Dental materials: Elastomeric Flashcards

1. Condensation silicones
2. Addition silicones
3. Polysulfide
4. Polyether

1955

Condensation silicones

Conventional silicone

For fixed partial dentures

45sec

45sec

30sec

2-4min

2-4min

3min

6-8min

4-6.5min

6min

The setting time of condensation silicon decreases with the increase of temperature and humidity

0.60%

0.15%

0.24%

It should be poured immediately

Because of shrinkage due to loss of ethyl alcohol

3000gm/cm

3000gm/cm

3000gm/cm

2 years

1-2 years

More than 2 years

Other than the mixing time, shelf life, dimensional change and tear strength it has:

1. Decrease in setting time due to higher temperature or humidity
2. Excellent detail reproduction
3. Pleasent tase and smell
4. Its hardness increases overtime

Condensation silicones because its hardness increases overtime

Their viscosity depends on how many inert fillers_{(they are materials you add that modify the viscosity of impressions but don't take part in the chemical reaction)} You add

1. Adequate working & setting time.
2. Pleasant odor & no staining.
3. adequate tear strength
4. Better elastic properties on removal than polysulfide.
5. Less distortion on removal.

1. Poor dimensional stability if wasn't poured immediately
2. Putty-wash_{(Which is when you put a viscous material in the bottom of the impression mold for the overall shape and a less viscous material on top of it to catch the finer details)} is sensitive on it
3. More expensive than polyether

B

1975

C

Poly vinyl siloxane

It can stay dimensionally stable even after 1 week

Other than the mixing time, shelf life, dimensional change and tear strength it has:

1-good detail reproduction

2-extremly hydrophobic

3-can be used to duplicate cast models_{(models that have already been used to record the patient's mouth details)}

4-low flexibility

5-sulfur can cause retardation_(increase) of setting time or even no polymerization_{(mixing between base and catalyst)}

6-expensive

30mins, because they release H₂ on setting

Addition silicones

They have inadequate dimensional stability when it comes to maintain their shape during production of working cast thats why they are syringed in the place on to the tooth for accuracy

1965

In germany

For a few type of teeth impressions that doesn't have deep undercuts because of their hardness and short working time

Other than the mixing time, shelf life, dimensional change and tear strength it has:

1. The sulfonic ester causes skin reaction
2. Good dimensional stability
3. Decreased flexibility by 3%
4. Can cause allergy

1. short working & setting time
2. proven accuracy
3. adequate tear strength
4. long shelf life
5. less distortion on removal
6. Good dimensional stability

1. Can't deal with undercuts due to stiffness
2. Expensive
3. Can't be re-poured becuase of its stiffness

Synthetic rubber or rubber impression materials

• Removable partial dentures
• To take impression for edentulous(teethless) mouth to make complete dentures
• For dental implants
• For bite registration
• SPECIFICALLY Polyether is used for Border moulding

As two separate pastes:

• Base paste
• Catalyst paste

In jars

Elastomeric impression materials:

• Produce accurate surface details bc of their low viscosity
• are hydrophobic(except polyether)
• could be poured multiple times
• Have high coefficient of thermal expansion
• Experience dimensional changes after setting
• Have good adhesion(as long as you use adhesives too) that will decrease dimensional changes
• Excellent tear strength which makes them useful even in the form of thin sheets

Yes the mouth should be dried bc you need good flow since elastomeric impression materials are hydrophobic

1. Curing shrinkage(shrinkage while setting) because of loss of the impressions by-product
2. SPECIFIC TO polyether that absorbs water which makes it expand

Alcohol

Its volatile accelerators

After elastic recovery but before dimensional changes are set

The amount of filler that is added to the pastes

Heavy-bodied viscosity type of elastomeric impression materials bc it has more dimensional stability due to lower thermal contraction

By:

1. Hand
2. Static automixing
3. Dynamic mechanical mixing

1. Get equal lengths of base and catalyst paste
2. Mix them untill there is no streaks of colors are left
3. Coat the tray with two layer of adhesive materials
4. Load the tray with the impression material using either a syringe or directly in the tray

Polysulfide

1950

Mercaptan/ thymol

White

Grey or Brown

4-7min

7-10min

It could be workable for as long as 16min

It accelerates the setting of polysulfide

• Accurate surface reproduction
• Has the highest permanent deformation
• Hydrophobic
• Good tear strength
• Unpleasant smell and taste
• Mostly used for crown and bridge impressions and not used so much for other uses

0.4%

3-5%

7%

2mm

2 years

Polysulfide

Polysulfide

• Long working time
• Good accuracy
• High tear strength
• Long shelf life
• Inexpensive

• Must be poured with dental stone immediately
• Potential for significant distortion
• Bad taste and smell
• Re-pouring makes it less accurate

Expand becuase of high coefficient of thermal expansion