Compared to plaster, dental stone requires less
water in mixing and sets more slowly. When it is set, it
is harder, denser, and has a higher crushing strength.
These differences make stone the choice to use over
dental plaster when using it as a master cast for
complete dentures and partial denture construction.
Stone is more resistant to scratching and damage and
can withstand more pressure in acrylic processing.
Stone has many uses, including pouring, mounting
casts, and flasking dentures for processing. The initial
setting time of a typical stone mixture varies from 8 to
15 minutes. The final set occurs within approximately
Historically, die stone was only used for making
the first pour of a working cast for fixed prosthodontics.
Improved die stone now is being used for working
casts in removable prosthodontics.
Dental waxes are important in the construction of
dental prosthetic appliances. The waxes are supplied
in different types, with each designed for specific
Next we describe the waxes with which a
chairside prosthetic technician needs to be familiar and
be able to use.
Baseplate wax is used to create a spacer over the
cast before custom trays can be made. Another use is
as a block-out wax for undercuts on casts. It is
available in sheet and ribbon form and is pink in color.
Bite Registration Wax
Bite registration wax is a metal-impregnated wax
in sheet form. It is used to record the occlusal
relationships between a patient's opposing arches and
to later transfer this relationship to the cast for
articulation. Often without this record, it is impossible
for the dentist or the laboratory technician to properly
occlude the patient's cast.
Indicator wax is usually green in color and is
coated with a water soluble adhesive on one side. It is
used for registering occlusal contacts on natural teeth,
individual restorations, FPDs, RPDs, and CDs. It is
sometimes used by the dentist to evaluate high spots on
Sticky wax is made of beeswax, paraffin, and
resin. Its colors are orange and the darker shades of
blue, red, and violet. The resin gives the wax its
adhesiveness and hardness. An important requirement
of sticky wax is that it must break under pressure rather
than bend or distort. This property makes it useful for
holding the parts of a broken denture together so that it
can be repaired.
Utility wax is a red or colorless wax that comes in
It is extremely pliable and tacky at room
temperature, making it usable without heating. Its main
use is in beading (curbing) impressions before boxing
and pouring. It can also be used on the impressions trays
to avoid the flow of impression material to the back of
the throat and to avoid injury to the soft tissue.
There are a number of acrylic resins that you will
use and need to be familiar with in prosthetic assisting.
Polymerization is the term used to describe the
processing or curing of acrylic resins. Acrylic resins
can be classified by its method of curing. Some of the
more common acrylic resins include the heat-cured,
self-cured, and light-activated types. When handling
acrylic resins, you should be sure to read the
manufacturer's instructions and safety precautions
Methyl methacrylate is the most widely used
synthetic resin used in dentistry. The resin is usually
supplied in a fine powder (polymer) and liquid
(monomer). They are mixed to form a gel or dough and
processed into a rigid solid.
Clear heat-cured acrylic resin is used to construct
night guards and surgical templates. As a surgical
template (band-aid) it is used after extraction of
remaining teeth to show the possible interferences
between the alveolar bone and the immediate denture.