There are four basic types of margin preparations. The
Full Shoulder (Butt) preparation is usually suggested for
porcelain jackets. The other basic types are Bevel, Feather and
The Full Shoulder or butt preparation is used in
porcelain jacket work. There are to be no overextensions
and care should be taken to cover the
full shoulder of the preparation.
The shoulder with Bevel is cut with a long
tapered diamond instrument, or bur. This is
done to create a taper which provides and
permits the margin to be burnished.
The Feather is one which has no shoulder and
because of this, should be marked or ditched by
the doctor to avoid errors.
The Chamfer preparation is similar to the
butt except it is more rounded and may also be
burnished. This is usually done with a round
ended bur or diamond instrument. This also
requires a bevel at the margin