Intraoral scanner crown margins

JKraver

JKraver

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Ive never had one IOS returned for bad margin. Margin has been the one thing rock solid for years.
 
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Mike Fulton

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One of first experiences with iTero were fantastic and still are. We had a case early on with a very picky Dr.. There was a "Saw Tooth" margin and he saw that in the office and came in with the crown the next day all in a huff. Brought the case up on the screen and sure enough the margin was a "Saw Tooth" on the scan! Loved it!
For your concern about margins with Trios I would say it is right there with iTero perfect it you can see them. So I agree with the idea they may be scanning the die or some other unknown. It should not be in the digital work flow.
 
JKraver

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One of first experiences with iTero were fantastic and still are. We had a case early on with a very picky Dr.. There was a "Saw Tooth" margin and he saw that in the office and came in with the crown the next day all in a huff. Brought the case up on the screen and sure enough the margin was a "Saw Tooth" on the scan! Loved it!
For your concern about margins with Trios I would say it is right there with iTero perfect it you can see them. So I agree with the idea they may be scanning the die or some other unknown. It should not be in the digital work flow.
Admittedly that should of been a call about the margin before delivery? Are saw tooth margins popular in your part of the country? Excellent anti-rotational properties....
 
TheLabGuy

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elaborate on your answer please
Just an opinion, sure I could go down the research rabbit hole but it's easier said that some folks can make anything work better than others...just happens digital works for this guy.
 
Toothman19

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I would imagine this is the reason 99% of IOS cases are sent back because of the margin. The "HD scan" or prep scan is incorrectly scanned and processed leaving half the prep scanned properly and the other half scanned with a low-density scan. This will cause errors when the scans are meshed together as you see on the mesial of #19. The high-density scan should have started halfway on #20 to include the contact area and continued all the way past #18. If you solve this issue for your clients and explain it to them, you'll never have a problem with margin fits again. This was an iTero scan FYI
 

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TheLabGuy

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I would imagine this is the reason 99% of IOS cases are sent back because of the margin. The "HD scan" or prep scan is incorrectly scanned and processed leaving half the prep scanned properly and the other half scanned with a low-density scan. This will cause errors when the scans are meshed together as you see on the mesial of #19. The high-density scan should have started halfway on #20 to include the contact area and continued all the way past #18. If you solve this issue for your clients and explain it to them, you'll never have a problem with margin fits again. This was an iTero scan FYI
what option in exocad are you using to analyze that in the picture?
 
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LarryRDC

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what option in exocad are you using to analyze that in the picture?
Rob,
Go to tools>adjust light>special>toggle wireframe and there you go! This is an Itero scan scan as well EXO_wireframe.jpg
This is a Carestream scan where there is not any stitching. If you grab the whole "adjust light " box and move around, it will change the lighting shadows to highlight different areas
Exo_wireframe2.jpg
 
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TheLabGuy

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@LarryRDC @Toothman19
This is great Intel. Not all the scanners have hd mode out there but some of the big ones do and we have experienced this issue as well when this has happened and your explanation is a heck of a lot better than what I was trying to explain to the manufacturers.
 
Toothman19

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Rob,
Go to tools>adjust light>special>toggle wireframe and there you go! This is an Itero scan scan as well View attachment 40769
This is a Carestream scan where there is not any stitching. If you grab the whole "adjust light " box and move around, it will change the lighting shadows to highlight different areas
View attachment 40771
you can also right click on the mesh, go to visual properties, and then click wireframe. There are a list of other cool options too
 
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FASTFNGR

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I am a dentist and we have been using the 3shape Trios for about 3 mo. now. I have been using the same little C & B lab for ~10 years. They are excellent. With PVS, the margins of our crowns were fantastic. I am always able to send a PVS impression capturing at least 0.5mm below the margin, usually 1.0mm. I would have to say that after a few months of scanning, I think the margins are just acceptable, not excellent. Is this a problem with my lab or is scanning really not as good as advertised? Thanks you all for your help in advance.
You know that the camera has a certain qualification depending on which one you have. In Chicago last February I found out that some cameras scan at 20microns , some at 10microns. Take that and add the 3D printer from 50microns down to 25microns. Now go to the milling machine if we are skipping the digital scanner because you marked your own margins, it mills about 20 to 25% Larger to shrink after sintering for about 10hrs at about 1500* C. To shrink to 100% fit.
Question: is the milling machine calibrated? Or that oven is at correct temp? A lot of variants that can effect the fit.
Something to think about.
 

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