Lab procedures / dental education in india

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.comwww.indiandentalacademy.com

PRODUCTIONPRODUCTION OF MASTER CASTOF MASTER CAST
SURVEYING OF MASTER CASTSURVEYING OF MASTER CAST
BLOCKOUT AND DUPLICATIONBLOCKOUT AND DUPLICATION
REFRACTORY CASTREFRACTORY CAST
WAXING OF PARTIALWAXING OF PARTIAL
DENTURE FRAMEWORKDENTURE FRAMEWORK
INVESTING OF SPRUEDINVESTING OF SPRUED
PATTERNPATTERN
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INVESTING OF SPRUEDINVESTING OF SPRUED
PATTERNPATTERN
BURN OUTBURN OUT
CASTINGCASTING
FINISHING &FINISHING &
POLISHINGPOLISHING

 Design transfer: conveying the outline ofDesign transfer: conveying the outline of
the proposed prosthesis from thethe proposed prosthesis from the
diagnostic cast to master cast.diagnostic cast to master cast.
Colour coding

Examination of master castsExamination of master casts
Remounting of diagnostic casts by aligning the tripod marks
Transfer of the three spots on to master cast in exactly
same place as on the diagnostic casts
Tripod the master casts using these three marks.
Survey lines marked on the master cast

 Retentive undercuts markedRetentive undercuts marked
Rests are marked
Metallic portion of the design drawn on master cast

Tripod marks on diagnostic casts.
Survey lines marked on master cast
Oriented with the help of tripod marks

Design transfer on to the master cast

BeadingBeading
 Is the act of scraping the outline ofIs the act of scraping the outline of
the major connector in to master castthe major connector in to master cast
..
 PreventPrevent food particlesfood particles fromfrom
connecting beneath the framework.connecting beneath the framework.
 Depth should not exceedDepth should not exceed 1mm1mm andand
fade out as thefade out as the gingival marginsgingival margins areare
approached and in the midline of theapproached and in the midline of the
palate.palate.
 Bead lines are not used inBead lines are not used in
conjunction withconjunction with mandibular majormandibular major
connectors.connectors.
PIC

Block outBlock out
 Elimination of undesirable undercut areasElimination of undesirable undercut areas
on a cast to be used in the fabrication of aon a cast to be used in the fabrication of a
removable partial denture.removable partial denture.
 Block out wax be placed only below theBlock out wax be placed only below the
height of contour.height of contour.

Types of block out:Types of block out:
 Parallel blockoutParallel blockout
 Shaped (ledging)Shaped (ledging)
 ArbitraryArbitrary
 releifreleif

Parallel block out:Parallel block out:
 Extends from survey line to gingivaExtends from survey line to gingiva

 Could be madeCould be made
with 0,2,6 degreewith 0,2,6 degree
tapered styli –tapered styli –
depends ondepends on
increasedincreased
freedom of movt.freedom of movt.
of prosthesis inof prosthesis in
functionfunction

IndicationsIndications
 proximal tooth surfacesproximal tooth surfaces
 beneath all minor connectorsbeneath all minor connectors
 tissue undercuts crossed by rigidtissue undercuts crossed by rigid
connectors, origin of bar claspsconnectors, origin of bar clasps
 deep inter proximal spaces to bedeep inter proximal spaces to be
covered by major connectorscovered by major connectors
 beneath bar clasp arms to gingivalbeneath bar clasp arms to gingival
crevice.crevice.

Arbitrary blockoutArbitrary blockout
 All gingival crevicesAll gingival crevices
 Gross tissue undercuts situated belowGross tissue undercuts situated below
areas involved in design of frameworkareas involved in design of framework
 Tissue undercut distal to cast frameworkTissue undercut distal to cast framework
 Labial & buccal tooth & tissue undercutsLabial & buccal tooth & tissue undercuts
not involved in denture designnot involved in denture design
 To prevent distortion and tearing duringTo prevent distortion and tearing during
duplication ,areas of gross undercutduplication ,areas of gross undercut
should be eliminated.should be eliminated.

Shaped block outShaped block out
 Ledging may be onlyLedging may be only
in the area of the tipin the area of the tip
of the clasp.of the clasp.

 Blockout wax:Blockout wax:
4 ½ sheets baseplate wax4 ½ sheets baseplate wax
4 ½ sticks guttapercha4 ½ sticks guttapercha
3 sticks sticky wax3 sticks sticky wax
½ teaspoon koalin½ teaspoon koalin
½ tube lipstick.½ tube lipstick.
Roach carver no.7Roach carver no.7

 Block-out wax is easy to scrape and cut, and wasBlock-out wax is easy to scrape and cut, and was
developed for blocking out undercuts that have nodeveloped for blocking out undercuts that have no
clinical importanceclinical importance
 Even during temperature-controlled soaking, the waxEven during temperature-controlled soaking, the wax
retains its shape and adheres firmly to the modelretains its shape and adheres firmly to the model
 Blocking-out wax is hard and enables sharp contours toBlocking-out wax is hard and enables sharp contours to
be reproduced on the duplicate model for clasp profilesbe reproduced on the duplicate model for clasp profiles
 Blocking-out wax is easy to remove from the masterBlocking-out wax is easy to remove from the master
modelmodel
 Setting temperature approx. 68 °C, melting point 80-Setting temperature approx. 68 °C, melting point 80-
85 °C85 °C

 Addition ofAddition of waxwax is intended tois intended to
make the frameworks standmake the frameworks stand
away from the master castaway from the master cast
– Removable partial dentureRemovable partial denture
frameworksframeworks usually displayusually display
intimate contact with theintimate contact with the
teeth & soft tissues, howeverteeth & soft tissues, however
there are certain areas wherethere are certain areas where
contactcontact is not desirableis not desirable
– Addition of wax intended toAddition of wax intended to
make the frameworks standmake the frameworks stand
away from the master cast isaway from the master cast is
termed astermed as reliefrelief
A 2X2 mm stopper may be2X2 mm stopper may be
placedplaced
RELIEFRELIEF

 Lingual portion of the relief wax may serveLingual portion of the relief wax may serve
as anas an internal finish lineinternal finish line .A properly.A properly
formed internal finish line permitsformed internal finish line permits
formation of a butt joint between theformation of a butt joint between the
framework and the acrylic resin dentureframework and the acrylic resin denture
base.base.
 1mm relief space.1mm relief space.

Sprue guide placementSprue guide placement

Duplication:Duplication:
 Materials:Materials:
 Reversible hydrocolloid gelReversible hydrocolloid gel
 AlginateAlginate
 Poly vinyl chloride(reversible plastic gel)Poly vinyl chloride(reversible plastic gel)

Duplicating flasksDuplicating flasks
Metal base Plastic base

Duplicating siliconeDuplicating silicone

Refractory castRefractory cast
Gypsum bonded
refractory materials
,commonly called low
heat investment can
be heated to 704*c.
High heat investments-
1037*c.

Drying ovenDrying oven
Temperature -93* c

Bees wax dipBees wax dip
Temperature 138*c to 149*

Waxing the frameworkWaxing the framework
Design transfer
Waxing-contouring wax and preformed wax or plastic patterns
to form the pattern for a removable partial denture framework.

Tacky liquid-mixture of acetone and
plastic pattern scrap

Stippling makes it easier to
fixate food and weakens the
extent to which the tongue
senses foreign matter
CASTING WAX RANGE
SMOOTH CASTING WAX
0.25mm-0.80mm
STIPPLED CASTING WAX
0.35mm-0.60mm
COARSE,MEDIUM,FINE

BEADING
WAX
CONTINUOUS
CLASPS
CASTING
STRIPS

 Wax edge strips with retentions greatly reduce theWax edge strips with retentions greatly reduce the
modelling time for bases of partial maxillarymodelling time for bases of partial maxillary
denturesdentures
 The prefabricated shapes can be easily adapted toThe prefabricated shapes can be easily adapted to
individual requirementsindividual requirements
WAX EDGE STRIPS WITH RETENTIONSWAX EDGE STRIPS WITH RETENTIONS

 The half-peardropThe half-peardrop
– It is easy toIt is easy to finish & polishfinish & polish

WAX CLASP PROFILESWAX CLASP PROFILES

WAX CLASP PROFILES FOR RINGWAX CLASP PROFILES FOR RING
CLASPSCLASPS
WAX CLASP PROFILES FORWAX CLASP PROFILES FOR
GINGIVALLY APPROACHINGGINGIVALLY APPROACHING
CLASPS
WAX CLASP PROFILES FORWAX CLASP PROFILES FOR
RING CLASPS, STRAIGHTRING CLASPS, STRAIGHT

 Wax wires on rolls areWax wires on rolls are
available as medium-hardavailable as medium-hard
wax in the various colourwax in the various colour
commonly green, withcommonly green, with
diameters ranging from 2.5diameters ranging from 2.5
to 5 mm in 0.5 mmto 5 mm in 0.5 mm
incrementsincrements
WAX WIRES FOR SPRUESWAX WIRES FOR SPRUES

 Gold casting patterns slightly heavier thanGold casting patterns slightly heavier than
those used for cobalt chromium castings.those used for cobalt chromium castings.

Waxing techniqueWaxing technique

Nail head retention
Open retention without releif
12-14 gauge

Open retention with relief
16-18 gauge

Rest seats made concave

External finish line

28 0r 26 gauge12 gauge half round
6 gauge

Spruing the frameworkSpruing the framework
Spruing is attaching wax ,metal or plastic forms to the wax pattern
to provide an entrance to the molad space and to serve as a reservoir of
Metal during casting procedure
7mm from
casting ring.

7mm hole

10mm on pattern side
Sprue cones

 All sprue connectionsAll sprue connections
be rounded.be rounded.
 No constrictions in theNo constrictions in the
sprue lead.sprue lead.
 Main sprue,auxillaryMain sprue,auxillary
sprue.sprue.
 Avoid T shapedAvoid T shaped
junctionsjunctions
 Secondary sprues areSecondary sprues are
one third to one fourthone third to one fourth
the diameter of mainthe diameter of main
sprue.sprue.
7mm below
Central sprue

Adjust the height of the sprue leads so that base of the
cast will be approximately 8mm from one end of the investing ring
when wax crucible former is in flush with other end.

Main sprue 8 to 10 gauge,auxillary-14 gauge.
10 gauge

Investing the refractory castInvesting the refractory cast
 Investing is the process of covering orInvesting is the process of covering or
enveloping whole or in part an object suchenveloping whole or in part an object such
as a trial denture ,wax pattern or crownas a trial denture ,wax pattern or crown
with an investment material beforewith an investment material before
curing ,soldering or casting.curing ,soldering or casting.

 1.to provide necessary strength necessary to1.to provide necessary strength necessary to
resist the forces created by the stream of moltenresist the forces created by the stream of molten
metal.metal.
 2.smooth surface for mold cavity.2.smooth surface for mold cavity.
 Avenue for escape of gases created by burn outAvenue for escape of gases created by burn out
and casting.and casting.
 Compensate for the shrinkage of the moltenCompensate for the shrinkage of the molten
metal as it solidifies.metal as it solidifies.
(shrinkage of gold alloy-1-1.74%(shrinkage of gold alloy-1-1.74%
Chromium alloys-2.3%)Chromium alloys-2.3%)

7mm short of sprue end.
A layer of cellulose,asbestos substitute or ceramic fiber paper.

Paint on investment.
To prevent air entrapment
Allows better adaptation to wax pattern
Permit easier esacpe of gases formed during burn out.
Uniform thickness as possible to ensure even expansion of the mold
2nd
investment

Burn outBurn out
Early stages temperatureEarly stages temperature
will not rise above 100*cwill not rise above 100*c
until all water is vaporized.until all water is vaporized.
2hour-538*c2hour-538*c
After 2 hrs-675* -710*c-toAfter 2 hrs-675* -710*c-to
remove the carbonremove the carbon
residue resulting from theresidue resulting from the
vaporization and oxidationvaporization and oxidation
of the wax.of the wax.

castingcasting
 Heat for melting the metal may be suppliedHeat for melting the metal may be supplied
by a blow torch using gas and air,gas andby a blow torch using gas and air,gas and
oxygen,acetylene,electrical conduction oroxygen,acetylene,electrical conduction or
electrical induction.electrical induction.
 Adjust the torch to form a reducing flame.Adjust the torch to form a reducing flame.
 Heat the metal ,keeping the tip of the blueHeat the metal ,keeping the tip of the blue
cone on the suface of the metal.cone on the suface of the metal.
 Force is needed to inject the molten metalForce is needed to inject the molten metal
in to mold cavity,it might be eitherin to mold cavity,it might be either
centrifugal or air pressure.centrifugal or air pressure.

 Induction castingInduction casting
machine is based onmachine is based on
electric currents in aelectric currents in a
metal core inducedmetal core induced
from a magnetic field.from a magnetic field.

Recovering the castingRecovering the casting

Cleaning the casting.Cleaning the casting.
 Shell blaster or sandShell blaster or sand
blaster to be used.blaster to be used.
 Gold castings pickledGold castings pickled
in acid picklingin acid pickling
solutions.solutions.

 Excessive cracks inExcessive cracks in
the moldthe mold
 Pitted and discoloredPitted and discolored
castingcasting
 Portions of metalPortions of metal
frame work did notframe work did not
castcast
 Pattern failed to castPattern failed to cast
Casting ring not lined.Casting ring not lined.
Investment too dry when placed in ovenInvestment too dry when placed in oven
Temperature raised too fastTemperature raised too fast
Investment overheated
Metal too cold when cast
Improper spruing
Gas trapped in the mold.
Pattern seperated from crucible
former during investing.

Finishing and polishing theFinishing and polishing the
frameworkframework
High speed lathe

Accessible flash and sprue stumps removed
stone Seperating disk

Carbide bur Mounted stone
Mounted stones for gold and cobalt chromium cannot be used
interchangeably.

Refining undercut butt joint of the finish lines

 Rubber abrasiveRubber abrasive
wheels,knife edgewheels,knife edge
wheels and points.wheels and points.
 Rubber wheelRubber wheel
impregnated withimpregnated with
pumice used for goldpumice used for gold
 With carborundum forWith carborundum for
cobalt chromium.cobalt chromium.

Finish the metal surfaces that contact the teeth

 Felt cone with tripoliFelt cone with tripoli
produces aproduces a
completely smoothcompletely smooth
surface.surface.
 Jeweller’s rouge usedJeweller’s rouge used
next.next.

Tripoli impregnated cloth wheel.

solderingsoldering
Electro soldering unit.

Wrought wire claspsWrought wire clasps

Laser weldingLaser welding
Neodynium –yttrium aluminium garnet

Denture baseDenture base

Occlusal rims and bite registrationOcclusal rims and bite registration

waxingwaxing

InvestingInvesting

Dewaxing and packingDewaxing and packing

DeflaskingDeflasking

polishingpolishing

Thank you
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www.indiandentalacademy.com

Lab procedures / dental education in india

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