Exocad crown occlusal problems with intra oral scans (Will mail top shelf Scotch if you can help me)

Sda36

Sda36

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you'll want to use Correct antagonist and create overclosing in a uniform way, along the wear facets that exist, and then let the Articulator open those intrusions. if they are uniform, the act of opening should bring the scans to the correct bite. if the intrusions are not uniform, the bite will appear very open.

exocad's approach to this is either to give you a truly vertical opening by shifting everything along the Z or by using the theoretical patient approximation of the articulator hinge to open the jaws, which is why i suggested this to begin with.

however what you can then do is save the new relationship by exporting the scene as one stl or object file before proceeding with any design; once done, you can use this as the bite scan instead, and when aligned with the bite scan, it doesnt matter what the articulator does, they will spring back to the same spot everytime.

you can also use 3rd party software like blender, meshmixer, meshlab, etc, to re-orient and realign data. that lab's skill with mesh work probably stems from some years of familiarity with the digital space so i'm not sure what tools they'd use because everyone's bag of tricks varies; i've given you what i'd do in exocad. this is usually good enough to create jaw relationships with better centric relation and when push comes to shove there's always your software support who should be experienced enough to help you no matter what the problem is. over the years the go-to-answer for any product question of "what do i buy" has always culminated in "the product with the best support" usually for exactly these reasons.
Honestly Matt, you are far more accomplished and knowledgeable than I read in your 1st post. Have really enjoyed all of the responses so far and helpful insights. It just seems sometimes that no matter how much care and attention you put into your work with virtual articulator, surprises happen, just sucks sometimes. So many variables involved, quality of scan which may Look OK?????, import and manipulation. We had a case today for a bite splint, not ios and Man you couldn't find a true centric at all by hand. Dr. Took an open bite record without an anterior stop of any fashion, how is that remotely possible. Squirt in a bunch of pvs and close, but not close, anywhere -impossible! Was wider open in the molar region ×3 compared to the anteriors.
Been at this a while, trust in the Lucia Jig method, 3 bite records in which 2 of 3 must agree. This digital path is so far away from that approach its not even comparable. I do believe however that some excellent tools in digital may be nearer than farther away. That's my hope.

As far as correcting bite and distance from antagonist, its mainly a reflection from feedback from clients. Some need more, some less. Also as ps2thtec said there's no periodontal ligaments in any of our models, quality of provisionals is another concern. I always check my proximal contacts with shimstock, adjust until it pulls through without tearing. Had a new client experiencing proximal contact problems and I suggested they use this standard with the shimstock and bingo we're now having excellent results.
Lots to learn and experiment with, great topic Matt, hope it keeps on going 🙂
 
CoolHandLuke

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agree, theres really only so much you can do when you are missing half a scan.
 
ps2thtec

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Honestly Matt, you are far more accomplished and knowledgeable than I read in your 1st post. Have really enjoyed all of the responses so far and helpful insights. It just seems sometimes that no matter how much care and attention you put into your work with virtual articulator, surprises happen, just sucks sometimes. So many variables involved, quality of scan which may Look OK?????, import and manipulation. We had a case today for a bite splint, not ios and Man you couldn't find a true centric at all by hand. Dr. Took an open bite record without an anterior stop of any fashion, how is that remotely possible. Squirt in a bunch of pvs and close, but not close, anywhere -impossible! Was wider open in the molar region ×3 compared to the anteriors.
Been at this a while, trust in the Lucia Jig method, 3 bite records in which 2 of 3 must agree. This digital path is so far away from that approach its not even comparable. I do believe however that some excellent tools in digital may be nearer than farther away. That's my hope.

As far as correcting bite and distance from antagonist, its mainly a reflection from feedback from clients. Some need more, some less. Also as ps2thtec said there's no periodontal ligaments in any of

Not trying to finally derail this thread but for as much as I like impressions and stone models, this case came in for pvc bridge. Sent back to get a bite. Patient bit in protrussive and you can’t remount with just anterior teeth. Banghead
7EDF6D77-DF00-4AB0-B2AC-D4948A7446D7.jpeg
 
CoolHandLuke

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i don't need to tell you, we've all seen similarly bad and far worse, here on this very site in the Facepalm thread.

 
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miltonic

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i don't need to tell you, we've all seen similarly bad and far worse, here on this very site in the Facepalm thread.

Man, every single one of these posts...yes I totally relate to all these challenges. Building a large posterior bridge with no posterior stop...these dentists really don't understand what we do and expect miracles from us. Well I really appreciate all of you guys helping me out, I will for sure share my experiences with you regarding the occlusal outcomes.

Gru: Thanks for the kind response, and thanks to you guys for troubleshooting with me!

SDA36: I hear you brother, what can you do when you get bad impression information? I went to school for Computer Science, and on the very first day, the professors stressed a motto, "Garbage In, Garbage Out". That's basically what a poor impression and sometimes poor bite will accomplish. Can't remember if it was Mclaren or Spear but I thought one of them said, " you can get away with a bad prep, but you can't get away with a bad impression." What blows my mind is that these young new dentists I have conversations with are surprised at how critically important the impression is in the overall restoration. One of them said they didn't realize it was so important and that their schooling didn't cover it much. It seems like many of these dental schools have serious flaws in their teaching philosophy to overlook something so critical. Like ps2thtec said, we can only do so much with the information we are given. In regards to your proximal contact protocol with shim stock and pulling it through, I do the exact same thing, and it is very reliable! Glad we got proximal contacts down!

Regarding this whole IOS bite fiasco, technically I understand what the problem is and why it's happening, the challenge is getting the software to better accurately overlay the jaw scan data to the bite scan. With my desktop scanner, when I scan the bite relationship, and then the jaw models, I can trim the scans if I need to in order to help the software more accurately align them to the bite. Sometimes I will have to edit the scans significantly by selectively trimming in order to help the software find more matching reference points to be able to find common alignment points, and this editing will usually get a perfect alignment. But with the IOS scanners, this human finesse is taken out of the equation, and the bite alignment algorithms from the IOS scanner, or like Exocad's bite scan alignment function struggle to find a perfect match to the bite scan. When it attempts to match, often you will see the scan not quite overly perfectly, and this is a clear red flag that the jaws are off. In crown and bridge, a slightly misaligned bite is a mile off. Like CoolHandLuke was saying, I think these specialized digital dental labs are using separate software like Blender/Meshlab or who knows what else, and have found out how to reliably realign the jaw scans. In my particular situation, the IOS digital bite is the one main variable that is largely out of my control, and consequentially the cause of all my occlusion inaccuracy. That being said, I think ps2thtec's thoughts on bites usually being off vertically and not laterally is good food for thought. When trying to correct the antagonist in Exocad, I will try to do most of my adjustments through rotation of the bite to achieve uniform intensity across the arch. Sometimes I might find uniform intensity that matched wear facets but I moved the jaw too much to do that from the initial current scan, I think a centered buccal/lingual rotational approach might be a better way to start off trying to fix the bite uniformity, and not mess with any mesial/distal rotation. Then use CoolHandLukes approach to loading the new uniform bite into the articulator and opening the pin. This is what I will try while still seeing if I can search for a better bite alignment matching software approach through Blender or Meshlab.

I'll keep you posted with the results, Happy Sunday to y'all!

-Matt
 
Toothman19

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Man, every single one of these posts...yes I totally relate to all these challenges. Building a large posterior bridge with no posterior stop...these dentists really don't understand what we do and expect miracles from us. Well I really appreciate all of you guys helping me out, I will for sure share my experiences with you regarding the occlusal outcomes.

Gru: Thanks for the kind response, and thanks to you guys for troubleshooting with me!

SDA36: I hear you brother, what can you do when you get bad impression information? I went to school for Computer Science, and on the very first day, the professors stressed a motto, "Garbage In, Garbage Out". That's basically what a poor impression and sometimes poor bite will accomplish. Can't remember if it was Mclaren or Spear but I thought one of them said, " you can get away with a bad prep, but you can't get away with a bad impression." What blows my mind is that these young new dentists I have conversations with are surprised at how critically important the impression is in the overall restoration. One of them said they didn't realize it was so important and that their schooling didn't cover it much. It seems like many of these dental schools have serious flaws in their teaching philosophy to overlook something so critical. Like ps2thtec said, we can only do so much with the information we are given. In regards to your proximal contact protocol with shim stock and pulling it through, I do the exact same thing, and it is very reliable! Glad we got proximal contacts down!

Regarding this whole IOS bite fiasco, technically I understand what the problem is and why it's happening, the challenge is getting the software to better accurately overlay the jaw scan data to the bite scan. With my desktop scanner, when I scan the bite relationship, and then the jaw models, I can trim the scans if I need to in order to help the software more accurately align them to the bite. Sometimes I will have to edit the scans significantly by selectively trimming in order to help the software find more matching reference points to be able to find common alignment points, and this editing will usually get a perfect alignment. But with the IOS scanners, this human finesse is taken out of the equation, and the bite alignment algorithms from the IOS scanner, or like Exocad's bite scan alignment function struggle to find a perfect match to the bite scan. When it attempts to match, often you will see the scan not quite overly perfectly, and this is a clear red flag that the jaws are off. In crown and bridge, a slightly misaligned bite is a mile off. Like CoolHandLuke was saying, I think these specialized digital dental labs are using separate software like Blender/Meshlab or who knows what else, and have found out how to reliably realign the jaw scans. In my particular situation, the IOS digital bite is the one main variable that is largely out of my control, and consequentially the cause of all my occlusion inaccuracy. That being said, I think ps2thtec's thoughts on bites usually being off vertically and not laterally is good food for thought. When trying to correct the antagonist in Exocad, I will try to do most of my adjustments through rotation of the bite to achieve uniform intensity across the arch. Sometimes I might find uniform intensity that matched wear facets but I moved the jaw too much to do that from the initial current scan, I think a centered buccal/lingual rotational approach might be a better way to start off trying to fix the bite uniformity, and not mess with any mesial/distal rotation. Then use CoolHandLukes approach to loading the new uniform bite into the articulator and opening the pin. This is what I will try while still seeing if I can search for a better bite alignment matching software approach through Blender or Meshlab.

I'll keep you posted with the results, Happy Sunday to y'all!

-Matt
Can you share the files for the case? You mentioned it was a trudef case, can you share the .exo file and the .stl files. I'd like to take a look
 
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I would always suggest finding consistency first, then work on your settings. Too many times I've seen knee-jerk reactions and "this crown is too tight, let's bump up the settings" immediately.

For occlusion issues, yes it's the scans, yes it's also accuracy, yes it's fixable though. You have to know what you consistently want. Couple of starting questions and ponderances.

  • Is the scan properly in occlusion
  • Do you equilibrate stone models when you work analog?
  • How much paper pulled for you is good, and how thick is that paper
  • Are you trying model-less?
  • If models - are you following the proper procedures for printing and cleaning.
  • Preps vs. Implants
in the same order- the reason why I ask those, and why it's important.

  • First and foremost. check the scan. In Exocad and 3shape both, you can see when the teeth are collapsing through each other and when they touch exact. This is unique to digital, physically they cant collapse through each other. If they're messed up, print them, hand articulate, and scan that in as a bite. It's very tedious, but you can at least find consistency.
    • Look for the same "colors" every time. If every scan you correct the bite on has dark blue marks (barely touch in Exo) then every case you cut out the same amount will fit the same if the scan is accurate
    • if you have red/green on one case's existing dentition and light blue on another, cutting them both out at .25 will result in different occlusions.
  • If you used to equilibrate stone models by hand when mounting, do it digitally. If you go into edit mesh in Exocad, if the bite is collapsing then you can make the models "equilibrate" by cutting away intrusions. this can mean the bite is more stable once mounted, and you can find better consistency through this.
    • FIRST make sure you get the colors you're looking for consistent before cutting the occlusion with this method. You will have the same seating, but you will have different results in mouth. If you cut cut intrusions when it shows red, compared to blue, it will end up way more out of occlusion in the mouth, but be the same on the model.
    • You can correct antagonist to open or close the scans to get the consistent colors across the occlusion. Expert -> r'click the opposing. correct antagonist.
  • You can look up or measure the paper you use to pull as a starting point to what to cut your occlusion to. Once you have that starting point, begin to change it. You'll likely need "in occlusion" cuts, "regular occlusion", and "out of occlusion drive a truck between those bad boys". otherwise known as "let it grrrrrrooooooooow into occlusion" for all you Frozen fans. (please do full arch cases in occlusion. don't make them collapse weird)
  • Please don't try model-less until you've worked out a protocol for doing it with models where you can check it... please.
  • For printing, do not leave models in IPA overnight, most printers is 5min tops in IPA. I've seen it happen lots of times, it warps models. If you have major issues cross-arch differences between the scan and your model, consider a support pin on the distal of the arch for support. These help with those flexes. Basing models can also flex them some, since the stone will shrink or expand slightly which will bend the models cross arch as well sometimes. Don't over cure, just follow the guidelines...
  • Don't forget that your implants won't have the same periodontal ligaments to absorb shock, if only your implants seem high in the mouth, and you KNOW You lined up that flag right, cut it out of occlusion a pinch more.

Bonus fun:

When cutting contacts in the adjacents tab : freeform wiz step turn on "blockout neighbor collisions" this will take the height of contour of your contact and follow the path of insertion and cut your crown to that (make sure you have the POI correct for your contacts or the cut will be messed up).
No more grinding under the contact area to set the crown!

Also, if you're doing lots of single units, use the disc cutter (set to 0) to make perfectly flat contacts instead of that weird ( ) ) wraparound nonsense that happens if you just cut them to each other.
 
D

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Hi all, I'm at my wits end and have exhausted all of my mental ability and effort troubleshooting bite scan inaccuracy through intra oral scan cases we get from our clients. I would be more than happy to send a high end bottle of scotch or your preferred drink of choice if you can solve this once and for all for me. Yes, I'm that desperate for help.

I use exocad, and I have been unable to design a crown with any reliability regarding the occlusal accuracy if it is from an intraorally scanned case. Two different clients I work with use the 3M TruDef scanner. When I finish margin marking and load the exo. case file into exocad after margin marking, nearly every time the Trudef bitescan aligns the jaw scans in a way where they intersect each other significantly. I would say on average the occlusal plane of the jaw scans are intersecting about .4mm, and in some cases almost as much as 1mm or even more. Exocad recommends cutting away the scan inaccuracy, which if I proceed to do, will just gouge out the antagonist scan, which I highly doubt is accurate. Otherwise my only other choice is to leave the jaw scan unaltered, and do my best to reposition the antagonist so it has even contact everywhere. Obviously this is taking a guess at the patients centric bite, but it seems much more likely to be accurate than cutting out the opposing. I'd say the most common occlusion problem is the crown is too tall and the dr has to spend significant time grinding it down, in some cases much of the anatomy is lost. Of course, this is not how it is designed, and when I mill and test it on the 3d printed model, it is perfectly represented as it is in the CAD. When the Dr. puts it in the mouth, margins and proximal fit are usually perfect, but occlusion is almost always high.

I've been fighting this for two years, have tried many different solutions with no consistent accuracy, to the point where one of the dentists has stopped sending me digital cases and is sending them to a digital specialty lab, and I guess the lab has been getting great results. So obviously they have a reliable workflow, and I have not figured it out. I have self taught myself full arch hybrid cases with perfect seating results, but I can't figure this out...dental cad is bitch slapping me right now. Can anyone give me advice on how they use exocad to ensure close to accurate bite relationships so your crown occlusion is close to perfect at seating? Do you let Exocad cut away scan accuracies as recommended by Exocad? Are there any other details to consider? I do not have this problem when I scan cases in on my desktop scanner and design the crown, and my margins and proximal contacts are usually perfect. Just occlusion....just the goddamn intra-orally scanned occlusion. I really appreciate you all here, great forum and lab techs. Thank you so much for reading. And I'm very serious about the Scotch offer.

-Matt
Hi Matt,
This is an error with the intraoral scnner bite registration. I’ve seen this many times and there are 2 solutions; 1 is the dentist be aware of it and retakes the bite when this happens and 2; is you to raise the bite till there is no intersection.

I’m digital dentistry specialist for Dentsply Sirona and I know exactly what you’re talking about
 
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Old school here (fixed, removable, maxillofacial, early rapid prototyping for diagnostic models). I am getting a 3 unit implant bridge on the lower. I wanted to catch-on where things were with digital. This thread has been wonderfully instructive. You folks all seem to have you heads screwed on right - solving problems with digital casework. The only reason I am posting is that "no matter how things change they remain the same". There is still a great deal of "art" in our "science". Thanks everyone.
 

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