Shoulder margin for full metal

[DancingKoala]

I have tried both shoulder and chamfer margin and I don't understand why chamfer margin is recommended for metal portion of PFM, or full metal cast restoration.
Why can't we just use shoulder? I think shoulder is easier to prep 😛

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[TSDentSurg]

I have tried both shoulder and chamfer margin and I don't understand why chamfer margin is recommended for metal portion of PFM, or full metal cast restoration.
Why can't we just use shoulder? I think shoulder is easier to prep 😛

If you don't prep the shoulder perfectly, the crown won't fit, and decay can get in. It's harder to make a perfectly tight shoulder margin vs a chamfer.

 

[Mackchops]

I define a shoulder as a finish line that is 90* to the cavosurface. A chamfer is anything greater than 90*. Both have rounded internal line angles and can be "deep" or "light". A shoulder is necessary for porcelain because you want both the porcelain margin of your crown and the margin of your tooth to have maximum bulk so neither will fracture - metal won't fracture. The chamfer is recommended everywhere else because it's easier to prep.

 

[TuckerT21]

A chamfer is used because it has a vertical component to it (someone above said it is greater than 90 degrees). You can also use a shoulder with a bevel (the bevel creates a vertical component to the finish line). Metal has to be burnished at the finish line. If you do a shoulder there is no way to burnish it when it doesn't meet the margin correctly, and in most cases you are going to have an open margin.

 

[Genemyers]

Shoulder bevel is generally preferred when a metal collar is planned, to lower stress concentrations on the porcelain at the margins.
Whereas a chamfer finish line is preferred and used for metal margins as well as porcelain margin.
Chamfer is more preferred for metal finish line whereas Shoulder bevel for Metal collar.

 

[DrJeff]

With advances in modern indirect restorative materials and also CAD/CAM processing of impressions and coping fabrication, I fully agree with what my lab techs tell me nowadays. The most important thing about a finishline's style is that there's enough room for bulk of material, not whether it's a shoulder, chamfer, butt joint or feather edge. If you can prep that style fully 360 degrees around the tooth with enough room for the lab to fabricate the indirect restorative material of choice, you're going to get a great result for your patient