53
-KARAN HIRAL MEHTA BDS II YEAR DSCDS

Zoe cement-karan

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Page 1: Zoe cement-karan

-KARAN HIRAL MEHTABDS II YEARDSCDS

Page 2: Zoe cement-karan
Page 3: Zoe cement-karan
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•Have been used extensively in dentistry since 1890’s

•Vary widely in properties based on the use

•Low strength cements

•Least irritating of all dental cements

•Known to have an obtundant effect on exposed dentin

•To improve strength many modified ZOE cements have been

introduced

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•in vitro, eugenol from ZOE fixes cells, depresses cell

respiration, and reduces nerve transmission with direct

contact

•Effect of eugenol are dose dependent

•Diffusion through dentin dilutes eugenol by several orders of

magnitude

•ZOE may form a temporary seal against bacterial invasion

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Applications of ZOE in dentistry:-

1. Endodontic sealers

2. Root end filling materials

3. Periodontal coating

4. Inelastic impression materials

5. Cavity base

6. Temporary restorations

7. Luting agent

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Type I ZOE cement:-

•These are meant for short term luting

•Lacks strength and long-term durability and is used

for temporary cementation of provisional coverage

•Permanent restorations are also sometimes

cemented for a short period for the patient to try it.

•Low strength allows easy removal of the restoration

without damage

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Type I ZOE cement is further classified as:

1. Class I – setting cement2. Class II – non-setting cement

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Type II ZOE cement:-

•They are meant for long term cementation of

permanent restorations

•They are considered somewhat inferior to other

cements

•Has reinforcing agents added and is used for the

permanent cementation of cast restorations or

appliances (modified ZOE cements)

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Type III ZOE cement:-

•They are used for the interim period when a

tooth is under going treatment or until it is

ready for a permanent restoration

•Can also be used as bases under permanent

restoration

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Type IV ZOE cement:-

•Low strength materials

•Used as liners

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Available as:-

Powder and liquid

Two paste system

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*Eugenol is 4-allyl-2-methoxy phenol

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Setting reaction and microstructure are the same as that of the zinc oxide eugenol impression pastes.

First reaction:-Hydrolysis of zinc oxide

The reaction proceeds as a typical acid-base reaction

The chelate formed is an amorphous gel that tends to crystallize imparting strength to the set mass

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Structure of set cement:-

The set cement consists of a matrix of zinc

eugenolate in which particles of zinc oxide are

embedded.

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Compressive strength:-

•Relatively week cements

•Strength depends on its use

•Compressive strength ranges from 5 to 55 Mpa

•Lowest are the cavity liners (minimum 5 Mpa)

Type I 6 to 28 Mpa ISO-maximum of 35 MPaType II 45 to 55 Mpa ISO-minimum of 35 MPa

Factors that increase the strength:-

1. Smaller particle size

2. Reinforcing with alumina-EBA or polymers

Tensile strength: Ranges from 0.32 to 5.3 Mpa

Modulus of elasticity: Ranges from 0.22 to 0.54. Important property for

cements intended for use as bases

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Thermal conductivity: 3.98 [Cal. Sec-1 cm-2 (oC/cm)-1] X 10-4

Their thermal insulating properties are excellent and are

approximately the same as human dentin. The thermal

conductivity of zinc oxide-eugenol is in the range of insulators like

cork and asbestos.

Coefficient of thermal expansion: 35 X 10-6/ 0C

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•Solubility of set cement is highest among the cements

(0.4 to 1.5% wt)

•Solubility is reduced by increasing the P/L ratio

•They disintegrate in oral fluids

•This break down is due to hydrolysis of the zinc eugenolate matrix

to form zinc hydroxide and eugenol

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This property is important for those cements used for luting of

restorations (type I and type II)

The film thickness of ZOE cements (ISO maximum of 25

micrometer) is generally higher than other cements.

Do not adhere well to enamel or dentin

The set cement is opaque

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•pH: 6.6 to 8.0

•Effect on pulp: least irritating of all cements. Pulpal response is

mild

•Bacteriostatic property: inhibits the growth of bacteria

•Obtundant property: has an anodyne or soothing effect on the

pulp in deep cavities, reducing pain.

Reasons why ZOE cements are not often used for final cementation of crowns and other fixed dental prosthesis:-1. Does not adhere well to enamel or dentin2. Low strength3. High solubility

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•Powder to liquid ratio- 4:1 to 6:1 by wt.

•Bottles are shaken gently

•Measured quantities of powder and liquid are dispensed on to a cool glass slab

•Bulk of powder is incorporated into the liquid

•Mix in circular manner

•Zinc oxide eugenol exhibits pseudothickening

•Smaller increments are then added to complete the mix

•For temporary restorations a thick putty-like consistency is recommended

•ZOE cement instruments are cleaned using oil of orange.

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Equal measurements of each paste is mixed to get a uniform colour

Setting time is 4 to 10 minutes

ZOE cements set quicker in mouth due to heat

and moisture

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Factors affecting setting time

The complete reaction between zinc oxide and euginol takes about 12 hours. This is too slow.

1. Manufacture: the most active ZnO powders are those formed from

zinc salts like Zn(OH) and ZnCO3 by heating at 3000oC

2. Particle size: smaller zinc oxide particles set faster

3. Accelerators: Alcohol, glacial acetic acid and water

4. Heat: Heating the glass slab, slows the reaction

5. Retarders: glycol and glycerine

6. P/L ratio: higher the ratio, faster the set

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Page 31: Zoe cement-karan

Modified ZOE cements:-

EBA-alumina modified cements

Polymer reinforced

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Page 33: Zoe cement-karan

•Available as: white powder and pinkish liquid

•Its greater strength allows its use as an intermediate

filling material and as a base

•A part of liquid is substituted by orthoethoxy benzoic

acid (EBA)

•Alumina is added to powder

•The popularity of these cements as a retrograde filling

material is increasing because of high cost of MTA

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1. Long term cementation

2. Temporary and intermediate restorations

3. Root end filling material

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Zinc oxide : 60-75%

Fused Quartz or alumina : 20-35%

Hydrogenated Rosin : 6%

EBA : 62.5%

Eugenol : 37.5%

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Page 38: Zoe cement-karan

•More easier to handle

•Improved carvability

•Compressive strength: 55 to 60 MPa (8000 psi)

•Tensile strength : 4.1 Mpa (600 psi)

•Modulus of elasticity: 2.5 Gpa (0.36 psi X 106)

•Film thickness: 25 micrometer

•Solubility and disintegration in water is 0.05% wt. Despite their low

solubility, these cements disintegrated and wore more quickly

clinically when compared to the polymer modified zinc oxide

cement

•Effect on pulp: relatively mild to pulp

•Adhesion: Adhere well to tooth structure

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Page 40: Zoe cement-karan

•Modifications take the form of resins added to the powder

or the liquid

•Aim is to increase the strength and reduce the solubility

•Resin modified cements are among the strongest of the zinc

oxide-eugenol based cements

•High strength and low wear make them ideal intermediate

restorative material

•It can last as long as 1 year

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1. Luting agent

2. As base

3. As temporary filling materials

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Page 43: Zoe cement-karan

Zinc oxide : 70%

Finely divided natural or synthetic resins

Eugenol

Acetic acid : accelerator

Thymol : antimicrobial

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The zinc oxide powder is surface treated. The combination

of surface treatment and polymer reinforcement results in

good strength, improved abrasion resistance and

toughness.

Setting reaction:-

The reaction is similar to ZOE cements. Acidic resins if

present may react with ZnO and strengthen the matrix

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Page 46: Zoe cement-karan

•Improved mechanical properties

•Compressive strength: 48 MPa (7000 psi)

•Tensile strength : 4.1 Mpa (600 psi)

•Modulus of elasticity: 2.5 Gpa

•Film thickness: 32 micrometer

•Solubility and disintegration in water is 0.03% wt

•Effect on pulp: moderate effect which is same as

unmodified ZOE cements

•Improved abrasion resistance and toughness

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Factors affecting setting time:-

1. Low powder-liquid ratio increases setting time

2. Moisture: accelerates setting time

3. Cooling the glass slab slows the setting time

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Page 49: Zoe cement-karan

•ZOE is very popular as an endodontic sealer.

•Rickert’s and Grossman’s formula are the popular traditional formulations

•These are used with gutta percha in endodontic therapy to seal canals

•Some materials are used as therapeutic sealers and are formulated with ingredients

such as iodoform, paraformaldehyde or trioxymethylene which have therapeutic

value

•Some contain antibiotics such as tetracyclines or steroids as antiinflammatory

agents.

•Some formulations can also be used as pulp capping

•Endodontic sealers also contain radiopaque materials such as barium sulphate,

bismuth sulphate, bismuth salts or silver powder.

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GROSSMAN'S FORMULA

POWDER LIQUID

Zinc oxide 42% Eugenol

Staybelite resin 27%

Bismuth subcarbonate 15%

Barium Sulphate 15%

Sodium borate anhydrate 1%

Page 52: Zoe cement-karan

1.CRAIG’S RESTORATIVE DENTAL MATERIALS BY CRAIG

2.SCIENCE OF DENTAL MATERIALS BY PHILIPS

3.BASIC DENTAL MATERIALS BY MANAPPALLIL

4.SKINNER’S SCIENCE OF DENTAL MATERIALS BY SKINNER’S

5.INTERNET

Page 53: Zoe cement-karan