zinc phosphate cement

zinc phosphate is oldest of luting cements

supply :- suppled as powder and liquid.

composition :- a.) powder contains ==> zinc oxide 90% and magnesium oxide 10%

b.) liquid contains ==> phosphoric acid, aluminium phosphate, water.

powder/liquid ration:-1.4 grms powder to 0.5 ml liquid

setting :- when powder and liquid are mixed, the phosphoric acid attacks the surface of the particles and releases zinc ions into liquid, aluminum which is already forms complex with phosphoric acid, reacts with zinc yields a 'zinc aluminophosphate' gel on the surface of remaining portion of particles

'set cement contains core of unreacted zinc oxide particles in a cohesive amorphous matrix of zinc alumino phosphate'

its an acid base reaction

addition of water accelerates the setting reaction

reaction is exothermic, cooling of glass slab retards the chemical reaction

setting time :- 2.5 -8 min

physical properties :- 1.)compressive strength 104 Mpa

2.)tensile strength:- 5.5 Mpa

3.)modulus of elasticity 13.7 Gpa

retention:- by mechanical interlocking

PH :- high pH at the time immediately after mix 2 after 2 minutes 4 after 1 hr

zinc oxide eugenal cement

supply:- it is supplied as powder and liquid form or 2 paste form

composition:- composition of typical powder and liquid form is 1.)powder contains zinc oxide 2.)liquid contains eugenol

setting :- zno+H2o ----> zn(OH)2 zinc hydroxide react with eugenol to form a chelate water (H2O) is needed to initiate the reaction and is also form as by-product.

setting reaction accelerate by a.)zinc acetate dihydrate b.) high atmospheric pressure

c.)acetic acid

FASTER SETS by ===> high p/L ratio

properties :- 1.) compressive strength ranges from 3-55 Mpa

2.) free eugenal is bactericidal

disadvantage:- Eugenol allergy in some patients

types 4 types

type-1 for temperory cementation

type-2 long term cementation for fixed prosthesis

type-3 temporary fillings and insulating bases

type-4 intermediate restoration.