractory and devitrifying partially to leucite, a mineral with high thermal expansion.
The first glass frit, which is fusible and does not devitrify, is employed as such. On the other hand, the second glass frit is devitriFied, for example for approximately 12 hours at a temperature of the order of 900 C. During this thermal devitrifying treatment, an in situ crystallization phenomenon makes its appearance in a conventional manner.
It will also be noted that, during successive bakings, the fusible glass, at the limit of saturation wi-th leucite, does not dissolve the leucite in the second glass and consequently its concentration remains constant. In this way, a stable expansion is obtained.
A reduction in the hardness of the intermedia-te ceramic layers is obtained by an increase in the percentage of fluxes, favoring Na20. The ceramic layers are a ~;~5~3~i mixture of two glass frits con-taining, in total, approximately 20 to approximately 30 % by weight of fluxes, among which the soda Na20 is present in a proportion of approximately 7 to approximately 8 % by weight.
Given below, by way of an illus-trative example, is the following overall composition of intermedia-te ceramic layers:
SiO2 59 tc 59.5 % by weight A1203 15 to 16 % by weight 10 CaO 0.5 to 1.5 % by weight MgO O to 0.2 % by weight K20 11 to 13 % by weight Na20 7 to 8 % by weight B203 2.5 to 3.5 % by weight 15 BaO O to 3 % by weight CaF2 0.5 to 3 % by weight TiO2 0.2 to 0.5 % by weight.
The ceramic layers can also be modified so as to be capable of avoiding any background coloring phenomenon due to the metal substrates. These metal substrates are usually made from alloys of various me-tals, among which silver is particularly responsible for such background coloring. In fact, -the Ag~ ion migra-tes fairly readily in the ceramic and causes a greenish-yellow coloring when reduced to the metal state. It is precisely to avoid a phenomenon of this type that approximately 0.2 % by weight of cerium oxide CeO2, which is an active oxidizing agent which keeps the silver in the non-coloring oxide state, is added to the glass fri-t mixtures according to the ~'' 9 ZS~3(~

invention~ This cerium oxide is added after the grinding operation which produces the glass frit. The glass fri-ts are obtained in a conventional manner by melting and homogenizing a powdered mixture of the basic components required to produce the above-mentioned compositions.
To reduce shrinkage during the baking, the particle size distribution of the mixture of the two glass frits has been adjusted as a result of the following observation. The voidage of a population of large particles (40 to 65 microns) is of the order oF 40 %. By introducing particles of medium sizes (12 to 40 microns) in a proportion of approximately 50 % by weight relative to the large particles, the voidage drops to approximately 20 %. Lastly, when particles of much smaller sizes are introduced (below 5 microns), the voidage becomes still lower. Consequently, this results in lower shrinkage on baking. A particle size distribution of this type also makes it possible to obtain better plasticity of the paste at the time of its use.
To produce a glass frit intended for producing a transparent surface layer, it is desirable to employ a particle size distribution of the following type:
40 to 65 ~ .... approxima-tely 4/7 of the particles 12 to 40ju .... approximately 2/7 of the particles ~ 12~u ........ approximately 1/7 oF the particles.
In contrast, to produce a glass frit intended to form the incisal, which, when compared to the dentine, is characterized by higher translucency, i-t is preferable to reduce the proportion of -the finer particles. In practice, a particle size distribution o-f the Following type is satisfactory:
12 to 65,u ... approxima-tely 8.5/14 of the particles 12 to 4û~u ... approximately 4.5/14 of the particles < 12~u ....... approximately 1/14 of the particles.
Glass frits required for the production of transparent ceramic surface layers can be presented in the form of a paste ready for use and intended to facilitate the work o-F the user while achieving a saving in active lû product. Such frits are presented in the form of a paste containing a suitable quantity of a plasticizer, so as to permit them to be packaged in a tube or a paste dispenser of the aerosol type.
A typical example of a glass -Frit formulation, packaged in an aerosol dispenser, is shown below:
lOû parts by weight of active products, 30 to 40 parts by weight of plasticizer, lOû parts by weight of a propellant agen-t, such as Freon~.
The plasticizer is preferably chosen from diethylene glycol diethyl ether and propylene glycol methyl ether.
The base dentine can be subdivided into two separate dentines, namely an opaque dentine and a translucent dentine. The opaque dentine, less satura-ted in hue than the transparent dentine, contains a determined percentage of opacifier, which consists, for example, of an opacified glass frit or oF zirconia. The transparent dentine, on the other hand, is highly colored and very 3(~

slightly opacified. Consequently, by mixing these two types of den-tine and/or by placing them next to each other, the user will be better able to restore the many contrast zones present in a natural tooth. Of course, these various den-tine compositions may be packaged as a mixture with organic colorants which make it possible to visualize the structure of the tooth and which are removed during the baking.
The glass frit pastes may contain various colorants, in order to put at the disposal of the prosthesis producer a complete color range of ceramic layers matching the hues of the natural teeth of the various patients.
Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Ceramic intermediate layer intended for covering the ceramic basal layer for opacifying the metal coping of a ceramo-metallic dental reconstruction, forming the dentine and/or the incisal, a layer which is produced from a mixture containing at least two separate glass frits, namely:
a first glass frit which is fusible and does not devitrify, and a second glass frit which is more refractory and devitrifies partially to leucite, said glass frits having a particle size of less than about 65 µm, said mixture of the two glass frits contains approximately 20 to approximately 30 % by weight of fluxes which include from approximately 7 to approximately 8 % by weight of Na2O.

2. Ceramic layer as claimed in claim 1, in which the second glass frit is devitrified for approximately 12 hours at a temperature of the order of 900°C, before being mixed.

3. Ceramic layer as claimed in claim 1, which corresponds to the following overall composition:

SiO2 59 to 59.5 % by weight Al2O3 15 to 16 % by weight CaO 0.5 to 1.5 % by weight MgO 0 to 0.2 % by weight K2O 11 to 13 % by weight Na2O 7 to 8 % by weight B2O3 2.5 to 3.5 % by weight BaO 0 to 3 % by weight CaF2 0.5 to 3 % by weight TiO2 0.2 to 0.5 % by weight.

4. Ceramic layer as claimed in claim 2, which corresponds to the following overall composition:
SiO2 59 to 59.5 % by weight Al2O3 15 to 16 % by weight CaO 0.5 to 1.5 % by weight MgO 0 to 0.2 % by weight K2O 11 to 13 % by weight Na2O 7 to 8 % by weight B2O3 2.5 to 3.5 % by weight BaO 0 to 3 % by weight CaF2 0.5 to 3 % by weight TiO2 0.2 to 0.5 % by weight.

5. Ceramic layer as claimed in claim 1, 2 or 3, in which approximately 0.2 % by weight of cerium oxide CeO2 is added to the mixture of the two glass frits.

6. Ceramic layer forming the dentine, as claimed in claim 1 or 2, in which the said mixture of glass frits has a particle size distribution of the following type:
40 to 65 µ ....approximately 4/7 of the particles 12 to 40 µ ....approximately 2/7 of the particles < 12 µ ........approximately 1/7 of the particles.

7. Ceramic layer forming the incisal, as claimed in claim 1 or 2, in which the said mixture of the two glass frits has a particle size distribution of the following type:
12 to 65 µ ....approximately 8.5/14 of the particles 12 to 40 µ ....approximately 4.5/14 of the particles < 12 µ ......approximately 1/14 of the particles.

8. Ceramic layer forming the dentine, as claimed in claim 3 or 4, in which the said mixture of glass frits has a particle size distribution of the following type:
40 to 65 µ ....approximately 4/7 of the particles 12 to 40 µ ....approximately 2/7 of the particles < 12 µ .......approximately 1/7 of the particles.

9. Ceramic layer forming the incisal, as claimed in claim 3 or 4, in which the said mixture of the two glass frits has a particle size distribution of the following type:
12 to 65 µ ...approximately 8.5/14 of the particles 12 to 40 µ ...approximately 4.5/14 of the particles < 12 µ ......approximately 1/14 of the particles.

10. A preparation for producing a ceramic intermediate layer intended for covering the ceramic basal layer for opacifying the metal coping of a ceramo-metallic dental reconstruction, said preparation being in the form of a paste ready for use and containing a suitable quantity of a plasticizer, said plasticizer carrying a mixture of a first glass frit and a second glass frit, a first glass frit which is fusible and does not devitrify, and a second glass frit which is more refractory and devitrifies partially to leucite, said glass frits having a particle size of less than about 65 µm, said mixture of the two glass frits contains approximately 20 to approximately 30 % by weight of fluxes which include from approximately 7 to approximately 8 % by weight of Na2O.

11. A preparation as claimed in claim 10, in which the plasticizer is chosen from diethylene glycol diethyl ether and propylene glycol methyl ether.

12. A preparation as claimed in claim 10 or 11 contained within a package selected from the group of tube dispenser and aerosol type paste dispenser.

13. A preparation as claimed in claim 10 or 11, in which said mixture of glass frits has a particle size distribution of the following type:
40 to 65 µ....approximately 4/7 of the particles 12 to 40 µ....approximately 2/7 of the particles 12 µ .......approximately 1/7 of the particles.

14. A preparation as claimed in claim 10 or 11, in which said mixture of glass frits has a particle size distribution of the following type:
40 to 65 µ ....approximately 4/7 of the particles 12 to 40 µ ....approximately 2/7 of the particles 12 µ .......approximately 1/7 of the particles, and the following overall composition other than plasticizer:
SiO2 59 to 59.5 % by weight Al2O3 15 to 16 % by weight CaO 0.5 to 1.5 % by weight MgO 0 to 0.2 % by weight K2O 11 to 13 % by weight Na2O 7 to 8 % by weight B2O3 2.5 to 3.5 % by weight BaO 0 to 3 % by weight CaF2 0.5 to 3 % by weight TiO2 0.2 to 0.5 % by weight.

15. A preparation as claimed in claim 10 or 11, in which the mixture of glass frits is of the following composition other than plasticizer:
SiO2 59 to 59.5 % by weight Al2O3 15 to 16 % by weight CaO 0.5 to 1.5 % by weight MgO 0 to 0.2 % by weight K2O 11 to 13 % by weight Na2O 7 to 8 % by weight B2O3 2.5 to 3.5 % by weight BaO 0 to 3 % by weight CaF2 0.5 to 3 % by weight TiO2 0.2 to 0.5 % by weight.

16. A preparation as claimed in claim 10 or 11, wherein mixture contains approximately 80 % by weight of a first glass frit and approximately 20 % by weight of the second glass frit.

17. An intermediate ceramic layer of a ceramo-metallic dental reconstruction, which is produced from a mixture containing at least two separate glass frits, said mixture having the following overall composition:
SiO2 59 to 59.5 % by weight Al2O3 15 to 16 % by weight CaO 0.5 to 1.5 % by weight MgO 0 to 0.2 % by weight K2O 11 to 13 % by weight Na2O 7 to 8 % by weight B2O3 2.5 to 3.5 % by weight BaO 0 to 3 % by weight CaF2 0.5 to 3 % by weight TiO2 0.2 to 0.5 % by weight, and particles of said mixture having a size not greater than 65 µm.

18. Intermediate ceramic layer according to claim 17, forming the dentine, in which the said mixture of glass frits has a particle size distribution of the following type:
40 to 65 µ ....approximately 4/7 of the particles 12 to 40 µ ....approximately 2/7 of the particles < 12 µ ......approximately 1/7 of the particles.

19. Intermediate ceramic layer according to claim 17, forming the incisal, in which the said mixture of the two glass frits has a particle size distribution of the following type:
12 to 65 µ ...approximately 8.5/14 of the particles 12 to 40 µ ...approximately 4.5/14 of the particles < 12 µ .....approximately 1/14 of the particles.