IMPRESSION AND THEORIES IN CD

1. IMPRESSION & ITS THEORIES
FOR COMPLETE DENTURE
1
DR PRAKASH NIDAWANI
MDS
DEPT PF PROSTHODONTICS
NAVODAYA DENTAL
COLLEGE

2. 3
“Ideal impression must be in the mind of the dentist before it
is in his hand. He must literally make the impression rather
than take it”
- M.M. De Van

3. COMPLETE DENTURE
IMPRESSION :-
3
a complete denture impression is
a negative registration of the
entire denture bearing,
stabilizing and border seal areas
present in the edentulous mouth.
(GPT-9)
PRELIMINARY IMPRESSION :-
a negative likeness made for the purpose of diagnosis,
treatment planning, and/or the fabrication of a custom
impression tray preload . (GPT-9)

4. IMPRESSION TRAYS:-
It is a device used to carry ,confine & control
impression material while making an impression.

5. Classification of trays
Based on whether they are prefabricated or
individualized
• 1- prefabricated Stock tray: used for primary
impression procedure.
• Perforated trays
• Non perforated trays
• Rim lock trays

6. Based on material used for fabrication :-
• a) metallic.
• b) Non- metallic.
Material used for fabrication stock Tray :-
1- METAL
Tin-lead alloy
Stainless steel
2- PLASTIC

7. BORDER MOLDING :-
the shaping of impression material along the border
areas of an impression tray by functional or manual
manipulation of the soft tissue adjacent to the
borders to duplicate the contour and size of the
vestibule (GPT-9)
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v

8. Maxillary stress bearing and relief areas
primary
Hard palate on
either side of
raphae
Firm
tuberosity
Secondar
y
Rugae area
Crest of
Residual
Alveolar Ridge
Relief
Incisive Foramen
Mid Palatine Raphae
Palatal Tori
Sharp Spiny Processes
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9. Mandibular Stress bearing & Relief
areas
Primary
Buccal Shelf Area
Retromolar Pad
Secondary
slopes of
Residual Alveolar
Ridge
Relief
Mandibular Tori
Mental Foramen
Genial Tubercles
Prominent Retromylohyoid Ridge
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10. Principles
of
Impression
Making
Support
Retention
Stability
Esthetics
Preservation
of alveolar
ridges
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11. Retention
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• that quality inherent in the dental prosthesis acting to resist
the forces of dislodgment along the path of placement
• (GPT-9)
• It is the quality inherent in the prosthesis which resists
forces of gravity, adhesiveness of food and forces
associated with opening of mouth

12. Physical
Factors
affecting
Retention
Adhesion
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Cohesion
Gravity
Interfacial
Surface
Tension
Capillary
Attraction
Atmospheric
Pressure &
Peripheral
Seal

13. Anatomical Factors involved in Retention
•Maxilla – PPS, Retro zygomatic space
•Mandible – Pear shaped pad, Retro Mylohyoid
Space
13

14. Stability
the quality of a complete or removable partial denture to be
firm, steady, or constant, to resist displacement by functional
horizontal or rotational stresses (GPT-9)
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15. Support
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IT is the foundation area on which a dental prosthesis rests;
“the resistance to forces directed toward the basal tissue or
underlying structures” (GPT-9)
Esthetics
Role of esthetics in impression making refers to the development of
the labial and buccal borders, so that they are not only retentive
but also support the lips properly.

16. Preservation of the alveolar ridges
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DeVan (1952) stated that “the preservation of that which
remains is of utmost importance and not the
meticulous replacement of that which has been lost”
• Stress-bearing areas and non-stress bearing areas should be
recorded under stress and relief respectively.
• Peripheral tissues to be recorded without over extensions.
• Wide tissue coverage

17. Classification
Depending on
the theories of
impression
making
Muco-
compressive
Muco-static
Selective
pressure
Depending on
the technique
Open
Mouth
Closed
Mouth
Depending on
the purpose
of the
impression
Diagnostic
Primary
Secondary
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18. Definite pressure technique/ Muco-compressive
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• Introduced by Greene brothers
• The tissues recorded under functional pressure provide better support
and retention for the denture.
• Many advocate the use of closed-mouth impression techniques.
• Advocates of this theory believe that occlusal loading during
impression making is comparable to the occlusal loading during
function.

19. Advantages
• Better retention and
support during
functional
movements
• Provide more tissue
coverage
Disadvantages
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• The pressure applied
can overstress the
tissues.
• This often resulted in
good initial retention
but eventual bone
resorption and loose
dentures.
• Loss of retention during
rest due to tissue
rebound.

20. Minimal pressure theory/
Mucostatic:-
• Described by Addison, 1944 who attributed it to Henry L.
Page.
.
• Mucosa being more than 80% water, will react like a liquid in a closed
vessel & cannot be compressed.
•The impression material should record, without distortion, every detail
of the mucosa denture would fit all minute elevations &
depressions.
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21. • High regards for the
tissue health and
preservation
• Good stability due to
close adaptation of
denture bases
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• Less tissue coverage
• Reduced retention
• Lack of border-moulding
reduces
effective border seal
• Lack of border seal
permits food lodgment
• Compromised
aesthetics due to
short denture flanges
• Tissue variations at the
time of impression
making and insertion
may affect the results.
Advantages Disadvantages

22. Selective Pressure Technique
(Boucher):-
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• Principle – mucosa over the ridge is best able to withstand
pressure , mucosa covering midline is thin and has little
submucosal tissue.
• Forces acting on the denture confined to the stress-bearing areas.
• Non stress-bearing areas are relieved and the stress-bearing areas
are allowed to come in contact with the tray.

23. Disadvantages of selective pressure technique
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•Demands firm, healthy mucosal covering over the
ridge. Hence, it cannot be used in flabby ridges

24. Open mouth impressions:-
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• Made with a tray that is held by the dentist.
Advantages
• Visualization of the muscle trimming
• Various movements can be accomplished easily.
• Denture retention can be predicted inopen as well
as in closed mouth movements
• Pressure or pressure-less technique can be
employed by using this technique.

25. Closed mouth impressions:-
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• Supporting tissues are recorded in
functional relationship.
• Requires wax occlusal rims.
• Border moulding and secondary
impressionsare made

26. • Interferences of tray handles
and operator’s finger is
eliminated.
• Time saving -- Bordermolding,
final impression, jaw relation
(tentative/final) can be
completed in 1 time.
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• Rebound of the tissues during rest leads
to denture displacement.
• Tendency for over-extension or under-
extension
• Fatiguing to the dentist and patient.
• A constant pressure is exertedover
tissues, hence blood supply is
compromised leading to ridge
resorption.
Advantages Disadvantages

27. (1)Diagnostic Impression :-
• The negative replica of the oral tissues used to
prepare a diagnostic cast.
• Used for study purposes like measuring the
undercuts, locating the path of insertion.
• Is made as a part of treatment plan and to estimate
the amount of pre- prosthetic surgery required.
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Depending on the purpose of the impression

28. (2) Primary Impression :-
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• An impression made for the purpose of
construction of a special tray.
• There should be at least 6mm clearance between
the stock tray and the ridge for materials used in
making primary impression.
(3) Secondary Impression:-
• Making the wash impression.
• Developing the posterior palatal seal.

29. Operator position for maxillary
impression
Correct Incorrect
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30. Operator position for Mandibular
Impression
Correct 50
Incorrect

31. Making the preliminary impression
Tray should be
adjusted by bending
Selection of stock tray Position borders at
hammular notches
Lift the tray anteriorly,
3-5 mm space for
impression material
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32. Border of the tray
should be cut if
required
Borders should be
smoothened
Material
Manipulation
(hot water bath
at 140F)
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33. Placing the tray in the patients mouth.
Performing Movements to mold the material.
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34. • Impression compound is softened in a hot water bath at 140°F.
• After kneading it is loaded on to the tray and shaped roughly to
the shape of the ridge with the fingers.
• The distolingual flange areas can be molded with fingers to
simulate the final impression.
Mandibular Impression
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35. • The left posterior corner of the tray is inserted while retracting the
right cheek with operator’s left hand and tray is rotated and
centralized over the ridge.
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36. • Patient is instructed to lift the tongue, and tray is seated while applying
pressure
• Light border molding movements are performed including tongue
movements.
• Compound is allowed to harden and chilled after removal impression is
inspected.
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37. Border molding (Peripheral tracing ,
Muscle trimming)
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• Border molding materials
include:
• Modelling compound sticks
(Green Stick)
• Polyether impression paste
• Tissue conditioners
• Auto polymerizing acrylic
resin
• Impression waxes

38. Methods of border moulding
Labial and
Buccal
borders
Smiling
whistling
grinning
(1) Functional method :-
 Normal functional movements mold the borders
in harmony with muscle action
Buccal frenum
and Buccal
borders
Sucking
Lingual
borders
Licking the lips
and tongue
movements
Lingual border
and Floor of
mouth
Swallowing
Distobuccal
borders
Opening, closing
and side to side
movements
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39. (2)Digital manipulation :-
• Dentist manipulates the lips and cheeks
of the patient to simulate the influence
of these on the denture borders.
• Easy ; does not require much of patient
cooperation.
• Influenced by the direction of
movement and the force applied.
(3)Combined :-
• Border molding is usually done by a
combination of digital manipulation by the
dentist and functional movements by the
patients.
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40. Steps in Sectional border molding
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Softened compound added along dry
borders of required segment
Cheek outward, downward and
inward
Softened again with alcohol torch.
Tempered in warm water bath.

41. Labial Border Molding
outward, downward and inwards
Molding the Frenum
Compound placed on posterior border. Tray seated in mouth with firm press6u6re.

42. Compound placed on posterior border
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Compound added on buccal border
The tray gently seated in place.
The borders should be smooth,round
and symmetrical

43. Compound placed on labial border Labial Border Molding
outward, upward and inward
Lingual Border Molding Movements 72

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45. Secondary impression
The final impression material is mixed according to
manufacturer’s directions and uniformly distributed within the
tray.
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46. 79

47. CONCLUSION
109
• The main objective of impression making is to
fabricate dentures having maximum retention and
stability without causing any damage to the
supporting structures. Thus the choice of
impression technique and material is made by the
dentist on the basis of the oral conditions,
concepts of function of the tissues surrounding the
denture and ability to handle the available
impression material.

48. THANK YOU