Cracks in CAD/CAM Zirconium coping Bridges

[Narendra]

We are CAD/CAM Zirconium dental lab from India and we are having an issue.


Issue:


After Sintering we are seeing cracks in the zirconium bridges, No matter no. of units in the bridge like 4 or 5 or 10 units.


We are using the same material, milling and Sintering machine which we have been using for past 5 years. However from last one month we are facing this issue.


Sintering , we are running 12 degrees/min till 1550, Holding time :120 min and 12degrees/min till 250.

Your inputs would be helpful to resolve this issue. Thank you.

 

[CoolHandLuke]

do the cracks always appear in the same general areas ?

have you calibrated your furnace?

what milling machine have you been using and what are your practices concerning its maintenance ?

 

[CHOI]

In my case, before sintering, needs dry time 90 degrees with 2hours. And put some zir ball on the sintering plate and place it.

Check Milling machine with calibration.

Check Temperature in the furnace.

Check Zirconia block.

 

[RJS8669]

If you gently lick the crack it will disappear.

And, if you listen closely, you'll hear a soft moan....

 

[grantoz]

my wife has said the same thing

 

[griffmar79]

Did you change your beads yet?

 

[Gabriel]

If you say that all of the problems started a month ago, did you happen to have any serious crash during milling? I'm asking because it is possible that one of your axis ballscrews got damaged... I'm not sure what milling machine you are using, but the ballscrews can get damaged if the liniar rails or liniar ballbearings are not allowed to slide smoothly for any reason which could be due to poor maintenance as CoolHandLuke mentioned. If you used your machine for 5 years, in my opinion you should perform maintenance at least once a year. Depending on the machine the maintenance can be more or less of a headache, but lubrication is essential if you want to keep your machine out of trouble. Also, zirconia powder really does get through the smallest crack. So you could find it has made its way to the ballscrews and rails. Grease and zirconia powder mixed together will result in a very sticky and thick paste which will add a lot of stress on the motors that drive the axis up and down.
Try cleaning your machine really well and inspect the state of the mechanical moving parts to ensure they are still in good shape, check that the threads are still continuous. If there are any chipped edges, then the movement will suffer when the ballscrew reaches that certain area. This would mean enough disturbance in the movement as to create vibration, and we all know that vibration will cause cracks in zirconia.

 

[Techy]

Slow down the cooling process....

 

[Wayne CDT]

We are CAD/CAM Zirconium dental lab from India and we are having an issue.


Issue:


After Sintering we are seeing cracks in the zirconium bridges, No matter no. of units in the bridge like 4 or 5 or 10 units.


We are using the same material, milling and Sintering machine which we have been using for past 5 years. However from last one month we are facing this issue.


Sintering , we are running 12 degrees/min till 1550, Holding time :120 min and 12degrees/min till 250.

Your inputs would be helpful to resolve this issue. Thank you.

Had the same problem here...Lowered the temp to 1510 and no more cracks. What Zirconia sinters at 1550?

 

[mihir]

which zirconia is it. plz check basic temprature cycle. most zirconia final temorature is 1450 or 1530.
also check if u r using appropriate low temprature to dry milled zirconia copins,after using colouring liquids

 

[MrNeverFixit]

If you change your puck/brand then check the recommended manufacturer temperature/settings.