Hydrocolloid
A suspension of seaweed and sea kelp in water
Reversible hydrocolloid
Impression material that may be changed repeatedly from solid to liquid state
Irreversible hydrocolloid
Impression material that goes from a semi-solid state to a solid state and cannot be reversed. Alginate impression material used to create study materials
Working time
Time allowed to mix alginate, load tray and position in mouth
Setting time
Time required for chemical reaction to occur
Syneresis
Loss of water by evaporation as alginate is exposed to air. Material shrinks.
Imhibition
Taking up of additional water. Material swells.
Properties of inelastic rigid impression material
Low flexibility. No elastic. No spring like quality. Will permanently change when removed from mouth (breaks apart).
Uses of inelastic rigid impression material
Impression of edentulous mouths when making dentures. Seldom used anymore.
Properties of hydrocolloid impresson material
Elastic, spring like quality (like a rubber band). Can be bent and stretched without permanently changing shape. Can be removed from the mouth without causing distortion.
Uses of hydrocolloid impression material
Orthodontics. Crowns, bridges, inlays & onlays. Bleaching trays & mouth guards.
Application of reversible hydrocolloid impression material
Tube of material is heated in boiling water. Liquid is placed in an impression tray, placed in patients mouth and allowed to cool. Material goes back to a gel state and an imprint remains (highly accurate). Physical change occurs in the material (no chemi
Uses of reversible hydrocolloid impression material
Impression of teeth that have been prepared for crowns and bridges.
Application for irreversible hydrocolloid impression material
Supplied as an alginate powder. Chemical reaction occurs when mixed with water. Tray is seated from posterior to anterior. Once reaction has occured it cannot change back.
Uses of irreversible hydrocolloid impression material
Making study models for patient record. Orthodontic treatment. Bleaching or custom trays.
Temperature of water that allows material to set faster
Warm
Temperature of water that allows material to set slower
Cool
Steps to minimize inaccurate impressions
Rinse with water and spray with disinfectant, let sit for 10 minutes. Store impressions in 100% humidity prior to pouring by wrapping in damp paper towel. Pour impressions in plaster or stone within one hour after taking.
Properties of elastomer impression material
Rubber like quality. Extremely accurate detail. Can be removed from mouth without tearing or distortion.
Application of elastomer impression material
Supplied as two tubes of material (catalyst & base) that are mixed together on a mixing pad.
Four types of elastomer impression material
Polysulfide. Polyether. Condensation silicone. Polyvinylsiloxane.
Polyvinylsiloxane
Most popular. Used for impressions of teeth prepped for crowns and bridges. Highly accurate detail. Stable (maintains size and shape). Easy to mix. Use vinyl gloves only.
Uses for elastomer impression material
Crowns and bridges. Inlays and onlays.
Hydrocolloid
A suspension of seaweed and sea kelp in water
Reversible hydrocolloid
Impression material that may be changed repeatedly from solid to liquid state
Irreversible hydrocolloid
Impression material that goes from a semi-solid state to a solid state and cannot be reversed. Alginate impression material used to create study materials
Working time
Time allowed to mix alginate, load tray and position in mouth
Setting time
Time required for chemical reaction to occur
Syneresis
Loss of water by evaporation as alginate is exposed to air. Material shrinks.
Imhibition
Taking up of additional water. Material swells.
Properties of inelastic rigid impression material
Low flexibility. No elastic. No spring like quality. Will permanently change when removed from mouth (breaks apart).
Uses of inelastic rigid impression material
Impression of edentulous mouths when making dentures. Seldom used anymore.
Properties of hydrocolloid impresson material
Elastic, spring like quality (like a rubber band). Can be bent and stretched without permanently changing shape. Can be removed from the mouth without causing distortion.
Uses of hydrocolloid impression material
Orthodontics. Crowns, bridges, inlays & onlays. Bleaching trays & mouth guards.
Application of reversible hydrocolloid impression material
Tube of material is heated in boiling water. Liquid is placed in an impression tray, placed in patients mouth and allowed to cool. Material goes back to a gel state and an imprint remains (highly accurate). Physical change occurs in the material (no chemi
Uses of reversible hydrocolloid impression material
Impression of teeth that have been prepared for crowns and bridges.
Application for irreversible hydrocolloid impression material
Supplied as an alginate powder. Chemical reaction occurs when mixed with water. Tray is seated from posterior to anterior. Once reaction has occured it cannot change back.
Uses of irreversible hydrocolloid impression material
Making study models for patient record. Orthodontic treatment. Bleaching or custom trays.
Temperature of water that allows material to set faster
Warm
Temperature of water that allows material to set slower
Cool
Steps to minimize inaccurate impressions
Rinse with water and spray with disinfectant, let sit for 10 minutes. Store impressions in 100% humidity prior to pouring by wrapping in damp paper towel. Pour impressions in plaster or stone within one hour after taking.
Properties of elastomer impression material
Rubber like quality. Extremely accurate detail. Can be removed from mouth without tearing or distortion.
Application of elastomer impression material
Supplied as two tubes of material (catalyst & base) that are mixed together on a mixing pad.
Four types of elastomer impression material
Polysulfide. Polyether. Condensation silicone. Polyvinylsiloxane.
Polyvinylsiloxane
Most popular. Used for impressions of teeth prepped for crowns and bridges. Highly accurate detail. Stable (maintains size and shape). Easy to mix. Use vinyl gloves only.
Uses for elastomer impression material
Crowns and bridges. Inlays and onlays.