The wings are a distinct demarcation between the differences of reduction of the chamfer (lingual side) and the shoulder (buccal side) margins. This feature on the proximal surface shows where the deep reduction ends and shallower proximal reduction begins.

The primary reason for wings, is to preserve tooth structure, and it’s secondary effect is that it provides resistance to rotation. A winged preparation is not essential, and can be removed by gradually blending the chamfer margin with the shoulder margin.

Though this feature is very outdated and in terms of the quality of materials nowadays, porcelain and metal can accommodate crown preparations without wings, however, there are some programs that would ask you to do it.

Most schools will teach you to do wingless preps but one school doesn’t mind whether you do a winged prep or not is Indiana. However, a winged prep is a pretty difficult thing to do especially on smaller teeth like premolars. It is easy to mess things up especially at keeping the esthetics good. So we recommend not to do winged preps unless you have a good reason to do so. So for the time being, unless you are told to do so, do a wingless preparation.

Porcelain Fused to Metal (Winged Preparation)

Demo video prep with pictures for proximal wings