Design crown under partial?

[NicelyMKV]

Is it possible to design a crown under a partial using exocad? I tried to come up with a way to fabricate an antagonist including the clasp using putty but for obvious reasons that will not work. I am new to this software and have a few Doctors inquiring about Bruxzir under partials.

Thank you,
Jason

 

[Slipstream]

Last one we did, I think we gave up with the software option and just waxed a crown and used that as a pre prep scan - which is what the dentist should have done - pre prep impression, post prep impression - and you just recreate the difference which would save having to take the chrome from the patient for the days the case is in the lab.

 

[NicelyMKV]

Ahhh... So just scan pre op and overlay the die model? Sounds much easier thanks!

 

[CoolHandLuke]

while that method works, i have tinkered a bit with this kind of thing in the 3shape system and have a theory... what if we do a "pre-op" scan, and antagonist scan.

heres the trick: in the pre-op scan you can do alignment. so flip the partial over, and scan the appropriate area. in the antagonist scan place the partial on the cut die model. you will align the pre-op scan by flipping it over. in concept, it will align the upper pointcloud and lower pointcloud via similar buccal areas.

in effect you will have a clear "underside" of a clasp area, and wont need waxups.

anyone have a denture crown case to test this theory on ? i'm gonna hunt one down to try it if you guys dont.

and yes i know its not for the OP's system... but its on topic i hope.

 

[k2 Ceramic Studio]

while that method works, i have tinkered a bit with this kind of thing in the 3shape system and have a theory... what if we do a "pre-op" scan, and antagonist scan.

heres the trick: in the pre-op scan you can do alignment. so flip the partial over, and scan the appropriate area. in the antagonist scan place the partial on the cut die model. you will align the pre-op scan by flipping it over. in concept, it will align the upper pointcloud and lower pointcloud via similar buccal areas.

I love the way you think, this is the sort of stuff I do all day long.

 

[YMS96]

I was recently trying to do something similar in 3Shape and thought that scanning the partial in as an antagonist, then designing the crown and 'cutting to antagonist' would cut in the clasp area. It should work but I didn't get to actually try it out. As far as exocad.....no idea!

 

[CoolHandLuke]

that will work, however not as you might expect. the antagonist will be 1 sided; you will scan the denture's outer shell, not inner shell. your crown will be cut according to the outer shell and will accordingly be off slightly.

keep at it though, we're getting ever closer!

 

[NicelyMKV]

Could you not glue the partial in occlusion to the antagonist and then scan it all under antagonist?

 

[CoolHandLuke]

you sure could. i wouldnt be too sure of the accuracy of clasps when your model is so huge, but its definitely worth a shot. good thinking!

Edited to add: you may run into trouble articulating that conglomeration, but you should have enough data to trick the software. instead of wobbling the arches inside the scanner and risking anything you could fit the partial on the die model, and only scan this for your "upper and lower" scan, because your "antagonist scan" which includes the denture you should be able to align the buccal face for both scans.

in principle it could work. however i am sure you would probably use blue tac instead of glue lol

 

[YMS96]

that will work, however not as you might expect. the antagonist will be 1 sided; you will scan the denture's outer shell, not inner shell. your crown will be cut according to the outer shell and will accordingly be off slightly.

keep at it though, we're getting ever closer!

Not if you flip the partial over when you scan it, then put the partial on the actual model when doing them together. The only part of the partial that you need is the area that is touching the tooth (clasp) and you can scan that by scanning the underside of the partial. Technically it's the same as doing an upper/lower but I am almost positive it wouldn't work like that without being very buggy/difficult.

 

[YMS96]

The easiest way to do this is to just wax up the crown and scan it in as a waxup.

 

[NicelyMKV]

easy is boring and profitable YMS96! lol kidding. I am going to try gluing it to the antagonist monday or tuesday. Have to get a partial model from a friends removable lab. I am just concerned about how it will read the information. In my system you have to select the antagonists teeth to be scanned. I am wondering if it will freak it out when it sees a foreign object in the mix. I even thought about somehow scanning the antagonist and then selecting Add a scan, and inserting the partial to that scan so I will not get any interference when 1st trying to capture the occlusal details. I am the king of poorly punctuated run on sentences by the way.

 

[DMC]

Try very thin cheap trash can liner and kids modeling clay.

Then rip off plastic and scan.


Trim away the bogus scan data for the clay antagonist scan mesh until you get just the clasp/rest you are working with.


Your density/properties of clay will be the variable you need to experiment with.

I totally forgot where we found our favorite clay, but Yellow and Green scan well.
We use Black Clay for anti-data to speed up CPU processing when doing nesting scans.

Keep trying the clay route!

Scan that as antagonist and trim to "0" of course.