A positive replica of the teeth produced from impressions that create a negative representation of the teeth; commonly called study models and used for diagnostic purposes and numerous chairside and laboratory procedures.
Diagnostic Casts
An impression of the occlusal relationship of the opposing teeth in centric occlusion (patients normal bite.)
Bite Registration
A glue-like material composed of two or more substances in which one substance does not go into solution but is suspended within another substance; it has at least two phases, a liquid phase called a sol and a semisolid phase called a gel.
Colloid
A water-based colloid used as an elastic impression material.
Hydrocolloid
An agar impression material that can be heated to change a gel into a fluid sol state that can flow around the teeth, then cooled to a gel again to make an impression of the shapes of the oral structure.
Reversible Hydrocolloid
An alginate impression material that is mixed to a sol state and as it sets converts to a gel by a chemical reaction that irreversibly changes its nature.
Irreversible Hydrocolloid
A powder derived from seaweed that is a major component of reversible hydrocolloid.
Agar
A liquid state in which colloidal particles are suspended; by cooling or chemical reaction, it can change into a gel.
Sol
A semisolid state in which colloidal particles form a framwork that traps liquid. (e.g. jello)
Gel
The property of a material to have two different temperatures for melting and solidifying, unlike water, which has one temperature for both.
Hysteresis
A characteristic of gels to contract and squeeze out some liquid that then accumulates on the surface.
Syneresis
Hydrocolloids (two)
Agar and Alginate
Agar is irreversible or reversible?
Reversible
Alginate is reversible or irreversible?
Irreversible
Elastomers (PPS)
Polysulfides
Silicone rubber
Polyethers
Elastic impression materials...
Hydrocolloids *Agar *Alginate
Elastomers *Polysufides*Polyethers
*Silicone rubbers
Inelastic Materials...(GCZ)
*Plaster, Type 1 Gypsum (occlusal record)
*Compound (border mold custom tray)
*Zinc-oxide/eugenol (final impression, full denture)
Agar undergoes a blank reaction only.
Physical
Agar has blank characteristics.
Hysteresis; which means that it has two different temperatures in which is melts or solidifies, unlike water which only has one.
Agars sol-gel state is blank dependent.
Temperature
Agars solidification is caused by blank and is called blank.
Cold
Gelation
Agar is popular for Multiple preperations, but is unstable. True or False?
True
Agar is susceptible to blank and Blank.
Imbibition (absorbs moisture)
Syneresis (contracts and squeezes out liquid)
Mean old Borax and Agar retard poor old Blank from setting up. So Potassium Sulfate steps in to make it all better.
Gypsum
Borax is a...
Gel strengthener
Alkyl benzoate is a...
Antifungal
The composition of Agar includes...
*Potassium sulfate (needed for the proper set up of gypsum.)
*Borax
*Alkyl Benzoate
*Seaweed extract (agar-agar)
What are the advantages to Agar?
*Moist field
*accuracy
*Inexpensive, but wait the equipment is!)
What are the disadvantages to Agar?
*Only one pour
*Unstable- pour immediatly after disinfection!
*Deforms upon hard compression. So be nice!
Alginate undergoes what type of reaction?
Chemical...so it is irreversible.
Alginate and Agar are Aqueous. True or False?
True
What material is not temperature dependent, but will be accelerated by warm water and delayed by cold water?
Alginate
Alginate is susceptible to Blank and Blank.
Syneresis and imbibition.
Alginate is popular for study models, but is unstable. True or False?
True
What is the most commonly wide used impression material?
Alginate!
What is alginate not good for?
Nothing that needs a precise fit; Crowns and Bridges, inlays, onlays, or titanium removeable partial dentures.
Now mean old Alginate is having issues with Gypsum so again Blank has to come to the rescue.
Potassium Sulfate
Working time of regular set Alginate?
2-3 minutes
Working time of fast set alginate?
1.25-2 minutes (mix freaking fast!)
Set up time for regular set alginate?
Fast set?
2-5 minutes; 1-2 minutes
Adjusting the water/powder ratio is a super great thing to do to alginate? True or False?
Nope. Not recommended.
Rinse and disinfect alginate within how many minutes?
Ten
Pour into alginate impressions whenever the freaky freak you feel like it!
Or... maybe within one hour...
Alginate can be disinfected with...
1:10 Sodium Hypochlorite for 10-30 minutes.
Or 1:213 iodophors for 10-30 minutes.
Silicone can be disinfected with...
1:10 sodium hypochlorite for 10-30 minutes or 1:213 iodophors, glutaraldehydes, complex phenolics for 10 -30 minutes.
Gypsum cast must sit for 24 hours before disinfection. Gypsum casts only need to be disinfected if the impression was not disinfected.
Both statements are true.
You do not need to block out undercuts when using Elastomers. True or False?
