shammasm, intro to dentures, complete dentures, 3rd year

1. STOCK IMPRESSION TRAYS
AND CONSTRUCTION OF
DIAGNOSTIC CASTS

2. Learning outcomes
Define impression trays and list the
parts of the tray.
Describe the various types of trays.
Define preliminary impressions and
explain the objectives of making an
impression.
List the materials for making
impressions.

3. Patient Visit #1
Visit 1
Clinical
procedure
Lab.
procedure
Taking
case history
Selecting
the stock tray
Preliminary
Cast Pouring
Preliminary Casts
Preliminary
impression Wax Spacer
Custom Trays

4. Impression tray: A
device that is used to
carry, confine, and control
impression material while
making an impression.

5. Requirements of an impression tray
 Should be strong and rigid yet be
adjustable
 Should be able to sterilize effectively
 Should be made of biocompatible
material to be used in the oral cavity
 Should not react with any
impression material

6.  Should not distort during the setting
of impression material
 Should have sufficient flange height
to record the full sulcus depth
 Should cover all anatomical
landmarks of the oral cavity
 Should come in different sizes

7. Parts of an
Impression Tray
1. Handle
2. Flange
3. Body

8. Types of Impression
Trays

9. Impression trays can be of various
types:
1. According to the material used to
fabricate the trays:
a. Metallic trays (stainless steel,
Aluminum)
b. Non-metallic trays (plastic trays,
acrylic resin trays)

10. TYPES OF STOCK TRAYS
Plastic Perforated
tray
Metal Rim-lock tray

11. 2. According to the method of
fabrication of trays:
a. Stock trays
 Full arch trays
 Sectional trays
 Quadrant trays
b. Custom trays or Special trays

12. 3. According to the teeth
present /absent in mouth:
a. Edentulous trays
b. Dentulous trays

13. 4. According to the method of
interlocking of material:
a. Perforated trays
b. Non-perforated trays
c. Rim-lock trays
i. Water-cooled
ii. Non water-cooled

14. Rim lock trays:
i. Water- cooled
ii. Non water-cooled

15. Sterilizing trays
Trays should be cleaned
properly and sterilized before
use
Disposable trays are
recommended
Sterilization can be achieved by
autoclaving, dry heat or
chemical vapors

16. Preliminary
Impression: a negative
likeness made for the purpose of
diagnosis, treatment planning, or
the fabrication of a tray.

17. Objectives of an impressionObjectives of an impression
 PreservationPreservation
 SupportSupport
 StabilityStability
 EstheticsEsthetics
 RetentionRetention

18. Preservation: Preservation of the
remaining residual ridge

19.  The impression material and
impression technique has a
definite effect on health of both
hard and soft tissues of the
mouth.

20.  Pressure in the impression
technique is reflected as
pressure in the denture and
results in soft tissue damage
and bone resorption.

21. Support: Maximum coverage provides
the “snowshoe” effect,

22.  Which distributes applied forces
over as wide an area as
possible. This helps in
preservation, stability, and
retention.

23. Stability: Close adaptation to the
undistorted mucosa is most
important. Stability, or the
resistance to horizontal
movement, decreases with the
loss of vertical height of the
ridges or with the increase in
flabby, movable tissue.

24. Esthetics: Improve esthetics

25.  Border thickness should be
varied with the needs of each
patient in accordance with the
extent of residual ridge.

26.  The vestibule should be filled,
but not overfilled, to restore
facial contour.

27. Retention: Resistance to vertical
displacement away from the denture
bearing surfaces.

28. The factors affecting retention are:
i. Adhesion
ii. Cohesion
iii. Mechanical locking into undercuts
iv. Atmospheric pressure
v. Muscle control and patient
tolerance

29. Adhesion:
 Adhesion is the physical
attraction of unlike molecules
for each other.
 It is the attraction of saliva to
the mucous membrane and
the denture.

30. Cohesion:
 Cohesion is the physical
attraction of like molecules for
each other.
 It is a retentive force because it
occurs within the layer of saliva
that is present between the
denture base and the mucosa.

31. The chain of intermolecular forces between the
denture and the mucosa contributing to
retention.

32. Mechanical locking into undercuts:
 Undercuts of the lateral
tuberosities, maxillary premolar
areas, distolingual areas, and
lingual mandibular premolar
areas can be extremely helpful
to the retention of the dentures.

33. Undercut

34. Atmospheric pressure:
 Atmospheric pressure can act to
resist dislodging forces applied
to dentures, if the dentures have
an effective seal around their
borders.

35. For atmospheric pressure to be
effective, the denture must have a
perfect seal around its entire border.

36. Muscle control and patient
tolerance:
 Muscular control refers to the
functional forces exerted by the
musculature of the patient that
can affect the retention.
 This is primarily a learned
process.

37.  Certain patients have the ability
to wear their dentures and
function without complaint
despite the fact that they may be
ill-fitting, unstable or even broken
because of the adaptability of the
muscles of oral cavity and
patient tolerance.

38. 1. Elastic
A) Hydrocolloids
 Reversible hydrocolloid (Agar)
 Irreversible hydrocolloid
(Alginate)
B) Elastomers
– Polysulfide
– Addition Silicone
– Condensation Silicone
– Polyether
2. Rigid
 Zinc oxide
eugenol
impression
paste
 Impression
wax
 Impression
compound
 Impression
plaster
CLASSIFICATION OF IMPRESSION
MATERIALS

39. 1. Impression Compound
2. Irreversible Hydrocolloid
(Alginate)
3. Elastomers (Putty
consistency)
Materials used for making
preliminary impressions:

40. Preliminary Cast: a cast
formed from a preliminary
impression for use in diagnosis
or the fabrication of an
impression tray.

41. Materials used for making preliminary
casts:
1.Beta hemihydrate (dental plaster)
2.Alpha hemihydrate (dental stone)

42.  Dispense materials
Powder is ideally weighed on a scale and
water measured in graduated cylinder

43.  Mixing
Add water 1st
that slowly wet the
powder and get rid of any bubbles
trapped in the plaster/stone
Spatulate for 30-60 seconds in rubber
mixing bowl by hand
Vibrate mix to reduce bubbles

44.  Pouring the model
Dry the surface of the impression of excess
water
Hold impression on vibrator and let the mix
run from one end on the impression
Flow material all around impression and
vibrate lightly
Fill the impression sufficiently
Extra material from bowl will be used to
form the base of the cast

45. Inversion method of pouring the casts

46.  The base should have a
minimum thickness of 15-16
mm at its thinnest portion.

47. The cast should be separated
from the impression about an
hour after the initial set, trimmed
and finished.

48. Outline of Bases for Trimmed
Casts
 Follow the contour of the
ridges, with rounded angles
Mandibular Maxillary