Impression materials / dental implant courses by Indian dental academy

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INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS
 Introduction
 Definition
 History
 Classification
 Requirements of an Impression Material
 Impression Compound
 Zinc Oxide Eugenol Impression Paste
 Impression Plaster
 Impression Waxes
 Conclusion
 References www.indiandentalacademy.com

INTRODUCTION
 An impression, in general terms, is a mark produced on
a surface by pressure.
 The word “impression” is derived from the Latin word
impression.

DEFINITION
 Impression Material –
Any substance or combination of substances used for
making an impression or negative reproduction.
(GPT-2001).
 Impression-
A negative likeness or copy in reverse of the surface of
an object, an imprint of teeth & adjacent structures for
use in dentistry.(GPT-2001).

HISTORY
 Before middle of the 18th
century- Blocks of ivory & bone as IM.
 During 18th
century – Bees Wax, used in making impression.
 1786 Phillip Ptaff – Sectional wax impression of half arch at a time.
 1st
plaster model.
 1842 Montogomery – Discovered gutta percha.
 1848 Colburn & Blake – Gutta percha as IM.
 1844 Wescott, Dwinelle & Dunning – Used Plaster of Paris as IM.
 1857 Chales stens of England - Discovered & introduced modelling
plastic.
 J.W. Greene, P.T. Greene – 1900 – Discussed about manipulation of
Modelling plastic
 1925 Alphous Poller – 1st
suggested use of agar for dental impressionswww.indiandentalacademy.com

 1937 Sears – 1st
Recommended reversible hydrocolloid for fixed
prosthodontics.
 Late 1920’s – 1st
True functional impression waxes developed.
 1922 Everett – Used Fluid wax of 3 consistencies
 1930 Applegate – Series of true physiologic waxes developed.
 Early 1930’s A.W. Ward & E.B.Kelly – Gave impetus to ZOE
 1939 Trapozzano – Early techniques using ZOE paste.
 S.S. Wilding – Patent to use algin for impression.
 1936 Alginate- 1st
American patent.
 Middle 1950’s – Elastomeric impression materials introduced.
 1955 Pearsen – New elastic impression material of polysulphide base.
 1960’s – Polyethers introduced in Germany.www.indiandentalacademy.com

CLASSIFICATION
Impression Materials
Elastic Inelastic
Hydrocolloid Rubbers -Impression compound
Agar Alginate -Impression waxes
- Impression plasters
Mercaptan Polyether Silicones -ZOE
Condensation Addition

Other ways to classify :-
1. By their generic chemical name:-
eg. One may refer to silicone materials or ZOE materials.
2. According to the manner in which they harden:-
Chemical reaction Temperature change
(irreversible) (reversible)
- Plaster of Paris Thermoplastic Non Thermoplastic
- Zinc oxide Eugenol - Impression -Agar
- Alginate compound

3. According to the uses of materials in dentistry:-
a) Materials used for obtaining impressions in dentulous mouth-
- Alginate
- Agar can also be used for edentulous
- Non aqueous elastomers impressions
b) Materials used for obtaining impressions of edentulous mouth-
- Impression compound
- Impression plaster
- Zinc oxide Eugenol
- Wax

4. According to the viscosity or the tissue displacement:-
Mucostatic Mucocompressive
Impression plaster Agar Alginate Impression compound
5. According to the ability of the set material to be
withdrawn from undercuts:-
- Elastic
- Inelastic

REQUIREMENTS OF
IMPRESSION MATERIALS
 The requirements of impression materials can be discussed
as follows:
1. Factors which affect the accuracy of the impression.
2. Factors which affect the dimensional stability of the
impression.
3. Manipulative variables such as ease of handling, setting
characteristics etc.
4. Additional factors.

1. Accurate reproduction of surface detail:-
a) Rheological properties:-
- A low viscosity or a degree of pseudoplasticity is desirable.
b) Ability of impression material to adapt closely to both the soft &
hard tissues:-
- The way in which the materials interacts with saliva affects the
fine detail reproduction.

2. Dimensional accuracy & stability:-
a) The type of impression tray:-
i) The rigidity of the tray:-
- It may influence the accuracy of impression when
Flexible trays are used
ii) Tray bond with impression material:-
- A good bond between the tray & the impression material is
important.

b) Shrinkage of the impression material:-
- Whether impression material sets by a chemical reaction or some change in
physical state, both usually result in some shrinkage of impression material.
i) Tray contracts & reduces the impression space.
ii) The impression material contracts towards the tray & es the impression space.

c) Permanent set:-
- The impression material must be sufficiently flexible to allow
removal from the undercut regions without causing distortion.
- Elastic materials must be used, as most are actually viscoelastic
materials, there is a possibility of some permanent deformations.
- Degree of distortion depends upon:-
i) Severity of undercut
ii) Thickness of impression material
iii) Time impression is kept in compressed state

d) Good resistance to tearing:-
- On removing elastic impression materials from undercut areas,
they are often put under a considerable tensile stress.
- Impression materials should have sufficient mechanical strength
not to tear or undergo permanent deformation during removal.
- The thickest part of impression are
compressed against the tray
when they pass the widest part
of the tooth crown.

e) Storage stability:-
- There is usually a significant delay between the making of an
impression & when the model is poured.
- Therefore, it is important that the impression material neither
shrinks, nor expands, nor distorts at all normal degrees of
temperature & humidity during this time period.
f) Compatibility with model & die materials:-
- It is undesirable that the choice of the material for making casts
should be governed by the impression material.

3. Manipulative variables:-
a) Setting time:-
- Impression materials should have a setting time under the control
of the operator.
- For convienence & comfort, ideal impression material has a long
working time & short setting time.
b) Setting temperature:-
- The impression material should set or harden at or near mouth
temperature.
c) Ease of manipulation:-
- The setting characteristics of the material have an important effect
on ease of handling. www.indiandentalacademy.com

4. Additional factors:-
1. A pleasant odour, taste & esthetic color.
2. Absence of toxic or irritant constituents.
3. Adequate shelf life for requirement of storage & distribution
4. Economically commensurate with the results obtained.
5. Easy to use with the minimum of equipment.
6. Setting characteristics that meet clinical requirements.
7. Satisfactory consistency & texture.
8. Readily wets oral tissues.
9. Elastic properties with freedom from permanent deformation
after strain.

10. Adequate strength so it will not break or tear on removal from the
mouth.
11. Dimensional stability over temperature & humidity ranges
normally found in clinical & laboratory procedures for a period
long enough to permit the production of a cast & die.
12. Compatibility with cast & die materials.
13. Accuracy in clinical use.
14. Readily disinfected without loss of accuracy.
15. No release of gas during the setting of impression or cast &die
materials.

IMPRESSION COMPOUND
- One of the oldest dental impression materials.
- It is rigid, thermoplastic material with a glass transition
temperature of about 39ºC.

USES:-
1. As a preliminary impression for the construction
of individual trays.
2. To modify the fit of stock trays.
3. As a base in wash impression techniques.
4. To obtain peripheral seal.
5. For compression impressions.
6. In operative dentistry.

COMPOSITION:-
Ingredient Parts
1) Rosin 30
2) Copal resin 30
3) Carnauba wax 10
4) Stearic acid 5
5) Talc 75
6) Coloring agent Appropriate amount
- Composition varies from one product to another.

1. WAXES:
- Bees wax was used as an impression material & it may still be
one of the ingredients in some modern products.
- They are tasteless, odourless, colourless & greasy to touch.
- Waxes used in impression compound include beeswax &
colophany.

2. RESINS:
- They are amorphous organic substances, insoluble in water.
- Naturally occuring resins used in impression compound are
shellac, dammar, rosin or sandarac.
- This component is primarily responsible for the transition from a
solid to a liquid state.
3. PLASTICISERS:
- Waxes & resins, if used on their own, would tend to produce a
brittle material with a tendency towards tackiness.
- Brittleness is overcome by the addition of plasticisers, such as
shellac, glycerin, gutta percha & stearic acid.

4. PIGMENTS:
- A variety of pigments of coloring agents are added for the
purpose of identifying different brands or those of different
softening temperatures.
- Rouge, which produces a characteristic red color, is the most
common pigment.
5. FILLERS:
- Inert materials, added to strengthen or change the physical
properties of impression compound.
- They are chemically distinct from the principal ingredients.

- Waxes or resins are the principal ingredients & compose the matrix.
- Matrix is mostly non-crystalline in order to know the desirable
thermoplastic properties of the compound.
- This results in a relatively high flow & a low strength even at room
temperature.
- Consequently, a filler is added that can reduce the plasticity of the
matrix material by frictional action.
- Hence, both, the viscosity at temperatures above that of the mouth &
the rigidity of the compound at lower temperatures will be enhanced.
- Fillers also reduce the adhesiveness of the softened material to the
oral tissues & minimises shrinkage due to thermal contraction.

TYPES:-
• Based on the variation of the temperature at which softening takes place:-
1. High- fusing or Tray compound/ Type II compound
2. Low- fusing or Impression compound/ Type I compound
- Tray compound is used in the construction of dentures to form a tray
that can be employed with other types of impression materials for
reproducing the mouth tissues.
- Type I compound is referred to as a true impression compound & is used for
impressions of edentulous mouths.
- Tray compound is more viscous when it is softened & more rigid when it is
hardened as compared to impression compound.www.indiandentalacademy.com

PROPERTIES:-
1) Fusion Temperature:
- The “plateau” or horizontal straight- line portion of the curve,
characteristic of a pure crystalline material is ill- defined.
- The fusion temperature of approx. 43.5ºC is not a solidification
temperature since the glass transition temperature for this
particular compound is approx. 39ºC.www.indiandentalacademy.com

- The practical significance of fusion temperature is that it
indicates a definite reduction in plasticity during cooling.
- The fusion temperature of impression compound should
be such that at the time of insertion it should flow
enough to register the details of the oral mucosa & not
cause discomfort or tissue irritation.
2) Thermal Conductivity:
- Thermal conductivity is low.
- During softening of the material, the outside always softens first
& the inside last.

3) Thermal Contraction:
- The average linear contraction of impression compound from
mouth temperature to room temperature of 25ºC may vary
between 0.3 & 0.4%.
- The volume expansion over the same temperature range may be
as great as 1.38 to 2.29%.

4) Flow:
- The flow of impression compound can be beneficial or it can be a
source of error.
- The compound should soften at a point just above mouth
temperature & in this state exhibit adequate flow to adapt closely
to the tissues & register surface detail.
- Once the compound has solidified, any deformation should be
completely elastic, so that the impression can be withdrawn
without distortion of flow.

- The flow properties at mouth temperature (37ºC) & slightly above
45 ºC are very important.
- Minimum flow is required at mouth temperature, but sufficient
flow is needed at a temperature
only 8ºC above mouth
temperature to record the detail
in the impression.
- Compounds have widely differing
flow values between 1& 8% at
37ºC & between 81&93% at 45ºC.

- The higher amount of flow required of the impression compound at 45ºC is based on
its use as a final impression material,where as the tray compound is used only for
the initial impression(tray), & a second impression material such as zincoxide
eugenol paste will be used in the tray to record the final impression.
- Impression compound is the most viscous of the impression materials. Viscosity is
about 70 times greater than that for impression plaster & more than 100 times
greater than values for some of the light- bodied elastomers.
- The very high viscosity of impression compound is significant in 2 ways:-
1) It limits the degree of fine details which can be recorded in an impression.
2) It characterizes compound as a muco-compressive material.

5) Dimensional Stability:
- Softening the compound by a method that will not affect its physical properties
adversely by overheating or prolonged heating is important.
- In the mouth, adequate cooling of the compound is essential to avoid distortion
when the impression is removed.
- If the surface of the compound is hard, but the inside is soft, a relaxation will
occur immediately after the impression is withdrawn.
- Storage in a warm environment or for extended periods of time promotes
dimensional changes.
- So, a cast or die should be constructed as soon as possible after the impression
has been obtained – at least within the first hour.

- 3 factors that combine to produce significant internal stresses within
the compound impression are:-
1) The high value of coefficient of thermal expansion.
2) The poor thermal conductivity.
3) The relative large temperature drop from softening temperature to room
temperature.
6) Reproduction of Details:
- Impression compound has a high viscosity, so reproduction of
surface detail is not very good.
7) Rigidity:
- Impression compound is fairly rigid after setting & has poor elastic properties.

Clinical Presentation of the Compound:-
- For recording prosthetic impressions, such as preliminary
impressions of edentulous arches the material is supplied in
rectangular/circular sheets about 5-7.5 cm and 0.65 mm thick.
- Peripheral seal materials, supplied as stick forms of 10 cm long and
1cm in diameter are used for border extensions on impression trays.
- For copper brand impressions of inlays and crowns, the material is
supplied in stick form. Working temperature of green stick is
l22-129 °F black stick is 133-135 °F.

Manipulation:-
Cooling:-
Disinfection of the Impression:-
- The impression should first be rinsed to remove blood, debris &
saliva.
- Disinfection is done by immersion for a minimum of 10min. &
maximum of 30min.in a glutaraldehyde(eg. Cidex) or an iodophor
(eg. Biocide).
- A 20min. immersion in 2% ID210 solution has no adverse effects
on the dimensional stability or surface detail reproduction.
- ID210 is a virucidal, synergistic combination of aldehydes,

- Zinc-oxide eugenol impression pastes produce a rigid
impression with a high degree of accuracy & good
reproduction of surface detail.
ZINC-OXIDE EUGENOL
IMPRESSION PASTE

USES:-
1) Cementing medium
2) Surgical dressing
3) Temporary filing material
4) Root canal filling material
5) Temporary relining material for dentures
6) For stabilization of base pastes in bite registration
7) Bite registration material
8) In full denture prosthodontics to register final impressions under
saddle areas at try-in of the cast framework.
9) In partial denture prosthodontics as corrective washes.
10) In cases exhibiting pronounced nausea.

TYPES:-
- Impression pastes may be classified on the basis of eugenol content
as:
1) Eugenol containing impression pastes
2) Non-eugenol pastes
- ZOE impression pastes are available in 2 types as hard & soft set.
- Soft set material is tougher& not as brittle.
- Hard set material generally has a more fluid consistency when
mixed, a shorter final setting time & a higher resistance to
penetration when set.

COMPOSITION:-
- The major constituents are zinc-oxide & eugenol with additional
components.
- This impression material is dispensed as two separate pastes.
Tube No. 1
1) Zinc oxide 80-87%
2) Fixed vegetable or mineral oil 13-15%
Tube No. 2
1) Oil of Cloves/eugenol 12-15%
2) Gum or Polymerised rosin 50%
3) Filler 16-20%
4) Lanolin 3%
5) Resinous balsam 10%
6) Accelerator, colour & moisture 4-5%www.indiandentalacademy.com

Zinc oxide:
- It is a reactive ingredient which takes part in the setting reaction.
- The type of zinc oxide used may be critical i.e. it should be finely
divided & should contain a very slight amount of water.
Fixed vegetable or mineral oil:
- The zinc oxide base component is mixed with inert oils to form a
paste.
- The inert oils may be mineral oil or vegetable oil like olive oil or
linseed oil.
- It acts as a plasticiser & also aids in masking the action of eugenol
as an irritant.

Eugenol:
- Oil of cloves contain 70-85% eugenol.
- It is sometimes used in preference to eugenol because it reduces the burning
sensation in the soft tissues.
Gum Rosin:
- It is an important constituent & can be incorporated in either the zinc oxide or the
eugenol component or may be mixed in both.
- The rosin gives body & coherence to the mixed material & imparts the
thermoplastic properties to the set impression, so that it can be softened in hot
water for easy removal from the cast.
- Carnauba wax, Kauri gum or Coumarone resins can be substituted for gum rosin.
- Rosin facilitates the speed of the reaction & a smoother, more homogenous
product results.

Resinous Balsam:
- Canada balsam & Peru balsam are used to increase flow & improve mixing
properties.
Accelerator:
- It can be incorporated in either one or both pastes.
- Magnesium chloride/ calcium chloride hasten the normally slow- setting reaction
of a simple zinc oxide & eugenol mixture to a point convenient for clinical
impression procedures.
- Certain soluble salts & zinc salts such as zinc acetate are efficient accelerators.
- Other chemicals commonly used are metallic salts of hydrochloric & nitric acids,
primary alcohols & glacial acetic acid.
- Addition of water decreases the setting time of ZOE product.

CHEMISTRY:-
- The reaction between zinc oxide & eugenol is very complex & has
never been completely defined.
OH
OCH3 Structural formula for EUGENOL.
CH2-CH=CH2
ZnO + H2O Zn(OH)2 This reaction takes place either in
Zn(OH)2 + 2HE ZnE2 + 2H2O solution or at the surface of the
Base Acid Salt zinc oxide particles.
(Eugenol) (Zinc Eugenolate)

OH H2C=HC-H2C
OCH3
+ ZnO H2O
O CH3
CH2-CH=CH2 (excess) O Zn O
(eugenol) H3C O
(zinc eugenolate) CH2-CH=CH2

e
PROPERTIES:-
1) Setting Time:
- Setting time is important, since there must be sufficient time for mixing, filling
the tray & seating the impression.
- Once the material, in a plastic condition, has been carried to the mouth, only a
minimal time should elapse before the impression hardens.
- 2 setting times, initial & final, are recognised by the American Dental
Association Specification No. 16 for dental impression pastes.
- The initial setting time is the period from the beginning of mixing until the
material ceases to pull away or string out when its surface is touched with a
metal rod of specified dimensions. The impression should be seated in the
mouth before the initial set. Initial set may vary between 3&6min.
- The final set occurs when the rod fails to penetrate the surface of the specimen
more than 0.2mm under a load of 50gm. Final set should occur within
10min.for www.indiandentalacademy.com

Control of Setting Time:
- The setting time of ZOE is not as easily controlled by the operator.
- Methods by which the operator may control the setting time are:-
a) By adding small amount of zinc acetate or other accelerators.
Also, a small drop of water or alcohol may be mixed into the
paste containing eugenol before blending the 2 pastes.
b) When the setting time is too short, the cause is usually high
humidity & or temperature. Cooling the spatula & mixing slab
may help increase setting time.
c) The setting time can also be prolonged by the addition of certain
inert oils &waxes during the mixing, such as olive oil, mineral oil
& petrolatum. www.indiandentalacademy.com

2) Consistency & Flow:
- The consistency & flow of the freshly mixed paste when it is impressed against
the
tissues are of considerable clinical importance.
- A paste of thick consistency or high viscosity can compress the tissues, whereas a
thin, fluid material results in an impression that copies the tissues in a relaxed
condition with little or no compression.
- The thickness of the paste used is normally around 1mm.
3) Rigidity:
- The major restriction on the use of these materials is their lack of elasticity.
- The set material may distort or fracture when removed over undercuts.
- The materials are sometimes used to record small undercuts in soft tissues but the
tendency of some pastes to flow under relatively small pressures should bewww.indiandentalacademy.com

4) Strength:
- It is not a critical requirement for this impression material since it
is
supported by a tray & is not used in areas where it would be
required to withstand extensive deformation & stress during
removal from the mouth.
5) Hardness:
- The hardness of the set material varies with different products.
- It is measured by noting the extent to which a loaded needle will
penetrate a small specimen of the set material.
- It is expressed in terms of millimeters penetrated in a given time.www.indiandentalacademy.com

6) Dimensional Stability:
- The dimensional stability of most of the impression pastes is quite
satisfactory.
- ZOE impression materials shrink in the order of 0.1% or less at the
end of 30min. after mixing.
- No significant further change occurs at the end of 24 hours & these
materials can be considered to be reasonably stable in dimension.
7) Reproduction of Details:
- The relatively low initial viscosity of the mixed paste, coupled
with
its pseudoplastic nature, allows fine detail to be recorded in the
impression. www.indiandentalacademy.com

-Manipulation
- Pouring of the cast
- Disinfection of the impression.

Non eugenol pastes
- Occasionally, eugenol may promote an allergic response in some
patients . There may be a stinging or burning sensation when eugenol
contacts soft tissues.
- Alternative non-eugenol materials are based upon the reaction
between zinc oxide and a carboxylic acid such as orthoethoxybenzoic
acid, to form an insoluble soap (saponification reaction). The
carboxylic acid may be present as a liquid or as a powder dispersed in
a medium such as ethyl alcohol.
 ZnO + 2RCOOH -> (RCOO) 2
Zn + H2
0
- The reaction is not greatly affected by temperature or humidity.

IMPRESSION PLASTER
- It is a rigid, mucostatic impression material that sets by
chemical reaction.

COMPOSITION:-
- It consists of essentially the β- hemihydrate of calcium sulphate
which is calcined.
- Impression plaster consists of:-
1) Accelerator:
- They are the chemicals that are added to reduce the setting time
& control the setting the setting expansion.
- Potassium sulfate, potassium chloride & potassium nitrate
accelerate the setting time & reduce setting expansion.
- Potassium sulphate acts by increasing the solubility of the
hemihydrate.

2) Retarder:
- They are the chemicals that are added to increase the setting time.
- Sodium carbonate, sodium bicarbonate, potassium carbonate &
borax can be used as retarders.
- A balanced blend of accelerator & retarder to the raw hemihydrate
base plaster can reduce the setting expansion & at the same time
control setting expansion.
- Typical combinations are potassium sulfate- borax & potassium
sodium tartarate- sodium citrate.

3) Colouring agents:
- Alizarin red is a commonly used pigment.
4) Starch:
- The addition of starch gives a soluble impression plaster.
- When these soluble plasters are used, the impression can be
separated from the cast by immersion of both in hot water.
- Starch also produces a very smooth mix, with the added advantage
that it is slightly sticky & so will adhere to the tray.

5) Gums:
- Natural gums like tragacanth are added to change the handling
characteristics of the plaster mix.
- They give cohesion to the mass & facilitate border molding of the
impression in the mouth before the plaster sets.
6) Flavoring agents:
- These may be used to offset the bland taste of the plaster.
- Additives may be supplied as an aqueous solution to be mixed with
plaster.
Potassium sulphate 4%
Borax 0.4-1%
Alizarin red 0.04%
This solution is called “AE” or “ anti-expansion” solution.www.indiandentalacademy.com

PROPERTIES:-
1) Setting Time & Setting Expansion:
- The setting time of impression plaster is largely determined by the
controlling agents added by the manufacturer.
- Variation of the W:P ratio gives some control but at the same time
influence the consistency of the mass & the strength.
- The salts of many metals will reduce the setting time of plaster &
many of them also reduce the setting expansion.
- The addition of 4% potassium sulphate will make the setting
expansion clinically negligible but, at the same time will reduce
the setting time to about 1min.
- Addition of 0.4% borax to the potassium sulphate solution will
give a setting time of about 3min., which is a convenient time.www.indiandentalacademy.com

- Setting time & expansion can be controlled by the operator by:-
1) W:P ratio ed ST & ed SE
2) Spatulation time ed ST & ed SE
3) in Temperature upto 30ºC es ST
2) Accuracy:-
- The mixed impression material is initially very fluid & is capable of
recording soft tissues in the uncompressed state.
- Impression plaster allows very intimate contact between the
impression material, combined with the ability to remove moisture
from tissue & a minimal dimensional change on setting & results in
a very accurate impression.www.indiandentalacademy.com

3) Storage:-
- If impression plaster is exposed to air under conditions of high relative humidity
during storage, it will absorb water from the atmosphere.
- This causes crystals of calcium sulfate dihydrate to form on the surface of the
hemihydrate crystals.
4) Rigidity:-
- After setting, the plaster impression material is very brittle.
- It can undergo virtually no compressive or tensile strain without fracturing.
5) Impression plasters are non-toxic, but the water absorbing nature of these
materials often causes patients to complain about a very dry sensation after
having impressions recorded.
6) This material is most dimensionally stable & exhibits little dimensional change.

MANIPULATION:-
1) Proportioning & Mixing:-
-Impression plaster should be mixed in a rubber bowl using a stiff,
wide bladed spatula.
- The material is used at a higher W:P ratio than is normally used for
modelling plasters.
- The fluid mix is required to enable fine detail to be recorded in the
impression & to give the material mucostatic properties.

2) Impression Making:-
- Freshly mixed plaster is too fluid to be used in a stock impression
tray & is normally used in a special tray, constructed using a
1-1.5mm spacer. The tray may be made from acrylic resin or shellac
- Another technique is to record the plaster impression as a wash in a
preliminary compound impression.
- The compound is deliberately moved during setting to create space
for the plaster wash.
- One technique for recording impressions of undercut areas, commonly used
before
the advent of elastic materials, was to allow the impression plaster to set & then to
fracture it in order to facilitate removal from mouth. Material is weak & easily
fractures due to high W:P ratio.www.indiandentalacademy.com

3) Separating Media:-
- Alcoholic solutions of varnishes & waxes, soap solutions, water
glass( 60% solution of sodium silicate in water), liquid paraffin & a
variety of commercial preparations may be used.
4) Disinfection:-
- Impression plaster may be immersed for 20min in 2%ID210 solution.

IMPRESSION WAX
- Waxes were first used in dentistry in the early 18th
century for the purpose of recording impressions of
edentulous mouths.

USES:-
1) For corrective impressions of free- end saddle areas of partial
dentures.
2) In edentulous mouths.
3) Used in small quantities to fill in areas of impressions in which
insufficient material has been used or in which an “air blow” has
caused a defect.
4) As a bite- registration material.
5) A mixture of border corrective & denture body corrective waxes is
used in patients with heavy masticatory muscuature.

TYPES:-
- Dental waxes are classified as:
1) Pattern wax
2) Processing wax
3) Impression wax
- Impression wax is of 2 types:
1) Corrective wax
2) Bite registration wax

COMPOSITION:-
- Waxes used in dentistry may be composed of natural & synthetic
waxes, gums, fats, fatty acids, oils, natural & synthetic resins &
pigments of various types.
- Particular working characteristics of each of the dental waxes are
achieved by the blending of appropriate natural & synthetic waxes
& resins & other additives.

Natural waxes Synthetic waxes Additives
Mineral Acrawax C Stearic acid
- Paraffin Aerosol OT Glyceryl tristearate
- Microcrystalline Castorwax Oils
- Barnsdahl Flexowax C - Turpentine
- Ozokerite Epolene N-10 Color
- Ceresin Albacer Natural resins
- Montan Aldo 33 Rosin
Plant Durawax 1032 - Copal
- Carnauba - Dammar
- Ouricury - Sandrac
- Candelilla - Mastic
- Japan wax - Shellac
- Cocoa butter - Kauri
Insect- Beeswax Synthetic resins
Animal- Spermaceti - Elvax
- Polyethylenewww.indiandentalacademy.com

WAXES:-
- Waxes are inorganic polymers consisting of hydrocarbons & their
derivatives(esters & alcohols).
- The average molecular weight of a wax blend is about400 to 4000
which is low compared with structural acrylic polymers.
- The chemical components of both natural & synthetic waxes
impart characteristic physical properties to the wax, which are of
primary interest because the specific physical properties of a wax
or wax blend, determine its usefulness for intended applications.

a) Paraffin Waxes:-
- These are obtained principally from the high boiling point fractions of
petroleum
and are mixtures of chiefly straight- chain saturated hydrocarbons containing
26-30 carbon atoms.
- The melting range is low (50º-70ºC).
- Presence of oils lower the melting temperature.
- Paraffin waxes used in dentistry are refined waxes & have less than 0.5% oil.
- It is used in inlay & modelling waxes.
b) Ceresin:-
- It is derived from wax- bearing distillates from natural mineral petroleum
refining or lignite refining.
- They may be used to increase the melting range of paraffin waxes.www.indiandentalacademy.com

c) Carnauba & Ouricury Waxes:-
- Carnauba contains 85% alkyl esters of various kinds.
- These waxes are characterized by high hardness, brittleness & high melting
temperatures.
- They have melting temperatures from 84º to 91ºC, whereas ouricury melts at 79º
to 84ºC.
- They possess the outstanding quality of increasing the melting range & hardness
of paraffin waxes.
- eg. The addition of 10% of carnauba wax to paraffin wax with a melting range of
20ºC will increase the melting range to 46ºC.
- The addition of ouricury waxes produces a similar effect, but they are less
effective than carnauba wax.

d) Beeswax:-
- It is an insect wax and is a complex mixture of esters consisting
mainly of myricyl palmitate , saturated and unsaturated
hydrocarbons and high molecular weight organic acids.
- The melting temperature is 60°C to 70°C.
- It is brittle at room temperature but becomes plastic at body
temperature.
- It is used to modify the properties of paraffin waxes.

SYNTETIC WAXES:-
- These are complex organic compounds of varied chemical compositions.
- Although differing chemically from natural waxes, they possess certain physical
properties( melting temperature & hardness) akin to those of the natural waxes.
- They may differ from natural waxes in certain characteristics because of the high
degree of refinement they possess, in contrast to the contamination that is
frequently present in waxes from natural sources.
- Following are some of the synthetic waxes available:
a) Polyethylene waxes: melt at 100º to 105ºC & properties are similar to paraffin wax
b) Polyoxyethylene glycol waxes: melts at 37º to 63ºC .
c) Halogenated hydrocarbon waxes: prepared by reaction of chlorine with natural wax
d) Hydrogenated waxes:prepared by reaction of hydrogen with natural waxes
e) Wax esters:produced from the reaction of fatty alcohols & acids.

Gums:
- These are complicated substances, many of which are mixtures containing largely
carbohydrates & when they are mixed with water, they either dissolve or form
sticky, viscous liquids.
- Many waxes obtained from plants & animals resemble gums in appearance.
- Gum arabic & tragacanth are 2 natural gums that do not resemble waxes in either
their properties or composition.
Fats:
- Waxes are harder & have higher melting temperature than fats, but resemble fats
in some ways.
- Both are tasteless, odourless & colorless in pure form & are greasy to touch.
- fat may be used to increase the melting range & hardness of compounded wax.
Resins:
- They are complex, amorphous mixtures of organic substances. Natural resins are
obtained from trees & plants, except shellac, which is produced by insects.www.indiandentalacademy.com

PROPERTIES:-
1) Solid-Solid Transition Temperature:-
- A solid-solid transition occurs where the stable crystal lattice form
(orthorhombic in most dental waxes) commences to change to a
hexagonal form which is present below the melting point of the wax.
2) Thermal Expansion & Contraction:-
- Waxes expand when subjected to a rise in temperature & contracts
as the temperature is decreased.
- This fundamental property may be altered slightly when various
waxes are blended, but the response to thermal changes cannot be
reduced to negligible values.

3) Mechanical Properties:-
- Both the physical & mechanical properties that characterize a dental wax are
determined primarily by the amount of hydrocarbons & ester waxes present, by
the molecular weight distribution of each component & by the amount of
impurities present.
4) Flow:-
- Waxes deform when subjected to a load for a period of time.
- The property of flow is visualised as resulting from the slippage of molecules over
each other.
- Impression wax exhibit high flow at mouth temperature & distort on withdrawal
from undercuts.
- Flow is low when the temperature of the wax is below the solid-solid transition
temperature.
- As temperature is raised above the transition temperature flow property increases.

5) Internal Stresses:-
- Waxes have low thermal conductivities, so making it difficult to
achieve uniform heating.
- If a wax is moulded or adapted to shape without adequate heating
to above the solid-solid transition temperature, considerable
stresses will be set in the material.
- If the wax is subsequently warmed, relief of the stresses will occur,
resulting in distortion.

Corrective Impression Wax:-
- Corrective impression wax is used as wax veneer over an original
impression to contact and register the details of soft tissues.
- It is claimed that it records the mucous membrane and underlying
tissues in a functional state in which movable tissue is displaced to
such a degree that functional contact with the base of the denture is
obtained.
- Corrective waxes are formulated from hydrocarbon waxes such as
paraffin, ceresin & beeswax & may contain metal particles.
- The flow of several corrective waxes measured by penetration at
37ºC is 100%.
- These waxes are subjected to distortion during removal from mouth.

Bite Registration Wax:-
- Bite registration wax is used to articulate accurately certain
models of opposing quadrants.
- The wax bite registration of the copper formed die must provide
proximal & occlusal relations.
- Bite registrations frequently are made from 28 gauge casting wax
sheets or from hard baseplate wax, but waxes identified as bite waxes
appears to be formulated from beeswax or hydrocarbon waxes such
as paraffin or ceresin.
- Certain bite waxes contain aluminium or copper particles.
- The flow of several bite waxes at37ºC ranges from 2.5% to 22%
indicating that these waxes are susceptible to distortion on removal
from the mouth. www.indiandentalacademy.com

MANIPULATION:-
- Wax can be used in a fashion similar to that for ZOE paste on the
surface of a primary impression or custom impression tray.
- The major use of waxes as an impression material may occur during
full denture impression techniques.
- In case of impression techniques for partial dentures, it must be used
in a rigid base plates that fits positively against the natural standing
teeth.
- A cast must be prepared immediately from such an impression to
avoid distortion.

CONCLUSION

REFERENCES
1) “A historical review of complete denture impression materials”-
JADA- 1975,91(11) : 1037-1040
2) Anusavice K.J. – “Phillips’ Science of Dental Materials”
11th
edition, 2003
3) Combe E.C. – “Notes on Dental Materials” 6th
edition , 1992
4) Craig’s R.G., Powers J.M. – “Restorative Dental Materials”
11th
edition, 2002
5) “Determination of properties of impression materials”-
Br. Dent. J 1988, 164(4) : 221-225.
6) Ferrecane J.L.- “Materials in Dentistry”- Principles&Applications
7) Mc Cabe J.F. – “Applied Dental Materials” 7th
edition , 1992
8) Phillips R.W.-“Skinner’s Science of Dental Materials” 9th
edition , 1992

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