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Dental Lab Step #1
Pouring Models from Preliminary Impression and Pouring Models Pouring Models - Suggested Quality Procedures
  1. Read the prescription before beginning all procedures.
  2. Box master model impressions (Figures 1a and 1b). Diagnostic casts do not require boxing.

    Figure 1a
    Figure 1b
  3. Measure dental stone and water according to manufacturer's directions.
  4. Add powder to water rather than water to powder. For best results, vacuum mixing is recommended.
  5. Do not invert impressions to develop a base until the stone reaches initial set.
  6. Use gypsum products according to their intended use, for example
Plaster Stone
Diagnostic or Study Models Master Casts
Mounting Precision Mounting
Repairs/Matrix Denture Investment

Pouring Models - Recommended Fabrication Steps
  1. READ THE PRESCRIPTION
  2. Measure powder liquid ratios appropriate to the models to be poured.
  3. For alginate impressions rinse the impression and gently vibrate the Labstone into the impression and allow to set. Do not invert the impression, as this will cause the stone to flow away from the impression surface and lose detail.
  4. When the Labstone has set, prepare a thick mix of stone to form a base and invert the impression onto the stone patty. Allow to set.
  5. Remove the impression tray and alginate and recover the diagnostic cast. Adjust the peripheries of the diagnostic cast using the model trimmer in preparation for the construction of the custom tray.
NOTE: Wait least one half hour before removing the cast from the impression.

Pouring Models - Quality Standards
Master casts
  1. Base thickness must be 1/2-inch (13 mm) minimum for strength. This is measured from the deepest part of the palate on the upper (Figure 1c) or the "floor of the mouth" on the lower (Figure 1d).

    Figure 1c
    Figure 1d
  2. After trimming, the base of the model must be parallel to the residual ridge (figures 1e and 1f).

    Figure 1e
    Figure 1f
  3. The base must be indexed for mounting and remounting. Two methods are shown here. Other techniques are acceptable as long as the index allows accurate remounting of the model. (Figure 1g).

    Figure 1g
  4. The depth of the buccal sulcus is approximately 1-1.5-mm below the land area (Figures 1h and 1i).

    Figure 1h
    Figure 1i
  5. Positive defects (bubbles), if any, must be in non-vital areas and small enough to be easily removed (1-mm diameter or less as a guide).
  6. Negative defects (voids), if any, should be small and in non-critical areas. These should be filled with stone to blend with the surrounding anatomy.
  7. The master cast must include all anatomical surfaces in the final impression (Figure 1j).
    Figure 1j
Pouring Models - Quality Failures
  1. Inadequate final impression: contact clinician to discuss possible risks of proceeding with the case. (Figure 1k)

    Figure 1k
  2. Model fractures upon removal from impression.
  3. Large positive or negative defects, or flaws in critical areas.
  4. Poor surface quality of the model due to water/saliva/blood contamination or improper mixing of gypsum, showing a powdery, friable surface.
  5. Loss of or damage to critical areas during model trimming (examples: retromolar pad, hamular notch and muscle attachments).
Constructing Custom Impression Trays Custom Trays - Suggested Quality Procedures
  1. Read the prescription before beginning all procedures.
  2. Fabricate tray according to clinician's instructions.
  3. If no specific instructions are provided, fabricate tray to the following standard: Outline the tray 1-2 mm short of the mucobuccal reflection for both upper and lower models. This will allow room for border moulding material and save time for the clinician. The tray must extend to the depth of the hamular notches on the upper and should cover the retromolar pads on the lower (Figure 2a). The lingual extension on the lower should stop at the mylohyoid line in the posterior and at the junction with the floor of the mouth in the anterior section (Figure 2b).

    Figure 2a
    Figure 2b
  4. Place relief material such as baseplate wax to the outlined area and cut out three tissue stops. Avoid placing a tissue stop over the incisive papilla. (Figure 2c).

    Figure 2c
  5. Fabricate tray with material of choice to a uniform thickness with a handle in the anterior segment.
  6. Remove sharp edges on the processed tray with carbide cutters and polish if necessary.
Custom Trays - Recommended Fabrication Steps
  1. READ THE PRESCRIPTION
  2. Outline for relief wax is usually 2 to 3 mm short of the tray border. Cast undercuts may be blocked out with wax or modeling compound.
  3. Warm a single thickness of baseplate wax and adapt to the pencil line as drawn on the cast.
  4. Paint areas of the cast to which TRIAD® Custom Tray Material will be adapted-as well as the wax relief-with TRIAD Model Release Agent. Wipe off excess MRA as a thin coating is sufficient.
  5. Remove the tray material from the light proof pouch and carefully adapt it to the cast. Excess material may be trimmed with a sharp blade. Do not overthin the material on ridge portion or hammular notch areas of the cast.
  6. Attach a handle by moulding excess material into shape and blending edges into the tray material on the cast. (if using original Blue Tray Material, prior to processing, a paper clip or similar wire may be shaped and used to reinforce the handle.)
  7. Place the case with the adapted tray in the Triad Curing Unit and process for a maximum of 2 minutes for either Blue Tray Material or TruTrayT.
  8. Remove the cast from the turntable and gently remove the tray from the cast. peel softened wax out of the tray while the wax is still warm.
  9. Paint the entire tray with TRIAD Air Barrier Coating, (ABC). Place the tray on the turntable of the Triad unit tissue side up. Process for a minimum of six (6) minutes for Blue Tray Material, and a minimum of two (2) minutes for TruTray.
  10. When the cure cycle is completed, remove the tray form the curing unit. remove the water soluble ABC with brush and water. Dentsply Faskut® carbide cutters are recommended for adjusting and finishing borders to the desired outlines. Trays may be perforated to aid in retaining impression material.
Custom Trays - Quality Standards
  1. Unless specified otherwise by the clinician, the wax spacer is 1 mm thick and ends short of the final tray extensions. On the maxilla, wax must not cover the posterior palatal seal area.
  2. Tray is well adapted to the model with no voids.
  3. Tray must be of uniform thickness.
  4. Thickness must be sufficient in strength to prevent distortion or breakage in use. The required thickness will vary with the material used. In general, acrylic resin and similar materials (such as light cure resins) should be approximately 2 mm thick, and 1 mm short of the mucobuccal fold to allow for border moulding.
  5. The handle must be placed in the anterior so that it does not interfere with placement of tray or border moulding procedures. The handle may be placed approximately where the wax rim or anterior teeth would be positioned on a baseplate (Figure 2d).
    Figure 2d
  6. Unless specified otherwise by the clinician, the tray borders should be between 1 to 2 mm short of the mucobuccal reflection.
Custom Trays - Quality Failures
  1. Border extensions significantly longer or shorter than standard.
  2. Tray not stable (flexible) due to insufficient thickness.
  3. Tray cracked or damaged.
  4. Improper handle position (interferes with border moulding or insertion).
  5. Sharp and/or rough edges, which may irritate the patient.
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