Reasons for implant misalignment?

Affinity

Affinity

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Had a fairly straightforward Nobel active RP splinted crown case, on 2 custom dess abutments that didnt fit in the mouth. It was a beauty on the model, dropped down like no problem. Dr called and said there must have been some 'distortion' because he couldnt get it to fit, even after trimming the abutments down :banghead: .. same Dr called a week before to thank me for all the 'slam-dunks' on these style implants. Dontknow

My question is, how common is this with pickup style impressions? I cant see any reason why this shouldnt be exactly like it is in the mouth, the implants are in bone, impressions dont distort that much. On these peg abutments where the cervical margins are .5mm larger diameter than the screw hole, there isnt much that seats other than maybe a touch at the margins.

How do you troubleshoot these? Im going to scan the abutments on the old model, then transfer to the new model, scan and see if there was distortion between the two.
But anyone that can help me from going crazy please do.. Other than the Dr didnt place them in the right position ( they have very large flat surace on the buccal),how could these abutments be so misaligned compared to the model?
 
2thm8kr

2thm8kr

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Got pictures?
For one, have the doc splint the impression copings together with light cured material before taking the impression.
It is also wise to take a x-ray to confirm the impression copings are seated. Then they can hardly miss.
 
OP
Affinity

Affinity

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Yeah i might have to talk about protocols but this Dr is very sound technically speaking.. an LVI fellow.. I will pick it up in the AM and get it poured and compare.. I will try and get some pics up. What is a good software to compare two models? I dont have magics. I guess exocad will work..
 
J

J Pierce

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I will be interested to hear what you see on the new impression vs the orig!! As 2thm8kr stated above, there could be a slight distortion if the doc didn't splint copings together. We have done hundreds of these cases without issues, but have had a handful of these that don't and cause a lot of hairpulling as to why??
 
J

J Pierce

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Yeah i might have to talk about protocols but this Dr is very sound technically speaking.. an LVI fellow.. I will pick it up in the AM and get it poured and compare.. I will try and get some pics up. What is a good software to compare two models? I dont have magics. I guess exocad will work..
I think putting the orig restorations on the new model will tell you a lot!!!
 
JMN

JMN

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Had a fairly straightforward Nobel active RP splinted crown case, on 2 custom dess abutments that didnt fit in the mouth. It was a beauty on the model, dropped down like no problem. Dr called and said there must have been some 'distortion' because he couldnt get it to fit, even after trimming the abutments down :banghead: .. same Dr called a week before to thank me for all the 'slam-dunks' on these style implants. Dontknow

My question is, how common is this with pickup style impressions? I cant see any reason why this shouldnt be exactly like it is in the mouth, the implants are in bone, impressions dont distort that much. On these peg abutments where the cervical margins are .5mm larger diameter than the screw hole, there isnt much that seats other than maybe a touch at the margins.

How do you troubleshoot these? Im going to scan the abutments on the old model, then transfer to the new model, scan and see if there was distortion between the two.
But anyone that can help me from going crazy please do.. Other than the Dr didnt place them in the right position ( they have very large flat surace on the buccal),how could these abutments be so misaligned compared to the model?
One trick that will catch you and you'll never pin it down without having lots of memory.
The driver hole will impress as a positive on closed tray impressions. If the rotation of the impression post and screw don't match it will not seat back into the impresion fully. I would use a discoid to remove the positive of the driver hole, but that's what I'd check if you have anyone in the process who may not have full awareness of that chance.
 
Car 54

Car 54

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If you're splinting impression copings it needs to be open tray, right?
So if the Dr is used to closed tray, would need to get the right impression copings for the open tray technique for better impression retention and accuracy?

I had a Dr using the closed tray impression copings for his open tray impressions, including on side by side implants.
I showed him the difference between the 2 copings, the "fins" on the Zimmer open tray and the smoother 2 "sided" closed tray copings,
but he never changed, until he retired.
 
JMN

JMN

Christian Member
Staff member
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If you're splinting impression copings it needs to be open tray, right?
So if the Dr is used to closed tray, would need to get the right impression copings for the open tray technique for better impression retention and accuracy?

I had a Dr using the closed tray impression copings for his open tray impressions, including on side by side implants.
I showed him the difference between the 2 copings, the "fins" on the Zimmer open tray and the smoother 2 "sided" closed tray copings,
but he never changed, until he retired.
"But, it's an impression post, it's supposed to work"
 
rkm rdt

rkm rdt

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If you're splinting impression copings it needs to be open tray, right?
So if the Dr is used to closed tray, would need to get the right impression copings for the open tray technique for better impression retention and accuracy?

I had a Dr using the closed tray impression copings for his open tray impressions, including on side by side implants.
I showed him the difference between the 2 copings, the "fins" on the Zimmer open tray and the smoother 2 "sided" closed tray copings,
but he never changed, until he retired.
Most issues with alignment occur with closed tray impressions I have found.
Never ever would I suggest using a closed tray for more than one abutment/impression coping.
I always want an open tray because there is no guarantee that you have parallel implants .Locking in the impression copings is better than impressing 2 or more nonparallel copings.
Then again, your best option is to do an IOS.
 
Car 54

Car 54

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"But, it's an impression post, it's supposed to work"
Funny and Agree, as I think that can be the mentality of some of the Drs out there, "hey, as long as it's an impression coping, it doesn't matter".
 
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OP
Affinity

Affinity

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thanks for the response, these are closed tray impressions, the Dr even marks the impression coping so it goes back in the impression the same way, they send it with the analogs and copings in the impression.

Im more concernced about the rotation being off somehow, and adding 3rd party abutments doesnt help matters with Drs that are told by nobel to use only nobel parts.
 
Car 54

Car 54

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I figured I may be getting a little off topic, but thanks for your appreciation and follow up info as far as what your account is doing impression wise.
 
JMN

JMN

Christian Member
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thanks for the response, these are closed tray impressions, the Dr even marks the impression coping so it goes back in the impression the same way, they send it with the analogs and copings in the impression.

Im more concernced about the rotation being off somehow, and adding 3rd party abutments doesnt help matters with Drs that are told by nobel to use only nobel parts.
You are absolved of all if you don't do all. If it fit the model, then you cannot be responsible if you don't place the impression posts.

The rotation of the impression post and the timing of the screw will not always match up perfectly. If the screw is tighter or not as tight on the analog the screw timing will be different, and the positive of the driver hole will bite.

There are plenty of other things that can go wrong inserting an impression post into an impression, namely overseating and underseating.

This is a one time/first time thing, right? Does he have new staff?
 
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