Zinc phosphate

surely helpful for dental students

1. ZINC PHOSPHATE “I was created to create beautiful smiles” -Random Dentist

2. CONTENTS INTRODUCTION HISTORY COMPOSITION TYPES SETTING REACTION MANIPULATION PROPERTIES ADVANTAGES AND DISADVANTAGES MODIFIED ZnPh CEMENT QUESTIONS

3. INTRODUCTION It is one of the oldest cements introduced in dentistry. It is also the oldest luting agent. It has the longest clinical track record compared to the newer cements.

4. HISTORY Zinc phosphate cement was introduced c.1879, and although the formulation has been refined for more than a century, it is a luting agent that has consistently been successful in clinical practice and even today is still considered the ‘gold’ standard.

5. COMPOSITION POWDER : Zinc oxide: 90.2%- principle constituent Magnesium oxide: 8.2%- (sintering) Other oxide: 0.2%- improves smoothness of mix Silica: 1.4%- filler LIQUID : Phosphoric acid: 38.2%- reacts with ZnO Water: 36%- control rate of reaction Aluminum phosphate: 16.2%- buffer Aluminum: 2.3% Zinc: 7.1%

6. TYPES TYPE 1: Fine grained for luting Film thickness should be less than 25 µm TYPE 2: Medium grain for luting and filling Film thickness should be more than 40 µm

7. SETTING REACTION When the powder is mixed with liquid the phosphoric acid attacks the surface of the particles and release zinc ions into the liquid. The aluminum, which already forms a complex with the phosphoric acid, reacts with the zinc and yields a zincaluminophosphate gel on the surface of the remaining portions of the particle. Thus, the set cement is a cored structure consisting primarily of unreacted zinc oxide particles embedded in a cohesive amorphous matrix of zinc aluminophosphate.

8. MANIPULATION Dispense the cement P/L: 1.4 gm/0.5 ml. Divide the powder in one corner of the glass slab into increments depending on the products. Dispense the correct amount of liquid, to area of the slab away from the powder. Add the powder to liquid in portions at 15 sec at 15 sec intervals for a mixing time 60-120 sec.

9. Mix it over a large area of the slab with a flexible metal spatula. Test the consistency of the cement before adding the last portion of powder. Only part of that portion of powder may be necessary to reach the desired consistency. The cementing strings above 1 inch above the slab. The technique generally used for mixing zinc phosphate cement is ”FROZEN GLASS SLAB TECHNIQUE”.

10. PROPERTIES Compressive strength – 104Mpa Tensile strength – 55Mpa Modulus of elasticity – 13.7Gpa Retention is mechanical At insertion pH at 2 min – 2 at 24 hrs – 5.5 Damage to pulp occurs during first few hrs of insertion.

11. ADVANTAGES AND DISADVANTAGES ADVANTAGE DISADVANTAGE Most popular for cast restorations. Adequate strength Reasonable working time Excess material can be easily removed Acceptable effect over the dental pulp Manipulation less critical than other cements Pulp irritation. Lack of antibacterial action. Brittleness Lack of adhesion Solubility in acid fluids.

12. MODIFIED CEMENT COPPER & SILVER CEMENT: Black copper cement: Cupric oxide Red copper cement: Cuprous oxide Depending on the type of copper cement, concentration of the copper varies between 2% and 97%. Lower P/L ratio – for satisfactory manipulation characteristics. Less anticariogenic property Silver cements: contain small percentage of salts of silver phosphate.

13. FLUORIDATED CEMENT Stannous fluoride(1 – 3%) Higher solubility and lower strength – due to dissolution of fluoride. Fluoride uptake by enamel: Reduced enamel solubility and anticariogenic.

14. QUESTIONS

15. THANK YOU GUYS.. BY: M.P.YUVAN SAI IInd YR BDS