Method to increase the strength of a form body of a lithium silicate glass ceramic

Patent metadata

Field	Value
Publication number	US-2016340238-A1
Application number	US-201615160529-A
Country	US
Kind code	A1
Filing date	May 20, 2016
Priority date	May 22, 2015
Publication date	Nov 24, 2016
Grant date	—

Abstract

The invention relates to a method to increase the strength of a form body of lithium silicate glass ceramic, which after it has a desired end geometry and after the application of a material which influences its surface to form a coating, is subject to a heat treatment. To create a surface compressive stress through the replacement of lithium ions by alkali ions of greater diameter at least that region not covered by the application layer is covered by a melt or paste consisting of or containing a salt of an alkali metal with ions of greater diameter and the form body is in contact with the melt or paste for a period of time t at a temperature T and the melt or paste is subsequently removed from the form body.

First claim

1 . A method to increase the strength of a form body of lithium silicate glass ceramic in the form of a dental object comprising the steps of:
applying a material to the surface of the form body except for at least one region of the form body; applying a melt or a paste of a salt or a melt or a paste including a salt of an alkali metal or a number of alkali metals with ions of greater diameter than lithium ions to the at least one region of the form body; after the step of applying the melt of paste, heat treating the form body to generate a surface compressive stress through the replacement of lithium ions by alkali ions of greater diameter in the at least one region covered by the melt of paste, wherein the at least one region of the form body is in contact with the melt or paste for a time t at a temperature T; and removing the melt or paste from the form body.

2 . The method according to claim 1 , wherein the form body during the ion exchange is completely covered by the melt or the paste.

3 . The method according to claim 1 , wherein a portioned quantity of salt is used for the melt.

4 . The method according to claim 1 , wherein the paste is only applied to the at least one region of the form body not covered by the material.

5 . The method according to claim 1 , wherein the at least one region of the form body that is subject to a tensile stress remains uncovered by the material.

6 . The method according to claim 1 , wherein the at least one region includes at least a plurality of regions of the form body which are subject to a tensile stress, which does not have a coating that is formed by application of the material and subsequent heat treatment.

7 . The method according to claim 1 , further comprising the step of preparing a salt body from the salt as the portioned quantity from the alkali metal/alkali metals through pressing or compression and that the salt body is laid on the form body or the form body is laid directly or indirectly on the salt body and then the salt body is melted.

8 . The method according to claim 1 , further comprising the step of laying the form body in a receptacle having perforations, and that thereafter
the receptacle with the form body is dipped in the melt, or the receptacle with the form body is introduced into the salt and the salt is then melted, or the receptacle with the form body is placed on the salt or the salt body and the salt is melted concurrently with immersion of the form body in the melt which is forming.

9 . The method according to claim 3 , further comprising the step of enveloping the form body with a heat-resistant foil that contains the portioned quantity of salt and that the salt is then melted.

10 . The method according to claim 3 , wherein the portioned salt is made available in a receptacle with a closure that can be removed.

11 . The method according to claim 1 , wherein the alkali metal salt, which enables ion exchange, is a phosphate salt, and is added for the binding of lithium ions.

12 . The method according to claim 1 , wherein the alkali metal ions are selected from the group consisting of Na, K, Cs, Rb ions, or any combination thereof to generate the surface compressive stress.

13 . The method according to claim 1 , further comprising the step of annealing the form body in a melt including potassium ions, or a melt containing sodium ions, or in a melt containing a mixture of potassium ions and sodium ions.

14 . The method according to claim 1 , further comprising the step of annealing the form body at a temperature T where ≧T 300° C., for a time t.

15 . The method according to claim 1 , further comprising the step of preparing the form body from a glass melt which includes at least the following as starting components: SiO 2 , Al 2 O 3 , Li 2 O, K 2 O, at least one nucleating agent, and at least one stabilizer.

16 . The method according claim 15 , wherein the form body or a blank from which the form body is manufactured, is prepared from a glass melt that includes the following components in percentage by weight:
SiO 2 50-80, at least one nucleating agent 0.5-11 Al 2 O 3 0-10, Li 2 O 10-25, K 2 O 0-13, Na 2 O 0-1, ZrO 2 0-20, CeO 2 0-10, Tb 4 O 7 0-8, optionally an oxide or a number of oxides of an earth alkali metal or a number of earth alkali metals selected from the group consisting of magnesium, calcium, strontium, and barium 0-20, optionally one or more additives selected from the group B 2 O 3 , MnO 2 , Fe 2 O 3 , V 2 O 5 , TiO 2 , Sb 2 O 3 , ZnO, SnO 2 and fluorides 0-6, optionally one or more oxides of the rare earth metals with the atomic numbers 57, 59-64, and/or 66-71, 0-5.

17 . The method according to claim 15 , wherein the glass melt includes the following as starting components in percentage by weight
SiO 2 58.1±2.0 P 2 O 5 5.0±1.5 Al 2 O 3 4.0±2.5 Li 2 O 16.5±4.0 K 2 O 2.0±0.2 ZrO 2 10.0±0.5 CeO 2 0-3, Tb 4 O 7 0-3, Na 2 O 0-0.5.

18 . The method according to claim 15 , wherein the blank is formed from the glass melt in the course of cooling or following cooling to room temperature, said blank then being subject to at least one first heat treatment W 1 at a temperature T W1 for a time t W1 , wherein 620° C.≦T W1 ≦800° C., and/or 1 minute≦t W1 ≦200 minutes.

19 . The method according to claim 18 , wherein the first heat treatment W 1 is carried out in two steps, wherein in particular in the first step a temperature T St1 is set where 630° C.≦T St1 ≦690° C. and/or in the second step a temperature T ST2 where 720° C.≦T St2 ≦780° C. and/or the heating rate A St1 up to the temperature T St1 is 1.5 K/minute≦A St1 ≦2.5 K/minute and/or the heating rate A St2 up to the temperature T St2 is 8 K/minute≦T St2 ≦12 K/minute.

20 . The method according to claim 18 , wherein the lithium silicate glass ceramic blank is subjected, after the first heat treatment W 1 , to a second heat treatment W 2 at a temperature T W2 for a time t W2 , wherein 800° C.≦T W2 ≦1040° C., and/or 2 minutes≦t W2 ≦200 minutes.

21 . The method according to claim 18 , wherein after the first or second heat treatment step, the form body is prepared from the blank through grinding and/or milling or pressing, wherein the heat treatment step or steps is/are carried out during or after pressing.

22 . The method according to claim 1 , wherein the form body or at least one region not covered by the coating is coated with a viscous solution or dispersion of the salt as the paste.

23 . The method according to claim 22 , wherein the paste is applied to the form body or to the at least one region not covered by the material through spraying on to the form body.

24 . The method according to claim 22 , further comprising the step of preparing the paste by mixing the salt with at least one substance selected from the group consisting of a non-flammable substance, monohydric or polyhydric alcohols, halogenated hydrocarbon compound, water, and a mixture of one or more substances.

25 . The method according to claim 22 , wherein the paste is applied to all the surfaces of the form body at a thickness D of at least 0.5 mm.

26 . A form body of lithium silicate glass ceramic comprising
a surface of the form body; a coating that is confined exclusively to one or more regions of the surface of the form body; and at least one region of the surface of the form body not covered by the coa

Assignees

• Dentsply Sirona Inc

Inventors

• Völkl Lothar
• Fecher Stefan

Classifications

• A61K6/853

  Silicates · CPC title

• A61K6/804

  comprising manganese oxide · CPC title

• A61K6/20

  Protective coatings for natural or artificial teeth, e.g. sealings, dye coatings or varnish · CPC title

• A61K6/818

  comprising zirconium oxide · CPC title

• A61K6/822

  comprising rare earth metal oxides · CPC title