5. Impressions and Gingival Management Flashcards
Requirements of an impression material (2)
Accuracy
Dimensional stability
Impression material accuracy requirements (2)
Low viscosity
Wetting ability
Impression material dimensional stability (3)
Immediate and long-term (contraction, deformation, viscoelasticity, rigidity) Handling characteristics (strength, tear resistance) Miscellaneous factors (cost, taste, colour)
Material choice depends on (7)
Accuracy Setting time Dimensional stability Rigidity Ease of handling Long-term dimensional stability Readability
Types of synthetic elastomeric impression materials (4)
Addition silicones
Polyethers
Condensation silicones
Polysulphides
Features of addition silicones (6)
Hydrophobic Can be difficult to pour Adequate tear resistance Variable consistency Ideal elasticity Dimensional stability
Features of polyethers (7)
Polyether pre-polymer and inert filler paste; mixed with catalyst (aromatic sulphonic acid ester)
Addition type reaction
Adequate tear resistance and elasticity
Good dimensional stability
Hydrophilic
High rigidity when set
Variable viscosities (dilutant oils can reduce viscosity)
Types of impression trays (2)
Stock
Custom
Features of stock impression trays (2)
Should be rigid (as relaxation of grip after seating can cause distortion)
Perforated
Features of special impression trays (2)
Advised whenever possible
Made from acrylic/chairside silicone lab putty
Not perforated
Impression technique (6)
Ensure visibility
Isolate and dry preparation (tissue management)
Inject material from syringe around margin
Gently blow material over preparation
Syringe material over whole of preparation
Seat loaded tray
Gingival management consists of (4)
Moisture control
Haemostasis and exude control
Retraction
Removal of excess tissue
Features of electrosurgery (5)
Removes excess gingival tissue Contours tissue to optimal form Can allow minor crown lengthening Haemostasis Gingival shrinkage
Impression taking procedure (9)
Practice the preparation on model
Have study models ready
Have special trays ready
Make an index from the study model or wax-up
Ensure a satisfactory provisional is made
Have everything ready
Control the soft tissues
Leave the patient supine (seated upright)
Don’t move until material is set
Impression problems (10)
Poor bond of impression to tray Lack of occlusal detail Ledges Drags Delamination Seating error Surface inhibition Contact with pre-set tray material Inconsistent mixing Surface contamination
