Dental Impression Materials: Types, Properties, and Procedures

What are the three groups of impression materials?

Inelastic impression materials, aqueous elastomeric impression materials, and nonaqueous elastomeric impression materials.

What does dimensional stability mean in the context of impression materials?

They should not distort for a period of time after the impression is made, allowing for model pouring.

What are stock trays in dental impressions?

Pre-manufactured trays usually made of plastic or metal, available in limited sizes.

What is a custom tray used for in dental impressions?

For precise fitting restorations like long-span bridges and dentures, made from a preliminary model.

What is an alginate impression?

An irreversible hydrocolloid used for taking dental impressions.

What are the components of the gel state in alginate?

A solid carbohydrate polymer network and water trapped in small pockets.

What is the function of bite registration trays?

To record the occlusal surface for proper alignment of dental restorations.

What is the significance of the sol state in alginate?

It is the viscous liquid state before the material sets.

What is the primary use of zinc oxide-eugenol (ZOE) in dentistry?

It was used as an impression material but is rarely used today.

What is the role of articulators in dentistry?

To simulate the movement of the jaw for proper fitting of dental restorations.

What type of hydrocolloid is alginate?

Irreversible hydrocolloid that won't re-liqueify upon heating.

What kind of reaction does alginate go through?

Chemical reaction

What is hysteresis?

The characteristic of melting and gelling at different temperatures.

What happens during synerisis?

Slow discharge of water after the impression sets, causing contraction.

What is imbibition?

The impression absorbs water, swells, and distorts.

What is the role of trisodium phosphate in alginate?

It acts as a retarder to slow the reaction and allow working time.

What are the four types of nonaqueous elastomeric impression materials?

Polysulfides, Condensation silicones, polyether's, and addition silicones

What is a byproduct of condensation silicones?

They produce ethanol

What is the recommended disinfection technique for alginate impressions?

Spray with iodophors or sodium hypochlorite and store in a sealed plastic bag.

What is the function of surfactants in impression materials?

They increase wetting and help pour models easier.

What are the general procedures a hygienist can perform regarding impressions?

Making impressions for study casts, bleaching trays, and occlusal guards.