Dental furnace

Patent metadata

Field	Value
Publication number	US-9557114-B2
Application number	US-201514684535-A
Country	US
Kind code	B2
Filing date	Apr 13, 2015
Priority date	Mar 5, 2008
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

The invention relates to a dental furnace wherein a firing chamber is heated up in a first heating-up period at a first heating-up rate of more than 501 K/min, in particular more than 1001 K/min, which heats the furnace to at least 10001 C, in particular to 1100-12501 C. The first heating-up period is followed by an intermediate heating period, which is at least five minutes long, in particular at least ten minutes long, the gradient or heating-up rate of which is adapted to the material to be sintered in the dental furnace ( 10 ), and wherein this is followed by an end heating-up period ( 44 ) during which heating up is effected at a heating-up rate of more than 301 K/min, in particular approximately 501 K/min, and wherein during this the furnace temperature is held for at least five minutes, in particular for at least 25 minutes, above the temperature toward the end of the first heating-up period, and wherein forced cooling of the furnace ( 10 ) is performed after this.

First claim

What is claimed is:

1. A dental furnace for sintering oxide-ceramic materials comprising
a heating chamber surrounded by heating elements and a thermal insulation layer, wherein the dental furnace is configured such that
the heating chamber is heated up in a first heating-up period at a first heating-up rate of more than 50° K/min, which heats the furnace to at least 1000° C.,
the first heating-up period is followed by an intermediate heating period having an intermediate heating-up rate which is at least five minutes long, wherein during the intermediate heating period about 90 percent of final density of the oxide-ceramic material being sintered is achieved,
the intermediate heating period is followed by an end heating-up period during which end heating-up is effected at a heating-up rate of more than 30° K/min,
during the end heating-up period the furnace temperature is held for at least five minutes, above a temperature that has been measured at the end of the first heating-up period, and wherein forced cooling of the furnace is performed after the furnace temperature is held for at least five minutes, and
the end heating-up period has a rate that is slower than the first heating-up rate.

2. The dental furnace as claimed in claim 1 ,
wherein the dental furnace is further configured such that
the maximum temperature in the heating chamber is approximately 1600° C. and
the furnace can be heated up to 1600° C. proceeding from room temperature in its heating chamber, within less than 30 minutes.

3. The dental furnace as claimed in claim 1 ,
wherein the dental furnace is further configured such that
the intermediate heating-up rate is lower than the initial heating-up rate by approximately a power of 10.

4. The dental furnace as claimed in claim 1 , wherein the heating chamber of the furnace is surrounded by a heat-resistant insulation comprising a pressed shaped part composed of fiber having a wall thickness between 15 and 25 mm.

5. The dental furnace as claimed in claim 1 ,
wherein the dental furnace is further configured such that
the intermediate heating period is chosen in terms of a temperature and/or a time such that it covers an intermediate stage of a sintering process of the dental material to be sintered, in which a sintering rate, plotted against the temperature/time, is the highest.

6. The dental furnace as claimed in claim 1 , wherein the dental material to be fired is presintered and/or precompacted and prior to sintering has a strength which is lower than the final strength of the sintering material.

7. The dental furnace as claimed in claim 1 ,
wherein the initial heating-up rate is configured such that it corresponds to a maximum heating-up rate at which no overshoot arises upon the transition from the first heating-up period to the intermediate period, but is at least 50° K/min.

8. The dental furnace as claimed in claim 1 ,
wherein the dental furnace is further configured such that
after the holding time has elapsed, the furnace cools down at a first cooling-down rate, which is less than the heating-up rate of the first heating-up period and greater than the heating-up rate of the intermediate heating-up period, and wherein a higher, second cooling-down rate is set after this.

9. The dental furnace as claimed in claim 1 , wherein the dental furnace is a microwave furnace.

10. The dental furnace as claimed in claim 1 ,
wherein the dental furnace is further configured such that
the heating chamber is heated up in the first heating-up period at the first heating-up rate of more 100° K/min, which heats the furnace to at least 1100° C.,
the intermediate heating period is at least ten minutes long,
the end heating-up period is effected at a heating-up rate of more than 50° K/min, and
during the end heating-up period the furnace temperature is held for at least 25 minutes above the temperature toward the end of the first heating-up period.

11. The dental furnace as claimed in claim 4 ,
wherein the dental furnace is further configured such that
the intermediate heating-up rate is lower than the initial heating-up rate by a factor of 10 to 50.

12. The dental furnace as claimed in claim 6 , wherein the strength of the presintered and/or precompacted dental material prior to sintering the dental material to be fired is less than half the magnitude of the final strength of the sintering material.

13. A dental furnace for sintering oxide-ceramic materials,
wherein the dental furnace is configured such that
a sintering material to be sintered is heated up in a first heating-up period at a heating-up rate of more than 50° K/min,
between an end of the first heating-up period and a beginning of an end heating period there is an intermediate heating period at a heating-up rate lower than 50° K/min,
the first heating-up period and the end heating period are set in a material-independent manner,
the intermediate heating period is defined, with regard to its length and its heating-up rate, in a manner dependent on the material to be sintered,
during the intermediate heating period about 90 percent of final density of the dental material being sintered is achieved, and
the end heating-up period has a rate that is slower than the first heating-up rate.

14. The dental furnace of claim 13 ,
wherein the dental furnace is further configured such that
the heating-up rate of the intermediate heating period is lower than 10° K/min.

15. A total firing method for sintering a dental material comprising:
heating a heating chamber in a first heating-up period at a first heating-up rate of at least 50° K/min, which heats up the furnace to at least 1000° C.,
continuing to heat the chamber in an intermediated heating period, wherein the first heating-up period is followed by the intermediate heating period, which is at least five minutes long, and
continuing to heat the chamber in an end heating-up period, wherein the intermediate heating period is followed by the end heating-up period, during which heating-up is effected at a heating-up rate of more than 20° K/min, wherein the end heating-up period has a rate that is equal to or slower than the first heating-up rate, and
holding the temperature in the end heating period for at least five minutes, above a temperature that has been measured at the end of the first heating-up period, and
force cooling the furnace after the end heating period for a cooling down of the dental material to a removal temperature of approximately 400° C., in less than or equal to 60 minutes,
wherein the total firing method takes place over a time span from a start of the first heating-up period at room temperature to the cooling down of the heating chamber to room temperature,
wherein the heating chamber has a temperature higher than 1100° C. at least 68% of the time span of the total firing method,
wherein during the intermediate heating period about 90 percent of final density of the dental material being sintered is achieved.

16. The method as claimed in claim 15 , wherein the dental material comprises a dental tooth replacement material and is sintered in dry fashion or in liquid sintering, wherein the dental material comprises an oxide ceramic which is composed of ZrO 2 , of Al 2 O 3 and compositions thereof and comprises a doping auxiliary.

17. The method according to claim 15 , wherein the heating-up rate of the intermediate heating period is less than 10° K/min.

18. The method according to claim 15 , wherein the cooling of the furnace is performed in 20 to 60 minutes.

Assignees

• Ivoclar Vivadent Ag

Inventors

• Rohner Gottfried
• Pokorny Walter
• Grunenfelder Robert
• Rothbrust Frank

Classifications

• F27D2019/0037

  Quantity of electric current · CPC title

• C04B2235/656

  characterised by specific heating conditions during heat treatment · CPC title

• F27D11/04

  with direct passage of current through the material being heated · CPC title

• F27D9/00

  Cooling of furnaces or of charges therein (casings, linings, walls or roofs incorporating cooling arrangements F27D1/12) · CPC title

• F27D19/00 Primary

  Arrangements of controlling devices · CPC title