protho seminar

1. Presented by
Shiji margaret
Final Year BDS

2. INTRODUCTION
 An impression is defined as a negative likeness of the
teeth and/or edentulous areas where the teeth have
been removed, made in a plastic material which
becomes relatively hard while in contact with these
tissues

3. MATERIALS AVAILABLE FOR
MAKING IMPRESSION
Reversible hydrocolloids (agar-agar)
Irreversible hydrocolloids (Alginate)
Elastomeric impression materials

4. STEPS IN IMPRESSION MAKING
Position of patient & dentist
Tray selection
Mixing the material & loading into the tray
Impression making & removal
Inspecting, cleaning & disinfecting the impression

5. POSITION OF PATIENT &
DENTIST
Dentist should stand & patient should sit upright
Occlusal plane should be parallel to the floor
MAXILLARY IMPRESSION- dentist should stand
at the right rear of the patient
MANDIBULAR IMPRESSION- dentist should
stand at the right front of the patient

6. Mandibular impressionMaxillary impression

7. IMPRESSION TRAY SELECTION
Stock trays for dentulous & partially edentulous
arches are of 3 types:
Rimlock trays
Perforated metal trays
Plastic disposable trays

8. MIXING IMPRESSION MATERIAL
Bowel Spatula Scoop and
Measuring jar

9. REMOVAL OF IMPRESSION FROM MOUTH
Clinically the initial set of alginate is determined
by loss of surface tackiness
Release seal by retracting lips & cheek
Then impression is removed by a sudden jerk

10. INSPECT THE IMPRESSION FOR
DEFECtS
Mandibular impressionMaxillary impression

11. IMPRESSION TECHNIQUES
 Mc LEAN’S PHYSIOLOGIC IMPRESSION
 FLUID WAX FUNCTIONAL IMPRESSION
 SELECTIVED PRESSURE IMPRESSION

12. Mc LEAN’S PHYSIOLOGIc IMPRESSION
Procedure
 A custom impression tray is constructed over a
preliminary cast
 Functional impression of distal extension ridge is
made. Patient applies some biting force with
occlusion rims
 Then an Alginate impression is made with the 1st
impression held in it’s functional position with
finger pressure

15. FLUID WAX FUNCTIONAL
IMPRESSION
 Make an anatomic impression of the arch using alginate
 Fabricate a refractory cast using this impression
 Fabricate the partial denture framework over the refractory
cast

17.  Draw the outline of the denture base
 Cast is coated with separating medium
 Wax Spacer is adapted over the crest of the
edentulous ridge

19. Framework is placed over the spacer
Auto-polymerizing resin is mixed to dough stage and
is adapted and contoured over the framework along
the length of the ridge
Borders of the tray are trimmed

21. SELECTIVED PRESSURE
IMPRESSION
• More force are applied to areas that can absorb stress
without adverse response & protect that areas that is least
able to absorb force
• Stress bearing areas are the buccal shelf area & the lingual
slopes of residual ridge stress bearing areas
• The denture base made from this impression will be closely
adapted to & in firm contact with the tissues in buccal shelf
area

22. CONCLUSION
An accurate impression is vital for the success of a cast
partial denture. So proper selection of
material, impression technique and the skill of the
dentist plays a key role in the success of the overall
treatment.

23. REFRENCE
 Mc Cracken’s Removable Partial Prosthodontics
 REMOVABLE PARTIAL PROSTHODONTICS-STEWART’S 4TH EDISION