Impression materials are used to take impressions of natural teeth and supporting tissues. They should be non-toxic, elastic, and dimensionally stable after setting. Common impression materials include alginate (irreversible hydrocolloid), elastomers like polysulfide and silicones, zinc oxide eugenol paste, and wax. Each material has advantages and disadvantages for accuracy, ease of use, toxicity, and shelf life. Accurate impressions are important for crowns, bridges, and dentures.
2. • Impression: It is the negative imprints of the
natural teeth and their supporting tissue.
3. 1.Full mouth or full arch Impressions.
For edentulous arch : A. Upper and lower B. Primary or initial C.
secondary or final.
For dentulous arch : A.upper B.lower
2. Copper band or matrix band Impressions.
It is used to take impression of a single tooth.
3.Impression of a quadrant of a mouth.
It is a sectional impression
4.Wash impression
It is done for edentulous patients after primary impression ,It
records more appropriate.
4.
5. The Material used To take impression of Natural
teeth And their supporting tissue are called as
impression materials
6. It should be nontoxic and non
irritant.
It should be elastic in nature.
It should have good flow.
Manipulation should be easy.
It should be dimensionally stable
after setting.
It should be cheap and easily
available.
Setting should be less than 5 minutes.
It should have good shelf life.
7. According to elasticity of materials.
1. Non elastic :
A. rigid impression
Ex- plaster of paris
B. Plastic impression material;
a. Thermoplastic impression materials
Ex – compo, wax
b. Paste impression materials
Ex – ZoE paste
8. 2. Elastic: A . Hydrocolloid
1. Reversible hydrocolloid (agar)
2. Irreversible Hydrocolloid (alginate)
B. Elastomer a. polysulphide
b. silicones
(1. Condensation silicone. 2. Addition
silicone.)
C. polyether.
According to mode of setting (hardening)
Set by chemical setting Ex- Alginate,
elastomer
Set by physical setting Ex- agar, wax,
compound
10. Dental plaster or type III plaster is the beta form of calcium sulfate
hemihydrate (CaSO4,1/2H2O)
A mixture of plaster of paris and water is placed in an impression
tray and pressed against the tissues of ,for Ex a patients edentulous
jaw. The plaster is allowed to harden or set and the impression is
taken.
It is now used to fill the flask used in denture construction when
setting expansion is not critical and the strength is adequate
according to limits cited in the ADA specification.
It is usually marketed in the natural white colour, Thus contrasting
with stones which are generally coloured.
11. COMPOSITION FUNCTION
1. Steric acid -20 P/W
2. Oleic acid -4 P/W
3. Gum coal -19P/W
4. Kauri resin -17P/W
5. Powder soapstone or French
chalk -40P/W
It gives the plasticity and flow.
It also gives plasticity and flow.
It gives the bulk and increases
hardness.
It gives hardness.
It gives hardness and plasticity.
12. ADVANTAGES DISADVANTAGES
1. Can be reused easy to use
2. Non irritant and non toxic
3. It is cheap and easily available
1. Poor dimensional stability
2. Easy to distort when withdrawn
from mouth
3. Does not have sufficient flow
13. Used to recordthe final
of edentulous arches.
Supplies as two pastes which are mixed together on a paper pad or glass
slab. Zinc oxide paste being white and eugenol paste reddish brown in
colour.
This enables thorough mixing as homogeneous colour,free of streaks.
Pastes are dispend in toothpaste like tubes and are mixed in equal vol
Proportion is achieved by equal length of each paste on mixing slab.
It is classified as rigid,irreversible, impression material.
14. Cementing and insulating medium
Temporary filling
Root canal filling material
Bite registration paste
Temporary relining material for
dentures
Impression material for edentulous
patients
15. Oldest recorded wax
Use of wax is limited to non-undercut
edentulous portion of mouth
1. Bite registration waxes
2. Corrective waxes
Usually contain aluminium or copper
particles
Supplied in horseshoe shapes,to conform
maxillary/mandibular biting surfaces
16.
17.
18. Colloid means gelatin
substances.
Materials used to obtain
preliminary final impressions.
1. Irreversible (agar)
19. Material cannot return to solution
state after it becomes a gel
Alginate is the Irreversible
hydrocolloid most widely used for
preliminary impression
20.
21.
22.
23.
24. These are used where a high degree of accuracy is needed,especially in
crown and bridge work.
They have two main advantages over the hydrocolloid- good tear
resistance and dimensional stability. They are mainly hydrophobic
rubber based materials. All of these materials come in different viscosity
ranging from low to high viscosity. The light bodied material maybe used as
a wash impression over a medium or heavy bodied material.
25. First synthetic elastomeric impression material introduced in 1950
2 paste system
Available in low ,medium and high consistencies
Made up of a base and accelerator/reactor
Properties
Dimensionally stable.
Excellent surface detail.
Viscosity depends on the brand used
Very good tear resistance
Very small setting contraction
Good shelf life
26. Advantages
Dimensional stability
Accuracy
Comes in number of different viscosity
Long working time
Long shelf life
Disadvantages
Lead oxide in base plate may have toxic effects
Staining of clothes due to the lead oxide
Messy to work with –unpleasant rubbery smell
Can only be used in a special tray
27. Base
- polysulfide polymers
-fillers
- plasticized
Catalyst
- lead dioxide or copper
- fillers
By product
- water
28. Supplied in two pastes
Base paste
Polyether
Filler
Catalyst paste
Sulphonic acid Ester
Inert oils
When mixed the polymer and sulphonic acid ester react to form a stiff
Polyether rubber. Setting time occurs in about 6 minutes.
Properties
Hydrophilic
Good shelf life upto 2 yrs
Non toxic
Poor tear strength
Excellent surface detail
Good dimensional stability
29. Advantages
Accuracy
Good on undercuts
Ease of use
Disadvantage
May cause allergic reaction
Poor tear strength
Rapid setting time
Stiff set materials
30. Supplied as a paste and liquid or two pastes,in
light;medium, heavy or very heavy bodied
(putty)
Base paste
Silicone polymer with terminal hydroxy groups
Fillers
Catalyst paste
Crosslinking agent
Activator
On mixing the two pastes react ,cross linking
occurs and setting takes about 7 minute.
31. Properties
Hydrophobic
Hydrogen gas evolution on
setting
Moderate shelf life and tear
strength
Shrinking of impression over time
Non toxic and non irritant
Very elastic (near ideal)
Good surface detail
Advantages
Accurate
Ease of use
Can be used on severe undercuts
Disadvantages
Hydrogen evolution
Liquid component of paste
/liquid system may cause
irritation
32. Properties
Good shelf life
Dimensionally stable
Moderate tear strength
Excellent surface detail
No gas evolution
Non toxic and non irritant
33. Advantages
Accurate
Ease of use
Fast setting
Wide range of viscosity
Disadvantages
Hard to mix
Sometimes difficult to remove
the impression from the
mouth.