Impression making is an “Ideal impression must be in mind of the dentist before it is in his hand. He must literally make the impression rather than take it”

1. Principles & objectives of impression making for
Complete Dentures-1

2.  Impression making is an
“Ideal impression must be in mind of the dentist before it is in his hand.
He must literally make the impression rather than take it”
“ M.M Devan”

3. Impression:
 It is a negative reproduction of dental structures from which a positive
cast can be made.
• Impression material:
any substance or combination of
substances used for making an
impression or negative reproduction

4. Primary impression
It is an impression made in a stock tray for making a study cast on which a
custom tray is constructed.
Final impression
The impression made in a special tray for the purpose of fabricating a prosthesis
Study cast
 It’s a positive representation of the primary impression.
 It is a positive reproduction of the form of the tissues of the upper or lower
arch over which denture bases and other dental restorations may be
constructed.

5. • Impression tray :
a device that is used to carry, confine, and control impression
material while making an impression
• Stock trays
• These are ready made trays available in different sizes
and forms
• Special trays
• These are trays that are individually constructed for each
patient.

7. Types of stock trays:
Stock trays for dentulous patients
• Have flat floor.
• Long flanges.
• Straight handle.
Stock trays for edentulous patients
• Have rounded floor.
• Short flanges.
• L-shape handle.

8. Principles for making an impression
• Tissues of the mouth must be healthy.
• Impression should include all of the basal seat within the limits of the
health and function of the supporting and limiting tissues.

9. The borders must be in harmony with the anatomical and physiological
limitations of the oral structures.
Selective pressure should be placed on the basal seat during the making
of the impression
Principles for making an impression

10.  Proper space for the selected impression material should be provided
within the tray 2-3mm.
 Guiding mechanism should be provided for correct positioning of the
imp. tray.
Principles for making an impression

11. Principles for making an impression
 Tray and imp material should be made of dimensionally stable
materials.
 Impression must be removed from the mouth without damage to the
mucus membranes of the residual ridges.

12. Objectives of impression making
1- Preservation of Alveolar Ridges
2- Support
3- Retention
4- Stability
5- Esthetics

13. 1.Preservation of Alveolar Ridges(maintain the health of oral
tissue)
Preservation of what remains rather than replacement of what is missing
2.SUPPORT
Ability of the denture to resist displacement, to vertical forces of
mastication and or other forces applied in direction toward the basal seat
 Can achieved by wide tissue coverage and impression technique
Objectives of imp.

14. 3.RETENTION
• Ability of the denture to resist displacement, vertical forces acting away
from the basal seat.
• Can achieved by: maximum coverage ,perfect peripheral seal and intimate
tissue contact.
Objectives of imp.

15. Factors for retention
Adhesion
Cohesion
Interfacial surface tension
Atmospheric pressure
Oral and facial masculature
Mechanical interlocking into undercuts
Objectives of imp.

16. 4.STABILITY
• Ability of the denture to resist displacement to forces acting in horizontal
direction.
• Factors affecting stability:-
1. retention.
2. Non interfering occlusion
3. Proper orientation of occlusal plane
4. Proper teeth arrangement.
5. Proper form & contour of the polished surfaces
6. Good control and coordination of patients musculature
Objectives of imp.

17. 5. ESTHETICS(providing lip support)
It refers to development of labial and buccal borders so that they are not
only retentive but also support the lips and cheeks properly

18. Preparation of the mouth
• There should be no inflammation or distortion of the denture
foundation tissues
• Most effective way of resolving the inflammation is to leave the
dentures out for at least 24 hours before the impressions are made
• Soft liners/ tissue conditioners

19. • Knowledge of Basic anatomy
• Knowledge of basic technique
• Knowledge and understanding of impression materials
• Skill
• Patient management

20. Limiting structures of the maxillary denture
• These are structures that limit the border extension of
the maxillary complete dentures.
Buccal frenum
Buccal vestibule
Soft Palate
Vibrating line
Labial frenum
Labial vestibule
Hamular notch

22. Mandibular anatomical landmarks
Labial frenum
Retromolar pad
Buccal frenum
Buccal shelf
Labial vestibule
Lingual sulcus
Lingual frenum
Mylohyoid bone
Buccal sulcus
Residual ridge
Lingual sulcus

24. STEPS IN MAKING AN IMPRESSION
1-Preliminary examination of the patient
2-Seating the patient
3-Selection of the tray
4-Selection of the material
5-Making impression- primary impression
- border molding
- secondary impression

25. 1-Preliminary examination of the patient
• complete case history and clinical examination is done.
• Factors that can complicate impression making are identified.
Steps of imp.

26. 2-Seating the patient
• The pt is seated in upright
position
Position of dental chair
Lower impression
The pt mouth should be on
level with operators shoulder
Upper impression :
The pt should mouth should
be on level with the
operators elbow.

27. 2-Seating the patient
Position of the operator
Lower impression :
the operator should be in
front of the pt and on the
right side.
Upper impression :
the operator should be to
the right and a little behind
the pt

28. 3-Selection of the stock tray
• A good impression starts with the selection of the correct stock tray.
• The tray should provide 2-3mm space between tray and tissue for impression
material.
• Examine the posterior extension of the tray by dropping the handle down .
• It must cover the hamular notches and vibrating line in upper and retromplar
area in lower

29. 4. Selection of the material
– Alginate is the preferred material to make preliminary
impression(manibulation is simple, setting fast, pleasant to pt and cheap)
But impression compound can also be used.
• 5- making the impression
• It is advice that lower impression is made first :
• 1- the upper impression causes greater discomfort to pt
• 2-a foreign body placed in the mouth increase rate of
salivation

30. Mandibular alginate impression

33. Completed mandibular primary impression

34. Maxillary impression

36. • Tray modification : Deficient in borders are corrected by adding wax or
compound
• for upper tray if vault are deep the central portion of tray are build up
with wax.

39. Completed maxillary primary impression with rounded and
molded peripheries

40. Primary impression with impression compound

43. Common faults in impression
 Insufficient depth in posterior lingual pouch
 Insufficient depth in lingual,labial and buccal
sulci.
 Edge of the tray showing through the
impression.
 An asymmetrical impression.
 Deficiency in the midline of palatal
vault.

44. Causes of inaccurate impression:
1- impression made on inflamed tissue:
• It will change the form of the surface to be recorded.
• Most effective way of resolving the inflammation is to leave the dentures
out for at least 24 hours before the impressions are made

45. 2- improper selection of the tray:
A- the use of short tray :
The use of short tray posteriorly will cause rolling and sagging
of the impression.
The use of short tray buccally ,labially or lingually will result
in unsupported impression border .
B- the use of too long tray:
Lead to displacement of the resilient tissues in the depth of
vestibule and interferes with action of the muscles surround it
Solution
Use proper size of tray

46. 2- improper selection of the tray:
C- the use of too small tray:
• Result in tearing of impression during removal from the mouth
• Present of pressure spots
• The tray shows through the impression material.
D- the use of too large tray:
• Result in impression with excessively thick borders and
difficulty to identify the position of reflection area.

47. 3- improper position of the tray:
A-incorrect centralization of the tray
Result in thin border on one side and thick border on
opposite side.
B- tray placed too forward in relation to ridge
• Results in excessive thickness of labial border or border
of tray may show through the impression
C- tray placed too far backward :
• Results in thin borders of the impression and failure to
record the proper depth and width

48. d- insufficient seating pressure(in adequately seated tray)
cause lack of surface details
e- excessive seating pressure
cause presence of pressure spots where tray shows through the
impression.

49. 4- presence of voids on the impression
• A- the use of too soft impression mix
• B- insufficient seating pressure
• C- excessive space between the tray and the tissue
5- partial dislodgment of the impression from the tray
• Due to forcibly removal of the impression without care.