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Distal Extension Denture Base

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					                    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
     Microwave
     Injection
                       Processing Technique
   Compression molding
       Conventional method
            More than 60 years
            Time consuming
                     Master cast
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
                              2
             1                             3




Split mold


     Denture flask (ejector-type, three piece)
     1. The drag (bottom)
     2. The cope (middle)
     3. The cap (thin top)
Split mold
          STIPLE WAX ON FLANGES.




TINFOIL
BASE OF
 CAST.

 CHECK CLEARANCE
   WITH FLASK.
             CHECK PERIPHERAL
                CLEARANCE.



LOWER HALF
 OF FLASK
  POURED.

   POURING STONE FOR
     THE UPPER HALF.
   Maxillary denture with the index in place
    and embedded in the flask Soap, or a
    gypsum separator, is used between the two
    pours of dental stone in the lower and
    upper portions of the flask.
                      CLEAR THE
                   LINGUAL TROUGH.




CLEAR THE TEETH.
•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.
Second pour (upper half of flask)
       STONE CAP


          UPPER
        HALF STONE



        STONE CAST

     LOWER HALF STONE




COMPLETED FLASKING.
         STONE CAP




           UPPER
         HALF STONE

         STONE CAST
       LOWER HALF STONE




COMPLETED FLASKING FOR
   THE MANDIBULAR
  COMPLETE DENTURE.
Boil-out
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
  .
The record base is soft and can be easily removed in
  one piece, along with any remaining wax.
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 mins
to 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
  groove
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.
Packing
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.
•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 cellophne
•Heat cure in water bath with temp. set at
 160-165°F for at least 8 hrs. with constant
 pressure
8 hrs 160-165 F
             Occlusal correction
Laboratory 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 Technique
3. Injection
3.1 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 Technique
3. Injection
3.2 Success System (Dentsply, International, Inc, York, PA)
      PMMA Lucitone 199
      90 PSI, use heat-polymerized resin
Success
                                   Flasking or Investing




                  After Boil out



                                      Divesting
Flask is closed
Insert plastic nozzle           Flask in injecting unit




   De-flasking          Master cast Recovery
Master cast removed from invest material




Finished 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.
Deflasking
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.
Remounting and Occlusal Equilibration
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
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 remount
The dentures are not yet separated.
 Dentures and master casts are remounted
 in the articulator.
Checking the condylar guidances
The condylar guidances are still set at the
 patient’s individual condylar path angle.
Equilibrating the occlusion in centric relation
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.
Flasking
Packing
Curing
Deflasking
Finishing
Polishing

				
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posted:2/18/2012
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