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Laboratory Procedures FINAL IMPRESSION TRAYS
Definition Objective
Tray Outline Maxillary Tray 2. Continue the line until the disto-buccal area of the opposite pterygomaxillary notch is reached. 3. Allow 1mm clearance for the buccal and labial frenae as the rigid tray must not impinge on these structures. 4. The posterior portion of the tray will end at the pencil line previously marked.
Mandibular Tray 2. 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.
Final Impression Trays Final Impression trays for complete dentures can be made either using light cured tray resin (Triad) or auto-polymerizing tray resin (Formatray). Triad is supplied for your use in the clinics. You may select either technique. Both are described below: 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 the Both 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. 2. Apply a light coat of Vaseline over the entire tissue surface of the cast to serve as a separating medium. 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. 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 for 2 minutes 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 6 minutes
Mandibular Tray
Auto-polymerizing Resin Technique Maxillary Tray 1. Block out excessive undercuts with baseplate wax. Do not overwax or the tray will not fit the mouth 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. 2. Apply a light coat of Vaseline over the entire tissue surface of the cast to serve as a separating medium. 3. Apply Vaseline to the side of the rolling board marked 'thick." also, apply Vaseline to the wooden roller and your fingers to prevent the resin from sticking. 4. Properly proportion the powder and liquid according to the manufacturer's direction in a paper cup. Plastic cups may dissolve. Mix the auto-polymerizing tray resin thoroughly. When the mix gets to the dough stage, place it on the thick side of the rolling board. Using the roller, form a uniformly thick wafer. 5. Gently lift the layer of tray material from the roller board and place it over the lubricated cast. 6. Adapt the resin to the cat with light finger pressure. Too much pressure will cause thin areas in the tray. The excess material may be trimmed with a sharp knife. 7. After the material has set, remove the tray from the cast. Allow the material to fully polymerize prior to removing the tray from the cast to prevent distortion of the tray. 8. Examine the tissue surface of the tray. The marks from the pencil should have transferred to the tray. With abrasive arbor bands and acrylic burs, carefully trim the tray to the outline.
Mandibular Tray Follow the same procedure for the fabrication of the mandibular impression tray except the resin wafer should be sliced down the center starting 2-3 cm from the labial edge of the wafer. This will make it possible to adapt the lingual edge of the wafer.
Impression Tray Handle The impression tray handle should approximate the size and shape of the missing teeth to properly support the lips and cheek. Tray handles can be made of impression compound. Handles should be occlusion rim type handles. Tray handles must not distend or distort the lips or vestibules. This is especially important in the maxillary arch where the future lip support of the denture will be influenced by the position of the impression tray handle. 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 handle
Final impression trays for complete dentures must be graded by one of the faculty prior to visit 2. These are the grading criteria for this procedure.
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