(1) Edentulous impression trays. Two types of edentulous impression trays
are available. One type is for use with modeling plastic or compound and is made of a
pliable metal alloy that can be shaped by bending and cutting to fit the individual patient.
Mandibular tray sizes are Nos. 51, 53, and 46. Maxillary tray sizes are Nos. 41 and 45.
The second type is for use with hydrocolloid impression material and is made with
rimmed borders to retain the impression material. Sizes available are small, medium,
medium large, and large. Both types of trays are used for impressions when no teeth
remain in the arch.
(2) Dentulous impression trays. These trays are made with rimmed borders
to retain the impression material in the tray when the impression is removed from the
mouth. Trays can be bent, within limits, to accommodate either a wide arch or a narrow
arch, but they should not be cut. They are available in small, medium, medium large,
large, extra large, and extra-extra large sizes for both maxillary and mandibular
impressions. They are used when teeth are present in the arch.
(3) Orthodontic impression trays. These trays have deeper flanges than the
standard edentulous trays. They are provided in large, medium, medium-small, and
small sizes for maxillary impressions and in large, medium, and small sizes for
mandibular impressions.
(4) Partial impression trays. Partial impression trays are provided in three
designs for making impressions of anterior portions of the dental arch. The designs are
maxillary anterior medium, maxillary anterior small, and mandibular anterior.
(5) Crown and bridge tray. A single-size crown and bridge tray is adaptable
for making impressions of a small segment in any location of either arch.
(6) Custom acrylic trays. Often, the procedure performed requires
impression trays constructed especially for the patient being treated. The custom-made
trays are made from self-curing acrylic resin and constructed by a dental laboratory
specialist. The custom acrylic trays obtain an accurate impression of edentulous and
partially edentulous dental arches by maintaining a uniform thickness (1 to 2 mm) of the
impression material. Custom acrylic trays may be used during treatment requiring
construction of complete dentures, removable partial dentures, or fixed partial dentures.
b. Alcohol Torch (BLOWTORCH, ALCOHOL). The alcohol blowtorch (figure
5-2) is designed to be held and operated in one hand. It has a plunger which, when
pushed in, ejects a stream of air to produce a pinpoint flame used to apply heat to small,
localized areas of wax, modeling plastic, or other material. Either ethyl or methyl
alcohol may be used for fuel.
MD0503
5-5
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