1

CONTENTS Hydrocolloids. Sol-Gel Transformation. Agar AgarIntroduction Uses Composition Preparation Types Manipulation Properties Impression techniques. AlginateIntroductionComposition

Uses Types Chemistry Manipulation Packaging Shelf LifePropertiesLatest advances Types of Failure Disinfection of

impression material Conclusion Refrences

2

HYDROCOLLOIDS HYDROCOLLOID are lyosol basically

consists of gelatin particles suspended in water and water is the dispersion medium .

Solution – uniformly dispersed solute and solvent e.g. salt in water – exist as a single phase

Suspension – visible insoluble particles in solute e.g. dust in water

Emulsion – visible insoluble liquid in liquid e.g. oil in water

3

Solvent and Solute

Solution

single phase, which means a homogenous mixture, where the solute exists as small molecules or ions in the solvent.

Colloids

Emulsion

heterogeneous two-phase system, a dispersed phase of particles of at least sufficient size to be seen microscopically, dispersed in a medium.

Hydrocolloids

4

SOL-GEL TRANSFORMATION Hydrocolloids can exist in 2 different forms – SOL

and GEL.

Sol – has the appearance & characteristics of a viscous liquid.

Gel – a jelly like elastic semi-solid – produced from sol by a process called GELATION – by formation of fibrils or chains or micelles of the dispersed phase which become interlocked – brush heap structure

GELATION – thus, the conversion of sol to gel .5

6

BRUSH HEAP STRUCTURE

It occurs in two ways.

1. By temperature changes: Gelation is brought about by a reversible process. E.g.

Agar. The fibrils are held together by secondary molecular forces. So that they break at slightly elevated temperature and become reestablished as the hydrocolloid cools to room temperature.

The temperature at which these changes occurs is the Gelation temperature.

The Gel is converted to sol when it is heated to a higher temperature which is known as Liquificationtemperature.

The temperature lag is known as hysterisis.7

2. By chemical change Conversion of sol to gel is brought about by chemical

reaction, the fibrils thus formed are held together by primary bonds and are unaffected by temperature. Hence they are called irreversible hydrocolloid e.g. Alginate.

Gel can be converted to sol (liquid) by heating, cooling a sol causes it to become a gel.

Agar (hot) cool to 43 C Agar (cold)

(Sol) heat to 100 c (gel)

8

AGAR - AGAR

9

1925 – Alphous Poller – Negacol.

Modified & introduced in dental

profession as Dentacol in 1928.

Agar is an organic hydrophilic colloid (polysaccharide) extracted from certain types of seaweed( kelp plant).

It is a sulphuric ester of a linear polymer of galactose.10

INTRODUCTION

USES OF AGAR:

1. Widely used at present for cast

duplication .

2. For full mouth impression without deep

undercuts .

3. As tissue conditioner.

4. Was used for crown & bridge before the

advent of elastomers.11

COMPOSITION Water - 84 % - dispersion medium

Agar - 13 - 17 % - gelling agent, dispersed phase

Borates - 0.2 - 0.5% - improves strength and retards

setting of plaster or stones

K sulphate - 1 - 2% - it counters the retarding effect of borates and provide good surfaces on gypsum models/dies

Alkyl benzoates - 0.1 % - preservatives

Fillers like diatomaceous earth, clay, silica, wax, rubber, and inert powders for control of strength, viscosity and

rigidity.

Colour and flavoring agents (traces) 12

COMMERCIAL BRANDS Acculoid / Cartrilloid (Van R)

Sugident (Lactona)

Cohere / SuperBody / SuperSyringe (Ghingi-pak)

Indentic (Cadco)

SUPPLIED AS solid gel in collapsible tubes (for impressions)

No. of cylinders in a glass jar (syringe material)

In bulk containers (for duplication)

13

PREPARATION OF AGAR Cleanliness, maintenance, and care of the conditioner

and strict adherence to time and temperature are mandatory.

The water pots should be clean and free of any foreign material, eg, wax, calcium deposits, and "scum" from the boiling water.

Conditioners stay clean.

Failure to keep the pots clean will result in temperature variations.

Clean, cool, distilled water is placed in the three pots.14

The conditioner is turned on.

Thirty minutes should be allowed for the water to reach the desired temperatures before proceeding.

The boiling pot temperature should be maintained.

The water is brought to a boil, and boiling is continued for 10 minutes.

Tooth preparation – should be caries free , without undercuts( if present – should be filled with cements resins or composites)

The cervical margins should be distinct.15

TYPES OF AGAR1. Heavy bodied – in poly tubes or flex

skins

2. Medium bodied

3. Regular bodied

4. Light bodied – in syringes16

•Trays should be selected and tried in the patient's mouth before the impression material is placed in them.

•There should be 3 mm of impression material around the teeth occlusally and laterally.

MANIPULATION The following steps are recommended

Heat in water at 100° C (212° F) for 8 - 10 minutes.

Store in water at 65° C (149° F) for 8-10 hours

Place in a tray at 65° C (149° F)

Temper in 46° C (115° F) water for 2 minute before taking the impression to increase the viscosity and pressure applied to the syringe material, also making comfortable for the patient.

The solution is taken directly from the

storage compartment, is first ejected at the

base of the preparation and then the

remainder of the prepared tooth is covered.

17

In the meantime, tray material is tempered, water soaked outer layer is soaked with a dry guaze before placing to ensure good union between tray and syringe material. The tray material is positioned with passive pressure.

ADA specifications no.11 specifies that gelationtemperature must not be less than 37°C (98.6°F) or more than 45°C (113°F).

Gelation is accomplished by circulating cool water with a time not less than 5 minutes.

After gelation, impression is withdrawn in one piece, parallel to line of withdrawal of prepared tooth. 18

Excess is trimmed and impression is stored in 2 % potassium sulfate, controls water volume and has better surface integrity in stone for 5 to 20 mins.

The potassium sulfate solution gives a harder surface to the stone die material.

The potassium sulfate should not be washed out of the impressions before the dies are poured.

The impression must be blown carefully; the impression should not be dehydrated, but an excessive amount of water or moisture should not be left in the impression.

Impression must be poured immediately after retrieval, and disinfected with iodophor, bleach or glutaraldehyde.

The cast should be kept in contact with impression for at least 30minutes, or preferably 60 minutes.

19

20

BOILING /

LIQUIFACTION

SECTION

• 1 0 mins in boiling water (1 0 0 c)

• Every time material is reliquified, 3

mins should be added. this is

because it is more difficult to break

down the agar brush heap structure

after a previous use.

STORAGE

SECTION

• 65 – 68ºC Temp. is ideal. It can be

Stored in the sol condition till

needed.

TEMPERING

SECTION

46ºC for 2-10 mins with material

loaded in the tray.

CONDITIONING UNIT

21

PROPERTIES1. Gelation Temperature - after boiling for 8

minutes, the material should be fluid enough to be extruded from the container. After tempering, the sol should be homogeneous and should set to a gel between 37" and 45" C when cooled.

2. Permanent deformation - The ANSI/ADA Specification requires that the recovery from deformation be greater than 96.5% (permanent deformation be less than 3.5%) after the material is compressed 20% for 1 second.

22

3. Flexibility - 4% to 15%. Materials with low flexibility can be accommodated in areas of undercuts by providing somewhat more space for the impression material so it is subjected to a lower percentage of compression during removal.

4. Strength –

compressive strength - 8000 g/cm2.

tear strength - 800 to 900 g/ cm.

Because agar hydrocolloid impressions are viscoelastic, the strength properties are time dependent, and higher compressive and tear strengths occur at higher rates of loading.

5. Compatibilty with gypsum - Agar is more compatible with gypsum model materials than alginates 23

6. Distortion during gelation

Contraction occurs during physical change from sol to gel.

If the material is held rigidly in the tray , material will shrink towards the centre of its mass , thereby creating larger dies.

Since sol is the poor thermal conductor , rapid cooling may cause conc. Of stress near the tray where gelation first takes place.

Therefore water at 20 degree celcius is suitable for cooling.

24

IMPRESSION TECHNIQUES Full arch impression

Sectional arch impression

Sectional arch impression techniques follows same procedure as for full arch.

Selected tray should cover the tooth and its adjacent two or more teeth.

Indication:

1. Working model for inlay preparation.

2. Single or more teeth preparation.25

LAMINATE TECHNIQUE: - [Schwartz (1951)]

It is a modified procedure using both reversible and irreversible hydrocolloid. Tray hydrocolloid is replaced with a mix of chilled alginate that bonds syringe agar. Alginate sets by chemical reaction whereas agar by temperature change.

The equipment needed for taking an agar impression can be minimized by use of an agar-alginate, syringe-tray combination impression.

In this procedure a syringe type of agar in a cartridge is heated in boiling water for 6 minutes and stored in a 65'c water bath 10 minutes before use.

The tray alginate of the regular set type is mixed with 10% more water than normally recommended and it is placed in a tray.

26

The agar is injected around the preparation and the mixed alginate is promptly seated on top of the agar. The alginate sets in about 3 mins, and the agar gels within this time as a result of being cooled by the alginate.

During the setting of the alginate and gelling of the agar a bond forms between them. The impression may be removed in about 4 minutes.

Since the hydrocolloid, not the alginate, is in contact with the prepared teeth, maximum detail will be reproduced.

bond together better than others, with tensile bond strengths ranging from 600 to 1100gm/cm2.

Values at the high end of the range resulted in cohesive failure of the agar, where as those at the low end produced adhesive failure between the agar and the alginate. It is therefore advisable to follow the manufacturer's suggestions for appropriate combinations.

27

ADVANTAGES Agar provides tissues details and solidifies

when it comes in contact with alginate prepared in water at 70°F, Preventing rapid gelation.

the elimination of water-cooled impression trays.

agar is more compatible with gypsum model materials than alginates.

the accuracy is acceptable. Economical and simple. Liquification and storage of agar not

required Decreased setting time (3minute). 28

WET FIELD TECHNIQUE In this, tooth surfaces are purposely left wet and

areas are actually flooded with warm water.

The syringe material is introduced quickly, liberally and in bulk to cover occlusal / incisalareas only.

While the syringe material is still liquid, tray material is seated, the hydraulic pressure of the viscous tray material forces the syringe material into areas to be restored.

This motion displaces the syringe material, blood and debris throughout the sulcus.

29

ADVANTAGES OF AGAR1. Helps in preparing dies accurately.

2. Good elastic property and reproduces most undercut areas.

3. Good recovery from distortion.

4. Non hydrophobic.

5. Palatable and well tolerated.

6. Cheap.

7. Can be reused. 30

DISADVANTAGESDoes not flow properly.

Cannot be electroplated.

Due to heat , it may be painful.

Tears relatively easily.

31

Alginate

32

The word Alginate comes from ‘Algin’ which is a peculiar mucous extract yielded by certain brown seaweed.

Alginates are based on anhydro-ß-d mannuronicacid or anhydro-P-D-guluronic acid.

S. Willium Wilding 1940s introduced.

Alginate was used as a substitute for agar when it became scarce during World War II (Japan was a prime source of agar)

Current status – alginate more popular than agar .

33

COMPOSITION1. Ester salt of alginic acid (sodium or potassium

or triethanolamine alginate) – 15 % - dissolves in water and reacts with calcium ions to form gel.

2. Calcium sulphate – 16 % - reacts with potassium alginate & forms insoluble calcium alginate

3. Zinc oxide – 4 % - filler and influences physical properties and setting time of the gel.

4. Potassium titanium fluoride/silicate or k sulphate – 3 % - gypsum hardener

5. Diatomaceous earth – 60 % - filler34

6. phosphate – 2 % - retarder and Delays gelation byreacting with calcium sulphate in preference to soluble alginate to form insoluble gel.

7. Glycol - small amount - To make powder dustless

8. Chemical indicators - small amountpH changes from alkaline to neutral to indicate

different stages in manipulationViolet – during spatulationPink - ready to loadWhite - ready for insertion into mouth

9. Wintergreen/peppermint - trace amount

10. Disinfectants ( ammonia salts and CHX) - small amount

35

USES1. Complete denture prosthesis & orthodontics

2. Mouth protectors

3. Study models and working casts

4. Duplicating models

TYPES: Type I – Fast setting.

Type II – Normal setting.36

COMMERCIAL BRANDS Coe Alginate (GC America)

Integra (Kerr)

Jeltrate (Dentsply Caulk)

Zelgan (DPI)

Kalginate, Supergel, Surgident, UnigelII, Vemog

SUPPLIED AS:- Bulk containers

- Pre-weighed packets for single impression

- paste / paste system37

CHEMISTRY The alginate when mixed with water becomes a sol. Gelation occurs by a chemical reaction .

The simplest and the popular method is reacting the soluble alginate with calcium sulphate to produce insoluble calcium alginate gel.

Chief ingredient is one of the soluble alginates which is a linear polymer of the sodium salt of anhydro-beta-d-mannuronic acid.

Calcium sulfate (Reactor) reacts with potassium or sodium alginate in an aqueous solution.

38

Production of Calcium alginate is delayed by the addition of soluble salts acting as retarder like sodium or potassium phosphate, oxalate or carbonate.

2Na3PO4 + 3CaS04 Ca3(PO4) + 3Na2SO4

When supply of sodium phosphate is exhausted, calcium ions begin to react with potassium alginate to produce calcium alginate.

K2Alg + CaSO4 + H2O K2SO4 + Ca Alginate.

ADA no 18 describes two types of alginates

Type I (fast setting) - 1 to 2 min

Type II (normal setting) - 2 to 4.5 minutes39

MANIPULATION Fluff or aerate the powder by inverting the

container with the lead on several times –ensures uniform distribution.

A clean flexible plastic bowl, a clean wide bladed stiff metal / plastic spatula.

Tray selection : perforated metal rim lock tray or plastic tray with retentive holes.

An excess of saliva around the teeth should be removed -may cause bubbles in the interproximal areas and on the occlusal surfaces of the teeth. 40

41

42

•Powder is added to liquid to wet the powder with water and to reduce entrapment of air.

•One scoop of pre-dispensed powder products is used with the amount of water specified by manufacturer (16g of powder to 38 ml of water)

•Once the powder is moistened, rapid spatulation by swiping, or stropping against the side of the bowl.

•A vigorous figure of 8 motion can also be used.

Mix by hand spatulation / mechanical spatulation with or without vacuum vigorously for smooth creamy mix with minimum voids (mixing time 45sec- 1 min) .

Air bubbles can be minimized by careful application of the impression material to tooth and into vestibular area with finger pressure before placement of filled tray.

43

Filled tray is held passively and motionlessly and material is left for 2 -3 minutes, till it becomes firm because of adequate maturation of chemical set.

The thickness of the gel between tray and the tissues should be 3 mm .

Working time 1 – 2 min

44

Tray should separated immediately suddenly with a jerk -to avoid rocking and possible deformation of impression.

Excess material is trimmed .

The impression is washed in cold water to remove salivastored in an environment of 100% humidity or covered

with a damp napkin to prevent drying.

Impression should be poured within 10 mins for accuracy.

Cast should be separated from alginate impression as soon as the stone has reached the optimal stage of rigidity i.e. after 45 - 60 minute.

45

46

47

If allowed to remain for longer time, alginate dehydrates and damaging changes take place in the surface of stone.

The mixing time also affects strength of the gel structure. The strength of gel can be reduced as much as 50% if mix is not complete.

Under mixing can lead to grainy mix which leads to reduced tissue detail reproduction.

Prolonged mixing results in weakened gel structure as fibrils once formed will be broken up. This will also lead to reduced working time 48

Manual Technique

A mixing time of 45 seconds to 1 minute is sufficient .Mixing should result in a smooth creamy mix that does not drip off the spatula, when it’s raised from the bowl.

49

Automated Technique

A variety of mechanical devices are available for

spatulating the alginate impression material. The

required quantity of powder and water are

dispensed in a bowl. Spatulation is

carried out until a smooth creamy mix

of alginate is obtained. This results in a

superior mix than obtained manually.

50

PACKAGING Alginate is supplied as a powder i.e. packaged in bulk

in a sealed screw top plastic container or hermetically sealed metal can. A plastic scoop and cylinder is provided .

Preweighed packets constructed of plastic or metal foil. it increase storage life and decrease moisture contamination.

Automatic mixing systems have been developed for paste/paste alginates. These systems consist of a mixing unit that mixes - an aqueous base paste – sodium alginate polyacrylic

acid - an organic initiator paste - calcium sulphate-

hemihydrate and sodium phosphate. 51

SHELF LIFE Alginate impression material deteriorates rapidly at

elevated temperatures by depolymerisation of the alginate constituent. Materials stored for one month at 65 degree Celsius are unstable for use as they do not set at all or set too rapidly for any practical use. Even at 54 degree Celsius there’s evidence of deterioration.

The ADA specification number 18 for alginate impressions specify that storage within original container for 1 week at 60 degree Celsius in a relative humidity of 100% the compressive strength of the gel should not be less than 0.255Mpa.

52

POURING THE CAST

The pouring of the cast should start from one end of arch. Afterwards it is placed in a humidator while stone hardens. Stone cast or die should be kept in contact with the impression preferably for 60 minutes or for a minimum of 30 minutes.

NEW METHOD

A proper dental stone mixed with an accelerator is painted over the entire anatomic surface of the impression. A base is added only after the first application of stone sets. This method protects against volume change of the irreversible hydrocolloid impression material and distortion of the unsupported portions of the impression.

53

ADVANTAGES

Easy to manipulate Comfortable for patient Economical Viscosity and setting time can be altered. Hydrophilic nature allows small presence of water on the

tissueswithout causing major inaccuracies in the impression.

DISADVANTAGES

Distortion begins immediately after removal from the mouth .

Surface details and accuracies are poor. Retention of alginate to non-perforated trays is

inadequate. 54

PROPERTIES1. Taste & odor: variety of colors and flavors.

2. Flexibility : 14% at a stress of 1000 gm/cm2.

3. Elastic recovery : 97.3% Permanent deformation is less if set impression is

removed from mouth quickly.

The ANSI/ADA Specification requires that the recovery from deformation be more than 95% (or a permanent deformation of less than 5%) when the material is compressed 20% for 5 seconds at the time it would normally be removed from the mouth.

55

4. Reproduction of tissue details : lower than agar.

ADA Sp. Requires material to reproduce a line that is 0.075 mm width.

5. Strength :

Compressive strengths – 5000-8000 gm/cm2

Tear strength - 350-700 gm/cm2

6. Dimensional stability: poor

7. Storage : cool, dry, tightly closed lid.

56

MIXING

TIME

WORKING

TIME

SETTING

TIME

TYPE 1

(fast set)

45 sec 75 sec 1-2.0

mins

TYPE 2

(normal

set)

60 sec 120 sec 2-4.5

mins

57

CONTROL OF SETTING TIME Lengthening the setting time is better accomplished by reducing

the temperature of the water used with the mix than by reducingthe proportion of powder.

Reducing the ratio of powder to water reduces the strength andaccuracy of the alginate.

The setting reaction is a typical chemical reaction, and the rate canbe approximately doubled by a temperature increase of 10" C.

using water cooler than 18" C or warmer than 24" C is not advisable.

The clinical setting time is detected by a loss of surface tackiness.

58

CONTROL OF GELATION TIME The gelation time is measured from the beginning of

the mixing until gelation occurs. It must allow sufficient time for the dentist to mix the material, load the tray and place it in the patient’s mouth.

Once gelation starts the impression must not be disturbed because growing fibres will be fractured and impression would be sufficiently weakened.

Optimal gelation time - 3 – 4 mins at temperature of 200C.

ADA specification no:18 for alginate have described two types of alginate based on gelation time.

Type I (fast setting) : 1 – 2 minutes Type II (normal setting) : gelation time 2.5 - 4

mins59

Gelation time is best regulated by the amount of retarder added during manufacturing.Inanother way the clinician can safely influence gelation time by altering the temperature of water used to mix the impression material.

Increase in temperature

leads to a decrease in

gelation time and vice

versa. However using

water cooler than 180C

and warmer than 54 c

is not recommended. 60

COMPATIBILITY WITH GYPSUM

Gypsum casts is not compatible with both type of hydrocolloid impression. To ensure maximum surface hardness, methods employed are :

1. Immersing the impression in a solution containing an accelerator for setting of gypsum products before pouring impression with gypsum. This acts by two ways

(a) accelerates setting of gypsum.(b) Reacts with gel to produce a surface layer that

reduces or prevents syneresis and eliminates the retarding action of the gel.

Potassium sulphate, Zinc sulphate, manganese sulphate, potash alum etc are chemicals usually used in hardening solutions. Most effective is 2% K2SO4 solution. 61

2. Incorporating a plastic hardener or accelerator inthe material by the manufacturer. Potassiumtitanium fluoride is most commonly usedhardening agent.

In general a hardening solution is not requiredunless specified by the manufacturer as most of thecommercially available alginates contain a hardenerin them.

62

LATEST ADVANCES MODIFIED ALGINATES:

1. In the form of a sol, containing the water. A reactor of

plaster of Paris is supplied separately.

2. Paste system, one containing the alginate sol, the

second the calcium reactor. These materials are said

to contain silicone and have superior tear resistance.

63

3. ALGINOT it is an extremely cost-effective, reliable

alternative.

High quality material that delivers accuracy and performance.

Available in a faster set time to increase patient comfort and reduce chair time without compromising performance or working time.

The improved thixotropic consistency reduces slumping and displacement from the impression tray.

Indications: Preliminary impressions, provisional crown and bridge impressions, study models, registration/opposing dentition impressions, impressions for orthodontic models, sports guards, bleaching trays and more.

64

4. SILGINAT(Kettenbach LP)

It is a medium viscosity addition-curing elastomeric polyvinyl silioxane impression material with alginate-like consistency, specially developed for taking impressions of the opposing jaw, temporary crowns/bridges and fabricating splints.

The use of an A-silicone for opposing jaw impressions as well as for precision impressions and bite registration leads to an optimal standardized interaction.

Silginat is stable, has a low tear resistance and is easy to disinfect.

Quantity - Cartridge (38 mL) Working Time - 76 - 90 seconds Complete Set Time - 2 min 30 secs Viscosity - Medium Body Set Times Available - Regular Set 65

5. SILGINAT FOIL BAG ALGINATE SUBSTITUTE MATERIAL

Quantity Foil Bag - (362 mL)

Working Time - 90 seconds

Dispensing Plug & Press Dispensing System

Complete Set Time - 3 minutes

Viscosity - Medium Body

Set Times Available - Regular Set

66

6. STATUSBLUE(dmg america) StatusBlue is an efficient, clean and stable alginate alternative.

A-silicone formula makes it quick and easy to take situation impressions for temporaries, model-cast dentures, orthodontic models, and opposing jaw models.

100% dust-free and cold disinfected, allowing for clean and safe impression taking and delayed pouring, or re-pouring of impressions.

Quantity - StatusBlue for Automix Guns Canister 7 (+1 FREE) 50ml Cartridges 16 Automix Tips

Working Time - 1:15 Dispensing - Gun Complete Set Time - 1:45 Viscosity - Type Medium Bodied ( < 35mm) Set Times Available - 1:45

67

7. FREEALGIN MAXI( Zhermack , inc) A-silicone, alginate alternative, fast setting, medium

viscosity for all alginate indications. Packaged for all automatic mixing machines.

1:1 mixing ratio.

Quantity - 6 X 380 mL Cartridge

base and catalyst

2 bayonet ring

Dispensing - Automatic Mixing

Machine

Scent/ Flavor - Mangustan Flavour

68

8.POSITION™ PENTA™ QUICK VPS ALGINATE REPLACEMENT Accurate, dimensionally stable preliminary

impressions that take less time.

The material offers a fast working

and setting time, and is ideal for all

typical alginate impression indications.

Multiple pour capabilities save time and money, no need to pour immediately, and no cleaning of bowls and spatulas.

it is dispensed at the touch of a button through 3M ESPE’s fully automated Pentamix™ 3 Automatic Mixing Unit.

69

Quantity - Kit includes: 1 base paste – 300ml; 1 catalyst – 60ml; 1 Penta™ cartridge, lavender; 6 Directed Flow Impression Trays (1 each size S, M, L, Upper and Lower)

Working Time - 1 min 10 sec (including mixing)

Dispensing - Automatic Mixer

Complete Set Time - 2 min 40 sec

Viscosity - Medium Bodied

Set Times Available - 3 min (Position Penta) and

2 min 40 sec (Position Penta Quick)

70

9.ANTISEPTIC ALGINATE IMPRESSION MATERIAL Introduced by Tameyuki Yamamoto,

patented in 1990.

An antiseptic containing alginate impression material contains 0.01 to 7 parts by weight of an antiseptic such as glutaraldehyde and chlohexidine gluconate per 100 parts by weight of a cured product of an alginate impression material.

The antiseptic may be encapsulated in a microcapsule or clathrated in a cyclodextrin. 71

10. CAVEX COLOR CHANGE Material with color indications

avoiding confusion about setting time.

Color changes visualizes the major decision points in impression making

initially - whiteend of mixing time - violetend of setting time – pink to white

Other advantages of this material areimproved dimensional stability (upto 5 days)Good tear and deformation resistanceDust freeSmooth surface, optimum gypsum compatibility.

72

11.LOW DUST ALGINATE IMPRESSION MATERIAL

Introduced by Schunichi in 1997.

This composition comprises an alginate a gelationregulator and a filler as major components which further comprises sepiolite and a tetraflouroethylene resin having a true specific gravity from 2-3.

The material generates less dust, has a mean particle size of 1-40microns.

73

ADVANTAGES

Easy mixing

Excellent stone surface

Unsurpassed smoothness

Fine detail

Packed in 1 lb poly- aluminium pouches to increase shelf life and reduce storage space.

2 scoops impression per pound.

Available in 2 forms – identic dustfree and kromaFaze

74

12. CHROMATIC DENTAL ALGINATE

Material changes colour signaling when to carry out each stage of the procedurePurple – spatulatePink – load traywhite – insert for impression

The color change is because of the indicator present: PHENOLPHTHALEIN

Total elapsed time from start to finish is just over 1 minute.

Impression can be kept over 100 hours without distortion or shrinkage by simply rinsing and enclosing in a plastic bag.

75

13. ALGINMAX (FUNG INT.) High precision chromatic dental alginate.

Excellent dimensional stability allows casting of the impressions even after 5 days (if impressions are correctly stored in sealed containers).

Dust free alginate and lead and cadmium free.

Excellent gypsum compatibility and biocompatibility.

Very high compressive strength and recovery from deformation.

Flavour – vanilla mint

Color – pale blue

Setting time – 3 min

Shelf life – 3 years76

77

Specifically designed for use with

any automatic delivery and mixing

system, Kettosil incorporates all of

the advantages of polyvinyl siloxane for accurate, fastand easy impressions in any indication where an alginatewould normally be used .

Excellent Dimensional Stability.

Extremely low linear dimensional change value of 0.20% comparable to polyvinyl siloxanes.

fullest possible recovery after removal from mouth, low shrinkage during setting

14. KETTOSIL

Kettosil impressions can be poured 30 minutes after removal from the mouth and up to 21 days after impression taking.

Highly thixotropic properties for smooth, controlled flow under pressure while minimizing material slump and patient gagging.

Supplies bubble-free reproduction of surface detail and critical areas such as gingival crevices and occlusal grooves.

Reproduces every oral detail in stone study or opposing models. Perfectly defined margins.

78

High Recovery From Deformation of 99.2% .

No Wasted Material Activated cartridges of Kettosil can be sealed by leaving unused material in the filler tip.

For the next impression, simply remove the previous tip, then dispense as per routine.

Total working time of 1 minute 20 seconds.

maintains accuracy, saves time and maximizes patient comfort.

79

Agar Alginate

3) Dimensional accuracy

PROPERTIES

1) Flow

2) Elasticity

4) Dimensional stability

Excellent

Elastic

98.8%

Imbibition and synersis

Can record fine details

Elastic 97.3%

No dimensional changes

Imbibitionand synersis

No dimensional changes

80

5) Adhesion

With the tray

6) Compatibility

with Cast

Manipulation Special equipments No Special

equipments

Addition accept addition Does not accept

Tear strength

Electroplating Can not be it can be

Dipped in 2% K2SO4

Special perforated tray

More compatible.

needs perforated stock tray

Dipped in 2% K2SO4

Less compatible

81

agar alginate

TYPES OF FAILURES

DISTORTION -Delayed pouring of impression.

-Movement of the tray during

seating.

- Early removal from mouth.

- Improper removal from mouth.

GRAINY

IMPRESSION

- Inadequate mixing

- Prolonged mixing

- Less water in mix

TEARING - Inadequate bulk

- Moisture contamination

- Too early removal from mouth

- Prolonged mixing

82

CAUSES

BUBBLES - Early gelation

- Air incorporation

VOIDS - Excess moisture or

debris on tissues

ROUGH OR

CHALKY

STONE CAST

- Improper cleaning

- Premature removal of

cast

- Improper manipulation of

stone

83

Alginate (Irreversible hydrocolloid):

All the instrument i.e. rubber bowl, spatula aresterilized or disinfected by spraying with 0.5%NaOCl or 2% glutaraldehyde.

Spray technique -Rinse under tap water to clean saliva or organic debris.Trim excess alginate from non-critical areas to decrease amount of Microbial contamination.

Spray the entire impression surface and the reverse side of the tray as well. It can be kept in a plastic bag or humidor for the recommended exposure time. .84

DISINFECTION OF IMPRESSION PROCEDURE

MATERIALS

When it reached the lab, it is again cleaned with water and stone cast is poured.

For immersion technique, disinfectant with short exposure time is selected to minimize distortion and deterioration of cast.

Aluminium sulfate treatment of alginate impression:

After disinfection, the impression is sprayed with aluminium sulfate and kept for 90 seconds in a humidor.Casts produced have better details and surface smoothness than impression disinfected but untreated.

85

CONCLUSION

Success of alginate hydrocolloid impression material since its emergence as an alternative to reversible hydrocolloid was mainly due to its ease of manipulation , comfort to the patient and less cost .

But the facts like its dimensional instability, its incompatibility with gypsum and availability of better alternatives like elastomers which produce better surface detail has replaced it but still it is the impression material of choice in the field of dentistry.

86

REFERENCES Philip’s science of dental materials (11thEdition)-Anusavice KJ

Restorative Dental Materials (11thEdition)- Craig RG, Powers JM

Fundamentals of Fixed Prosthodontics (3rdEdition) – Shillngberg Jr HT et al

Contemporary fixed prosthodontics – Rosensteil Textbook of Operative Dentistry – Sikri VK

Basic dental materials – 1st edition – manapallil JJ

Operative Dentistry Modern Theory and Practice (Indian ed. 1) - Marzouk MA, Simonton AL, Gross RD

87