Primary impression

1. Impressions in Complete DenturesImpressions in Complete Dentures
An imprint / negative likeness of the teeth
&/or edentulous areas where the teeth have
been removed, made in a plastic material
which becomes relatively hard or set while in
contact with the tissues.
A complete denture impression is a
negative registration of the entire denture
bearing, stabilizing & border seal areas present in
the edentulous mouth.s

4. ClassificationClassification
Depending on theories of impression making
 Mucostatic / passive impression (Richardson
& Henry L. Page)
 Mucocompression / functional impression
(Carole Jones & Greene brothers)
 Selective Pressure impression (Boucher)

5. ClassificationClassification
Depending on the technique
 Open mouth / Closed mouth technique
Hand manipulation for functional movements
(Dynamic impression)
Depending on type of tray
 Stock tray / Custom tray impression

6. ClassificationClassification
Depending on purpose of the impression
 Diagnostic / Primary / Secondary
Depending on the material used
 Agar, Alginate, Impression Compound, Plaster,
Wax, Silicone, Thiokol rubber impression.

7. Principles of impression makingPrinciples of impression making
 Oral tissues must be healthy
 Impression should include basal seat within limits
 Borders must be in harmony with anatomical & physiological limitations
of oral structures
 Selective pressure tech. shd be used
 Sufficient space should be provided within impression tray for imp.
material
 Guiding mechanism (tissue stops & handle) shd be provided for correct
positioning of tray
 Imp. Shd be removed from mouth without damaging the mucosa
 Materials used shd be dimensionally stable
 External shape of impression shd be similar to ext. form of complete
denture

8. Objectives of impression makingObjectives of impression making
 PP – preservation of remaining natural structures– preservation of remaining natural structures
 RR – retention– retention
 EE – esthetics– esthetics
 SS – stability– stability
 SS – support– support

9. Preservation of remaining naturalPreservation of remaining natural
structuresstructures
Impression shd record details in appropriate form to prevent
injury to the tissues
 Relief to non-stress bearing areas, thus preventing damage
 Avoid overextensions

10. RetentionRetention
 That quality inherent in the prosthesis which resists the force of
gravity, adhesiveness of foods, and the forces associated with the
opening of the jaws
 It is the ability of denture to withstand displacement against the
path of insertion
Factors affecting retention
 Anatomical ----size & quality of denture bearing area
 Physiological – viscosity of saliva (thick/thin)
 Physical -------- adhesion, cohesion, surface tension,
capillarity & atmospheric pressure
 Mechanical ---- undercuts, retentive springs, magnets,
adhesives, suction chambers/discs
 Muscular ------ Neutral zone

11. StabilityStability
 The quality of a denture to be firm, steady, or constant, to resist
displacement by functional stresses & not to be subject to
change of position when forces are applied
 It is the ability of the denture to withstand horizontal forces.
Factors affecting stability
 Vertical height of ridge -- resorbed ridge – poor stability
 Quality of soft tissue ---- firm / flabby tissues
 Quality of impression---- accurate, smooth, stable
 Occlusal plane ------------ should be parallel to ridge
 Arrangement of teeth --- balanced occlusion
 Contour of the polished surfaces

12. SupportSupport
 The resistance to vertical forces of mastication,The resistance to vertical forces of mastication,
occlusal forces & other forces applied in aocclusal forces & other forces applied in a
direction towards the denture bearing area.direction towards the denture bearing area.
 Achieved by covering as much area as possibleAchieved by covering as much area as possible
 This helps to distribute forces - snowshoeThis helps to distribute forces - snowshoe

13. EstheticsEsthetics
 Thickness of flangesThickness of flanges
 Impression should reproduce width & height ofImpression should reproduce width & height of
sulcussulcus

14. Recording the Preliminary ImpressionRecording the Preliminary Impression
 TRAY – A receptacle into which a suitable material is placed to make
an impression
 A device which is used to carry, confine & control an impression
material while making an impression
 Stock tray – metal / plastic, 2-3mm clearance, shd cover tuberosity &
hamular notch
 Special tray – A custom made device prepared for a particular patient
which is used to carry, confine & control an impression material while
making an impression
 Material used shd be well adapted, stable, 2mm thick, contrast in
colour & 2mm short in sulcus
 Fabrication of tray – shellac, self cure resin, thermoplastic resins,
vacuum formed Vinyl or Polystyrene
 Storing the trays

18. The End