As seen in the name this impression material is made up of Zinc Oxide and Eugenol (Oil of cloves).

Classification:

It is classified by ADA with the ADA Specification N.o: 16

• Type I: Hard
• Type II: Soft

Composition:

This Impression material is available in paste form in 2 tubes:

• Base Paste (White)
• Accelerator Paste/ Reactor/ Catalayst Paste (Red)

Base Paste:

• Zinc Oxide   –    87%
• Olive Oil      -    13%

Accelerator Paste:

• Oil of Cloves                           –      12%
• Gum or Polymerized Rosin       -      50%
• Filler(Silica type)                       -      20%
• Lanolin                                     -       3%
• Resinious Balasam                    -      10%
• Accelerator Solution                 -       5%

Setting Reaction :

ZnO + H₂O ? Zn (OH)₂

Zn (OH)_{2 +} 2HE ? ZnE₂+ 2 H₂O

Manipulation:

1. Dispense equal length of the 2 pastes. Variation in length alters setting time.
2. Paper pad is used as a mixing slab & a stiff stainless steel spatula with an 8-10 cm blade should be used.
3. Mixing is done for 30-40 sec until no color streaks in the mix are seen & a uniform consistency is obtained.
4. The mix is then transferred to a impression tray to take an impression.
   

   

Factors controlling setting time:

Decreasing setting time:

· Small amt. of zinc acetate

· Accelerators

· Small drop of water mixed in the paste containing eugenol

· Increasing the mixing time.

· Increasing accelerator paste while mixing.

Increasing setting time:

· Cooling the spatula & mixing slab

· Addition of inert oils & waxes during mixing to reduce hardness like: olive oil.

· Increasing base paste while mixing.

Properties:

i) consistency & flow

-thick consistency compress the tissues.

ii) dimensional stability

-quite satisfactory,

-less than 0.1 % shrinkage occurs during hardening.

iii) reproduction of details

-good.

Biologic considerations:

Some patients experience burning sensation in the mouth due to eugenol & can also cause tissue irritation. This maybe overcome by using a non eugenol paste.

Uses:

1. cementing & insulating medium

2. temporary filling

3. root canal filling material

4. surgical pack in periodontal surgical procedures.

5. bite registration pastes

6. temporary relining material for dentures.

7. impression material for edentulous patients.

Advantages:

1. Good dimensional stability

2. good detail reproduction

3. impression surface can be modified by adding in deficient areas

4. easy to manipulate

5. long working time, so border moulding can be done while relining dentures.

Disadvantages:

1. burning sensation due to eugenol.

2. messy to work with

3. sticks to skin & instruments , difficult to clean.

4. rigid so tends to break off in areas of undercuts.