A variety of natural waxes and resins have been used in dentistry for

specific and well defined applications.

Waxes are thermoplastic materials which are solids at room temperature

but melt without decomposition to form mobile liquids. They consist of two or

more components which may be natural or synthetic waxes, resins, oils and

pigments.

DEFINITION [GPT 8]

One of several esters of fatty acids with higher alcohols, usually

monohydric alcohols.

PROPERTIES OF WAXES

Melting range

Co efficient of thermal expansion

Transition temperature

Mechanical properties

Flow

Residual stress

MELTING RANGE

Waxes have a melting range rather than a melting point.

Example : paraffin 44 – 620C

carnauba 50 – 900C

Significance:

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Mixing of waxes can change their melting range.

CO EFFICIENT OF THERMAL EXPANSION

Waxes expand when there is increase in temperature and contract when

there is decrease in temp.

Dental waxes have the greatest co-efficient of thermal expansion than

any other restorative materials in dentistry.

Eg: CET of type 1 wax is[ between 220C and37.50C] is 323×10 _6/0C

Significance:

The CET of inlay waxes are high enough that temperature changes in

wax pattern after the establishment of critical dimensional relationships may

serve as a major contributing factor in inaccuracy of finished restoration.

TRANSITION TEMPERATURE

On heating the thermal expansion rate increases abruptly above a certain

temperature

Orthorhombic crystal lattice Hexagonal form

This change is stable and progressive

Significance:

Waxes which need to be rigid should have a transition temp above 370C

eg: inlay wax.

FLOW

Is the slippage of wax molecules over each other. Measure of flow is the

measure of the degree of plastic deformation of material at a given temperature.

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Depends on

♣ The temperature of waxes

♣ Composition of wax

♣ Force causing deformation

♣ Length of time force is applied

Significance:

A greater flow of above 500C or above oral temp helps to record details.

Negligible flow at 370C reduces distortion due to internal stresses.

RESIDUAL STRESSES

Stress remaining in wax as a result of manipulation

May be due to

Occluded air

Processing

Carving

Removal from mold

During storage

Elastic memory of wax

MECHANICAL PROPERTIES

Compressive strength , proportional limit, elastic modulus of waxes are low.

These properties strongly depends on the temperature

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As the temp decreases mech properties improve

COMPONENTS

Dental waxes contain

Natural waxes

Synthetic waxes

Additives

NATURAL WAXES:

1. Minerals:

Microcrystalline

Paraffin

Barnsdahl

Ozokerite

Ceresin

Montan

2. Plants:

Carnauba wax

Ouricury wax

Candelia wax

Japan wax

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Cocoa butter

3. Insect:

Bee’s wax

4. Animal::

Spermaceti wax

SYNTHETIC WAXES :

Acra wax C

Epolene

Aerosol OT

Albacer

Castor wax

Dura wax

Flexo wax

ADDITIVES

Fats

Stearic acid

Glyceryl tristearate

Oils

Turpentine

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Color

Natural resins

Copal

Dammar

Sandarac

Mastic

Shellac

Kauri

Synthetic resins

Elvax

Polyethylene

Polystyrene

CHEMICAL NATURE

Two principle groups of organic compounds :

Hydrocarbons : saturated alkanes

Esters : myricyl palmitate [bees wax]

Some waxes in addition contains free alcohol and acids

CLASSIFICATION

BASED ON USE

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PATTERN WAXES :

Inlay casting wax

RPD Casting wax

Base plate wax

PROCESSING WAXES :

Boxing wax

Utility wax

Sticky wax

IMPRESSION WAXES

Corrective impression wax

Bite registration wax

PATTERN WAXES

Inlay wax

It is a type of pattern wax.

It is used to make patterns for metallic restorations.

Ideal requirements

Inlay wax should be uniformly softened. There should be no irregularities.

It should have good color contrast. This helps to identify the margin

between the die and the wax pattern at the finish line.

It should not flake or chip off during carving.

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It should be smoothly contoured, otherwise it will produce a rough surface

on the casting.

It should be completely eliminated during burnout with no residue.

It should be dimensionally stable from the time of fabrication till the burnout.

When used intraorally it should have good flow at the oral temperature, but

once removed and cooled it should become rigid.

The flow should be more than 70 % at 450C and less than 1 % at 370C

Classification

Classification I (ADA Sp. No. 4)

Type IType I: Medium wax employed in direct technique.

Type II:Type II: Soft wax used for indirect technique for inlays and crowns.

Available as: Blue, green or purple sticks of 7.5 cm length and 6 mm

diameter. Also available as small pellets and cones.

Commercial names: Harvard, Kerr, Peck.

Plastodent C, Jelenko green wax, S-U Dental blue wax, S-U dental green wax.

GC blue, Shofu color

Composition

i. Paraffin wax (40-60%)

Main ingredient.

It determines the melting point.

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Main disadvantage is-it flakes when trimmed. It does not give a smooth

surface, so to modify it other waxes are added.

ii. Ceresin (10%) is added to partially replace paraffin.

Reduces flakiness.

Makes it easy to contour.

iii. Gum Dammar (1%) or Dammar resin

It is a natural derivative from pine trees.

Increases the finish and gives a smooth surface.

Increases resistance to cracking and flaking making it harder.

iv. Carnauba wax (25%)

It has a high melting point.

It increases the hardness.

It decreases the flow at mouth temperature.

It gives glossiness to the surface.

v. Candellila wax

It can be used instead of carnauba wax.

It has a lower melting temperature than carnauba wax.

It is not as hard as carnauba wax.

Synthetic waxes

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In modern inlay waxes, carnauba wax is often replaced partly by certain

synthetic waxes. They have high melting point.

This allows greater paraffin content of the wax which improves working

characteristics.

Properties of inlay wax

1. Flow

Maximum flow

Type I waxes is 1 % at 370C

Type II waxes is 1 % at 300C

Maximum flow-type I and II 75 to 90 % at 450C

Significance:

Type I wax flows well at oral temperature and so can be used for direct

pattern technique.

Type ii is more rigid and needs higher temperature to soften and so used for

indirect technique.

The wax should be softened at 450C and placed into the prepared cavity.

Only at this temperature it has the highest flow. This allows accurate detail

recording.

2. Thermal properties

Coefficient of thermal expansion:

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Inlay wax has the largest CTE compared to any other material used in

restorative dentistry.

It has a linear expansion of 0.7%

Thermal conductivity :

The thermal conductivity of waxes is low.

It is difficult to heat wax uniformly.

There can be contraction during cooling

ii.

Significance:

The pattern can get distorted due to uneven heating and cooling.

This effect is seen during direct technique when there is a difference

between oral temperature and room temperature.

The pattern should not be cooled under pressure as this increases the

coefficient of thermal expansion. This can cause distortion.

Wax distortion:

When waxes are heated they soften but stresses are induced. On cooling

these stresses are released which causes distortion.

Distortion of the wax can occur due to the following reasons:

Improper heating of wax. The wax may not be heated uniformly.

When wax is not held under uniform pressure during cooling.

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When additional wax is added to an existing layer of wax, there is

difference in temperature between layers.

Stresses can be incorporated during carving the pattern.

Wax contracts on cooling to room temperature and this can cause distortion.

Gas bubbles can get incorporated during fabrication. The escape of these

gases can lead to distortion.

Constantly changing the manipulation temperature by reheating and cooling

(pooling of wax) the pattern can induce stresses.

Prevention

Some of the factors causing distortion are inherent to the property of waxes

and cannot be completely eliminated.

It can be minimized by the operator.

Minimal carving and avoiding reheating the layers of wax.

Uniform temperature of wax by uniform heating.

The stresses are released over a period of time, so by investing the pattern

immediately distortion can be minimized.

Heating instruments for carving uniformly.

A wax bath can be used. The wax is usually uniformly melted at the ideal

temperature and the die is dipped into the wax bath.

If necessary, it should be stored in a fridge.

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Uses: Patterns for inlays, crowns and bridges is first made in wax, and then

converted into metal or ceramic by casting.

Effect of physical properties of waxes on investments and casting shrinkage

[JPD1996].

The flow charac, bending strength, and softening temp of 6 industrial and 7

dental waxes were studied.

A direct relation between flow of wax and casting shrinkage was found.

It was found that as flow increased casting shrinkage decreased.

If a wax with a low flow and high strength is used, a larger casting ring

should be considered.

A study on heating and cooling of crown wax patterns [JPD 1994].

6 Different waxes were studied.

Conclusion: increase in flow by increase in temp was shown in the range of

370C -470C for majority of the materials

Rate of expansion varies during increase in temp ie. Transition temp

Most mat show flow by 61%-82% at 470C -520C

Manipulation of Inlay Wax

i. Direct Technique

It is called so because the prepared cavity is recorded directly. The pattern is

then invested.

The inlay wax is manipulated over an open flame.

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The stick should be rotated over the flame for uniform heating.

It is then placed into the cavity under finger pressure.

It should be allowed to cool gradually to mouth temperature.

The pattern should be handled to the minimum to prevent temperature

changes.

It is then invested.

The main advantage of this technique is that it saves time because there is

no need to prepare a die.

ii. Indirect Technique

Pulled pattern technique

A die is prepared from the impression.

The die is coated with a die spacer to provide space for luting agent.

A die lubricant is applied for easy removal of the pattern.

The die is dipped into a wax bath with melted inlay wax (dipping method).

The pattern is made by adding additional layer of waxes (incremental wax

addition technique)

Finally wax pattern is carved finished and polished with silk cloth.

Precautions

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Should not be softened with warm water as solvents leach out and splattering

can occur due to presence of water.

Invest all wax patterns as soon as possible to avoid distortion.

Prolonged heating should be avoided as it causes the wax to evaporate.

Accuracy of wax, auto polymerized, and light-polymerized resin pattern

materials.

When measured on intra- and extra coronal master dies, the light

polymerized, diacrylate resins had equal or better marginal fit, compared with

wax or auto polymerized acrylic resin, and were less affected by placement

technique and storage.

Casting wax

It is a type of pattern wax.

Classification (According to FDI Specification No. 140)

i. Class A 28 gauge, pink

Flow of about 10 % at 350C.

Easily adaptable at 40 to 450C.

ii. Class B 30 gauge, green

Minimum flow of 60 % at 380C.

Adapts well to the surface.

not brittle on cooling.

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iii. Class C readymade shapes, blue

Will burnout at 5000C leaving no carbon residue

Supplied As

Sheets 0.40 and 0.32 mm thickness.

Readymade shapes

Round (10 cm), half round and half pear shaped rods.

Mesh work.

Readymade sheets or in bulk.

Shaped like clasps.

Commercial name :metrodent casting wax, SPI wax

Composition

Paraffin wax

Ceresin

Beeswax

Resins

Other waxes

Base Plate Wax

It is a type of pattern wax used mainly in preparing wax patterns for

prosthesis.

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Classification (ADA Sp. No. 24)

Type I-Soft: For building veneers.

Type II-Medium: To use intraorally (in normal climates not in too warm

climates).

Type III-Hard: For use in tropical climates

Supplied as: Sheets of pink or red color.

Composition:

Generally consist of

hydrocarbon waxes-70 to 80%.

Paraffin or ceresin 8%

Beeswax 12.0%.

Carnauba 2.5%.

Natural or synthetic resins 3.0%

Microcrystalline 2.5 %

Other coloring agents.

Requirements

Linear expansion not greater than 0.8%

Should not flake during carving.

Softened sheets should cohere at 230C.

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Smooth finish on flaming.

Coloring should not stick to the plaster surface during flasking.

Uses: These waxes are used for the following purposes

Used in making occlusal rims. These are used to record jaw relations for

complete denture patients.

They can be used to fabricate patterns for removable partial denture.

To make patterns for prostheses which are processed in acrylic resins.

Processing Waxes

Processing waxes are those waxes used in the laboratory procedures for

the construction of restorations and appliances, e.g. boxing wax, beading wax,

utility wax and sticky wax.

Boxing Wax and Beading Wax

Use: Beading wax is adapted around the impression borders to create the

land area of the cast.

Boxing wax is used to build up vertical walls around the impression in order

to pour the gypsum product to make a cast base.

Supplied as: Boxing wax as sheets, beading wax as strips.

Composition

Boxing wax may contain.

Low melting hydrocarbon waxes.

Beeswax.

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Properties

Smooth and glossy on manipulation over a flame.

Seals easily.

Pliable at 210C.

Does not distort at 350C.

Commercial name : metro boxing in wax, cavex , kerr, metro ribbon wax

Uses

Beading and boxing procedure: It is a laboratory procedure after final

impression making for complete denture patients.

The beading wax is usually a thin rope of wax which is pliable at room

temperature.

This wax is adapted and fused to the margins of the impression.

Onto the beaded margins the boxing wax is adapted and the impression is

poured.

The final cast should have 2 to 4 mm of land area around the sulcus which

will be formed by the beading wax.

The cast should have a height of about 10 to 15 mm in the deepest portion.

This height of the cast is formed by the boxing wax.

Advantages

Preserves the anatomic contours.

Gives a definite thickness to the borders.

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It gives a definite form and thickness to the base.

Conserves laboratory material.

Utility Wax

Composition

Beeswax.

Petrolatum.

Resins.

Supplied as: It is available in the form of sticks and sheets. Orange or dark red in

color. In orthodontics, periphery wax is white in color.

Properties: Flow at 37.5 0C- min 65 % and max 80% . Pliable and tacky at 21-

240C.

Uses

It can be used to alter the stock tray extensions.

The following alterations can be made

• Height of the tray can be increased

• The posterior extensions can be increased.

• The palatal vault depth can be increased.

Sticky Wax

Composition

Yellow beeswax

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Rosin

Natural resins such as gum dammar.

Supplied as: Yellow colored sticks.

Properties

Sticky when melted, with a max 5 %flow at 300C and 90 % at 430C.

It adheres closely to the surfaces when applied to it.

If movement occurs the wax tends to fracture than distort.

The pieces can be easily joined in a proper relationship.

At room temperature the wax is brittle and breaks easily.

Uses

It is used to align fractured parts of acrylic dentures.

It is used to align fixed partial denture units before soldering.

It is used to seal a plaster splint to the stone cast during porcelain firing.

Impression waxes

Wax in combination with resins of low melting point can be used in

corrective impression technique in partial and complete denture prosthesis. The

peculiarity of impression wax is that they flow at mouth temperature.

Availability : sheets or cakes

Commercial names

Korecta wax, Kerr's impression wax, Iowa wax, Aluwax

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Korecta waxes are available in four grades.

The physical properties vary to make each more capable of serving a

particular function

THE NO.1 WAX

* Colour is tissue pink

* Very hard with practically no flow at mouth temperature

* Principal use is to support and extension of the impression wax when there

is need to carry it beyond the border of the temporary base.

* It congeals very quickly. Also it shows very little shrinkage. Hence used for

final wax-up of porcelain or resin teeth after they have been adjusted to the

desired position.

* It is also be used as a support to reposition the extension partial denture for

a short period of wear before making the rebase impression.

THE No.2 WAX

• Colour is yellow

• Has slight flow at body temperature

• Its ability to adapt very slowly to the ridge structures makes its useful as a

temporary lining of a base which should be worn for a short time.

THE No.2 wax

• Colour is yellow

• Has slight flow at body temperature

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• Its ability to adapt very slowly to the ridge structures makes its useful as a

temporary lining of a base which should be worn for a short time.

NO. III WAX

• Colour is red

• Flow greater than No. II wax but less than impression wax

• Used to correct minor areas of discrepancy placing the impression wax.

NO. IV WAX

Colour is orange

High rate of flow at body temperature

Used for making correctable impression

Must always be carried by a temporary base when it is recording the

supporting contour of the sub basal structures.

Must have sufficient flow to allow the release of any excess waxes in a

reasonable length of appointment time.

REQUISITIES

• A series of waxes is needed, each adapted to a special use.

• Each wax should be distinctly coloured for easy and positive identification.

• Adhesiveness is necessary in order to secure proper binding of successive

layers.

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• In this series, one wax should be sufficiently hard and strong to give

adequate reinforcement of an extended periphery.

• The wax surface should become glossy when it is receiving tissue support

• Should give a smooth surface with fine details accurately recorded.

• Possess sufficient flow at mouth temperature so that any excess can escape

to the periphery, thus preventing any surface impingement beneath the

extension base.

MELTING IMPRESSION WAXES

To avoid over heating, melting of the wax should be done in a

double boiler. Where additions are needed, these waxes can be added most

smoothly if they are kept at about 200-2100F.

Double boiler

Application of impression waxes

The brush used should be medium stiff bristles about 3/8 inch in length.

A separate brush should be used for each kind of wax needed in a given

impression.

Taking impression

It records the mucous membrane and underlying tissues in a

functional state. It is loaded on the tissue surface of a cast removable partial

denture frame work or complete denture. It records the tissue details under

masticatory load. The cast should be poured immediately as distortion may

occur.

Impression is properly completed

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• All the contacting surface is glossy

• The roll or turn at the wax periphery is continuous.

3. The appliance has been kept under continuous seating pressure for along

enough period (8-12min.) to let any excess wax escape to the periphery.

4. No areas of base showing through impression

5. The periphery has been thickened to record the bulk which the cul-de-sac

structures can accommodate.

The impression has been removed from mouth without having the

periphery marred or distorted by coming in contact with tongue, cheek or

anything which could deform it.

IOWA WAX

The Iowa wax was developed for use in recording the functional or

supporting form of an edentulous ridge.

It may be used either as a secondary impression material or as an

impression material for relining the finished partial denture to obtain support

from the underlying tissues.

Mouth temperature waxes vary in their working characteristics.

Among these are the Jelenko Adaptol impression material and the stalite

impression material.

Both of these have a more resinous base.

They are designed primarily for impression techniques that attempt to

record the tissues under an occlusal load.

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Iowa wax will not distort after removal from the mouth at ordinary room

temperatures.

But the more resinous waxes must be stored at much lower temperatures

to avoid flow when they are out of mouth.

Resinous bases are not ordinarily used in partial denture impression

techniques, except for secondary impressions.

Uses

• Ideal for atrophic or knife edge residual ridge.

• Mainly used for functional impression for removable partial dentures in free

end saddle situations. For recording posterior palatal seal region in complete

denture fabrication.

• Used as a secondary impression material or as an impression material for

relining the finished partial denture to obtain support from the underlying

tissues.

• Also used to correct borders of impression made from other rigid material.

Advantages

♫ Easy to manipulate.

♫ Given sufficient time they allow a rebound of tissues that have been forcibly

displaced.

♫ They record tissues without over displacement and ensure uniformity of

support for the partial denture framework..

♫ They also have the advantage of being correctable.

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Disadvantages

♫ Can be easily distorted

♫ Not dimensionally stable

♫ Time required for manipulation

♫ Complex armamentarium.

Bite registration wax: is used to articulate certain models of opposing

quadrants.

Bite registrations are also made from 28 gauge casting wax sheets or

hard base plate wax.

Almore bite registration wax

Aluwax bite wafers

SUMMARY

From the early use of bees wax for impression to current techniques

such as casting or interocclusal records, waxes are among the most popular and

useful of dental materials. They are economical, suited for many purposes.

Proper knowledge of certain critical characteristics- such as effect of heating on

flow, thermal expansion and distortion – will enable easy effective and efficient

handling of the material.

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