Burs for Zirconia

Car 54

Car 54

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#43
Thank you! I'll be ordering some of those.
@RDA Maybe order a trial amount...3-4? I use the baskets which I cut the lip off, to use them in smaller glass jars I got on Amazon. Ron's were to big for me,
I was using to much liquid to get the "cover the units" amount. I didn't want that much liquid exposed on and off to air, depleting the water and changing
the intensity of the coloring liquid. I'd rather replenish a smaller amount from the original bottles. I'm a 1 man lab, so I'm not doing large quantities of FCZ a day.

Ron's work great for medium bridges, though. I also store all my jars and liquid in a light proof utility box(s),and puts the jars back when I'm done. Otherwise
there are jars that have baskets and shade tagged for identification but they're ~3x more expensive. Origin also sells them: https://www.bdiart.com/shop-2/

IMG_1838.JPG
 
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A

ABV

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#44
thats why i left that lab. i got feedback things were wrong but i was tightly controlled to NOT modify the CAM or machines for fear of voided warranties and broken machines. so fine you get crowns with wrong bites and thats the and of the story.

what i can now prove beyond reasonable doubt is that the CAM is the biggest source of problems for people doing CADCAM. its a little field of data science called Metrology. download free Metrology software for most purposes on a free restricted Trial basis if you like.

here is a Metrology scan of a bridge, the dark blue is the edges of the designed bridge, while red and yellow and Green areas indicate how off the mill made it. we are comparing a scan of the milled bridge, to the CAD, 3 different tries at the same file.
View attachment 31085 View attachment 31086 View attachment 31087

now, after modifying only the CAM parameters i was able to make that same bridge to this tolderance:
View attachment 31088

this bridge is now perfectly milled to my design.

thats how i know how off it is even before the ceramists judge design and grind the heck out of it for funsies anyway.
how do you work with that software? what scanner do you use for the milled bridge?
 
CoolHandLuke

CoolHandLuke

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#47
i have an imetric L1 scanner - the workflow is similar to all other box scanners.

i simply scanned it as a waxup, used the top-bottom holder, which held the bridge by its sprue (you can see the sprue sticking out on the bridge) and scanned sequentially first the top, then flipped over for the bottom and the software lined it all up.

to do this in 3shape you'd just need to add extra scans at the end of the scan stage to capture the bottom, but its the same thing.

from there GOM has an interface to walk you through the importing, marking which set of data is to be the control, and which set of data is to be inspected for inaccuracy.
 
B

Brandon Patrick

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#48
Does anyone leave zirconia crowns slightly out of occlusal contact and just allow opposing to (slightly; were talking microns not a millimeters here) super-erupt into contact? I know several techs that go this route. I brought it up one time to another tech and he got pretty upset and said "that shouldn't even be an option, you'll never read anyone publishing THAT as a correct technique."
As it turns out, nobody likes grinding zirconia, lab or dentist.. If you've ever happened to drop by the dental office during a crown seat you can almost hear them thinking, "I hope they don't notice the sparks flying off this zirconia." Then you make eye contact... make it awkward for them. You have the option to take it a step further while they're trapped in your gaze... look past their loupes, into their withering soul, and whisper "micro fractures."
 
Car 54

Car 54

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#49
Does anyone leave zirconia crowns slightly out of occlusal contact and just allow opposing to (slightly; were talking microns not a millimeters here) super-erupt into contact? I know several techs that go this route. I brought it up one time to another tech and he got pretty upset and said "that shouldn't even be an option, you'll never read anyone publishing THAT as a correct technique."
As it turns out, nobody likes grinding zirconia, lab or dentist.. If you've ever happened to drop by the dental office during a crown seat you can almost hear them thinking, "I hope they don't notice the sparks flying off this zirconia." Then you make eye contact... make it awkward for them. You have the option to take it a step further while they're trapped in your gaze... look past their loupes, into their withering soul, and whisper "micro fractures."
I just had one of my Dawson educated accounts mention that about 1 month ago, "keep it low and let it grow". For singles i'm ok with that (slightly out of occlusion). But on anteriors and bridges he still wanted some occlusal contacts and anterior guidance.

I like Dr Spear's way of going about it:
 
sidesh0wb0b

sidesh0wb0b

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#50
Does anyone leave zirconia crowns slightly out of occlusal contact and just allow opposing to (slightly; were talking microns not a millimeters here) super-erupt into contact? I know several techs that go this route. I brought it up one time to another tech and he got pretty upset and said "that shouldn't even be an option, you'll never read anyone publishing THAT as a correct technique."
As it turns out, nobody likes grinding zirconia, lab or dentist.. If you've ever happened to drop by the dental office during a crown seat you can almost hear them thinking, "I hope they don't notice the sparks flying off this zirconia." Then you make eye contact... make it awkward for them. You have the option to take it a step further while they're trapped in your gaze... look past their loupes, into their withering soul, and whisper "micro fractures."
any adjustments should be made with full irrigation.
otherwise it voids any sort of protocol for life expectancy
 
L

Lindsay Patterson

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#51
I understand your reasons Lindsay, but i'm only going to say i really am disappointed in the people here who accept faulty work coming from their machines, accepting it as Normal, and suggesting this is what happens for everyone. this is by far NOT the case for anyone who operates their milling or printing with Quality assurance and standard Quality Control checks in-and-out of the machines.

yes, I understand in this instance its not your bridge, not your mill, that does not mean these checks and balances don't apply. clearly whoever made this bridge for you needs their process examined.

the best way to mill a bridge is *right the first time* not "anything will do, even if i have to grind it"

you should not be accepting product from a machine that does not produce what you asked it to produce.

Measure your product qualitatively and modify the milling parameters to suit. the only part of this process that should be unacceptable is thinking that the machine and the CAM doesn't need modification straight out of the box. the people that do this need to have their products thoroughly examined.

all that being said, the ceramists i used to work with used to swear only by irrigated handpieces for grinding zirconia. as for the tools they used i can't say because i don't really know.
The bridge was already done. I had nothing to do with the design, mill, stain or glaze. The patient was completely unhappy with it so I did what I could to save them from starting all over. Not sure how the work flow is in your area but in mine, no is not an option or kiss that doctor goodbye. You have to make it happen.
The parameters in CAD are the only part of the process that remains the same no matter what (unless you change them) so you can pretty much eliminate that as a factor of inconsistent crowns. CAM maintenance is extremely important as well as having a good nesting software with good support. I have also found that the sintering oven, beads and firing trays can play a large role in inconsistency. Every technician has their own ways and opinions but I have met very few that has no adjusting after its sintered. The ones that get it perfect have way more time per crown to work on them than I do. I would like to note that every technician who preached perfection also had a recommendation of burs to use. Im guessing thats because a few of their crowns at one point or another weren't perfect:)
 
A

ABV

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#52
i have an imetric L1 scanner - the workflow is similar to all other box scanners.

i simply scanned it as a waxup, used the top-bottom holder, which held the bridge by its sprue (you can see the sprue sticking out on the bridge) and scanned sequentially first the top, then flipped over for the bottom and the software lined it all up.

to do this in 3shape you'd just need to add extra scans at the end of the scan stage to capture the bottom, but its the same thing.

from there GOM has an interface to walk you through the importing, marking which set of data is to be the control, and which set of data is to be inspected for inaccuracy.
Thanks, CoolHandLuke! I will give it a try!
 
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