Guidelines for the Fabrication of Custom Maxillary and Mandibular Visible Light Cure Impression Trays Where a Wax Spacer Will Be Used For an Additional Thickness of Impression Material.
- Outline the casts for the custom edentulous trays as indicated in the Handbook for Complete Denture Prosthodontics on pages 45 and 46.
- Warm a piece of pink base plate material and apply it over the tissue bearing areas of the cast. Trim this wax layer to the tray outline, which was drawn on the cast. Place additional wax in any area, which appears to still have an undercut.
- Cut three square holes, approximately 4mm. on each side, through the wax, down to the surface of the preliminary cast. One of the holes should be over the crest of the residual ridge at the midline and the other two should be in the left and right first molar areas.
- Coat the wax with a thin layer of model release agent or petroleum jelly.
- Remove a sheet of VLC material from its protective pouch. Pull off a small piece of the material and press it into each of the 4mm. holes in the wax spacers. Lay the rest of the VLC material over the tissue surface of the cast (two rhomboidal pieces on the mandibular cast).
- Give the material a moment to slump onto the impression surface of the cast.
- With a petroleum jelly coated instrument or your index finger, gently press the material into place with no voids, onto the palate, the peripheral rolls and/or the lingual areas. Be sure that the hamular notches and/or the retromolar pads are completely covered.
- Using a sharp instrument and/or scissors, trim excess material up to the custom tray outline which you previously drew in the cast. The material may be cut slightly beyond this outline and after curing trimmed back. Never, however, have the custom tray trimmed short of the outline on the cast at this point.
- Fabricate handles as illustrated on a separate guideline sheet. Be careful with the handles because you are frequently required to wait in line to use one of the curing machines. Handles can easily slump out of shape as you wait for your turn. To prevent this, partially cure the handles with your laboratory lamp to prevent slumping.
- Place the cast and tray into the VLC curing unit and process for two minutes.
- When the machine stops, take out the cast and tray. Separate the casts and the custom tray and carefully remove the wax from inside the custom tray.
- Return the tray to the curing unit and process for an additional six minutes.
- Be sure that the carousel in the curing unit is in the lowest position. Have no more than two trays being processed at any one time.
- Adjust and finish the borders of the trays to the tray outlines previously drawn on the casts. Scrub the trays with soap and water.
- For a clean, smooth outside finish, coat the external surface of the trays with a layer of petroleum jelly and place them in the curing unit for an additional two minutes. Wash with soap and water. Leave the tissue surface of the tray untreated.
For informational purposes:
VLC (Visible Light Cure) resins are urethane dimethacrylate based interpenetrating polymer networks. These materials also contain a small amount of silica, an organic filler, and a photoinitiator, camphoroquinone, and are cured with visible light in the blue light range of 400-500 nm. These resins are devoid of methylmethacrylate, packaged in opaque containers, and are presently available in three forms – sheet, rope, and gel.