Dental waxes

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DENTAL WAXESPRESENTED BY

DR.HASHMAT GUL

DEMONSTRATOR

DENTAL MATERIALS DEPT.

INTRODUCTION

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WAXES

� DEFINATION

Waxes are thermoplastic materials which are normally solids at room

temperature but melt without decomposition, to form mobile liquids.

� ORIGIN OF WAXES

MINERAL ANIMAL PLANT

1) Paraffin 1) Bees 1) Carnauba

2) Microcrystalline 2) Candela

DENTAL WAXES

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DENTAL WAXES

� DEFINATION : Dental waxes are thermoplastic moldable materials

that are solids at room temperature.

� GENERAL COMPOSITION OF DENTAL WAXES

• Hydrocarbon (e.g. Paraffin )* or Ester types

• High or low MW Acc.to desired properties

•Constitute the main bulk

Base wax

• Hydrocarbon or Ester type

• High or low MW Acc.to desired properties

• Traces To impart the desired properties in the final product

Modifier

Colorant

DENTAL WAXES-BASE WAX

BASE WAX

� Paraffin

� Microcrystalline

� PARAFFIN

� The major component of almost all dental waxes

� Obtained by fractional distillation of petroleum.

� Linear hydrocarbon

� Low MW (a couple dozen carbon atoms long) just high enough that it is

solid at room temperature.

� Not pure as a mixture of hydrocarbons

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DENTAL WAXES-MODIFIERS

MODIFIERS� Normally Dental waxes consist of two or more components which

may be natural or synthetic waxes, resins, oils, fats and pigments.

� Blending is carried out to produce a material with the desired properties for a

specific application e.g.

Wax Desired Property imparted by the Modifier wax

1). Bees Wax � Less brittle

� Increase stickiness

2). Carnauba wax &

Candelilla wax

� Control the softening temperature.

� Carnauba tend to increase the hardness and water resistance.

3).Micro- crystalline

wax

� Raise melting point.

� Lower the softening temperature

� Lower brittleness.

PROPERTIES OF DENTAL WAXES

� THERMAL PROPERTIES

� The softening temperature

� Melting point

� The coefficient of thermal expansion which affect

� Accuracy

� Dimensional stability

� MECHANICAL PROPERTIES

� Flow & Creep

� Brittleness & Toughness

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�THERMAL PROPERTIES

THE SOFTENING TEMPERATURE

� Also called SOLID-SOLID TRANSITION TEMPERATURE

� All the waxes used in dentistry have

� a predominantly crystalline structure

� a well-defined melting point

� On heating, a second endothermic peak exists at a temperature somewhat lower than the melting point. This peak is indicative of a solid– solid transition involving

� Change in crystalline structure of the wax , accompanied by a change in

mechanical properties i.e.

Brittle solid Softer, moldable material

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MELTING POINT: It is the temperature at which the wax converts into liquid-state & began to flow.

METHODS OF SOFTENING WAX PRIOR

TO MOULDING INCLUDE :

� A Bunsen burner

� A water bath

� An infra-red lamp

� A Wax Annealer

� Waxes are very poor thermal conductors and must be maintained

above the solid-solid transition temperature for long enough to allow

thorough softening to occur throughout the material. *

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THE COEFFICIENT OF THERMAL

EXPANSION

� DEFINATION : The fractional change in size per degree change in temperature at a constant pressure.

� Waxes exhibit high values of The coefficient of thermal expansion which affect

� Accuracy

� Dimensional stability

� PROBLEMS

� On cooling waxes undergo thermal contraction.

Low thermal conductivity values uneven Cooling* internal stresses Dimensional changes.*

� Greater stresses may also be incorporated if the wax is not properly softened before moulding

� MECHANICAL PROPERTIES

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FLOW & CREEP

� A major factor which determines the moldability and stability of a wax is

its flow value. This property is related to creep. *

� To prevent distortion , Waxes should, ideally, exhibit

� considerable flow at the molding temperature.

� little or no flow at mouth temperature or room temperature .

� CREEP AND FLOW ARE BOTH MEASURED by applying a load (2 kg) to a

cylindrical specimen (10 mm diameter by 6 mm height) and measuring

the extent to which the specimen becomes compressed after a given

time(10 min).

� The flow is recorded as the percentage change in the height of the

cylinder.

BRITTLENESS & TOUGHNESS*

� BRITTLENESS & TOUGHNESS are the important properties which the

manufacturers can, to some extent, control.

� EXAMPLES

� FOR DENTURE WAXES, toughness is required since the wax denture

base may have to be removed from a slightly undercut cast many

times without fracturing.

� FOR INLAY WAXES, brittleness is preferred in order that the wax will

fracture rather than distort on removal from an undercut cavity. This

will indicate to the dental surgeon that a modification to the cavity

shape is required

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CLASSIFICATION OF DENTAL WAXES

1. PATTERN WAXES

�Are used in the construction of metal

castings & bases for dentures through lost

wax technique.*

� TYPES

1) Inlay wax

2) Casting wax

3) Baseplate wax/Modeling wax

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PATTERN WAXES-Inlay wax

� COMPOSITION

� Paraffin + Carnauba + Ceresin + Beeswax + Colorant.

a) 60% Paraffin (and Microcrystalline) Wax = BASE Wax

b) 25% Carnuba (and Candelilla) Wax = MODIFIER Wax

c) 10% Ceresin = MODIFIER Wax

d) 5% Beeswax = MODIFIER Wax

e) < 1% Colorants = COLORANT

� USED to produce patterns for metal casting using the lost wax tech.e.g. inlays, onlays , crowns & pontics


� SUPPLIED IN:

�Several forms: sticks, pellets & tins.

�Dark colours : blue or green.

�They are labelled : hard, medium & soft (acc. to their

melting ranges).

�They are not sticky to touch

� REQUIREMENTS :

a) Good adaptation to dies .

b) Thermal stability at low temperatures.

c) Complete pyrolysis at high temperatures.

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� TYPES : There are two types:

� Type 1 Soft Indirect tech

� Type 2 Hard Direct tech


a). TYPE II INLAY WAX:

� Used directly in the mouth , softened & placed into

the prepared tooth in the direct waxing technique.*

� Has a lower melting range for the comfort of the

patient & the accuracy of the wax on removal.

� Has a softening point slightly higher than the mouth

temp.

�All the limitations of the mouth must be considered.

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b). Type I INLAY wax:

� More frequently used, where wax is melted onto a die outside the mouth in the indirect technique.*

� Softening temp. lower than mouth temp. for indirect tech.

� Most dentists prefer to use this & have a dental laboratory technician produce the wax pattern and casting.

INLAY WAXPhysical Properties – Melting Range

COMPOSITION (%)

TE

MP

ER

AT

UR

E (

C)

Paraffin Carnuba

40

30

20

60

50

70

80

90

25 50 75 100

LIQUID

LIQUID + SOLID

SOLID

Melting Onset (Solidus)

Melting Completion (Liquidus)

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INLAY WAXPhysical Properties – Thermal Expansion of Components

250ppm/°°°°C

0 25 30 40 4535 50

0

1.2

1.0

0.8

0.6

0.4

0.2

TEMPERATURE (C)

EX

PA

NS

ION

(%

)

KERRHARDWAX

INLAY WAXMechanical Properties & Chemical Properties

� MECHANICAL PROPERTIES:

1) Flow < 1%

2) Ductility = moderate

3) Residual Stress = none

� CHEMICAL PROPERTIES:

1) Homogeneity = good

2) Contact Angle = low

3) Oxidation = complete

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PATTERN WAXES-CASTING WAXES

� USED to construct the metal framework

of partial and complete dentures.

�Comes in sheets & preformed shapes.

� The physical properties are similar to

inlay wax except the melting range.

� The melting range is only important for

laboratory procedures, because

these waxes are not softened in mouth.

PATTERN WAXES-BASEPLATE WAX

� Also called Modelling wax.

� They are sheets of wax generally pink in

color to simulate the color of the gingiva.

� USES

1) Occlusal or bite rims *

2) Spacer in custom trays.

3) Pattern for plastic portion of dentures.

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� TYPES

� Type 1 soft wax building contours & veneers.

� Type 2 hard wax Used in Temperate climate.

� Type 3 extra hard most commonly used ‘coz it is hard

at mouth temperature.

� COMPOSITION

� paraffin wax and bees wax

� SOFTENED in Water bath to ensure even thickness of sheets.


� REQUIREMENTS

1) The wax must not distort at mouth temperatures.*

2) Should be tough in order to reduce the chances of fracture/distortion during removal from the stone model or shallow undercuts.

3) They can easily be trimmed with a sharp instrument without tearing, chipping or flaking atroom temperature.

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2.PROCESSING WAXES

� Used primarily to aid in dental procedures both clinically & in laboratory.

� TYPES

� Boxing wax

� Utility wax

� Sticky wax

� Alu wax

� Carding wax

PROCESSING WAXES- BOXING WAX

� USED to form the base portion of a gypsum

model.

The 1.5-inch-wide, red strip of boxing wax is

wrapped around the impression to produce a

form into which the gypsum is poured.

� MANIPULATION

� Easy

� Slightly tacky at room temperature,

allowing it to adhere to itself to secure

the boxed form.

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PROCESSING WAXES-UTILITY WAX

� Also called periphery wax

� Comes in ropes and sheets that are

easily

manipulated at room temp.

� Various colours of pink, white & red.

PROCESSING WAXES-UTILITY WAX

� USES OF WAX ROPES:

1). To adapt the periphery of the impression tray to customize the tray & aid in patient comfort.

Provide a better fit into the vestibule & control the movement of the impression material.

2). To cover sharp brackets and wires in orthodontic patients.

� USE OF WAX SHEETS:

1) May be layered to form a horseshoe shape & used for wax bite registrations

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PROCESSING WAXES-STICKY WAX

� Used to adhere components of metal,

gypsum, or resin together temporarily

during fabrication & repair.

� It comes in orange sticks that are hard &

brittle at room temp, but when heated

under flame become soft & sticky.

� Because it is brittle, even the slightest

torque will fracture the wax.

(Important alert for the operator).

PROCESSING WAXES-ALU WAX

� USED to get occlusal registration.

� Contains aluminium particles and it is brittle.

� Available in thin & thick sheets.

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PROCESSING WAXES-Carding wax

� Used by manufacturers for

attaching denture teeth to

display sheets.

3.IMPRESSION WAXES

� USED

� To obtain impressions of the oral structures.

� TYPES

1) Corrective Impression waxes

2) Bite-Registration waxes

� Bite-wafers

� Occlusal-indicator wax

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IMPRESSION WAXES-Corrective impression wax

� USED to correct small imperfection (e.g. airblows) in other impressions,

especial zinc oxide impressions(edentulous imp).

� Are thermoplastic materials, which flow at mouth temperature and are soft a room temperature. They do not set by chemical reaction.

� CONSIST OF paraffin wax and beeswax in a ratio of approximately 3:1 to ensure the wax flows at mouth temperature.

� DISADVANTAGE: Easily distorted so, A cast should be poured up immediately after taking the impression . These materials are not commonly

used.

� Replaced by ELASTOMERIC IMPRESSION MATERIALS.

IMPRESSION WAXES- BITE REGISTRATION WAX

1- BITE WAFERS:

� It is used to produce wax bite registrations for articulation of models.

� The preformed horseshoe shapes are often reinforced with metal particles to provide stability.

� It is susceptible to distortion at temp slightly higher than mouth temp.

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IMPRESSION WAXES-BITE REGISTRATION WAX

2. OCCLUSAL INDICATOR WAX:

� Used to detect areas of premature occlusal contact.*

�Supplied in scored strips & is dark green, yellow or blue in colour.

Health & Medicine

Dental waxes