Transcript
Dental Waxes
MANIVASAGAN.C
PG STUDENT
Dept of prosthodontics including
crown & bridge & implantology
Contents
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Introduction
History
Ideal properties
Classification
Characteristic properties
Different waxes & their uses
Conclusion
References
Introduction
• Definition :
One of several esters of fatty
acids with higher alcohols, usually
monohydric alcohols. Dental waxes are
combinations of various types of waxes
compounded to provide desired physical
properties.
(G.P.T. 8th Edn.
2005)
History
• Paraffin wax :parum = few or without
affinis = connection or attraction
most important natural wax
• To protect themselves from adverse weather
conditions, plants produce a layer of wax on
their leaves & stems
• Material from dead plants 100-700 million
years ago accumulate large quantities &
became buried beneath earth’s surface :: slow
decay :: crude oil/petroleum formed :: refined
to form clean, clear liquid, or solid milky white
block :: WAX
History
• Bees wax : introduced in 1711
• It is actually a refinement of honey
• It is used by honeybees in construction of
their honeycombs
• The wax appears in the form of small,
irregularly oval flakes or scales over the
abdomen of honeybees
Ideal Properties
• Should be tough & rigid at room
temperature but not brittle
• Should have a low softening temperature
• Should flow easily
• Should be dimensionally stable
• Should have a melting point well below
boiling point of water, so that wax can be
removed under boiling water
• Should have pleasant color & posses a
color contrast to help during carving
Classification
I. According to source/origin :
1) Natural waxes
i) Mineral waxes : paraffin
microcrystalline
bransdahl
ceresin
ozokerite
monton
Characteristic Properties
1) Melting range
2) Thermal expansion
3) Mechanical properties
4) Flow
5) Residual stress
6) Ductility
Melting Range
• Waxes have melting range rather than
specific melting point
Eg. Paraffin wax : 44-62o C
Carnauba wax : 50-90oC
• By varying compositions, it is possible to
change melting ranges suitable according
to use
Thermal Expansion
• Largest values of coefficient of thermal
expansion (150-400x10-6/oC)
• Contraction of wax pattern by 0.3-0.8%
when cooled from 37oC to room temperature
leading to inaccuracy of finished restoration
• Poor thermal conductors :: suitable
kneading & time is required to heat them
uniformly & cool them to room temperature
Mechanical Properties
• Modulus of elasticity, proportional
limit, flexibility & compressive
strength are low & decreases with
rise in temperature
Flow
• Flow increases as melting range of
wax is approached
• Depends upon temperature of the
wax, external deforming force & the
time the force is applied
Residual Stress
• Waxes tend to return to their original shape
after manipulation :: elastic memory.
• When wax is held under compression
during cooling, atoms & molecules are
forced closer together than when they are
under no external stress. After it is cooled
on room temp & load is removed, motion of
molecules is restricted, & this restriction
results in residual stresses in it.
Residual Stress
• When wax is heated, release of residual
stresses adds to normal thermal
expansion, & total expansion is greater
than normal
Ductility
• Increases with an increase in
temperature
• Waxes with low melting temperatures
have greater ductility than those with
higher melting temperature
Pattern Waxes
• Used to prepare predetermined size
& contour of an artificial dental
restoration which is to be constructed
of a more durable material such as
cast gold alloys, Co-Cr-Ni alloys or
poly methyl methacrylate resin
• Types : Inlay waxes
Casting waxes
Base plate waxes
Inlay Waxes
• Used to prepare wax
patterns of inlays, crowns,
& bridges for the lost wax
casting technique.
• Dispensing : supplied as
deep blue or purple rods or
sticks of about 7.5cm
length & 3mm diameter.
Also supplied in the form of
small pellets & cones.
Classification
• According to ADA specification No. 4
Type I : medium wax, used in direct
technique
Type II : soft wax, used in indirect
technique
Composition
Ingredients
1. Paraffin
wax
2. Carnauba
wax
3. Ceresin
wax
Weight
Functions
%
60 %
Used to establish melting
point. Likely to flake when
trimmed & does not give
glossy surface
20 %
Increases melting range,
decreases flow at mouth
temperature provides
glossiness of wax surface
5%
Improves carving
characteristics & modifies
Composition
Ingredients Weight
Functions
%
4. Bees wax 5 %
Reduces flow at mouth
temperature & reduces
its brittleness
5. Gum
dammar
3%
6. Synthetic 2 %
resins
Improves surface
smoothness, gives more
resistance to flakiness &
provides toughness
Gives stable flow
properties to the wax
Desirable Properties
• When softened, wax should be uniform
• Color should contrast with die material or
prepared tooth
• There should be no flakiness or surface
roughening when wax is molded for softening
• In Type I waxes, it should be sufficiently plastic at
a temperature slightly above mouth temperature
& become rigid at mouth temperature
Desirable Properties
• It should have a flow not less than 70% at
45oC & not more than 1% at 37oC
• Wax should not pull or chip with the carving
instrument when it is carved
• After the mold has been formed, wax should
burn out, forming carbon, which is later
eliminated by oxidation of volatile gases
• Wax pattern should be completely rigid &
dimensionally stable at all times until it is
eliminated.
Properties of Inlay Wax
• Flow
• Thermal conductivity
• Coefficient of thermal expansion
• Wax distortion
Flow
• The flow of wax is a measure of its potential
to deform under a small static load, even
that associated with its own mass
• Type I inlay wax exhibits marked plasticity
or flow at a temperature slightly above
mouth temperature
• Maximum flow for Type I waxes at 37oC is
1%
• Both Type I & Type II waxes must have flow
between 70% & 90% at 45oC, i.e., when
waxes are inserted into the prepared cavity
Thermal Conductivity
• Thermal conductivity of waxes is low,
sufficient time is required both to
heat them uniformly throughout & to
cool them to body or room
temperature
Coefficient of Thermal
Expansion
• Inlay waxes have a high coefficient of
thermal expansion
• Linear expansion of 0.7% with increase in
temperature of 20oC & contract as much as
0.35% when cooled from 37oC to 25oC
• ADA specification No.4 contains no
requirements for thermal expansion for Type
II waxes. A maximum of 0.6% linear change
in dimension is permitted for Type I waxes
when they are heated from 25oC to 37oC
Wax Distortion
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Most serious problem
Wax Distortion
• Results from thermal changes & release of
stresses that arise from :
1.Non-uniform contraction on cooling if wax
is not held under uniform pressure
2.Occluded gas bubbles
3.Non-uniform heating during insertion in
the cavity :: some parts of wax pattern
may contract more than others when
stresses are introduced
4.change of shape during molding, carving,
& removal
Wax Distortion
• Methods to minimize wax distortion :
1. Proper selection of waxes (Type I for direct
& Type II for indirect technique)
2. Soften the wax uniformly
3. Place the soften & molten increments
quickly to bound with earlier increment
4. Invest the pattern immediately after
removal from cavity (or store it in cold
water in a refrigerator)
Manipulation
Direct technique (Type I wax)
• Wax is softened with dry heat over a flame
(rather than in water bath) taking care not
to volatize it
• It should be twirled until it becomes shiny
• Kneaded together & shaped to the
prepared cavity
• Type I wax has adequate plasticity in a
temperature range safely tolerated by the
pulp
Manipulation
Direct technique (Type I wax)
• Hold under pressure until it sets either
with finger or by the patient biting on the
wax
• Allow it to cool gradually at mouth
temperature (not by cold water) & invest
the pattern as early as possible
Manipulation
Indirect technique (Type I wax)
• Impression of prepared cavity is made with a
rubber base impression material & die is
made
• Die is coated with a lubricant (containing
wetting agent)
• Melted wax may be added in layers with
spatula or it may be painted on with a brush
• Prepared cavity is overfilled, & and wax is
then carved to proper contour
• Wax pattern is removed & invested as early
as possible
Casting Wax
• It is one of the pattern
waxes used to prepare
wax patterns for metallic
framework of removable
partial dentures
• They are highly ductile
• Mode of supply :
Sheets : 0.4 & 0.32 mm thickness
Readymade shapes : round rods (10 cm
long)
half round rods
half pear shaped rods
Bulk form : for sprues & vent sprues
Preformed wax patterns : for cast RPD
frameworks
Composition
Ingredients
1. Paraffin wax
2. Ceresin wax
3. Bees wax
4. Natural
resins
Functions
To establish melting
point
Improves carving
characteristics
Reduces flow at
mouth temp & reduces
brittleness
Gives suitable flow
properties to wax
Uses
• To make metallic
framework of removable
partial dentures
• To provide uniform
minimum thickness in
certain areas of partial
denture framework
Base plate wax
• Also known as Modelling wax
• Mode of supply : sheets of pink/red
color
width- 7.5 cm
length- 15 cm
thickness- 0.13 cm
Composition
Ingredients
Weight
Functions
%
1. Ceresin wax
80 %
Improves carving
characteristics
2. Bees wax
12 %
Reduces brittleness &
reduces flow at
mouth temp & gives
glossy surface
3. Natural or
3%
Gives stable flow
synthetic resin
properties
4. Microcrystalline 25 %
To establish required
wax
melting point
Classification
• According to ADA specification No.24,
they are classified as :
Type I Soft - for building veneers
Type II Medium – tried in mouths in
temperate climatic conditions
Type III Hard – for trial fitting in the
mouth in tropical climates
Uses
• To make occlusion rims, which is used on base
plate to establish vertical dimensions, plane of
occlusion & initial arch form in complete
denture fabrication
• To produce desired contour of denture after
teeth are set in position
• To make patterns for orthodontic appliances &
prosthesis other than complete dentures
• To check various articulating relations in the
mouth & to transfer them to mechanical
articulators
White/Ivorian Wax
• Used for making
patterns to simulate a
veneer spacing
• For diagnostic wax-up
Processing Waxes
• Used mainly as accessory aids in
construction of a variety of restorations &
appliances either in the clinic or in the
laboratory
• These are :
Beading & Boxing wax
Utility wax
Sticky wax
Carding wax
Blockout wax
Carving wax
Beading & Boxing Wax
• Used mainly to bead & box the impression
to produce desired size & form of the base
of the cast
• Mode of supply :
Boxing wax ::
Sheets of width- 3 cm
length- 15 to 30
cm
thickness- 3 mm
Beading wax :: Ropes of thickness- 3 to 4
mm
length – 20 to 30
cm
Properties
• Preserves the extensions
• Controls the form & thickness of the base of cast
• Can be adapted easily as it is pliable
• Its tackiness allows it to attach to the impression
• It conserves the dental stone
Adaptation to the Cast
• Beading wax is adapted around the
periphery of the impression
• Should be appx. 4 mm wide & 3-4 mm
below the borders of the impression
• Height is adjusted until a boxing wax strip
extends appx. 13 mm above the highest
point on the impression
Uses
• To build up vertical walls around the
impression
• To produce desired size & form of the
base of the cast
• To preserve certain landmarks of the
impression
Utility Wax
• Consists mainly of bees wax, mineral wax
& other soft waxes in various proportions
• Can be molded at room temperature, as it
is pliable
• Its tackiness allows it to stick to the
impression
• Mode of supply : cakes, sticks & sheets
Uses
• To provide desirable contour to a
perforated tray for use with
hydrocolloids
• To build up flange of tray & raise the
palatal portion of the tray posteriorly
in recording impression of patients
with deep palate
Sticky Wax
• Also known as adhesive wax or model
cement
• Consists of yellow bees wax, rosin &
natural resins such as gum dammar
• It is sticky when melted & adheres closely
to the surface upon which it is applied
• At room temperature, it is free from
tackiness & is brittle
Uses
• To assemble metallic pieces temporarily in
position or to seal a plaster splint to stone cast
in the process of forming porcelain facings
• To join fragments of broken denture before
repair
• As it is brittle at room temperature, it will
break rather than become distorted if the
assembled pieces move– these pieces can
then be rejoined in their proper relationship,
rather than unknowingly using it in a distorted
relationship
Carding Wax
• Used for attaching broken parts of
the denture before denture repair
procedure
• Used to join metal pieces in soldering
procedures
• Used to attach artificial teeth
Block out Wax
• Used to fill voids & undercuts during
fabrication of removable partial
denture
Carving Wax
• Used for tooth carving procedures in
dental anatomy, laboratory
procedures
Impression Waxes
• Used to record non-undercut edentulous
portions of the oral cavity & are
generally used in combination with
other impression materials like
polysulfide, ZOE impression paste or
impression compound
• Important impression waxes are :
corrective impression waxes
bite registration waxes
Corrective Impression
Waxes
• Used as a wax veneer over an original
impression to contact & register the
details of the soft tissues
• Consists of paraffin, ceresin & bees wax
• Flow at 37oC is 100 % (can get distorted
while removing from the mouth)
Corrective Impression
Waxes
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1)
2)
3)
4)
These waxes are designed to flow at mouth
temperature
Four types of waxes can be used for this
technique
IOWA Wax , white , by Dr. Smith
Korecta Wax No.4 , Orange , by Dr, O.C.
Apllegate
H-L physiologic paste , yellow-white, by
Dr.C.S.Harkins
Adaptol , green , by Dr. N.G.Kaye
Corrective Impression
Waxes
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1)
2)
3)
4)
Advantages –
It is a physiologic method displacing the
tissues within their physiologically acceptable
limits
Overcompression is avoided
They can be used as corrective material for
imperfections in other impressions, particularly
those of Zinc oxide – Eugenol paste
They flow enough to prevent overdisplacement
Corrective Impression
Waxes
•
Disadvantages –
1) More time is necessary during the
impression appointment
2) Difficulty in handling the materials
3) Added care has to be taken during boxing
4) Material not easily available
5) Special Armamenterium required for
using the material
Armamentarium for the
fluid wax
technique
Fluid Wax
Technique
Uses
• Functional impression of distal
extension partial dentures
• To record posterior palatal seal
• Functional impression for obturators
Bite Registration Wax
• Used to record the occlusal relationship of
opposing quadrants
• Consists of beeswax, paraffin wax & ceresin
wax
• Flow at 37oC ranges from 2.5 % to 22 %
• Mode of supply : U-shaped thin sheets, which
are sometimes matallised or foil laminated
eg. Aluwax
Bite Registration Wax
• Bite Registration Wax is interposed
between the teeth & patient is asked to
bite in the position of jaw relation
recording
• The indentations thus formed on the wax
are used to place the cast in position &
then transfer it to the articulator.
SPECIAL WAXES
White wax
• White wax is used for making patterns
to simulate a veneer facing for
aesthetic restorations
Blockout• Wax
Applications:
Fills undercuts, covers
sharp edges and corrects
draw on dies with non
parallel walls. May be
applied to the die prior
to or after coating with
hardener and spacers.
• Properties:
- hard
- easy flow when molten
-excellent carvability for
smooth contouring on
die surfaces.
Hardness holds carved
edges and high fusing
temperature prevents
adhesion to coping wax.
DISCLOSING WAX
• Disclosing wax is sometimes known as
pressure indicator paste
• Used to determine unequal pressure
points in a denture
• Located by painting the wax on tissue
side of the denture base and holding
the denture in place under pressure in
the mouth.
• The wax flows away from the points
needing relief.
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LASER-WAX
Laser reading for the CAD/CAM
technique
Advantages
Laser readable
Appropriate for all laser scanning
systems
Good Modeling capacity
Pleasant color (pastel shade)
Can be milled
Extremely opaque
Redi-Form Pontic
• Eliminate tedious wax
buildup.
• Eliminates need to
individually place singlepontic forms, reducing
wax-up time dramatically.
• When softened allows the
four pontic section to be
carved, narrowed, or bent
to fit even the most
complex case without
loss of anatomical detail.
• When cooled, the fourpontic section becomes
rigid
ALUWAX
• ALUWAX dental wax is composite
material which contains powdered
aluminium
• Increase the integrity of the
compound
• Better heat retention properties
needed for efficient modeling
Retention pearls
RETENTION PEARLS ARE SPRAYED ON TO
THE WAX PATTERN FOR ADDED
RETENTION
S-U-CERAMO-WAXES
• Purest special waxes for pressceramics.
• Absolutely purest raw material
• Organic components only
• Immediate recognition of secondary
contamination
• Finest filtration of the raw material
used
• Protected against contamination by an
acrylic coping.
• Optimum for pressed all-ceramic
Review of literature
Randa Diwan, BDS, Yousef Talic, BDS, B Noura Omar, BDS,
And Walid Sadiq, BDS, Msc The Effect Of Storage Time Of
Removable Partial Denture Wax Pattern On The Accuracy
Of Fit Of The Cast Framework J Prosthet Dent 1997;77:375-81,
• This study - effect of storage time of the wax pattern before
casting and the influence of the palatal major connector
design on the accuracy of its fit on the master casts.
• Two designs -24 hours, 1 week and 1 month
The storage time of wax patterns on the refractory cast had
a significant effect on the accuracy of fit of the connector.
Modified Palatal Plate And
Anterior Posterior Palatal Strap
Design
Conclusions
• Greatest Inaccuracies – 1 Month Storage
Time
• Greatest Discrepancies- Modified Palatal Plate
Major Connector Design
• RPD wax pattern -invested as soon as
possible -1 hour or less.
M. Krane, Dds,a A. Patyk, BS, DDS, Phd,b And L. W. R.
Kobes, Prof Drc Study On The Surface Of Resins That Burn
Without Residues In The Lost-wax
Procedure(J Prosthet Dent 1998;79:389-92.)
• In this study, the surface structure of the
residue-free resins examined were in a range
acceptable for the dental casting technique.
• An increased application of residue-free resins
in dental casting technique is therefore
recommendable.
• These resins could not only complement
waxes or wax/resin compositions, but could
even, in whole or in part, replace them.
Conclusion
• Waxes find great utility in dentistry from
blocking undercuts, making rims,
impressions, wax patterns to casting
• Wide variety available for different uses
• Handling of wax is an art
• Its not only removing of unwanted but
also building-up of what is wanted
References
• Anusavice : Philips’ Science of Dental
Materials
Xth & XIth Edn.
• Craig : Dental Materials : Properties &
Manipulation
VIth, VIIth & VIIIth Edn.
• J. F. McCabe : Applied Dental Materials
VIIth Edn.
• Jack Ferracane : Materials in Dentistry
Principles & Application
• O. Applegate : Essential of R.P.D.
References
• S. Winkler : Essentials of Complete
Denture Prosthodontics
IInd Edn.
• Johnston : Modern practice in Crown &
Bridge Prosthodontics
IIIrd Edn.