The Die, Waxing, investment and casting-power point

The Die, Waxing,
The Die, Waxing,
investment and casting
investment and casting


Die:
Die:

It is the positive reproduction of the individual (single) prepared tooth on which wax pattern
is done. It is obtained from Working cast (master cast) of the final impression. It is the
positive reproduction of the form of the prepared tooth in any suitable substance. A
reproduction of a prepared tooth made from a gypsum product, epoxy resin, a metal or a
refractory material.


Adieisamodelofasingletooth,againpreparedfromanimpression.Thedieisapositivereproductionofthepreparedtoothandconsistsofasuitablehardsubstanceofsufficientaccuracyusuallyanimprovedstone,resinormetal.Thedieisamodeloftheindividualpreparedtoothonwhichthemarginsofthewaxpatternsarefinished.

Acastanddiesystemcapturesthenecessaryinformationsothatitcanbetransferredtothelaboratory.

itisnecessarytoobtainanaccuratereproductionofpreparedtooth,adjacentopposingtoothandsurroundingsofttissues.Sincedirectfabricationinthemouthisinconvenient,difficult,timesconsuming


Requirements
Requirementsof
ofthe
thedie
dieand
anddie
diematerials
materials:
:

1.Itmustreproducethepreparedtoothdetailsandallfinedetailsintheimpressionexactly.

2.Itmustbefreefromairbubbles,cracksandvoids.

3.Itmustreturntoitsexactpositiononthecastwhenitisremoved.

4.Itmustbestableintheirpositionevenwhenthecastisinverted.

5.Thedimensionalstability(oraccuracy)andabrasionresistanceduringtheconstructionofthewaxpattern.

6.Theyshouldbedimensionallystable.

7.Theyshouldbe;Settingexpansion,contractionanddimensionalvariationinresponsetosettingorchangeintemperatureshouldbeminimal


Requirements of the die and die materials:

8.The die should have a smooth surface that is sufficiently strong to withstand the
subsequent.

9.Manipulative procedures without abrasion of the surface that is it should have the ability
to resist abrasion.

10.They should be compatible with impression materials and there should be no
interaction between the surface of the impression and cast or die.

11.Toughness to resist breakage during fabrication or burnishing of fine edges.

12.Color of the die should be in contrast to the color of wax. This helps to facilitate the
manipulative procedures that will be carried out.

13.It should be reasonably easy to use without excessive manipulative procedures. It
should be relatively inexpensive.

14.Die must be given a form that allows easy handling during waxing and other
procedures. The die must have root like extension that serves as a handle.

15.The remaining unprepared tooth structure immediately cervical to finish line should be
easily distinguished on the die, ideally with 0.5 to 1mm visible. Adequate access to the
margin is necessary.


Types of dies according to materials investment use:
Types of dies according to materials investment use:

Investment materials
Investment materials

1. Silver-plated dies.

2. Copper-plated dies.

3. Amalgam dies.

4. Silicophosphatecement.

5. Stone dies.

6. Metal sprayed dies.

7. Epoxy resins.

8. Polyurethane Alternative die materials.

9. Ceramic die materials.

10. Flexible die materials.


11.Diestone-Investmentcombination.

12.Gypsumproducts-TypeIVDentalStoneTypeVDentalstone.

13.Electroformeddie(Besidesresins,electroplatingcanbeusedtoovercomethepoorresistanceofgypsum.Themetaldiesthatareproducedwhenanimpressionmaterialiselectroplatedhavemoderatelyhighstrength,adequatehardnessandexcellentabrasionresistance.Detailreproductionofaline4.-morlessisreadilyattainableonanelectroplateddiewhenanoaqueouselastomericimpressionmaterialisused).

Types of dies according to materials investment
Types of dies according to materials investment
use:
use:

Investment materials
Investment materials


Types of die according to construction:
Types of die according to construction:

1
1. Working cast with separated dies.
. Working cast with separated dies.

2
2. Working cast with removable dies:
. Working cast with removable dies:

a. Straight dowel pin.

b. Curved dowel pin.

c. Pindex system.

d. Di-Loktray.


Working cast with separated dies (Multiple pour system):
Working cast with separated dies (Multiple pour system):

Thefinalimpressionispouredtwicetoobtaintwoworkingcasts:oneofthesecastsissectionedtoobtaintheindividualdiesthatareseparatedfromthatcast,whiletheotherworkingcastisarticulatedonthearticulator.

Working
Workingcast
castwith
withremovable
removabledies
dies:
:

Thefinalimpressionispouredforonetimeonlytoconstructaworkingcastthatinvolvesremovabledies.

Thedowelpinsareready-mademetalpinswhichareusedasameansoforientingthedie(s)totheoriginalworkingcast,whichallowthedie(s)tobeeasilyremovedandaccuratelyreplacedintotheworkingcast.Thedowelpinistaperedandcylindricalwithoneflatsideforpositiveseating.


Inter
Inter-
-occlusal Record (Bite Registration) Objective of bite registration:
occlusal Record (Bite Registration) Objective of bite registration:

Totransfertherelationbetweentheupperandlowerdentalarchesfromthepatient’smouthtothearticulatorweneedbiteregistration.Properinter-occlusalrecordisimportanttoorientthedie(s)ofthesamearchtotheopposingarch.Whenenoughteetharepresentinbothdentalarcheswecantransfertherelationbyhandarticulationofthecasts.i.e.,nobiteregistrationisneededinsuchcases,sowecanoccludetheopposingcastsbyhand,andthenwemountthemonthearticulator.Iftheremainingteethareinsufficienttoproducehandarticulationofthecasts,wehavetorecordthebitebyusingeitherofthefollowings:

1.Pink base plate wax.

2.Bite registration paste.

3.Bite rim or occlusal rim.

The bite rim is used in the following cases:
The bite rim is used in the following cases:

1. Free end saddle.

2. When we need to restore the anterior teeth.

3. When we don’t have enough teeth to obtain the
centric relation.


Types of articulators:
Types of articulators:

The long–term successful restoration is dependent on:

1-Proper management of the occlusion.

2-The maintenance of occlusal harmony.

3-Avoid the creation of occlusal interferences.

Mostsinglecrownsandsimplefixedpartialdenturesarefabricatedonsimplehingearticulatorsthathavelimitedabilitytoduplicatemandibularmovementsornotatall.
Whilemanyoftheinaccuraciesproducedbythistypeofinstrumentmaybecorrectedinthepatientmouthusingvaluablechairtimeandtheendresultisanocclusionthatislessthanoptimal.Unfortunately,manyoftheseinaccuraciesarenotrecognizedandareallowedtoremaininthemouthasocclusalinterferenceswhichfrequentlyproducedsymptomsofocclusaldisease.

In dentistry we use:
In dentistry we use:

a-Simple hinge.

b-Semi-adjustable.

c-Fully adjustable.


Allrestorativedentistrypatienttreatment(allfillingstypes,inlaysandonlays)usesemi
semi-
-adjustable
adjustablearticulator
articulatorintheapplicationofthebasicprinciplesofocclusion,theimportanceofsuchinstrumentsasanaidinprovidingtheproperdiagnosisandtreatmentofocclusionforthesepatients.

Construction of Dental Restoration:
Construction of Dental Restoration:

1. Dental waxes.2. Casting investment.


Dental waxes:
Dental waxes:

Dentalwaxesarehydrocarbonsinnature(containO2,H,andC)andhavemanyapplicationsinDentistry.


Ideal requirements of pattern waxes:
Ideal requirements of pattern waxes:

1.Should be colored to be easy distinguished either from the die material or the tooth
structure.

2.Should be cohesive and not adhesive.

3.Should soften without flaking.

4.Should soften at reasonable temperature and harden at mouth temperature.

5.Should have adequate flow to record the details of the prepared tooth.

6.Should burn-out completely with no residue.


Casting Investment Casting investment:
Casting Investment Casting investment:

Is composed of silica particles (SiO
Is composed of silica particles (SiO2
2) bonded together with different binding agents.
) bonded together with different binding agents.

Requirements of ideal investment material:
Requirements of ideal investment material:

1.Should be stable (not decompose) on heating (Refractory).

2.Should show a kind of expansion to compensate for metal shrinkage.

3.Able to wet the wax surfaces registering its details.

4.Easily manipulated, not expensive, not irritant and no release of toxic.

5.Should be porous to permit escape of gases.

6.Withstand the impact of molten metal.

7.Not adhere to the surface of cast metal.

8.Easy breakdown after casting.


Types of investment materials relative to the type of silica particles used:
Types of investment materials relative to the type of silica particles used:

a-Quartz-based investment.

b-Cristobalite-based investment

Types of investment materials relative to the type of binder used:
Types of investment materials relative to the type of binder used:

a-Gypsum-bonded investment .. Uses (CaSo4. 2H2O) binder. For casting metal alloys that
melt below (i.e. gold alloys only)

b-Phosphate-bonded investment .. Uses magnesium ammonium phosphate. For casting
metal-ceramic alloys and some base metal alloys (Can be heated above

c-Silica-bonded investment .. Uses silica gel binder in both types Tridymitecould present
as impurity.

1000Co). 
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