Processing . Ideal denture base material: No trial packing needed Good shade match with surrounding tissues Dimensionally stable Complete polymerization Easily polished. Processing. Note: Master cast must be recovered from flasking for laboratory remount. Techniques Compression
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Mounting (with casts already indexed on the bases)
* Trim base of cast to the dimension
that will fit in the processing flask
prior to indexing
The surface of the third layer is left slightly rough to hold the fourth investment layer in
When the wax and shellac record base are completely warmed, the flasks can be opened. The teeth remain in the lower portion of the flask (left).
The record base is soft and can be easily removed in one piece, along with any remaining wax (right).
Both flask halves are thoroughly cleaned by rinsing with boiling water. The teeth are removed and also cleaned with boiling water. Ensure that the wax is completely removed by using a detergent.
to soften the wax
Feathered stone edges must be removed because they break off easily and can become embedded in the acrylic resin base material. A groove is made completely around the master cast for the purpose of allowing excess acrylic resin to escape (right).
The surface of the dental stone in both halves of the flask is coated with a gypsum separating medium. Each tooth is carefully placed in its original position. Make under cuts in the acrylic resin teeth similar to the diatorics in porcelain teeth.
Mixing the acrylic resin I and packing the dough
The autopolymerizing acrylic resin is mixed to a kneadable dough according to the manufacturer’s instructions (powder to liquid volume ratio usually 3:1) and placed in the cold flask halves in which the denture teeth are positioned.
(GC America Inc.3737 W. 127th Street, Alsip, IL 60803)
Use the split mold technique to form molds
ACRON MC microwave cured acrylic
Need special flask
(resin + small metal screws)
One minute microwaved to soften wax
Eliminate wax from mold
Three minute curing in microwave
Leave 15-20 mins before opening flask
Less VDO increase??
Easy to use
Low water absorption
3.1 Ivocap injection system, Ivoclar, Vivadent, Inc, Amherst, NY)
3.2 Success System (Dentsply, International, Inc, York, PA)
Flasking or Investing
After Boil out
Flask is closed
Insert plastic nozzle
Master cast Recovery
Dimensional change in CD fabricated by injected molding and microwave processing. Keenan, Radford, and Clark. J Prosthet Dent 2003;89:37-44.
Remove the flasking stone
The denture can be deflasked as shown without damage. The silicone index can be easily removed.
Denture after deflasking
Because the denture was carefully waxed and a silicone index was used, finishing around the teeth can be readily accomplished.
After the dentures have been deflasked they are mount ed in the articulator without removing them from their casts. Small errors can now be seen that occurred during the flasking and polymerization procedures. Although there is very little shrinkage during autopolymerization, occlusal contacts may have been slightly altered. For this reason, the first occlusal equilibration is performed so that a clear cusp-to-fossa relation can be obtained
The dentures are not yet separated. Dentures and master casts are remounted in the articulator.
The condylar guidances are still set at the patient’s individual condylar path angle.
Premature centric contacts
Polymerization shrinkage has caused a slight shift in the original cusp-to-fossa relations. Initial contacts are now premature or deflective, and must be selectively eliminated in order to restore proper intercuspation.
Below left: The occlusion is corrected with a round diamond stone. Avoid grinding the centric supporting cusps, which in complete dentures are primarily the maxillary palatal cusps and the mandibular buccal cusps.