Transcript Inlay Casting Wax - King George's Medical University

Dental Materials Lecture
BDS II Year
Dr. Raghuwar D Singh
Associate Professor
Prosthodontic Department
King George’s Medical University UP, Lucknow
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First procedure in the casting of an inlay or
crown is the preparation of a wax pattern.
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TECHNIQUES for WAX PATTERN
Preparation::
* Direct Technique
* Indirect Technique
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TYPES OF INLAY CASTING WAX --
* According to ADA Specification No. 4 ::
TYPE I = Medium Wax for Direct Technique
TYPE II = Soft Wax for Indirect Technique
COMPOSITION
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Paraffin wax = 40 to 60 %
Gum dammar
Carnauba wax
Coloring agent
PARAFFIN WAX :
* Derived from high boiling fraction of petroleum.
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* Depending upon Molecular Wt. & Distribution
can be obtained in a wide melting or softening
range.
* Paraffin used for Type I waxes have higher
melting point than the Paraffin used for Type II
waxes.
DISADVANTAGES –
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Flake when it is trimmed.
Does not present Smooth, Glossy surface.
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GUM DAMMAR or DAMMAR RESIN :
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Natural Resin.
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Added to improve the smoothness in molding.
Resistant to Cracking & Flaking.
Increases the Toughness of the wax.
Enhances the Smoothness of the surface.
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CARNAUBA WAX :
Occurs as fine powder.
Quite Hard in nature.
High Melting point.
Combined with paraffin to Decrease the flow
at mouth temperature.
Give more Glossiness to wax surface than
dammar resin.
CANDELILLA WAX can also be added to
replace the Carnauba wax.
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Its Melting point is lower.
Not as hard as Carnauba wax.
CERESIN may replace part of Paraffin to modify
the toughness & carving characteristics of wax.
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In modern Inlay Waxes, the Carnauba Wax is
often replaced in part with certain Synthetic
Waxes that are compatible with Paraffin wax.
Two waxes of this Types are ::
Complex Nitrogen derivatives of higher fatty
acids.
Esters of acids derived from Montan wax.
PROPERTIES OF INLAY WAX
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When softened wax should be uniform.
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Color should contrast with the die material.
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No Flakiness or similar surface roughness
when wax is bent & molded after softening.
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Should Vaporize completely during burnout
(5000c).
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Wax should not pull or chip during carving.
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Wax pattern should be completely rigid &
dimensionally stable.
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FLOW
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THERMAL PROPERTIES
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WAX DISTORTION
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MANIPULATION OF INLAY WAX
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OTHER DENTAL WAXES
FLOW –
Requirements according to ADA Specification no. 4,
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At 450C -- Both Type I & II should have a flow b/w
70 to 90 %.
At 370C -- Type I should not flow more than 1 %.
At 300C -- Type II should not flow more than 1 %.
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THERMAL PROPERTIES –
THERMAL CONDUCTIVITY :
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Low.
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Takes time to heat the wax uniformly.
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COEFFICIENT OF THERMAL EXPANSION :
 High.
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Thermal changes are higher than any other
materials.
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Linear expansion of 0.6 % when heated from 25
to 370C is permitted for Type I waxes.
This property is more significant in Direct Tech.
* Other Factors that influence the Coefficient of
Thermal Expansion are –
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Temperature of the Die.
Method used for applying pressure to the wax.
WAX DISTORTION –
 Most serous problem in Inlay wax.
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It is due to Release of Stresses in pattern due to,,
* Contraction on cooling.
* Occluded gas bubbles.
* Change of shape of wax during moulding.
* From Manipulation, Carving, Pooling &
Removal.
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CAUSES OF DISTORTION :
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If wax is not at uniform temp. when inserted in the
cavity.
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If wax is not help under uniform pressure during
cooling.
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If wax is added in an area of deficiency.
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TO AVOID DISTORTION OF WAXES :
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Minimal carving & change in temperature.
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Minimal Storage of pattern.
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Use warm instrument for carving.
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Store it in a Fridge if necessary.
MANIPULATION OF
INLAY WAX
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TECHNIQUES –
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DIRECT TECHNIQUE
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INDIRECT TECHNIQUE
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DIRECT TECHNIQUE ::
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Softened the stick of wax over the flame.
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Inserted into the cavity & held under finger
pressure.
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Allow to cool gradually at mouth temperature.
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Withdraw the wax pattern carefully.
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INDIRECT TECHNIQUE ::
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Pattern is prepared over a lubricated die.
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If molten wax used, very little stresses occur.
METHODS OF INDIRECT TECHNIQUE –
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Dipping Method –
* In full crowns.
* Die is dipped in hot liquid wax.
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Softening In Warm Water – Not recommended.
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Adding in Layer – Using spatula or brush.
OTHER DENTAL WAXES
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RPD WAXES
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PRECESSING WAXES
* Boxing & Beading Waxes.
* Utility Wax.
* Sticky Wax.
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IMPRESSION WAXES
* Corrective impression Wax
* Bite Registration Wax
RPD WAXES
USES –
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To make patterns of metallic framework of RPD.
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Pattern for RPD is made on a special cast known
as the Refractory Cast.
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SUPPLIED AS --
* Sheets .40 and .32 mm thickness.
* Readymade shapes, Round, Half round
Grid or Meshform
Clasp shapes
Other forms.
* Bulk.
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PROPERTIES –
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Highly Ductile, as they must adapt easily and
stick onto the refractory cast.
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Must Vaporize during burnout.
BASEPLATE WAX
or
MODELING WAX
Supplied as,
Sheets of pink or red colour.
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USES –
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To make Occlusion rim.
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To form the desired contour of denture after
teeth are set.
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To make patterns for Orthodontic appliances.
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CLASSIFICATION –
Type I
= Soft ; for building Veneers.
Type II = Medium
Type III = Hard
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COMPOSITION –
Paraffin wax or Ceresin
Beeswax
Carnauba wax
Natural or Synthetic resin
Microcrystalline
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80 %
12 %
2.5 %
3%
2.5 %
PROCESSING WAX
** Used mainly as accessory aids.
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Examples are ,
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Boxing Wax & Beading Wax.
Utility Wax.
Sticky Wax.
BOXING & BEADING WAX
USES -To build up vertical walls around the impression.
SUPPLIED AS –
Boxing wax as sheets.
Beading wax as strips.
UTILITY WAX
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Supplied as –
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Uses –
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Composition –
Sticks and Sheets.
To adjust the contour of perforated tray.
Petrolatum & other waxes.
** It is adhesive and can stick to the tray.
STICKY WAX
USES -
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To join metal parts before soldering.
To join fragments of broken dentures before
repair.
COMPOSITION --
Mainly Yellow Beeswax, Rosin & Natural
resins such as Gum dammer.
PROPERTIES –
Sticky when melted & Adheres closely to surface.
 Firm and Brittle at room temperature.
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IMPRESSION WAXES
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Used to record non – undercut edentulous
portions of the mouth.
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Examples are ,
** CORRECTIVE IMPRESSION WAX
** BITE REGISTRATION WAX
CORRECTIVE IMPRESSION WAX
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USES -To make functional impression of RPD.
To record Posterior Palatal Seal.
Functional Impression for Obturatures.
COMPOSITION -•
Paraffin wax
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Ceresin wax
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Beeswax
May contain metal particles.
PROPERTIES –
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FLOW at 37 0 C is 100 %.
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Should be poured immediately.
BITE REGISTRATION WAX
USES -To record the relationship between the upper and
lower teeth.
SUPPLIED AS -- U shaped rods.
COMPOSITION -- Beeswax, Paraffin, Ceresin.
MCQs
1. The role of gum dammar in Inlay casting wax is:
a) To improve cracking resistance
b) To provide strength to wax
c) To impact smoothness to pattern
d) All of the above
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2. Carnauba was is preffered to candelila wax as:
a) It is harder and has less flow
b) It has low melting temperature
c) It provides luster to the pattern
d) All of the above
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3. Inlay wax should have following requisites:
a) Its colour should be in contrast with tooth or
die material
b) It should have capability to be carved according
to tooth anatomy and there should be no
flaking.
c) When heated, it should be completely
eliminated from the mould.
d) All of the above.
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4. Which of the following waxes is used for
making of casting pattern:
a) Boxing wax
b) Inlay wax
c) Modeling wax
d) Utility wax
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5. The minimum flow of inlay wax at 450C
should be:
a) 60%
b) 6%
c) 70%
d) 100%
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6. Which of the following correctly describe type
I inlay casting wax:
a) Soft wax used for direct technique
b) Medium wax used for indirect technique
c) Soft wax used for indirect technique
d) Medium was used for direct technique
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7. The maximum ingredient of inlay casting wax:
a) Paraffin wax
b) Ceresin
c) Carnauba wax
d) Gum dammar
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8. Which of the following is added inlay casting
was to improve the smoothness:
a) Ceresin
b) Candellila wax
c) Gum dammar
d) Synthetic wax
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9. Percentage of Carnauba wax in inlay casting
wax is:
a) 40%
b) 60%
c) 25%
d) 10%
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10. Inlay casting wax is supplied as:
a) Sheets only
b) Mesh form only
c) Both of the above
d) None of the above
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