This document provides information about making impressions for complete dentures. It discusses the objectives and requirements of an ideal impression, including maximum extension without muscle impingement and intimate contact with covered tissue areas. It describes primary, secondary/final, and corrective impressions. The types of impression materials and trays are outlined, including stock trays, special/individual trays, and techniques like border molding and boxing. The document also summarizes different techniques for making final impressions, such as minimal pressure, mucocompressive, and selective pressure techniques.

1. Assistant professor: Sadeq Al-tayar
BDS, MSc, DDS (PHD) - Egypt
Department of Prosthodontics
Ibb University
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IMPRESSIONFOR
COMPLETE
DENTURE

2. Reproduce a positive form and shape of the same oral tissues (Cast)
 Impression: is a negative likeness or copy in reverse of the surface of an object.
Dental impression: is an imprint or negative likeness of the teeth and/or edentulous
area and adjacent tissue.
 Complete Denture Impression:
is a negative record or imprint of the tissues of the oral cavity that forms the
basal seat of the denture.
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3.  An ideal (requirements) impression should provide:
 Maximum extension without muscle impingement.
 Intimate contact with the tissue area covered.
 Proper form of the borders including the posterior border of the
maxillary denture.
 Proper relief of hard and sensitive areas.
 To equalize forces on the denture foundation area. (i.e even
stress distribution)
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4.  PRESS:-
1) Preservation of remaining structures.
2) Retention.
3) Esthetics.
4) Stability and Bracing.
5) Support.
Objectives of Impression Making
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5. • Not to use heavy pressure.
• Covering as much of the supporting areas as possible.
• Minimize the possibility of soft tissue abuse and bone
resorption.
1- Preservation of the alveolar ridges:-
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6.  Is the resistance to the forces which tries to dislodge the
denture in a direction opposite to the path of insertion.
( I.e vertical force against the tissue ward)
 It should be readily seen that if the other objectives are
achieved, retention will be adequate.
 (Retention depends on: Denture base + soft tissue).
2- Retention:-
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7. 3- Esthetics:-
 Thickness of the denture flanges.
Thicker denture flanges are preferred in long-term edentulous
patients ???? labial fullness and support.
 Impression should perfectly reproduce the width and height of
the entire sulcus for the proper fabrication of the flanges.
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8.  Is the resistance to functional horizontal or rotational
movements which try to dislodge the denture.
 Good retention.
 No interfering occlusion.
 Proper tooth arrangement.
 Proper form and contour of the polished surfaces.
 Proper orientation of the occlusal plane.
 Good control and coordination of the patient's musculature.
 (Stability depends on: Denture base + Bone).
4- Stability:-
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9. 5- Support:-
 The resistance to vertical forces of mastication and to occlusal or
other forces applied in a direction toward the basal seat.
• Enhanced by selective placement of pressures that are in harmony with the
resiliency of the tissues that make up the basal seat.
 (Support depends on: Denture base + Bone + soft tissue).
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11.  Preliminary impression:
Is an impression made for the purpose of diagnosis or for the construction of a special tray.
 Secondary or final impression:
It is made in a special tray and its used for the purpose of making the master cast on which
the denture is constructed.
 Corrective impression.
 Relining or rebasing impression.
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Impression
Materials
Non-elastic
Plaster
ZoO/Eugenol
Impression
wax
Compound
Elastic
Aqueous
Hydrocolloid
s
Agar
(Reversible)
Alginate
(Irreversible)
Non-
aqueous
Elastomer
Polysulfide
Silicones
Condensation
Addition
Polyether
IMPRESSION MATERIALS

13.  It is an impression made for the purpose of diagnosis, treatment planning and
construction of special tray.
 It is the first impression made for the patient and from which the study cast was
produced. These impressions are obtained by a stock tray.
• N.B:-
• The maxillary impression should include the hamular notches, fovea
palatina, frenum attachments, palate, and the entire labial and buccal
vestibules.
• The mandibular impression should include the retromolar pad, the buccal
shelf areas, the external oblique ridges, frenum attachments, sublingual
space, retromylohyoid space, and the entire labial and buccal vestibules.
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14. 1 Impression compound. (non Elastic thermoplastic)….1874
2 Alginate impression material. (Elastic hydrocolloid )……1938
3 Putty body silicon rubber base. (Elastic elastomer)
4 Plaster of Paris. (Non elastic 1800)
Impression compound primary impression for complete edentulous maxillary and mandibular ridges.
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15. Alginate primary impression for complete edentulous maxillary and
mandibular ridges. Plaster of Paris
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16. o In complete denture prosthesis, we make two impressions for the patient:
1- primary impression
2- secondary impression
 To make an impression we should have a suitable tray and impression material.
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17. Body
It consists of:
Handle
It is an extension in the middle region (midline), it is (L) in shape so that, it will not interfere
with lip during impression procedure.
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18.  There is upper tray and lower tray, the difference between them is that:-
 in the upper tray, there is a palatal portion that called (vault),
 in the lower tray, there is a (lingual flange).
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19.  TYPES OF TRAYS:
In general, There are 2 main types:
 Stock tray: It is used for primary impression procedure.
 Special tray (individual tray) (custom tray). It is used for final
impression procedure.
 Stock tray:
• This type of the trays can be used for several patients.
• They are made of different materials such as Al, Tin, Brass or Plastic, in variety
of shapes, size to fit different mouth.
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20. 1- Stock tray for dentulous patient.
2- Stock tray for edentulous patient.
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21. used with alginate impression material.
used with sticky impression material like
impression compound.
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22. 1- The type of material used in the primary impression procedure, like impression
compound we used non-perforated tray, because it will be stick on the tray.
And if we use alginate material we should use perforated stock tray for mechanical
retention of impression material to the tray surface.
2- Size of the arch, stock tray comes in different sizes.
3- Form of the arch, (ovoid, square, V-shaped).
 The stock tray must cover all the anatomical landmarks needed in complete denture
and give a sufficient space (4 mm) for the impression material in all directions.
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23. o The primary cast is produced by pouring the primary impression with
plaster which is the positive reproduction of the oral tissues.
o The plaster mixed with water by the saturation method in the rubber bowl and pour in the
impression compound (or other impression materials) after beading and boxing of the impression.
o When the plaster becomes hard, the cast is separated from the impression by the use of hot water
(55-60ºC).
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24.  It is an impression made for the purpose of fabrication of prosthesis on master cast.
 This impression is made with individual tray.
 Final impression must be poured with
stone material to produce the master cast.
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25. o SPECIAL OR INDIVIDUAL TRAYS:-
It is defined as a custom made device prepared for a particular patient which is used
to carry, confine and control an impression material for impression making.
 TYPES:
1. Shellac base plates
2. Modeling compound
3. Self & light curing acrylic resin
4. Cast or swaged metal.
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26.  Advantages of Special Trays
1 . Fit and More accurate border contour.
2 . Less impression material is used .
3 . More comfortable to the patient.
 Shim or spacer:-
“ One thickness of modeling wax or shellac base plate adapted
on the study cast under the special tray “
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27. Spaced special tray (without stoppers).
Spaced special tray (with stoppers).
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28.  CONSTRUCTING THE CUSTOM TRAY:(steps)
1) Outline for the wax spacer is drawn on the study cast.
2) The borders of the special tray and the relief areas should be marked.
3) The cast should be soaked in water.
4) Severe undercuts should be blocked out using wax.
5) Posterior palatal seal area on the cast is not covered with the wax
spacer – maxilla.
6) Buccal shelf not covered – mandible.
7) Baseplate wax approximately 1-2 mm in thickness is placed on the cast.
8) Application of separating medium on the spacer and exposed surface of
cast (stopper areas).
9) Self-curing acrylic resin material - uniformly adapted over the cast.
10)Tray thickness - 2 to 3 mm.
11) Resin handle is attached in the anterior region of the tray.
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30. • The tray should be rigid with sufficient even thickness that it will not fracture during its
use.
• The special tray must not impinge upon movable structures. The borders must be (2
mm) under extended.
• The posterior limits of the impression tray should be slightly over extended to ensure
inclusion of the posterior detail for development of the post-dam area in upper tray.
• The tray must have a handle for manipulation, and the handle must not interfere with
functional movement of the oral structures.
• The tray must be smooth on its exposed surfaces (stoper)s and should have no sharp
corner or edges which would injury the patient.
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31. MATERIALS USED FOR FINAL IMPRESSION
1-Zinc Oxide Eugenol impression material.
2-Alginate impression material.
3-Elastomers impression materials (Rubber base).
4-Impression plaster.
Irrespective of which material is selected, the optimum result will be achieved
only if the custom tray has been constructed and refined correctly.
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34.  Beading: is done to preserve the width and height of the sulcus in a cast.
 Boxing: is the enclosing of an impression with a beading wax to produce
the desired size and form of the base of the cast.
 Boxing impression can be used for primary and final impressions, this procedure
cannot usually be used on impression made from hydrocolloid materials (alginate)
because the boxing wax will not adhere to the impression material as well as the
alginate can be easily distorted.
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35. Minimum thickness for the base of cast 11-15 mm.
3 mm
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36. 1-Beading wax: a strip of wax is attached all around the outside of the impression
approximately (2-3 mm) below the border and sealed to it with a hot wax knife.
2-Boxing wax: a sheet of wax is used to made the vertical walls of the box and it is
attached around the outside of the beading wax strip so that it does not alter the borders of
the impression, the length of the boxing wax is about 9-15 mm.
3-Base plate wax: a sheet of wax can be used
to fill the tongue space in the mandibular
impression that is sealed just below
the lingual border of the impression.
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38. The basic differences in techniques for final impressions can be resolved as those that
record the soft tissues in a:
• 1- Functional position: (Closed mouth technique, Pressure technique).
• 2- Rest position:
• A- No pressure technique (Passive technique, Mucostatic technique).
• B- Selective pressure technique.
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39.  Final impression technique or theories:
1- Minimal pressure impression technique (mucostatic or Passive
Impression technique):
 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.
 Impression material of choice is impression plaster.
Retention is mainly due to interfacial surface tension.
 The mucostatic technique results in a denture, which is closely adapted
to the mucosa of the denture-bearing area but has poor peripheral seal.
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40. 2- Mucocompressive Impression:
 Records the oral tissues in a functional and displaced form.
The materials used for this technique include impression compound, waxes
and soft liners.
The oral soft tissues are resilient and thus tend to return to their anatomical
position once the forces are relieved.
Dentures made by this technique tend to get displaced due to the tissue
rebound at rest. During function, the constant pressure exerted onto the soft
tissues limit the blood circulation leading to residual ridge resorption.
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41. 3- Selective Pressure Impression:
 In this technique, the impression is made to extend over as much denture-
bearing area as possible without interfering with the limiting structures at
function and rest.
 The selective pressure technique makes it possible to confine the forces
acting on the denture to the stress-bearing areas.
 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.
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Thankyou