•The surface of the third layer is left slightly rough to hold the fourth investment layer in position.•Tinfoil separating medium is painted on the third layer.•The fourth investment layer is used to fill the remainder of the flask. The lid of the flask is pressed into place while the investing stone is still soft. The flask is set aside for min. 1 hr. before the wax elimination.
STONE CAP UPPER HALF STONE STONE CAST LOWER HALF STONECOMPLETED FLASKING.
STONE CAP UPPER HALF STONE STONE CAST LOWER HALF STONECOMPLETED FLASKING FOR THE MANDIBULAR COMPLETE DENTURE.
Boil-outWhen 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.
Placed in boiling water for 5 minsto soften the wax• Stiff, bladed instrument is used to open the flask. Upper portion of the flask is lifted as vertically as possible to avoid fracturing the investment layers.• The softened wax is removed from the mold. Remaining wax is flushed from the mold with a stream of boiling water. The mold is then cleaned with a soft brush and a powdered detergent. Detergent is removed by flushing the mold with clean boiling water.
Smooth all sharp edges and create an escape grooveFeathered 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.
PackingMixing the acrylic resin I and packing the doughThe 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.
•Trial packing (3000-4500 lbs over the entire flask area)•Use two sheets of cellophane between two layers of resin dough to allow opening of the flask without pulling acrylic resin.•Trim excess acrylic and flash•Repeat until no excess is visible•Final closure of the flask halves is accomplished without the intervening sheets of cellophane•Heat cure in water bath with temp. set at 160-165°F for at least 8 hrs. with constant pressure
Occlusal correctionLaboratory Remount to eliminate the processing error depends on Jaw relation technique instrumentation
Processing Technique Microwave System (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
Microwave system Three minute curing in microwave Fast, easy to use Allows more efficient use of time Produces denture in short processing time Denture repair Interim partial
Processing Technique3. Injection3.1 Ivocap injection system, Ivoclar, Vivadent, Inc, Amherst, NY) In Mid 1970 VDO is more stable compare with conventional Flask is closed during the procedure
Processing Technique3. Injection3.2 Success System (Dentsply, International, Inc, York, PA) PMMA Lucitone 199 90 PSI, use heat-polymerized resin
Success Flasking or Investing After Boil out DivestingFlask is closed
Insert plastic nozzle Flask in injecting unit De-flasking Master cast Recovery
Master cast removed from invest materialFinished denture
Eclipse™ Prosthetic Resin System(Dentsply)•Light-cured composite resin•New indirect build-up method for making dentures•Flask-free and monomer-free•Conditioning Oven to warm models and materials•Melting Pot to prepare and melt Contour Resin•Electric Spatula to apply Contour Resin•Hot Air Gun to replace flaming•Eclipse Processing Unit to polymerize materials•Resin materials and supplies•Eclipse Bonding Agent
Dimensional change in CD fabricated by injected molding and microwave processing.Keenan, Radford, and Clark. J Prosthet Dent 2003;89:37-44. 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Compression Success Acron MC Microbase VDO After storage
DeflaskingRemove the flasking stoneThe denture can be deflasked as shown without damage. The silicone index can be easily removed.Denture after deflaskingBecause the denture was carefully waxed and a silicone index was used, finishing around the teeth can be readily accomplished.
Remounting and Occlusal EquilibrationAfter 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
After all centric contacts are established, the eccentric excursions are equilibrated and the protrusive and retrusive movements are ground free from interferences. The occlusion is then refined with carborundum paste. Only now should the dentures be separated from the casts.Post-processing remountThe dentures are not yet separated. Dentures and master casts are remounted in the articulator.
Checking the condylar guidancesThe condylar guidances are still set at the patient’s individual condylar path angle.
Equilibrating the occlusion in centric relationPremature centric contactsPolymerization 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.