impression materials & procedures

1. IMPRESSION MATERIALS &
PROCEDURES
BY: SAglow007
DEPARTMENT: PROSTHODONTICS

2. CONTENTS
IMPRESSION MATERIALS
RIGID MATERIALS
THERMOPLASTIC MATERIALS
IMPRESSION WAXES
ELASTIC MATERIALS
RUBBER BASE IMPRESSION MATERIALS
POLYETHER IMPRESSION MATERIALS
SILICONE IMPRESSION MATERIALS
IMPRESSIONS OF THE PARTIALLY EDENTULOUS ARCH

3. IMPRESSION
MATERIALS• Rigid Materials
• Thermoplastic Materials
• Elastic Materials

4. RIGID MATERIALS
Plaster of Paris
• Used in dentistry for over 200 years
Metallic Oxide Paste
• Not used as primary impression material
• Never used for impression that include remaining natural teeth
• Not used in stock impression trays
• Used as secondary impression materials for complete dentures and for extension base
edentulous ridge areas of a RDP in custom impression tray
• Can also be used for relining as an impression material in distal extension denture bases.

6. THERMOPLASTIC
MATERIALS
Modeling Plastic
• Used for border correction of custom impression trays for Kennedy Class I & II RDP bases
• Manufactured in several different colors, each color being indication of temperature range
at which the material is plastic & workable
• Red (Red-Brown) material in cake form is used for corrected impressions of extension base
areas
• Red, gray and green material in stick form is used for border molding an impression or
impression tray.
• Green material is lowest fusing of the modeling plastics

8. IMPRESSION WAXES
• Iowa wax and Korecta wax
• Used for recording functional or
supporting form of an edentulous
ridge

9. ELASTIC MATERIALS
Reversible Hydrocolloids
• Used primarily as impression material for fixed restorations
Irreversible Hydrocolloids
• Used for making diagnostic casts and master casts for RDPs
• Can not be stored for any length of time, have low tear strength, provide less
surface detail as compared to rubber base and not dimensionally stable as other
materials
• Non toxic, non staining, inexpensive, have pleasant odor and hydrophilic in nature.

11. RUBBER BASE IMPRESSION
MATERIALS
• Used for secondary corrected or altered cast impressions
• High tear strength, moderately inexpensive, long working and setting time
• Long term dimensional stability is poor due to water loss after setting
• Do not recover well from deformation so not be used when large or multiple
undercuts are present
• Unpleasant odor, can stain clothes

12. POLYETHERIMPRESSION
MATERIALS
• Provides good surface details
• Hydrophilic
• Thixotropic
• Have low to moderate tear strength
• Shorter working and setting time
• Unpleasant taste
• Flow characteristics and flexibility is lowest of any elastic material, that limit its use
for impression in RDP

13. SILICONE IMPRESSION
MATERIALS
• Condensation and Addition reaction
• Addition reaction are most accurate and easier to use
• Pleasant odor, moderately high tear strength
• Excellent recovery from deformation
• Available in Hydrophobic and hydrophilic form
• Sulfur in latex gloves and aluminum and ferric sulfate in gingival retraction cord
may inhibit polymerization.
• More expensive

15. IMPRESSIONS OF THE PARTIALLY
EDENTULOUS ARCH
• Impression of the partially edentulous arches must record accurately anatomic
form of teeth and surrounding tissues.
• Materials that could deformed by removal from teeth or tissue undercuts should
not be used.
• Irreversible hydrocolloid is most commonly used material for recording impression
of edentulous arches.