ZINC PHOSPHATE CEMENT

CONTAINS- INTRODUCTION CLASSIFICATION AVAILABLE AS COMMERCIAL NAME COMPOSITION MANUFACTURE SETTING REACTION PROPERTIES MANIPULATION ADVANTAGES DISADVANTAGES APPLICATION

:INTRODUCTION: ADA SPECIFICATION NUMBER-

96.

Zinc phosphate is the oldest of the luting cements and thus serves as a standard with which newer cements can be compared.

:CLASSIFICATION: ADA Spa. No. 96. designates them as:

Type I: Fine grained for luting. Film thickness should be 25micrometer. Type II: Medium grained for luting

and filling. Film thickness should not more then 40micrometer.

:AVAILABLE AS_

1. Powder and liquid system.

2. Capsules of

preproportioned powder and liquid.

:COMMERCIAL NAMES:

- Confit.

- Harvard.

- Zinc Cement Improved.

- Modern Tenacin.

:COMPOSITION: )(. POWDER: - Zinc Oxide- 90.2%. >. Principal constituent. - Magnesium Oxide- 8.2%. >. Aids in sintering. - Other Oxide- 0.2%. >.Improve smoothness of

mix. - Silica- 1.4%. >.Filler.

)(. LIQUID: - Phosphoric Acid- 38.2%. >.React with zinc oxide.

- Water- 36.0%. >.Control rate of reaction.

- Aluminium Phosphate- 16.2%. >.Buffer.

- Aluminium- 2.5%. - Zinc- 7.1%.

:MANUFACTURE: The ingredients are mixed and heated

at temperatures b\w 1000‘C. and 1400’C. [SINTERING].

After sintering ,the cake formed is cooled quickly.

This cause the material to crack which helps in grinding of the material to a fine powder.

This process is known as FRITTING.

:SETTING REACTION:@. When the powder is mixed with

liquid, phosphoric acid attacks the surface of the particles and releases zinc ions.

@. The aluminum in the liquid is essential for cement formation.

@. The aluminum complexes with the phosphoric acid and the zinc ions to form a zinc aluminophosphate gel.

@. The reaction is EXOTHERMIC.

@. Setting Time: 2.5-8 mins.

:PROPERTIES:#. COMPRESSIVE STRENGTH: 103.5MPa.[15,000GPa].

#. TENSILE STRENGTH: 5.5MPa.[800psi].

#. MODULUS OF ELASTICITY: 13.5GPa.

#. SOLUBILITY: 0.06%.

#. THERMAL PROPERTIES: Good Thermal Insulator.

#. ADHESION PROPERTIES: Not form a chemical bond

with enamel or

dentin.

#.BIOLOGICAL PROPERTIES: -At the time of cementation the pH

is 2. -Starting pH is 3.5. -After 24 hours the pH is 5.5.

#. OPTICAL PROPERTIES: OPAQUE.

:MANIPULATION:1. Stainless steel spatula and clean

cool glass slab are use for mixing.

2. Mixing Time:- 1 min. 15 sec.

3. P/L Ratio:- 1.4gm/0.5ml.

4. The powder is added in small increments.

5. Mixing is done with stainless steel spatula using brisk circular motion.

6. Each increments is mixed for 15-20 sec.

7. A large area is covered during mixing in order to dissipate the exothermic heat.

:HOW TO MANIPULATE THE ZINC PHOSPHATE CEMENT:-

:ADVANTAGES:

}{. Good compressive strength.

}{. Good thermal insulation ability.

}{. Dose not dissolve in oral fluids.

:DISADVANTAGES:

}{. No chemical adhesion.

}{. Pulp irritation.

}{. Poor esthetics.

:APPLICATION:::- Luting for restoration.

::- High strength bases.

::- Temporary restoration.

::- Luting for orthodontic bands and brackets.

THANK YOU…