prosthodontic-lec2-Impression for complete denture

2. Impression: A negative likeness or copy in
reverse of the surface of an object.
Complete denture impression: is a negative
registration of the entire denture bearing,
stabilizing, and border seal areas present in the
edentulous mouth
Primary impression: is an impression made for
the purpose of diagnosis or for the construction
of a special tray.
Final impression: the impression that
represents the completion of the registration of
the surface or object.

3.  Requirements for making impression:
 1-Knowledge of Basic anatomy
 2-Knowledge of basic reliable technique
 3-Knowledge and understanding of impression
materials
 4-Skill
 5-Patient management
 Objectives of impression:-
 1-retention
 2-stability
 3-support
 4-esthetic
 5-preservation

4. 1-incorrect tray position in the mouth
2-excessive areas of the impression tray showing
through the impression material.
3-any void or discrepancy too large to accurately
correct on the cast.
4-incorrect border formation as a result of
incorrect border length of the tray.
5-obviously distorted impression because of
movement of the tray during the setting of the final
impression material.
6- poor detail in the impression because of a poor
mixing technique

5. Primary support area:
-Maxillary:- a)posterior ridge b) flat areas of the palate
-Mandibular:- a)buccal shelf area b)Posterior ridge
c)pear shaped pad
Secondary supporting area:
- Maxillary :- anterior ridge ,rugae & all ridge slopes
- Mandibular:- anterior ridge & all ridge slopes

6. 1-Depending on theories of impression
making:
2-Depending on the technique
3-Depending on the tray type:
4-Depending on the purpose of the impression:

7. mucostatic
mucocompressive
Selective pressure

8.  The impression is made with the oral mucous
membrane and the jaws in a normal, relaxed
condition. Border molding is not done here.
The impression is made with an oversized
tray or called spaced tray.
 Impression plaster or light body
 The mucostatic technique results in a
denture, which is closely adapted to the
mucosa of the denture- bearing area but has
poor peripheral seal.(stable but not retentive)

9. Mucocompressive Impression: Records the oral
tissues in a functional and displaced form. The
materials used for this technique include
impression compound, zinc oxide impression
material, and soft liners. The oral soft tissues
are resilient and thus tend to return to their
anatomical position once the forces are
relieved.

10. in reality it is likely that tissue adaption to the
presence of either a denture made with a
mucostatic or a mucocompressive technique
make little difference between the two in the
long term.

11. the impression is made to extend over as much
denture-bearing area as possible without
interfering with the limiting structures at
function & rest. This is achieved through the
design of the special tray in which the non
stress-bearing areas are relieved and the
stress-bearing areas are allowed to come in
contact with the tray. Both the advantages of
muco static and muco compressive techniques
are achieved.

12. Open mouth
Close mouth

13. a tray which carries the impression material of
choice into the desired contact with the
supporting tissues and into an approximate
relation to the peripheral tissues when the
mouth is opened and without applied pressure.
The rationale behind this method is that the
dentures do not dislodge when subjected to
biting force.

14. The patient is made to close on bite rims and
the patient manipulates his tissues by closing,
grimacing, sucking and swallowing to form
peripheral borders.

15. Stock tray
Custom tray

16. Diagnostic
Primary
Final or
secondary

17. rimary impression

18. Final impression:

20. Impression technique for
flabby ridge:

21. Impression technique for flabby ridge:

22. 1-Full tracing technique of the special tray then the
impression is taken with tracing compound after
that the final impression done with zinc oxide or
light body silicon material.
2-Neutral zone technique: neutral zone: the
potential space between the lips and cheeks on one
side and the tongue on the other, that area or
position where the forces between the tongue and
cheeks or lips are equal. The concept considers the
actions of the tongue, lips, cheeks, and floor of the
mouth during a specific oral function, to push the
soft material into a position where buccolingual
forces are neutralized.

23.  Primary impression of the upper and lower jaws are taken in impression
compound.
 Upper wax rims and lower special tray are constructed.
 The special tray is a plate of acrylic without a handle, with spurs or fins
projecting upwards toward the upper arch. These help with retention of the
impression material. Occlusal pillars have been built up on the top of the lower
tray in green stick to the correct occlusal height.
 Then thick mix of viscogel is then placed around the rest of the lower special
tray distally and mesially to the occlusal pillars. The patient is the asked to
swallow, talk…..etc.
 After about 5-10 minutes, the set impression is removed from the mouth and
examined. The viscogel material would have been molded by the patient's
musculature into a position of balance

25. -Impression between oral space and border of denture
-Physiological molding by lips, cheeks and tongue improve
function and comfort so that the polished surface of the
denture is functionally compatible with muscle action.
- Try in procedure was done and then, the wax surrounding
the teeth was removed and replaced with light body
elastomeric impression material or zinc oxide. Trial denture
bases were reinserted into the patient's mouth & the patient
was instructed to perform various orofacial movements so as
to record the polished surface of the denture in harmony with
the orofacial musculature.
-after the impression material had set the trial denture
removed, packing & curing then the final denture just
polished lightly not over finishing in order not to destroy the
details that recorded.

27. Thank
you