Chipping on implant crown margins

[JeffT]

Hi all....
Haven't posted for quite some time.

Having a problem with Occasional chipping on margins. Sometimes they are perfect and other times chipping.
I milled 2 crowns back to back yesterday. One chipped and the other was fine.

Both are Straumann wn. Mill is a DX52 with newish burs, calibrated and cleaned weekly and DME are current.
Cam is millbox.
The only difference was with the disk sizes used. Upper molar was in a 14mm and the lower was in an 18mm.
Any ideas appreciated.
See pics.
Lower molar is first pic and milled perfect.

Thanks

 

[Davor RDT]

Have you tried increasing horizontal thickness of margin ? In your CAD ?

 

[JeffT]

Have you tried increasing horizontal thickness of margin ? In your CAD ?

Hi Davor.
No, I Haven't played with any of the factory settings in 3shape settings?

 

[Davor RDT]

Hi Davor.
No, I Haven't played with any of the factory settings in 3shape settings?

Good start , if it is persisting go to CAM and look at your tool life and swap out tools that are not newish , anything past 85 percent of tool life. At times with ASC on implant frames , and longer implants in general , it helps to increase milling area as well so tools have easier access . Similarily, you might consider slowing spindle down by 5 percent or so .
!

 

[JeffT]

Have adjusted cavity fit in millbox to -0.01. (crowns were very tight on to the ti bases)
Will replace appropriate burs. Will look at other tips you suggested and see how it goes.
A matter of trial and error from here.

Thanks for the help Davor

 

[Artin]

Hello so the one milled perfectly was placed on a 14mm puck ?

 

[JeffT]

Hello so the one milled perfectly was placed on a 14mm puck ?

Hi Artin,
The good one was in the 18mm disk.
Crown height in the puck for the chipped crown was 11.5mm in the 14mm.

 

[Artin]

I remember having a similar problem and what helped was to increase the offset, cause what it looks like your bur is touching your margin while it’s milling other parts of the crown. Good luck and hope it helps

 

[JeffT]

I remember having a similar problem and what helped was to increase the offset, cause what it looks like your bur is touching your margin while it’s milling other parts of the crown. Good luck and hope it helps

Ok Thanks for that!
I will increase the offset. Current offset is 2.7mm. I will increase to 3mm and so on and see how it goes.

 

[Artin]

Ok Thanks for that!
I will increase the offset. Current offset is 2.7mm. I will increase to 3mm and so on and see how it goes.

Let us know what works best

 

[JeffT]

Let us know what works best

Will do.

 

[sidesh0wb0b]

Ok Thanks for that!
I will increase the offset. Current offset is 2.7mm. I will increase to 3mm and so on and see how it goes.

2.7mm should be a good enough offset. and if it wasnt, then you would most likely see the same issue in both pucks. (i am presuming the offset on both was 2.7mm)

was the chipped unit nested close to the bottom of the puck? we just ran into a tooling error for the first time regarding a unit nested too close to the top of the puck. not saying it would cause chipping, just tossing out ideas.
otherwise i lean toward tool life. margins look plenty thick enough, and 2.7mm offset is more than the standard 2.5mm we run on 90% of our units. what size tools do you run? 2mm, 1mm, .6mm, .3mm?

 

[MrNeverFixit]

Having the same problem. Tools are new. Collet clean and grease, automatic correction pass. I took the spindle out and reseat. Still Chipping. Roland called me the other day getting some replacement parts, and i ask it does like this, the tech think its the spindle motor (Could be a belt). So i had an old motor fairly new. I installed it today and will try it monday (Nextweek) see if its the motor.

Also had the same issue with other 52D. Reseating the spindle fix the problem. Milling without any chip.

Check you spindle motor hours. Go to vpanel, maintenance, Get Log or Log. it will be saved as zip. Open zip folder, look for file System Report, scroll down all the way to Spindle Motor....if its more than 1400hrs, then its time to replace. Whats your spinlde hours as well?

EDIT: well i just saw its an old post, almost a month. have you found a fix on this one? Just ignore the above.

 

[tehnik]

Roland spindels last 4k hours no problem. The machine itself needs regular cleaning, calibration and collet tightening.

 

[JeffT]

2.7mm should be a good enough offset. and if it wasnt, then you would most likely see the same issue in both pucks. (i am presuming the offset on both was 2.7mm)

was the chipped unit nested close to the bottom of the puck? we just ran into a tooling error for the first time regarding a unit nested too close to the top of the puck. not saying it would cause chipping, just tossing out ideas.
otherwise i lean toward tool life. margins look plenty thick enough, and 2.7mm offset is more than the standard 2.5mm we run on 90% of our units. what size tools do you run? 2mm, 1mm, .6mm,

 

[JeffT]

Thanks all for replies.
I changed out my 1mm and .6 bur.
I am using Sierra Mid Range. Perhaps I need to keep a closer eye on wear, although haven't had any chipping on normal crown margins.
I have cleaned the Collett and upgraded Millbox to the 22 vers.
Seems to be finishing nicer now, but still finding the implant crowns to be super tight on the ti bases. All brands.

 

[tehnik]

I actually started have the same exact problem with jobs that have ti-bases. They are very tight. This is with millbox v22 bevore I had 20 and no problems.

 

[MrNeverFixit]

I actually started have the same exact problem with jobs that have ti-bases. They are very tight. This is with millbox v22 bevore I had 20 and no problems.

There is a core update for millbox, may be get it from your reseller or ask cims to send it to you. Try updating it and if it fix this issue. ( i got it from cims like two weeks back)

For chipping i still had an issue, if i nest two crowns, one will be fine and the other is chip. But if i mill just one crown, it came out fine. I did a test this morning, mill a two crowns, but one at a time. It came out both fine. Then i mill a live case crown with two units, both chip.

Probably i will have roland tech come in and have a look at it (hopefully it gets fixed). Problem after problem

 

[FASTFNGR]

Hi all....
Haven't posted for quite some time.

Having a problem with Occasional chipping on margins. Sometimes they are perfect and other times chipping.
I milled 2 crowns back to back yesterday. One chipped and the other was fine.

Both are Straumann wn. Mill is a DX52 with newish burs, calibrated and cleaned weekly and DME are current.
Cam is millbox.
The only difference was with the disk sizes used. Upper molar was in a 14mm and the lower was in an 18mm.
Any ideas appreciated.
See pics.
Lower molar is first pic and milled perfect.

Thanks

I always make my margins a bit thicker in the design phase for that reason exactly and just in case my bur is getting older.

 

[JeffT]

Thanks FASTFNGR
Have been doing the same now