September 30th, 2008 by admin

Custom impression Tray

The cast is made of artificial stone poured into the irreversible hydrocolloid impression

The outline for a wax spacer, which will provide space in the tray for the final impression material, is drawn in pencil on the cast

A wax spacer about 1 mm thick is placed over the crest of the residual ridge and the slopes of the ridge

The buccal shelf on each side and the retromylohyoid spaces on the cast are left uncovered
Extra wax can be placed over the lingual slopes of the cast below the level of the mylohyoid ridge

This will provide additionnal space for the action of the mylohyoid muscles when the final impression is madeSelf-curing ( cold-curing or autopolymerizing ) acrylic resin tray material is mixed and uniformily distributed over the cast so that the final impression tray will be approximately 2 to 3 mm thick
An anterior resin handle is centered over the labial flange in the approximate position of the anterior teeth and shaped as not to interfere with the position of the lip

The anterior handle is used to carry the final impression tray into the mouth and position it over the residual ridge
The flanges of the tray should be contoured like the flanges of the completed denture

When the acrylic resin tray is removed from the lower preliminary cast, the wax spacer is left inside the tray
Retainning the spacer allows the tray to be properly positioned on the lower residual ridge for bolding procedure
The available space for the impression is again observed in the patient’s mouth and compared with the length and widht of the flanges of the final impression tray

The buccal and lingual flanges of the impression tray are marked in pencil and reduced until the borders are short of the limiting anatomic structures
The anatomic custom tray is now ready to border molding compound