ZINC OXIDE EUGENOL ZINC OXIDE EUGENOL CEMENTCEMENT

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By SMIJAL

ZINC OXIDE EUGENOL ZINC OXIDE EUGENOL CEMENTCEMENT

Zinc oxide eugenol (ZOE) cement have been used extensively in dentistry since 1890s.

They are cements of low strength. Also they are the least irritating of all dental cements and are known to have an obtundant effect on exposed dentin.

CLASSIFICATIONCLASSIFICATION

Type I ZOE: For temporary cementationType II ZOE: Permanent CementationType III ZOE: Temporary filling and thermal baseType IV ZOE: Cavity Liners

ZOE cement is available as

Powder and liquid orTwo – paste system

SETTING SETTING REACTION REACTION

In the First Step Hydrolysis of Zinc Oxide to its hydroxide takes place . Water is essential for the reaction (dehydrated zinc oxide will not react with dehydrated eugenol )

ZnO + H2O →Zn (OH)2

The reaction proceeds as a typical acid – base reaction

Zn (OH)2 + 2HE → ZnE2 +2H2O

(Zinc hydroxide)( Eugenol)- (Zinc eugenolate ) The Chelate formed is an amorphous gel that tends to crystallize imparting strength to the set mass. Structure of set cement: The set cement consists of particles of zinc oxide embedded in a matrix of zinc eugenolate. Setting time is around 4-10min.

FACTORS AFFECTING FACTORS AFFECTING SETTING TIMESETTING TIME

Particle size: Smaller zinc oxide particles set faster Powder to liquid ratio: Higher the ratio, faster the set Addition of accelerators, e.g. alcohol, glacial acetic acid and water makes the cement set faster. Cooling the glass slab: Slows the reaction The set can be retarded by addition of glycol and glycerine which act as retarders.

MANIPULATIONMANIPULATION Power – Liquid System Powder/liquid ratio: 4:1-6:1 wt% After shaking the bottles gently, measured quantity of powder and liquid are dispensed onto a cool glass slab. The bulk of the powder is incorporated into the liquid and saturated thoroughly in a circular motion with a stiff bladed stainless steel spatula. Smaller increments are then added until the mix is complete.

TWO PASTE SYSTEMTWO PASTE SYSTEM

Equal lengths of each paste are dispersed and mixed until a uniform colour is observed.

MODIFIED ZINC OXIDE EUGENOL CEMENTSThe modified ZOE cements are as follows: EBA- alumina modified cements Polymer reinforce ZOE cementThese were introduce to improve the mechanical properties of zinc oxide eugenol cement.

PROPERTIESPROPERTIESCompressive strength – relatively weak cements ranges from a low of 3 to 4 MPa up to 50-55 MPa.Tensile strength – ranges from 0.32 to 5.3MPaModules of elasticity – 0.22 to 5.4GPaThermal properties – their thermal insulating properties are excellentSolubility and disintegration – The solubility of the set cement is highest among the cements (0.4% - wt) they disintegrate in oral fluidsAdhesion – they do not adhere well to the enamel and dentin. This is one reason why they are not often used for final cementation of crowns and bridges.Biological properties.PH and effect on pulp (pH is 6.6 to 8) they are the least irritating of all cements. Pulpal responses are mild.They have soothing effect on the pulp.

USESUSES

For temporary and permanent cementationFor temporary fillings.Cavity lines and basePulp capping agentSecondary use – root canal restorations.

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