-By Daraksha Sheikh

IMPRESSION

IT IS THE NEGATIVE LIKENESS OR COPY IN

REVERSE TO THE SURFACE OR OBJECT..

IDEAL REQUIREMENTS OF IMPRESSION MATERIAL.... It should have pleasant taste,odor and

aesthetic Should not contain any toxic or irritating

ingredients Should have good shelf life Should be used with minimum equipments Adequate strength so it will not break or tear

while removing It should be dimensionally stable it should be electroplated It should be viscous enough to contained in

the tray and seated in the mouth

THEORIES OF IMPRESSION....

Mucocompressive theory Mucostatic theory Selective pressure theory

CLASSIFICATION OF IMPRESSION MATERIALS

A. Based on its property- rigid and elastic

B. Based on its setting- reversible and irreversible

C. Based on its use- use in dentulous and in edentulous patient

mode of setting

Rigid

Elastic

Set by chemical rxn{irreversible/ thermoset}

• Impression plaster• ZOE

•Alginate•Elastomers

Set by temperature changes

{reversible/ thermoplastic}

•Impression comp•waxes

•Agar

IMPRESSION COMPOUND

IMPRESSION COMPOUND It is thermoplastic impression material It is classified as rigid, reversible

impression material which sets by physical change.

It is also called as modelling plastic.

Types- Type 1-low fusing comp-(40-45 C)

Type 2-high fusing comp-(60-65 C)

TYPE 1-This is soften by heat loaded on tray and pressed against the tissue before cooledAlso used for making single tooth impression called tube impression

TYPE 2Initially used for taking impression then used as tray so we also called it as tray compoundIt is more viscous when soft and more rigid when hard.

MODE OF SUPPLYStick,cakes and cones

COMPOSITION Waxes and resins-30%

Shellac -30% Stearic acid -5% Gutta percha -5%

Filler -25%

Colouring agent -trace

Principal ingredient that comprises of matrix

Improves plasticity and workability

Increases viscosity at temp above the mouth temp and increases rigidity of compound.

REQUIREMENTS OF IDEAL IMPRESION COMPOUND It should solidify at or little above mouth

temp It should not be injurious or harmful to

oral tissue It should not contain irritating or toxic

ingredients It should not undergo permanent

deformation or fracture while withdrawing from mouth

Should be dimensionally stable

APPLICATION• For making primary impression• For individual tooth preparation• Border moulding type I is used to duplicate functional sulcus depth• To check undercuts in inlay preparation

PROPERTIES1} Low thermal conductivity2}Glass transition temp -39 C(loses its hardness}3}Fusion temp-43 C(soft to manipulate)4}Co-efficent of linear expansion high due to

presence of resin and wax-0.3%5}flow- type1-3% at 37 C 80-85%at 45 C type2-2% at 37 C 70-80% at 45 C

MANIPULATION Small amt is softened over flame (not to

be boiled it because plasticizer are volatile)

If large amt like cakes are used then they are softened by keeping in temp controlled water bath

Comp is removed, worked with finger to obtain uniform plasticity throughout mass loaded in the tray and impression is taken

After impression cast should se pour immediately

PRECAUTIONS Overheating in water bath is not

indicated as the compound becomes brittle and grainy because some of the low molecular wt ingredients get leached out so the composition might change.

Advantages1)It can be reused

for same patient2)It is correctable3)Material can be

extended beyond the tray border

Disadvantages1)Because of high

viscosity difficult to to record details

2)While taking impression due to pressure soft tissue get compressed

3)Distortion due to poor dimensional stability.

DISINFECTION Disinfectant solution for compound is

2% alkaline glutaraldehyde solution. The impression should immersed in this

solution for the required amt of time, rinsed and the pour immediately.

RIGID IRREVERSIBLE IMPRESSION MATERIAL

Zinc oxide eugenol impression paste.

A.D.A spec no. : 16

By Nidhi Pandya

Classification

Type I Hard Type II Soft

Available as:

Base paste (white in color). Accelerator or reactor or catalyst paste

(red in color).

Composition Base paste:Zinc oxide(87%)

Should be finely divided and should contain slight amount of water.

Vegetable or mineral oil(13%)

Acts as plasticizer and masks the action of eugenol as irritants

Catalyst paste Oil of clove or Eugenol(12%)Reduces burning sensation.Gum or polymerized Rosin(50%)Speeds the reaction.Filler(20%)Lanolin(3%)Canada balsam(10%)Improves flow and mixing.Other catalysts like zinc acetate and glacial acetic acid

Setting Reaction Acid base reaction Chelation Auto catalytic reaction

1. ZnO + H2O Zn(OH)2

2. Zn(OH)2 + 2HE ZnE2 + 2H2O (water) (Base) (Eugenol) (Zinc eugenolate)

Setting time

Initial setting Final setting Type I 3-6mins 10mins Type II 3-6mins 15mins

Factors affecting setting time

Particle size of ZnO powder: Small particles make the setting time less.

Varying the length of the two pastes. Longer the mixing, shorter is the setting time. High atmospheric temp. and humidity

accelerate setting. Setting delayed by cooling the mixing slab. Zinc acetate or drop of water or acetic acid

decreases setting time by increasing the speed of formation of Zn(OH)2.

Manipulation

Manipulation

Two pastes of equal lengths. Oil impervious paper or glass slab. Spatula method (uniform color with no

streaks should be formed). Pouring of the impression.

Advantages Sufficient flow. Minimum tissue distortion. Ease in beading and boxing. Not washed out by saliva. Adequate dimensional stability. Adequate working time. Can be checked in mouth repeatedly. Does not require separating media. Minor defects can be corrected.

Disadvantages Requires special trays. Sticky. Causes tissue irritation. Temperature and humidity affect setting time. Profuse secretion causes distortion. Cant be used in undercut areas. Brittle and require support.

Uses As final impression material. As corrective or wash impression. As bite registration paste. Used as stabilizing base plates and as

temporary relining material. As surgical pack. For temporary cementation.

Other zinc oxide paste Surgical paste: Used after certain periodontal

surgeries where sutures cannot be placed. The paste is placed over the wound for retention of medicament.

Noneugenol impression and surgical paste: These reduce the burning sensation and disagreeable taste caused due to eugenol. ZnO + 2RCOOH (RCOO)2Zn +H2O

Bite registration paste: These are used for recording occlusal relationship between two occluding surfaces. These have shorter ST to prevent distortion and more plasticizer to prevent it from sticking.

THANK YOU!

AGAR(REVERSIBLE HYDROCOLLOID)

-By Suheb Quereshi

INTRODUCTION In 1925, Alphous Poller was granted a British patent for a

totally different type of impression material. Later Poller’s Negacol was modified and introduced to the dental profession as Dentacol in 1928

Agar hydrocolloid was the 1st successful elastic impression material to be used in dentistry.

It is an organic hydrophilic colloid extracted from sea weed.

Agar is a sulfuric ester of a linear polymer of galactose.

CLASSIFICATIONType I - High consistency ( for use as tray material )Type II - Medium consistency ( for use as tray or syringe

material )Type III – Low consistency ( for use as syringe material )

USES1. Widely used for cast duplication.2. For full mouth impressions without

undercuts.3. As a tissue conditioner4. It was used extensively for FPD impressions.

SUPPLIED AS Gel in collapsible tubes. As cartridges In bulk containers.

COMPOSITIONIngredients

Agar (13-17%)Borates (0.2-0.5%)Potassium sulphate (1-2%)

Wax (0.5-1%) Thixotropic materials (0.3-

0.5%)Alkylbenzoates (0.1%)Coloring & flavoring agents Water (around 84%)

Functions- Basic constituent- Improves the strength- Ensures proper setting of the

cast- It acts as a filler- It acts as a plasticizer

- It acts as a preservative- For patient comfort- Acts as the dispersion medium

GELATION OR SETTING OF AGAR Agar changes from the sol to the gel state & vice versa by a

physical process. As the agar sol cools to form fibrils called micelles. The fibrils branch & intermesh together to form a brush –

heap structure. The fibrils form weak covalent bonds which break easily at

higher temperature in causes gel turning to sol. The process of turning gel to sol is known as

LIQUEFACTTION (temp.. 70-100° C ) On cooling agar reverses to the gel state, the process is called

GELATION. (occurs at or near mouth temp. to avoid injury to oral tissues)

Materials Required for Manipulation

Agar Hydrocolloid conditionerHydro colloid materialWater cooled rim lock traysSyringe materialDuplicating mouldRubber hose

The Hydrocolloid ConditionerIt includes 3 sections,Boiling or Liquefaction section

( agar is placed in boiling water at 100° C for 10 min.)Storage section

( 65-68° C is ideal & can be stored in sol condition)

Tempering section ( 46° C for 2 min. with the material loaded in tray) It makes the material viscous.

Impression traysRim lock trays have a feature of water circulation through

the trayIt is a beeding on the inside edge which helps to retain the

material.It has an inlet & outlet for connecting the water tubesShould allow a space of 3 mm.It extend distally to cover all teeth.

Working & Setting timeWT ranges b/w 7-15 min.ST is about 5 min.

Properties of Agar HydrocolloidsGelation temp.: the sol should revert to a gel at a temp. of

37° C but not more than 45°CLiquefaction temp. : it occurs at higher temp. at 70°C.Hysteresis : the temp. lag b/w liquefaction & gelation.Syneresis : the gel may lose water by evaporation from its

surface or exuding of fluid.Imbibition : if the material is immersed in water, it

absorbs water by this process. Flow : the material is sufficiently fluid to record the fine

details.

Elasticity : they are highly elasticAccuracy & dimensional change : they are highly

accurate at the time of removal, but shrink when stored in air or 100% humidity and expand when stored in water.

Gel strength : it can withstand great stresses particularly shear stress, without flow.

thus the impression should be removed as rapidly as possible to avoid distortion.

Laminate TechniqueAlso known as Agar-Alginate combination technique.Syringe material is injected on the area to be recorded.An impression tray containing chilled alginate is placed,

so it will bind to agar that is already positioned. The alginate sets by chemical reaction and agar by the

cooling effect of the alginate.ADVANTAGESLess air bubblesWater cooled trays are not requiredIt sets faster

Wet Field TechniqueThe areas to be recorded are flooded with warm water.Then the syringe material is introduced quickly in bulk to

cover the occlusal or incisal areas.While the syringe material is still liquid, the tray material

is seated.The hydraulic pressure of the viscous tray materials forces

the fluid syringe down into the areas to be restored.This displaces the syringe material, blood and debris

through out the sulcus.

Impression Disinfection Iodophor

Bleach

Glutaraldehyde

AdvantagesAccurate dies can be prepared.Good elastic properties help reproduce undercut areas.Good recovery from distortion.HydrophillicIt is economical compared to synthetic elastic materials.Low cost because it can be reused.Can be reused when used as a duplicating material..

DisadvantagesRequires special & expensive equipment.Doest not flow wellCan’t be electroplated.Patient may feel thermal discomfort.Only 1 model can be poured.Has to be poured immediately.Impossible to sterlize.

THANK YOU!!

IRREVERSIBLE HYDROCOLLOIDALGINATE-By Yogita Singh Rathore.

The word alginate comes from the term ‘Algin’

It is the peculiar mucous extract yield by certain brown seaweed(algae).

It is classified as elastic irreversible material that sets by chemical rxn.

TYPES

Type 1-fast setting

Type 2-normal setting

Mode of supplyIt is supplied as a packed powderIn bulk or in tinsA plastic scoop is supplied for dispensing

the bulk powder and the plastic cylinder for measuring

COMPOSITIONSodium or potassium

or alginate -15%Calcium sulphate-16%

Zinc oxide - 4%Potassium titanium

fluoride -3%

Dissolves in water and reacts with calcium ion

Reactor reacts with potassium alginate and forms insoluble calcium alginate

Acts as fillerGypsum hardner

Diatomaceous earth -60%

Sodium phosphate -2%

Coloring and flavouring agents -traces

Acts as filler

retarder

Setting rxnWhen alginate powder is mixed with water

a sol is formed which later sets to form gel by chemical rxn

The final gel i.e insoluble calcium alginate is produce when sodium alginate reacts with calcium sulphate

The reaction is retarded by using retarder sodium phosphate.

Sod. Alginate+ cal. Sulphate + water Ca alginate(gel) + water

Gel structureGelation is the conversion of sol to gel.The final gel consist of a brush heap of

calcium alginate fibril network enclosing unreacted sodium alginate sol, excess water, filler particles and reaction by product .

Fibrils are held by primary bond rather then intermolecular forces.

Control of gelation timeBy addition of retarderBy altering the temp of water colder water longer is the gelation

time. warmer water shorter is the gelation

time.Even the mixing bowl and spatula can be

cooled to prolong the gelation time.

MANIPULATIONFor mixing, we need a clean flexible plastic bowl. a clean wide bladed stiff metal spatula.

METHODTumbling the container is done for the uniform

distribution of constituent before mixing.Top is opened carefully so that to prevent very

fine particles to being distribute around the room.

•The recommended w:p ratio is 38ml:16gm.•Scoop supplied by the manufacturer is taken the powder is level and sprinkle on water •Mixing is done rapidly with stirring motion to wet the powder with water•After that rapid spatulation is done against the side of the bowl •A vigrous figure of 8 motion is used with the mix being a wiped or stropped against the side of the rubber mixing bowl and prevent entraption of air bubbles.

Mechanical device are also available for spatulationIts advantages are:1)speed2)covenience3)elimination of human variable

The mix should be smooth creamy with minimum voids and dose not drip off the spatula when raised from the bowl

Over mixing•Reduction in final strength as the gel fibrils are destroyed as they form•Reduction in working time Under mixing

•Inadequate wetting, lack of homogeneity and reduced strength•The mix become grainy and poor recording of details

MIXING TIME Fast set alginate-45 sec Normal set alginate-60sec

WORKING TIMEFast set alginate-1minNormal set alginate-2 min

IMPRESSION MAKINGLoading the tray- the alginate is mixed and loaded on a perforated

tray so that it can mechanically interlocked the adhesive such as sticky wax or methyl

cellulose can be applied to the tray the thickness of the gel between the tray and

tissue should be 3 mmSeating the tray- before making the impression the saliva should be wiped of to

prevent the material flowing along the throat and causing nausea to the patient.

the impression is seated on the posterior portion first then the anterior portion is seated.

Since the material sets from the tissue to the peripheral any movement during this time can cause distortion

After removing the impression from the mouth it should be washed to remove saliva

Covered with damp napkin to prevent syneresisCast should be poured as soon as possible;

preferably within 15 mins after making impression.

Impression disinfection

The irreversible hydrocolloid may be disinfected by 10 min immersion in or spraying of antimicrobial agent e.g sodium hypochlorite, glutaraldehyde without significant dimensional changes.

PROPERTIES1)Setting time- for fast setting material-1 to 2 min for normal setting material- 2 to 4.5min2) flexibility- 14% at the stress of 1000g/cm sq3)Elasticity- it is elastic but less as compared to agar4)Reproduction of details- suface detail reproduction is less as compared to agar5)strength- compressive sterngth-5000 to8000 g/cm sq tear strength vary from 350-700 g/cm sq

6)Dimensional stability- alginate impression loses water by evaporation and shrinks on standing air. if its placed in water it swells. so kept in 100% humidity for least dimensional change7)Shelf life- it has short self life. material is stored in cool and dry environment.8)Biological properties- silica particles present in dust which rises after fluffing alginate powder is health hazardous so there are also dust free alginate.

APPLICATION

1) Used for making impression when there are undercuts

2) For making impression for orthodontic and study models

3) For duplicating models

RECENT ADVANCEDust free alginate- to avoid inhalation problem of alginate

dust some material have been introduce in the dustless version in which the powder is coated with glycol.

Some products contain a chemical disinfectant in the alginate powder for infection control.

ADVANTAGEIt is easy to mix and

manipulateMinimum requirement

of equipmentFlexibility of the set

impressionAccuracy if properly

handledLow costIt is hygienic as fresh

material to be used for each impression

DISADVANTAGES It is not possible to make the

metal die which have high resistance to abrasion

It is not accurate enough for crown and bride in impression

It cannot be used alone for compressing the tissue

It cannot be corrected Distortion may occur if the

material is not held stationary in relation to the tissue through out he setting period

ELASTOMERIC IMPRESSION MATERIALA.D.A SPEC NO-19-By Sunbul Tabrez

TYPES Acc to chemistry: 1. Polysulfide. 2. Polysilicones-

a. Condensation siliconesb. Addition silicones.

3.Polyether. Acc to viscosity: 1. Light body or syringe consistency 2. Medium or regular body

3. Heavy body or light consistency. 4. Very heavy or putty consistency. Acc to wettability: 1. Hydrophilic 2. Hydrophobic.

USES

Used in FPD for impression of prepared teeth. Impression for dentulous mouth for RPD. Impression for edentulous Mouth for CD. For bite registration. Polyether used for border molding of edentulous

custom trays. Silicone duplicating material for refractory casts.

SUPPLIED AS

Collapsible tubes Putty consistency supplied in jars Light and regular body material supplied in

cartridges.

PROPERTIES

Excellent reproduction of surface details. Generally hydrophobic (except polyether). Nearly complete elastic recovery. Tear strength is excellent. Dimensional inaccuracies may occur due to

curing shrinkage, loss of byproducts of reaction, thermal contraction, removal before complete setting.

MANIPULATION

Single mix technique. Multiple mix technique. Reline technique:

- Two stage putty wash technique- One stage putty wash technique.

This is the first elastomeric impression material introduced in 1950.Also known as Mercaptan or Thiokol.

POLYSULFIDES

SUPPLIED AS

Light bodied. Medium bodied. Heavy bodied.

COMPOSITION

Liquid polysulfide polymer (80-85%)

Inert fillers like titanium dioxide, zinc sulfate, copper carbonate (16-18%)

Lead dioxide (60-68%)

Dibutyl Phthalate (30-35%)

Sulfur (3%) Retarders (2%)

BASE PASTE REACTOR PASTE

SETTING REACTION

Mercaptan + Lead dioxide

Polysulfide + Water

It is an exothermic reaction and loss of water causes shrinkage.

PROPERTIES Unpleasant color and odor. Materials are extremely viscous and sticky. MT 45secs ST 12-16mins. Excellent reproduction of surface details. Dimensional stability (highest permanent

deformation and elastic recovery improves with time).

High tear strength. Low hardness and good flexibility. Hydrophobic.

ELASTOMERSSILICONE RUBBER IMPRESSION MATERIALSBy Sahid Hassan Khan

TYPES

The silicone impression materials are of two types based on the type of polymerization reaction:

Condensation silicones Addition silicones.

Both silicones are available in different colors like pastel pink, purple, blue, green, orange, etc.

CONDENSATION SILICONES

SUPPLIED AS: Paste: Supplied as two pastes in unequal

sized collapsible tubes. Base paste in a large tube and catalyst paste in a small tube.

Putty: Supplied in a single large plastic jar. Catalyst as paste or liquid form.

They come in variety of colors. Base and catalyst in contrasting colors to aid in mixing.

Available in Three viscosities

Light bodied Medium bodied Putty.

COMPOSITION

Polydimethyl siloxane

Colloidal silica or microsized metal oxide filler.

Color pigments.

Orthoethyl silicate

Cross linking agent. Stannous octoate

Catalyst.

Base Catalyst

SETTING REACTION. Dimethyl siloxane + Orthoethyl silicate

Stannous Octoate

Silicone rubber + Ethyl alcohol.

The ethyl alcohol formed as a by product evaporates from the set rubber leading to shrinkage.

PROPERTIES Pleasant color and odour. ST 6-9mins MT 45secs. Excellent reproduction of surface details. Dimensional stability is less. Tear strength lower than polysulfides. Stiffer and harder than polysulfides. Hydrophobic. Self life less than polysulfides.

ADDITION SILICONES

SUPPLIED AS:

Tubes: Base and catalyst paste in equal sized tubes.

Cartridge form. Putty jars: Two equal sized plastic jars

containing base and catalyst.

Available in four viscosities: Light bodied. Medium bodied. Heavy bodied. Putty.

COMPOSITION

Poly(methyl hydrogen siloxane).

Other siloxane prepolymers.

Fillers.

Divinyl polysiloxane. Other siloxane

prepolymers. Platinum salts-

catalyst. Palladium or

hydrogen absorber. Retarders. Fillers.

Base Catalyst

SETTING REACTION Vinyl siloxanes + Silane siloxane

Pt salts

Silicone rubber

PROPERTIES Pleasant odor and color. May cause allergic reaction so direct skin

contact to be avoided. Excellent reproduction of surface details. ST 5-9mins MT 45secs. Has best dimensional stability among

elastomers. Has good tear strength. Hydrophobic. Lower flexibility and harder than polysulfides. Self life ranges from 1-2yrs.

POLYETHER RUBBER IMPRESSION MATERIAL-By Divya Solanki.

106 POLYETHER

Good mechanical properties.

Good Dimensional Stability.

Base and accelerator in collapsible tubes.

Accelerator tube is smaller.

Available in 3 viscosities-

• Light Bodied

• Medium Bodied

• Heavy Bodied

AVAILABLE AS-

107 COMPOSITION

Polyether Polymer

Colloidal Silica Filler

Glycolether or Phthalate Plasticizer

Aromatic Sulfonate Easter Cross linking agent

Colloidal Silica Filler

Glycolether or Phthalate Plasticizer

BASE

ACCELERATOR PASTE

108CHEMISTRY AND SETTING

REACTION

It is cured by the reaction b/w aziridine rings which are at the end of branched polyether molecule.

The main chain is a co-polymer of ethylene oxide and tetrahydrofuran.

Cross linking is brought about by the aromatic sulfonate ester via the imine end groups.

The reaction is exothermic (4 to 5 C)

Polyether + Sulfonic ester Crosslinked rubber

109 PROPERTIES

1. Pleasant odor and taste.

2. Sulfonic ester can cause skin reactions.

3. Setting time – 6 to 8 mins.

4. Mixing time – 30 sec

5. Dimensional stability is very good.

6. It is extremely stiff (flexibility 3%)

7. Tear strength is good (3000 gm/cm).

8. It is hydrophilic.

9. It can be electroplated with silver or copper.

10. Shelf life is excellent (more than 2 years).

110 MANIPULATION

• With addition silicon – equal scoop of base and accelerator.

• With condensation silicon - required no. of scoops of base and recommended amount of liquid or paste accelerator is taken.

• In both cases mixing is done by kneading b/w the fingers.

• Unlike addition silicon the quantity of catalyst paste is very little. The 2 pastes therefore are of unequal length and diameter.

PUTTY

PASTE

CONTD…

• The required amount thinner may be added to the base and accelerator depending on the viscosity needed.

• The quantity of accelerator needed is very little.

• The ratio is usually displayed on a mixing pad. Mixing time 30 sec.

111

FOR POLYETHER

1. Impression can be made in custom or stock trays

2. Elastomer do not adhere well to the tray

3. An adhesive should be applied to the tray and allowed to dry before making impressions.

4. Perforatd stock trays are used because perforations helps to retain the putty in the tray.

5. Spacing is given b/w 2-4 mm.

6. Bulk of impression should be made with heavier consistency

112TECHNICAL

CONSIDERATIONS

METHODS OF MAKING IMPRESSIONS113

SINGLE MIX TECHNIQUE

Tray used – Resin custom tray with 2-4 mm spacing

Viscosity used – regular

MULTIPLE MIX TECHNIQUE

Tray used - – Resin custom tray with 2-4 mm spacing

Viscosity used – (a) Heavy bodied

(b) Light bodied

CONTD… RELINE TECHNIQUE ( 2 STAGE PUTTY-WASH TECHNIQUE)Tray used – Perforated stock tray

Viscosity used – (a) Putty

(b) Light Body RELINE TECHNIQUE ( 1 STAGE PUTTY-WASH TECHNIQUE)Tray used – Perforated stock tray

Viscosity used – (a) Putty

(b) Light Body

114

AUTOMATIC DISPENSING AND MIXING DEVICES

05/01/2023

115

• Double barrel caulking gun with mixing tip is used.

• The tip contain spirals, forcing the base and accelerator through these spirals result in mixing.

CONTD…

ADVANTAGES

• More uniform mix.

• Less air bubbles incorporated in mix.

• Reduced working time.

116

117REMOVAL OF THE

IMPRESSION

The impression is dislodged from the mouth as quickly as possible for the following reasons –

• Elastic recovery is better.

• Tear strength is higher.

INFECTION CONTROL

Rubber impression materials are disinfected by immerging them in 2% glutaraldehyde for 10 mins or in chlorine di-oxide solution for 3 mins.

In case of polyether a spray of chlorine di-oxide is preffered.

118