PFM for bench exam- let's discuss

[ilovegoldens]

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Ok guys, since most schools require a PFM preparation , let's discuss it.

amount of reduction, type of burs , finish line design etc etc etc

I heard a lot about the schools finding it worse when there is over reduction than under reduction.

Those who took the exam before please share your experience!

There are different ways of preparing a PFM, especially if we consider the finishing line. LET'S CONSIDER TOOTH #8

So... I normally follow Shillimburg basic rules and this is what I would do:

1) reduce labial surface in two planes
2)For labial reduction I would use FLAT END TAPPERED
3) Proximal reduction I would use a chamfer/ long thin
4)Lingual axial reduction Chamfer
5)Lingual reduction could be some type of wheel to follow the curvature

And add details such as finish with a gingival bevel and rounded incisal corners

I have doubts especially regarding the margin. Should we consider doing the gingiva bevel? I know that that would be the traditional way and that nowadays we can always consider a margin with pure porcelain and etc

So... what should we follow on the day of the exam????

 

[ilovegoldens]

Ok guys, since most schools require a PFM preparation , let's discuss it.

amount of reduction, type of burs , finish line design etc etc etc

I heard a lot about the schools finding it worse when there is over reduction than under reduction.

Those who took the exam before please share your experience!

There are different ways of preparing a PFM, especially if we consider the finishing line. LET'S CONSIDER TOOTH #8

So... I normally follow Shillimburg basic rules and this is what I would do:

1) reduce labial surface in two planes
2)For labial reduction I would use FLAT END TAPPERED
3) Proximal reduction I would use a chamfer/ long thin
4)Lingual axial reduction Chamfer
5)Lingual reduction could be some type of wheel to follow the curvature

And add details such as finish with a gingival bevel and rounded incisal corners

I have doubts especially regarding the margin. Should we consider doing the gingiva bevel? I know that that would be the traditional way and that nowadays we can always consider a margin with pure porcelain and etc

So... what should we follow on the day of the exam????

60 views and no opinion 🙁

Gonna try and simplify
My doubt is:

According to " books" such as Shillinburg's we are supposed to do a margim bevel on the bucal, sholder on the bucal using flat end tappered, and chamfer on lingual with a little less reduction.

However in practice we all know things are different. And nowadays we basically would do a heavy chamfer with a rounded tip bur instead of a flat and make sure we leave no lip. which means the traditional preparation for a PFM became pretty similar to a porcelain crown preparation for an anterior.
the traditional wing on the proximal area as well as the smaller reduction of lingual are not that important anymore..

which type of preparation should we do on the day of the test?



Please, anyone who has been accepted could help with this?

 

[uabsfm]

so that means we should give shoulder margin on the facial side and shamfer on interproximal and lingual, is that correct?

I think we dont give bevel on any side of the margin..

I have one q that if we do PFM on posterior tooth then we have to do 1.5 mm reduction on the functional cusp and 1.0 mm on nonfunctional cusp, right?

and for full cast crown its even of 1.0 mm ?

plz correct me , if wrong

 

[ilovegoldens]

so that means we should give shoulder margin on the facial side and shamfer on interproximal and lingual, is that correct?

I think we dont give bevel on any side of the margin..

I have one q that if we do PFM on posterior tooth then we have to do 1.5 mm reduction on the functional cusp and 1.0 mm on nonfunctional cusp, right?

and for full cast crown its even of 1.0 mm ?

plz correct me , if wrong

You are correct about more reduction on functional then nonfunctional. And in a posterior I would do the shoulder + bevel for bucal and Chamfer lingual since there is no need for worrying about aesthetic.

I just dont know about anterior.. If we do deep chamfer on bucal or shoulder with bevel... anyone??

 

[patata]

as you mentioned an exaggerated chamfer of sort or u can say a shoulder with a rounded internal line angle

 

[helpfuldoc]

so that means we should give shoulder margin on the facial side and shamfer on interproximal and lingual, is that correct?

I think we dont give bevel on any side of the margin..

I have one q that if we do PFM on posterior tooth then we have to do 1.5 mm reduction on the functional cusp and 1.0 mm on nonfunctional cusp, right?

and for full cast crown its even of 1.0 mm ?

plz correct me , if wrong

Shoulder on buccal or shoulder with bevel on buccal are both accepted PFM designs with a lingual chamfer margin. I prefer doing just a shoulder as the more steps you put in the higher the chances to mess it up. Keep it simple 🙂
1 mm deep shoulder at 120 degree to cavosurface at or 0.5 mm supragingival to the gumline is ideal.

 

[dentbombay]

dont be too fixated with the burs..... u can use any, as long as u have the prep right...and u know y u r doing wht u r doing...
i agree...with the margins
buccal: shoulder...1.2 mm
lingual : 0.5mm chamfer
interproximal: u need to carry ur shoulder up, past the contact point, to ensure tht the metal margins r not seen..and so mesio and disto lingual portions alone will be chamfers.
a buccal shoulder is perfectly accceptable but the problem is that it doesnt blend with the chamfer, so u need to bevel it to ensure u blend it ( thts y 120degrees) with the chamfer ,without incorporating irregularities...a smooth , well demarcated, finish line tht is abt 0.5 mm coronal to the gingiva is wht u r aiming for..
hope this helps
good luck.