What is the most stable impression material?
Elastomers are the most commonly used impression material in dentistry . Within this group, polyethers (PE) and addition silicones/vinyl polysiloxanes (VPS) exhibit excellent dimensional stability against distortion under various storage conditions .
What are some of the advantages of polyether impression material?
Polyether provide good accuracy and sur- face detail as well as low shrinkage upon setting. Its flexibility is also very low and stiffness is high (3,12). A further advantage of polyether is its short setting time in the mouth (less than half the time required for polysulfide).
What is the effect of storage time on the accuracy and dimensional stability of the reversible hydrocolloid impression material?
The distance between abutments remained relatively constant for storage times up to and including 60 minutes. For times longer than 60 minutes, the distance between abutments was reduced and more difficult to read.
Which of the following impression materials has the best dimensional stability?
Polyethers have excellent dimensional stability. They also have excellent wettability, resulting in minimal voids and excellent reproduction of detail. Wettability An impression material should have intimate contact with the tooth and underlying soft tissues and should not form bubbles or voids.
What impression material is least dimensionally stable?
In the present study, PVS (heavy body) was found to be the most dimensionally stable and PE (medium body) was found to be the least dimensionally stable impression material.
How long are impressions taken with polyether impression materials dimensionally stable?
Dimensional accuracy Polyvinyl siloxane and polyether impression materials remain dimensionally accurate for 1 to 2 weeks . Polysulfide impression material is dimensionally accurate if poured within 1 to 2 hours of making the impression .
What are the two dimensional changes that occur in hydrocolloids impression materials?
Two impression materials are considered to be hydrocolloid materials because their major component is water. Both materials change from a viscous liquid state, called the sol, to a semisolid, rubbery state, called the gel. The sol state is a solution of one material dissolved in another.
How many types of impression materials are there?
Four types of elastomeric impression materials are available in the market: addition silicone, also known as polyvinyl siloxanes (PVS), condensation silicone, polyether, and polysulfide. Elastomers can present in different consistencies, including putty, heavy body, medium body, and light body.
What is meant by dimensional stability?
Dimensional Stability is a measurement of the linear dimensional change resulting from exposure to temperature. The test gives an indication of lot-to-lot uniformity with regards to internal stress introduced during processing. The test is mostly used for sheeting or film made by extrusion or calendar processes.
What is polyether impression material made of?
Polyether impression materials are supplied as a base (containing moderate length polyether macromonomer with terminal ethylene imine rings, silica filler and a plasticizer) and a catalyst (2,5 dichlorobenzene sulfonate, thickening agents and colorants). 1 The polymer is formed during the cationic polymerization and opening of the imine rings.
What is polyether?
Polyether is an impression material rigid enough to hold the encapsulators and O-rings within the impression when it is removed from the mouth. Polyethers are presented as a base and activator paste of the same viscosity.
What are the advantages and disadvantages of polyether?
The polyethers are also hydrophilic, which produces good wetability for easy cast forming. The polyethers have low to moderate tear strength and much shorter working and setting times, which can limit the usefulness of the material. The flow characteristics and flexibility of the polyether materials are the lowest of any of the elastic materials.
What is siloxane polyether?
With the siloxane groups on the polymer chain, a material that is dimensionally stable and recovers from deformation is combined with polyether properties. The material has a platinum catalyst, and the setting reaction is contaminated when powdered gloves are used to mix the material.