(b) Modeling plastic may also be used for making preliminary
impressions. Figure 5-11 depicts instruments and materials used for modeling plastic
impressions. In using modeling plastic, the dental specialist should lubricate the
edentulous tray (selected by the dental officer) with petrolatum. The compound heater
is filled with enough water to cover the compound and the heating element is adjusted
to the proper temperature. After the modeling plastic has softened in the water bath,
the lubricated tray is loaded. For maxillary impressions, the material is rolled into a ball
and formed into the maxillary tray. For mandibular impressions, the material is rolled
into a cylindrical shape and formed into the mandibular tray. After brush flaming and
tempering of the material, the tray is passed to the dental officer who makes the
impression. After the dental officer positions the tray in the mouth, the dental specialist
may help speed the set of the modeling plastic by spraying cool water from the water
syringe over the tray containing the material. If this is done, the saliva ejector is used to
remove water as it collects in the patient's mouth.
Figure 5-11. Instruments and materials for modeling plastic impressions.