2. 1
Laboratory Procedures
Special TRAYS
Definition
An individualized impression tray made from a cast recovered from a preliminary
impression. It is used in making a final impression
A device which is used to carry, confine and control an impression material
while making a final impression
Objective
To fabricate a rigid impression tray of uniform thickness adapted to the contours of the
preliminary cast with borders approximating the outline of the complete denture
Equipment and Materials
Triad, custom tray resin (light
curing)
Vaseline
Bunsen burner
Hanau torch
Straight handpiece
Wax spatula, wax knife
Base plate wax, pink
Pencil,
General notes:
Special tray preparation:
1. 2-3 mm short of the peripheral role
2. Outline the depth of vestibule
3. Through hamular notches across vibrating line
4. Provide room for frenal attachments movements
3. 2
Tray Outline
Maxillary Tray
1. Mark the depth of the vestibule with the first line
2. Mark the outline of the tray starting at the disto-buccal side of the pterygomaxillary
notch. Make a line 2mm medial and parallel to the depth of the vestibule. (Line one
previously drawn) note that the tray will be made short of the vestibule by 2mm.
3. Continue the line until the disto-buccal area of the opposite pterygomaxillary notch is
reached.
4. Allow 1mm clearance for the buccal and labial frenae as the rigid tray must not
impinge on these structures.
5. The posterior portion of the tray will end at the pencil line previously marked.
Mandibular Tray
1. Mark the depth of the vestibule with the first line
2. Outline the mandibular final impression tray starting at the disto-buccal area of
the retro-molar pad. Draw this line approximately 2 mm medial to the depth of
the vestibule. (line one previously drawn)
4. 3
3. Continue this line, allowing clearance for the frenae, until you reach the disto-
buccal area of the opposite retro-molar pad. Note that the tray will be made
2mm short of the buccal and labial vestibule.
special Impression Trays
special Impression trays for complete dentures can be made either using
1. light cured tray resin (Triad) T
2. auto-polymerizing tray resin. :
3. Shelac
Light-cured resin (Triad) technique
Maxillary Tray
1. Block out excessive undercuts with baseplate wax. Do not over wax or the tray will
not fit accurately. Be especially conservative with your wax blockout in the maxillary
labial flange area. Too much wax blockout can cause just as many problems as too
little blockout. Areas to block (labial sulcus, buccal to Maxillary tuberosity)
2. Apply a light coat of Vaseline over the entire tissue surface of the cast to serve as a
separating medium.
5. 4
3. Place a sheet of Custom Tray Triad resin in the palate of the cast and adapt the
resin gently moving from the depth of the palate to the borders of the vestibules to
avoid trapping air bubbles under the tray material. And make a small vertical handle (or
45o angulated handle) which should not pull vestibule.
4. Carefully trim the material to the line previously marked. Make the borders of the
tray as smooth as possible prior to curing the resin as it is much easier to smooth when
it is soft. Take care not to use excessive finger pressure and thin out the resin.
5. Cure the material in the Triad unit.
6. Remove tray from the cast and gently trim and smooth borders while the resin is
partially cured.
7. Invert tray and complete curing for extra time
Maxillary Tray Handle
The tray handle should be approximately 3-5mm wide in the area previously occupied
by the anterior teeth. The length from the highest point on the labial flange to the
incisal edge is approximately 22mm.
Mandibular Tray
Follow the same procedure as above except the resin should be adapted to the lingual
6. 5
vestibule, and adding three small vertical handle. The two auxiliary Handles are placed
at area of 2nd premolars / 1st molars
Mandibular Tray handle:
The handle is formed in a manner similar to that used for the maxillary handle. It
should be 5-7mm wide in the molar area, tapering to 3 to 5mm wide
anteriorly. Measuring from the anterior arch of the tray, the height is 15-18mm. the
handle will terminate 8-10mm from the distal area of the final impression tray.
Criteria for correct tray:
1. Tray not significantly under-extended (shorter than 3 mm)
2. Stable, does not rock on cast or in mouth
3. Tray not significantly overextended (shorter but not more than 1mm)
4. Uniform thickness
5. Tray flange adapted as closely to residual ridge as possible
6. Wax relief over mobile tissue, undercuts
7. Labial and buccal notches properly placed
8. Borders rounded, not sharp
9. Small handles, properly positioned
7. 6
Wax Spacer
1. One thickness of base plate wax over the cast (provide 3mm space)
2. Trim line in vestibule ( 2 -3 mm shorter)
3. Trim to “butterfly” configuration glandular tissue ( to get the posterior palatal seal)
Acrylic stoppers
1. Three holes will be made in the wax spacer to act as stoppers
2. Acrylic stoppers will be made to support the tray on the residual ridge. To provide
uniform space for the impression material
3. As a guide for border molding and impression making
