border markings as drawn by the dentist and shown in
figure 8-34(D). Use the bench lathe with an arbor band
to remove bulk. The posterior border of the maxillary
custom tray is supposed to extend a short distance onto
the soft palate. Mandibular custom trays cover the
retromolar pads. Use acrylic finishing stones and burs
for finer details. Be sure there are no sharp edges on the
FABRICATING A TRAY WITH SPACERS
The preceding paragraphs described trays that
were closely adapted to the diagnostic cast. In
contrast, custom trays for fixed restorative patients
are always made over wax spacers. The design for this
type of tray appears in figure 8-35(A). With the
exception of the tray's design and the use of a wax
spacer, the procedures for fabricating a fixed custom
tray are the same as we mentioned before. Let's briefly
look at the differences.
Applying a Wax Spacer
After the dentist traces the outline on the
diagnostic cast, you can fill the undercuts, and adapt
two layers of baseplate wax to the tray area on the cast.
Adapt each layer of wax, one layer at a time. Cut out
four small pieces of the baseplate wax over the crest of
the ridge areas outlined in the molar and cuspid regions
for tissue stops as shown in figure 8-35(B). Remove
the spacers from the cast and apply a tinfoil substitute
to the gypsum surfaces of the cast to prevent the acrylic
resin from sticking. Place the spacer back on the cast
and apply a thin layer of petrolatum to the surface of
the baseplate wax. This will make removal of the wax
from the polymerized tray easier.
Fabricating the Tray
Use the self-curing dough method to make the tray.
After the resin is hard, remove the tray from the cast
and pull the baseplate wax off the tissue surface of the
tray. (Four tissue stops should appear on the ridge
areas where the four pieces of baseplate wax were
originally cut out.) Trim any excess acrylic resin to the
outline border on the cast. Round and smooth the
borders of the tray. Your finished trays should appear
like those in 8-35(C). Be certain to clean away all
traces of petrolatum that might be present on the
tissue surface of the tray. (Sandblasting does this
very effectively.) Clean and disinfect the tray, place it
on the cast for storage.
FABRICATING MOUTHGUARDS AND
In addition to pouring and trimming study casts,
and fabricating custom trays, you may be called upon
Figure 8-35.Fabricating custom trays over wax spacers.