Flasking Flasking

D.SIRAG AL-HAMADID.SIRAG AL-HAMADI

CLINICAL DEMONSTARATOR CLINICAL DEMONSTARATOR

PROSTODONTIC DEPARTMENTPROSTODONTIC DEPARTMENT

TRIPOLI UNIVERSITYTRIPOLI UNIVERSITY

DENTAL FACUALTYDENTAL FACUALTY

Processing

Ideal denture base material:Ideal denture base material:No trial packing needed No trial packing needed Good shade match with surrounding tissuesGood shade match with surrounding tissuesDimensionally stableDimensionally stableComplete polymerization Complete polymerization Easily polishedEasily polished

Processing

Note: Master cast must be recovered from flasking for laboratory remount.

TechniquesCompressionMicrowaveInjection

Processing Technique Compression moldingCompression molding

Conventional methodConventional method More than 60 yearsMore than 60 years Time consumingTime 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

Split mold

Denture flask (ejector-type, three piece)1. The drag (bottom)2. The cope (middle)3. The cap (thin top)

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Split mold

STIPLE WAX ON FLANGES.STIPLE WAX ON FLANGES.

TINFOILTINFOILBASE OFBASE OFCAST.CAST.

CHECK CLEARANCECHECK CLEARANCEWITH FLASK.WITH FLASK.

CHECK PERIPHERAL CHECK PERIPHERAL CLEARANCE.CLEARANCE.

LOWER HALF LOWER HALF OF FLASK OF FLASK POURED.POURED.

POURING STONE FOR POURING STONE FOR THE UPPER HALF.THE UPPER HALF.

Maxillary denture Maxillary denture with the index in place with the index in place and embedded in the flask Soap, or a and embedded in the flask Soap, or a gypsum separator, is used between the two gypsum separator, is used between the two pours of dental stone in the lower and pours of dental stone in the lower and upper portions of the flask.upper portions of the flask.

CLEAR THE CLEAR THE LINGUAL TROUGH.LINGUAL TROUGH.

CLEAR THE TEETH.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)

COMPLETED FLASKING.

STONE CAP

UPPERHALF STONE

STONE CAST

LOWER HALF STONE

COMPLETED FLASKING FORTHE MANDIBULAR

COMPLETE DENTURE.

STONE CAP

UPPERHALF STONE

STONE CASTLOWER HALF STONE

Boil-outBoil-out

When the wax and shellac record base are When the wax and shellac record base are completely warmed, the flasks can be opened. completely warmed, the flasks can be opened. The teeth remain in the lower portion of the flask The teeth remain in the lower portion of the flask (left).(left).

The record base is soft and can be easily removed in The record base is soft and can be easily removed in one piece, along with any remaining wax (right).one piece, along with any remaining wax (right).

Both flask halves are thoroughly cleaned by rinsing Both flask halves are thoroughly cleaned by rinsing with boiling water. The teeth are removed and with boiling water. The teeth are removed and also cleaned with boiling water. Ensure that the also cleaned with boiling water. Ensure that the wax is completely removed by using a detergent.wax is completely removed by using a detergent.

• 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.

Placed in boiling water for 5 minsto soften the wax

Smooth all sharp edges and create an escape Smooth all sharp edges and create an escape groovegroove

Feathered stone edges must be removed because Feathered stone edges must be removed because they break off easily and can become embedded they break off easily and can become embedded in the acrylic resin base material. A groove is in the acrylic resin base material. A groove is made completely around the master cast for the made completely around the master cast for the purpose of allowing excess acrylic resin to escape purpose of allowing excess acrylic resin to escape (right).(right).

The surface of the dental stone in both halves of the The surface of the dental stone in both halves of the flask is coated with a gypsum separating medium. flask is coated with a gypsum separating medium. Each tooth is carefully placed in its original Each tooth is carefully placed in its original position. Make under cuts in the acrylic resin position. Make under cuts in the acrylic resin teeth similar to the diatorics in porcelain teeth.teeth similar to the diatorics in porcelain teeth.

PackingPacking

Mixing the acrylic resin I and packing the doughMixing the acrylic resin I and packing the dough

The autopolymerizing acrylic resin is mixed to a The autopolymerizing acrylic resin is mixed to a kneadable dough according to the manufacturer’s kneadable dough according to the manufacturer’s instructions (powder to liquid volume ratio usually instructions (powder to liquid volume ratio usually 3:1) and placed in the cold flask halves in which the 3:1) and placed in the cold flask halves in which the denture teeth are positioned.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

8 hrs 160-165 F

Occlusal correction

Laboratory RemountLaboratory Remountto eliminate the processing errorto eliminate the processing errordepends ondepends on

Jaw relation techniqueJaw relation techniqueinstrumentationinstrumentation

Processing Technique Microwave System Microwave System

(GC America Inc.3737 W. 127th Street, Alsip, IL 60803)(GC America Inc.3737 W. 127th Street, Alsip, IL 60803)

Use the split mold technique to form moldsUse the split mold technique to form molds ACRON MC microwave cured acrylicACRON MC microwave cured acrylic Need special flask Need special flask (resin + small metal screws)(resin + small metal screws) One minute microwaved to soften waxOne minute microwaved to soften wax Eliminate wax from moldEliminate wax from mold Three minute curing in microwave Three minute curing in microwave Leave 15-20 mins before opening flaskLeave 15-20 mins before opening flask Less VDO increase??Less VDO increase?? Easy to useEasy to use Low water absorption Low water absorption

Microwave system

Three minute curing in microwave Three minute curing in microwave Fast, easy to use Fast, easy to use Allows more efficient use of timeAllows more efficient use of time Produces denture in short processing timeProduces denture in short processing time Denture repairDenture repair Interim partialInterim partial

Processing Technique

3. Injection3. Injection3.1 Ivocap injection system, 3.1 Ivocap injection system, Ivoclar, Vivadent, Inc, Amherst, NY)Ivoclar, Vivadent, Inc, Amherst, NY)

In Mid 1970In Mid 1970 VDO is more stable compare with conventionalVDO is more stable compare with conventional Flask is closed during the procedureFlask is closed during the procedure

Processing Technique

3. Injection3.2 Success System (Dentsply, International, Inc, York, PA)

PMMA Lucitone 199 90 PSI, use heat-polymerized resin

Success

Flasking or Investing

DivestingFlask is closed

After Boil out

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. Dimensional change in CD fabricated by injected molding and microwave processing. Keenan, Radford, and Clark. J Prosthet Dent 2003;89:37-44. Keenan, Radford, and Clark. J Prosthet Dent 2003;89:37-44.

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Compression Success Acron MC Microbase

VDO After storage

DeflaskingDeflasking

Remove the flasking stoneRemove the flasking stone

The denture can be deflasked as shown The denture can be deflasked as shown without damage. The silicone index can without damage. The silicone index can be easily removed.be easily removed.

Denture after deflaskingDenture after deflasking

Because the denture was carefully waxed Because the denture was carefully waxed and a silicone index was used, finishing and a silicone index was used, finishing around the teeth can be readily around the teeth can be readily accomplished.accomplished.

Remounting and Occlusal EquilibrationRemounting and Occlusal Equilibration

After the dentures have been deflasked they are After the dentures have been deflasked they are mount ed in the articulator without removing mount ed in the articulator without removing them from their casts. Small errors can now be them from their casts. Small errors can now be seen that occurred during the flasking and seen that occurred during the flasking and polymerization procedures. Although there is polymerization procedures. Although there is very little shrinkage during autopolymerization, very little shrinkage during autopolymerization, occlusal contacts may have been slightly occlusal contacts may have been slightly altered. For this reason, the first occlusal altered. For this reason, the first occlusal equilibration is performed so that a clear cusp-equilibration is performed so that a clear cusp-to-fossa relation can be obtained to-fossa relation can be obtained

After all centric contacts are established, After all centric contacts are established, the eccentric excursions are equilibrated the eccentric excursions are equilibrated and the protrusive and retrusive and the protrusive and retrusive movements are ground free from movements are ground free from interferences. The occlusion is then interferences. The occlusion is then refined with carborundum paste. Only refined with carborundum paste. Only now should the dentures be separated now should the dentures be separated from the casts.from the casts.

Post-processing remountPost-processing remountThe dentures are not yet separated. The dentures are not yet separated.

Dentures and master casts are remounted Dentures and master casts are remounted in the articulator.in the articulator.

Checking the condylar guidancesChecking the condylar guidances

The condylar guidances are still set at the The condylar guidances are still set at the patient’s individual condylar path angle.patient’s individual condylar path angle.

Equilibrating the occlusion in centric relationEquilibrating the occlusion in centric relationPremature centric contactsPremature centric contactsPolymerization shrinkage has caused a slight shift in the original Polymerization shrinkage has caused a slight shift in the original

cusp-to-fossa relations. Initial contacts are now premature or cusp-to-fossa relations. Initial contacts are now premature or deflective, and must be selectively eliminated in order to deflective, and must be selectively eliminated in order to restore proper intercuspation.restore proper intercuspation.

Below left: The occlusion is corrected with a round diamond Below left: The occlusion is corrected with a round diamond stone. Avoid grinding the centric supporting cusps, which in stone. Avoid grinding the centric supporting cusps, which in complete dentures are primarily the maxillary palatal cusps complete dentures are primarily the maxillary palatal cusps and the mandibular buccal cusps.and the mandibular buccal cusps.