1) Why is die preparation done?
Excess root must be trimmed away from the die, margins must be clearly defined, and undercuts must be
eliminated before wax patterns can be waxed
2) What is a margin?
A margin is the surface junction between the natural tooth and the restorative material.
3) What is “cavo-surface”?
Cavo-surface is the portion of unprepared tooth surface beyond the margin.
4) What are the major steps in preparing the die in chronological order?
a - Trimming the excess root portion (tissue portion) of the die
b - Definition of the margin
c - Preparation of the die surface
5) What are you allowed to trim when you are trimming the die? What are you not allowed to trim when
trimming?
A technician is allowed to trim only the tissue part of the die. A technician is should not trim any part of
the tooth, including the prep, the margin, or any existing cavo-surface that may be visible. Abrading the
margin is especially taboo. The technician should also avoid abrading the dowel pins.
6) Why is the margin the most important aspect of crown and bridge?
It is important because it is where the interfacial surfaces (the prepared tooth and the restoration) meet.
Having a sealed margin is imperative in order to prevent further tooth decay. If the margin is not sealed,
bacteria can get between the tooth and the cavo-surface and decay the tooth from underneath the crown.
7) What is “ditching the die?”
Ditching the die is altering contour of the cavo-surface angle so that the margin is easily identified quickly.
8) Why is it important to ditch precisely on the finish line?
A proper finish line outlines a good cavo-surface angle and allows the margin to be easily seen. A good
cavo-surface angle assists in finding the proper contour of the restoration. If the finish line is not
contoured well, the surfaces may get over-extended or over-contoured.
9) What is over-ditching the margin? Why should it be avoided?
Over-ditching the margin will loose the cavo-surface angle that a technician wants to have. In addition,
the die may become fragile and snap at the neck.
10) What is bifurcation?
Forked or divided into two branches. A bifurcated root is a root that is divided into two branches.