Figure 8-32.Trimmed maxillary and mandibular cast.
FABRICATING CUSTOM IMPRESSION
method and the vacuum method. We will limit this
discussion to the more frequently used dough method.
Prefabricated trays are made to fit everyone
moderately well, but will not fit anyone very well. On
the other hand, a custome tray provides a dentist with an
impression material carrier that permits the dentist to
make a more accurate impression that they could make
using a stock (prefabricated) tray. The custome tray is
made on a diagnostic cast. The dentist draws the
border outlines of the proposed custom tray on the
diagnostic cast, as shown in figure 8-33(A), and gives
other directions, such as handle position and the need
for vertical stops. You may then make the tray so it
conforms to the design. Two of the most popular ways
of making custom trays are self-curing resin dough
The dentist will usually prefer a custom tray that
provides room for a controlled thickness of impression
material. Spacers used to develop vertical tissue stops
accomplish this purpose. The stops are made to hold
the tray off the cast by a distance equal to the thickness
of the spacer. When the spacer is removed and the tray
is placed in the patient's mouth, the stops hold the inner
surface of the tray out of contact with the patient's
tissue. The subsequent space between the tray and
tissue is then later filled with impression material.
Figure 8-33.Design and blockout for a custom tray.