Indications
- diagnostic casts
- working casts for indirect reconstruction
- bite registration
name this type
- impression compound
- impression plaster
- zinc oxide eugenol
- impression wax
non-elastic
what are the non-elastic kinds?
- impression compound
- impression plaster
- zinc oxide eugenol
- impression wax
Name the type
-Hydrocolloids
non-aqueous -elastomers
Elastomer impression materials
what are hydrocolloids
reversible (agar)
-irreversible (alginate)
what are non-aqueous elastomers?
- polysulfides
- silicon rubber
- polyethers
what are choice and use of trays?(7)
- the tray should have enough spacer
2. use perforated trays
3. make sure the tray is clean
4. apply only a thin layer of adhesive
5. wait appropriate time before taking impression
6. don’t mix adhesives and impression materials
what advantages of manual mixing technique?
- low viscosity
- less viscous is easier
- silicones are easiest to mix
- followed by polyethers and polysulphides
what 4advantages of automatic
- reduces mixing time
- reduces bubbles
- homogenous mix
- use correct mixing proportions
what are the layering techniques
- single stage, -2 stage (double impression)
- twin mix (2 phase impression)
Define:
- single stage
- two stage (double impression)
- twin mix (2 phase impression)
- one material, one setting
- first material set then another material added as a second layer
- two material layers are put together and set together
Requirments of impression material
- accuracy
- dimensional stability
- tear resistance
identify:
ability to replicate the intraoral surface details
-ability to retain its absolute dimensional size over time
-ability to resist tearing in thing sections (such as through the feather-edged material within the gingival sulcus)
- accuracy
- dimensional stability
- tear resistance
what’s important to the patient?
- neutral taste and odor
- short setting time
- small tray
- easily removed impression
- no retakes
- non-toxic
- cost
whats important to DENTIST
- EASILY MIXED
- SHORT WORKING TIMES
- GOOD QUALITY IMPRESSIONS
- LOW COST
- EASILY DISINFECTED
- SIMPLE PROCEDURE
ability of a liquid to cover the surface of the substrate completly
good wettability
Why do we want good wetting?
- fewer voids
- less entrapment of oral fluids by displacing water and other oral fluids from the surfaces in the mouth
- bubble-free in the impression then in dies and models
- fewer retakes
- improve adaptation of gypsum so as to prevent voids in the casts
dimensional accuracy and stability
- choice and use of tray
- setting shrinkage
- permanent set
- storage stability
one may not see 100% recovery of original dimensions in mouth
permanent set
what are elastomeric impression materials
- polysulphides
- polyethers
- silicones
Base paste: -polysulphide -filler (TiO2) Activator paste -lead dioxide -sulphur -plasticizer (dibutyl phthalate)
polysulfide impression material
Base paste: -polyether -filler (colloidal silica) -plasticizer Activator paste -aromatic sulphonate -filler -plasticizer (dibutyl phthalate)
polyether impression material
Base paste -silicone polymer -filler(colloidal silica) -organo-tin compound Activator paste -silicone polymer -filler(colloidal silica) -Tetra-ethyl silicate
silicone impression material
poor dimensional stability due to evaporation of alcohol(must be poured immediately after removal from mouth)
silicone impression material (condensation cured)
