Shoulder margins are indicated for the preparation of full ceramic crowns and the buccal surface of a metal-ceramic crown.

There is more reduction in here and the finish line has a well defined angle instead. This margin accommodates space that is thick enough for the porcelain and metal to be place. Also with the property of the porcelain as a brittle material, it needs to be thick enough to withstand fracture.

We must use a bur with a flat tip, with well defined corners like 847KR-016 bur or Flat-end Tapered Modified bur. On using this bur, the whole shape of the bur should be fully engaged within the margin.

Same as with any other margins, shoulders are made first by creating orientation grooves (but are a lot deeper than chamfers). It is recommended not to establish the depth immediately to allow leeway for polishing. For example, at least 0.3-0.5 less than the required amount of reduction.

Step by Step

This is a metal ceramic preparation on an upper first molar tooth. The occlusal reduction has been done. If you want to review the occlusal reduction for this tooth, please refer to the following page.

LINK “Occlusal Reduction Upper Molars”

Step 1: Visualization and Placing Guide Grooves

This has the same process with the axial reductions of full gold crowns but a lot deeper. One tip for bur angulation, get the general slope of the whole buccal surface. The general slope should be along the upper 2/3, before the slope curves in at the cingulum.

Put at least 3 guide grooves in here. Do place the tip of your bur slightly away from your prospective area of the margins. We will place the margins as we connect and reduce this area.

Step 2: Buccal Reduction and Shoulder Margins

Unlike the chamfer, a shoulder margin needs to be deep and bold. Give that definite wide shoulder margin using the whole bur. Extend as far interproximally as you can. The whole shape of the bur should be in contact with the whole surface. The entire bur should be utilized to make a shoulder margin.

Add video here

When checking the margins, run your explorer and feel that the margins should be continuous and smooth.

The lingual portion of a metal-ceramic crown is a chamfer, proceed to this page for a demo.

LINK “Lingual Reduction – Porcelain Fused to Metal”