Implant Margins

[Ken Knapp]

Dentist returned two screw retained implant crowns for margins based on X-ray.

Crown on left for zirconia overhang on margin, on left. Crown on right for open margin, on right.

To me they seem acceptable.

What is the objective standard for crown/implant margins?

Thoughts?

Ken

 

[CatamountRob]

They both look slightly open on the mesial, like the contact might need to be adjusted? Bacteria is the issue with an open margin.

 

[Ken Knapp]

They both look slightly open on the mesial, like the contact might need to be adjusted? Bacteria is the issue with an open margin.

Screw retained. Crown is precemented on abutment.

What is the standard?

The margins look under 50um. Current crown standard is under 75um.

 

[doug]

Does the doctor know what the standards are for the materials?

 

[Ken Knapp]

Does the doctor know what the standards are for the materials?

I'm not exactly sure what your question is?

She knows the zirconia material, cement and OEM abutment standard.

 

[Ken Knapp]

I find one of the biggest problems in dentistry is the lack of objective standards. Every dentist has a different standard.

My largest implant dentist, not the dentist above, does his own implants with in house cone beam x-ray. He would consider the above crown/implants acceptable.

 

[ztech]

I would not send out either of those. Reasoning is that the both areas are not cleansable by the patient and in the long term create a potential for bone loss. Looking at both, I think my clients would have less of a problem with the open margin and more problem with the anatomic form at the margin. My goal is to make an emergence similar to the interproximal margins between the two implants. I would also agree that the mesial contact is tight creating the open margin.

 

[zero_zero]

Looks like the crown on the right wasn't sitting all the way down on the Ti insert, I wouldn't sent them out. We always use a rubber wheel to smooth the joint as much as possible, and no visible gaps under magnification...cement can erode away with time creating a slight gap where bacteria could thrive.

 

[CatamountRob]

Screw retained. Crown is precemented on abutment.

What is the standard?

The margins look under 50um. Current crown standard is under 75um.

Those would be returned to me, I don't know what the standard is but a visibly open margin will get returned, as it should in my opinion.

 

[Sevan P]

Looks like the crown on the right wasn't sitting all the way down on the Ti insert, I wouldn't sent them out. We always use a rubber wheel to smooth the joint as much as possible, and no visible gaps under magnification...cement can erode away with time creating a slight gap where bacteria could thrive.

I don't think he did it with a Ti insert, lately I have been seeing stock abutments with a crown with a hole over it cemented then placed in the mouth, a faux screw retained crown. But yes smoothing down the ledge at the ti interface is always a good idea.

 

[Ken Knapp]

I would not send out either of those. Reasoning is that the both areas are not cleansable by the patient and in the long term create a potential for bone loss. Looking at both, I think my clients would have less of a problem with the open margin and more problem with the anatomic form at the margin. My goal is to make an emergence similar to the interproximal margins between the two implants. I would also agree that the mesial contact is tight creating the open margin.

Standards, objective standards..Every dentist has a different preference. Some want the emergence profile as you noted but most want the crown adapted to the tissue for a natural tooth emergence from the tissue. My largest implant dentist, who does his implants likes the crowns adapted to the tissue.

My understanding is that there isn't clinical results supporting your argument.

 

[Ken Knapp]

I don't think he did it with a Ti insert, lately I have been seeing stock abutments with a crown with a hole over it cemented then placed in the mouth, a faux screw retained crown. But yes smoothing down the ledge at the ti interface is always a good idea.

Exactly, cemented over stock abutment with screw hole.

 

[Ken Knapp]

Does anyone have objective references on implant margins ?

 

[JohnWilson]

Such harsh criticisms here, its Friday lighten up

Some thoughts....

There is a reason why you can buy radiopaque cement.

There is a reason why bone level fixtures have this offset.

There is a reason why multiple cad base manufacturers have different offsets.

There is a reason why the wall thickness on zirconia is supposed to be .6 MIN

There is a reason why I have a tool that protects the ti base and allows me to bevel the edge of the zirc after cementation. Its a hand made tool that one day may be produced and NO you can not steal my design

Pretty sure those ti bases did not come from the Implant manufacturer for a non eng splint, but not judging

At the end of the day the verdict is your account is right. Is it acceptable restoration that will give years of great service? Hell yeah, its not going to do a damn thing wrong this way. Does the client have a right to bitch? Hell yeah they are the client.

Side notes the Resin cements we use today are SOOOOOO much better and are not going to wash out and fail like their predecessors.

There are tricks to cementing splints properly you didn't implement them

 

[Ken Knapp]

Such harsh criticisms here, its Friday lighten up

Some thoughts....

There is a reason why you can buy radiopaque cement.

There is a reason why bone level fixtures have this offset.

There is a reason why multiple cad base manufacturers have different offsets.

There is a reason why the wall thickness on zirconia is supposed to be .6 MIN

There is a reason why I have a tool that protects the ti base and allows me to bevel the edge of the zirc after cementation. Its a hand made tool that one day may be produced and NO you can not steal my design

Pretty sure those ti bases did not come from the Implant manufacturer for a non eng splint, but not judging

At the end of the day the verdict is your account is right. Is it acceptable restoration that will give years of great service? Hell yeah, its not going to do a damn thing wrong this way. Does the client have a right to bitch? Hell yeah they are the client.

Side notes the Resin cements we use today are SOOOOOO much better and are not going to wash out and fail like their predecessors.

There are tricks to cementing splints properly you didn't implement them

1) Ti bases are stock straumann.
2) Crowns are not splinted.
3) Objective standards?

It is Friday enlightenment!

Ken

 

[JohnWilson]

Interesting radio graph


Sent from my iPhone using Tapatalk

 

[Gru]

I've never seen any "objective" standard published, however, when I asked my account that does the most screw retained with me how he judges acceptability of the metal/ceramic interface he said if he can feel it catch anywhere with an explorer (checked before seating) he smooths it or sends it back. Not sure this is useful to you.

 

[zero_zero]

There is a reason why you can buy radiopaque cement.

To mask poor workmanship ? Not in my book...

Side notes the Resin cements we use today are SOOOOOO much better and are not going to wash out and fail like their predecessors.

The cement its still the weakest link, no matter how much better it became... I'd still plan for the worst and hope for the best...

 

[Ken Knapp]

I've never seen any "objective" standard published, however, when I asked my account that does the most screw retained with me how he judges acceptability of the metal/ceramic interface he said if he can feel it catch anywhere with an explorer (checked before seating) he smooths it or sends it back. Not sure this is useful to you.

Published JPD works on margin adaptation, which I have one, shows the explorer resolution to be 75 microns. Digital radiography can show open margins below the detection limit of the "explorer".

I have some fundamental questions:

1) What is or should be the crown/implant adaptation value based on peer reviewed published clinical results?
2) Is the crown/implant margin acceptability value different then crown/tooth margin value?

 

[JMN]

There is no objective standard. Some docs can't manage to show margins in impressions, some use 20 feet of retraction cord per tooth. They will both have different standards, and defend them, internally at least.
This is part of what makes the job fun, the problem solving to arrive above each doc's standard.

That said, I've always been told (with the source of "they say") that margins should be 25 microns.

You can impose a standard for your lab, but it will still be your standard.