WTH Screw retain prob

rkm rdt

rkm rdt

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So Argen called me back and it's because I started the case as a hybrid, zr with Ti base, then realised my mistake when designing and changed it to screw retained. That apparently is a big no-no as 3shape doesn't change it...er something
you went there
 
JohnWilson

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So Argen called me back and it's because I started the case as a hybrid, zr with Ti base, then realised my mistake when designing and changed it to screw retained. That apparently is a big no-no as 3shape doesn't change it...er something

Go hit "AGREE" on my post as somehow I am right again :) not that I am keeping score or anything HAHAHAHAHAH
 
RileyS

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Go hit "AGREE" on my post as somehow I am right again :) not that I am keeping score or anything HAHAHAHAHAH
Well, smart a$s, I didn't think that was my problem since I didn't change size or brand of implant...plus I'm an idiot.

On a more infuriating note for me but proly something you jerks will get a good chuckle at, I just dropped the bloody model and broke it from the plaster base.
#mothersdon'tletyourbabiesbedentaltechs
 
2thm8kr

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@JohnWilson It's no wonder I am not getting anymore hate mail and letter bombs sent to my inbox. It's all being redirected to the know it all cyber bully.
 
RileyS

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Ok......
I wanted to mill two of the six out of PMMA to check alignment and fit before going to zr. Why did they mill so bloody damn tight? They were able to make it half way onto Ti base then I had to grind it out till it fit down to margin. The simple single unit screw retained cases I've done fit great in zirc. What's the dealio?
 
JohnWilson

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Milling temps on cad bases and the respected fit has more to do with you managing your cam/mill. The drill compensation is built into the cad design via the library and the tolerances are tight. Get your directions slightly off and undermill a tad and this is a problem. If your CAM will allow you to run std deviation simulation to check use it. RED is not good.

Also there is a thing called Tool deflection that most do not talk about or discuss. It basically say as the force of the spindle pushes the bur laterally you have a tool that bends. This feed rate combined with the step over/rpm can be adjusted on certain CAM software to help eliminate this problem. Setting a strategy to do fine milling inside the holes 2 times on PMMA can also solve the problem.

Also there is a reason why some cad base mfg have std and oversize cad files for their bases as a band aid as most techs do not want to learn past push and nest.
 
zero_zero

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Mr Wilson figured it out already ...:Congrats:
There's zero deflection short reach tools what can be used to precisely cut the holes for the Ti inserts or even reamers could be used. Plastics also require high rake angle tools.
20170308_091924.jpg
 
KentPWalton

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Ok......
I wanted to mill two of the six out of PMMA to check alignment and fit before going to zr. Why did they mill so bloody damn tight? They were able to make it half way onto Ti base then I had to grind it out till it fit down to margin. The simple single unit screw retained cases I've done fit great in zirc. What's the dealio?

Milling PMMA is slightly harder since it mills 1/1. When you mill Zr, it mills about 1/1.22, so you have a little more wiggle room in Zr.
 
prestige.dental

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Not happy using the 2 - connect
Multiple 2 connects snapped off after 2-3 year of function, leaving the broken screw in the patients mouth in the implants.

These were 3 unit bridges
 

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prestige.dental

prestige.dental

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Why would you use the 2 connect on a 3 unit bridge?
Hello RKM:

That's the reason of the post

Don't do use 2 connect for unilateral bridges, like the poster is using.

So how do u do your

a 3-4-5

and

a 4-5-6 3 unit screw retained
 
zero_zero

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I'd guess the bridge wasn't seated passively thus strained the screws when force was applied over the cones...I only use 2-connect or angled abutments when the angulation between the implants is too severe to get away with regular inserts...
 
rkm rdt

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Hello RKM:

That's the reason of the post

Don't do use 2 connect for unilateral bridges, like the poster is using.

So how do u do your

a 3-4-5

and

a 4-5-6 3 unit screw retained
I will use one engaging and one non engaging abutment or modify an engaging abutment to maintain as much vertical structure as possible.
This ensures a positive seating and provides stability during lateral forces.
I do the same for all splinted cases as well.
 
PRO ARTS DL

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Milling temps on cad bases and the respected fit has more to do with you managing your cam/mill. The drill compensation is built into the cad design via the library and the tolerances are tight. Get your directions slightly off and undermill a tad and this is a problem. If your CAM will allow you to run std deviation simulation to check use it. RED is not good.

Also there is a thing called Tool deflection that most do not talk about or discuss. It basically say as the force of the spindle pushes the bur laterally you have a tool that bends. This feed rate combined with the step over/rpm can be adjusted on certain CAM software to help eliminate this problem. Setting a strategy to do fine milling inside the holes 2 times on PMMA can also solve the problem.

Also there is a reason why some cad base mfg have std and oversize cad files for their bases as a band aid as most techs do not want to learn past push and nest.

How does tool wear affect the fit on this type of situations? Older tools will give you worse/poor fit?

I've been told the fit of PMMA gets worse as tools wear. I've had to adjust some PMMA temporaries that had really bad fit and thats the answer I got, but to be honest it seems more like the CAM may not be accounting for this. I dont know.
 
Andrew Priddy

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Not happy using the 2 - connect
Multiple 2 connects snapped off after 2-3 year of function, leaving the broken screw in the patients mouth in the implants.

These were 3 unit bridges
I have a hunch these were over torqued.. but like others have said.. maybe other options are the best
 
KentPWalton

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How does tool wear affect the fit on this type of situations? Older tools will give you worse/poor fit?

I've been told the fit of PMMA gets worse as tools wear. I've had to adjust some PMMA temporaries that had really bad fit and thats the answer I got, but to be honest it seems more like the CAM may not be accounting for this. I dont know.

PMMA mills 1 to 1 ratio, so if the tool is worn, then the internal aspect will be undersized.

Zirconia mills 1 to about 1.25 ratio, so the wear on the tools is less noticeable.
 
KentPWalton

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I have a hunch these were over torqued.. but like others have said.. maybe other options are the best

Or they weren't cemented properly.

Apply put the cement on the Ti insert, place it in the Zr (do two at a time opposite sides of the arch),screw down the restoration to the model and let cement cure. Repeat until all Ti inserts are done. If the steps were followed properly, you will have a passive fitting bridge. Easy peasy!
 
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