Requirements of dental Impressions Prerequisites of dental impressions tissue health moisture control displacement of tissues retraction cord, displacement cord single viscosity impression putty wash technique of condensation silicone automixing addition silicone

1. TISSUE MANAGEMENT,
CUSTOM TRAY FABRICATION
AND IMPRESSION MAKING
By:
Khalid Mohamed Mostafa Mohamed Ibrahim
Supervisor:
Prof. Dr. Samir Bakry

2. REFERENCES
1) Contemporary Fixed Prosthodontics, S, Rosensteil, 6e,
Ch.14, Tissue Management and Impression Taking.
2) Schillingburg's Fundamentals of Fixed Prosthodontics, 5e,
Ch.15, Ch16.

3. OUTLINE
1) Requirements of a dental
impression
2) Prerequisites of impression
taking:
a) tissue health
b) tissue displacement
c) Moisture control
3) Impression materials
4) Factors affecting choice
of impression material
5) Reversible Hydrocolloid
Impression Technique
6) Elastomeric Impression Technique
a) putty-wash technique
b) Single viscosity impression
technique

4. REQUIREMENTS OF
DENTAL IMPRESSIONS

5. REQUIREMENTS OF A DENTAL
IMPRESSION:
1) Sufficient unprepared adjacent structures must be
captured in the impression so the dentist and
technician can identify the margins of the prepared
structures.

6. REQUIREMENTS OF A DENTAL
IMPRESSION:
2) The unprepared tooth structure apical to the
margins of the preparation must be recorded,
otherwise, the margins of the restoration will not be
manufactured correctly.

7. REQUIREMENTS OF A DENTAL
IMPRESSION:
3) All teeth in the arch and the soft tissue
surrounding the tooth preparation must be recorded
for proper articulation and contouring of the final
restoration.

8. REQUIREMENTS OF A DENTAL
IMPRESSION:
4) Free of air bubbles, tears, thin steaks, and other
imperfections

9. PREREQUISITES
OF IMPRESSION
TAKING

10. PREREQUISITES OF IMPRESSION
TAKING
1) Tissue Health
2) Moisture Control
3) Tissue Displacement

11. PERQUISITES OF IMPRESSION TAKING:
1) TISSUE HEALTH:
Proper preparation produces minimal tissue
damage.
Subgingival preparations produce minimal transient
tissue trauma if:
A) Properly polished, contoured, marginally
integrate interim restoration is fabricated.
B) Proper hygiene measures are undertaken by the
patient.

12. COMPROMISED
EMBRASURE FORM
AND EXCESSIVE
CONTOUR DUE TO
POORLY
FABRICATED
INTERIM
RESTORATION

13. 2) MOISTURE CONTROL Ideally, rubber dam
should be used.
However in cases of
subgingival
preparations, other
methods must be utilized.
Cotton rolls
Saliva ejector
Svedopter
Speejector

15. MOISTURE CONTROL (CONT.)
SVEDOPTER
(RIGHT)
SPEEJECTOR
(LEFT)

16. MOISTURE CONTROL (CONT.)
Local anaesthesia is also helpful in reducing salivary
flow due to anaesthetization of periodontal
ligaments.

17. PREREQUISITES OF IMPRESSION TAKING:
3)DISPLACEMENT OF GINGIVAL TISSUES
CHEMOMECHANICAL:
RETRACTION CORD
MECHANICAL:
COPPER BAND
CHEMICAL:
ALUMINUM
SULFATE
SURGICAL:
ELECTOSURGERY/
LASER

18. MECHANICAL TISSUE DISPLACEMENT
Copper Band:
A copper band or tube can
serve as a means of
carrying the impression
material as well as a
mechanism for displacing
the gingiva to ensure that
the gingival finish line is
captured in the impression.

19. DISADVANTAGES OF COPPER BAND
May cause injury to the gingiva, however, recession
is minimal.

20. CHEMOMECHANICAL MEANS OF
TISSUE DISPLACEMENT
DISPLACEMENT CORD
•Is placed into the
gingival sulcus for an
adequate length of time
to mechanically stretch
the periodontal ligament
fibres to produce space
for impression material
to record details.

21. The cord may or may
not be impregnated with
an astringent
(Haemostatic agent) to
reduce seepage of fluid
in the sulcus.

34. HAEMORRHAGE CONTROL
1) Ferric Sulphate is
delivered to the
bleeding area via a
syringe.

35. HAEMORRHAGE CONTROL
2)
The area is
water sprayed
generously

36. HAEMORRHAGE CONTROL
3) Once
bleeding has
stopped, a
retraction cord
may be placed.

37. CHEMICAL MEANS: DISPLACEMENT
PASTE
AlCl3 paste is injected directly into the sulcus.
Advantage:
- Haemostasis and Less discomfort.
Disadvantage:
-Less displacement, meaning that die trimming will be
more problematic.

38. CHEMICAL MEANS: DISPLACEMENT PASTE
The paste is injected around preparation
Then it is pushed into the gingival sulcus
Left for 1 to 3 minutes

39. CHEMICAL MEANS: DISPLACEMENT PASTE
Thorough cleaning with water spray
The preparation after cleaning and before impression taking
Impression taking

40. VOLUMETRIC EXPANSION TISSUE
DISPLACEMENT
Polydimethyl Siloxane
with a tin catalyst which
cause gas release
resulting in fourfold
increase in space.

41. VOLUMETRIC EXPANSION TISSUE
DISPLACEMENT
(Foam Cord)
The paste is applied and pressure is then exerted onto the
paste by a cotton roll to cause apical flow of the paste.

42. OCCLUSAL MATRIX IMPRESSION TECHNIQUE FOR
TISSUE DISPLACEMENT•A polyether
index is taken
of the
prepared
area.
•Trimmed 1 or
2 mm above
the restoration
intended
margin.

43. OCCLUSAL MATRIX IMPRESSION TECHNIQUE
FOR TISSUE DISPLACEMENT
Medium bodied impression
material is placed in the
index and placed in the
patient’s mouth.
The pressure applied while
seating will cause apical
flow of the material and
thus tissue displacement.

44. OCCLUSAL MATRIX IMPRESSION TECHNIQUE
FOR TISSUE DISPLACEMENT

45. ELECTROSURGERY
Minor removal of inner epithelial lining by a high
frequency current from large electrodes to smaller
ones.

46. ELECTROSURGERY: CONTRAINDICATIONS
•Patient with electromagnetic devices
•Thin attached gingiva
•The use of metallic instruments (metallic mirrors,
etc..)

47. ELECTROSURGERY: PRECAUTIONS
•Profound soft tissue anaesthesia is mandatory.
•Unmodulated alternating current mode because it
minimized damage to deeper tissues.
•Electrode should not contact metallic restorations.
•Irrigation with hydrogen peroxide before placement
of the retraction cord

48. FABRICATION OF
CUSTOM TRAY

49. A custom tray improves the accuracy of an
elastomeric impression by limiting the volume of the
material, thus reducing two sources of error:
stresses during removal
thermal contraction.

50. In hydrocolloid impressions, dimensional change is
caused by water loss (or gain) from the surface of
the impression.
A bulky hydrocolloid impression has a lower ratio
of surface area to volume and is therefore less
subject to dimensional change.

51. Custom trays can be made
from auto-polymerizing
acrylic resin, thermoplastic
resin, or photo-polymerized
resins.
Thermoplastic materials can
be softened in a water
bath and adapted either
manually

52. or with a
vacuum
former with a
heating
element

53. COMPARED TO AUTO-POLYMERIZING
RESIN
The accuracy of impressions made with a
thermoplastic tray material or light-
polymerized materials is comparable with that
of impressions made with an autopolymerized
resin.

54. Light-polymerized materials:
convenient because a storage period is not needed for the
completion of polymerization.
Less susceptible to distortion in moisture, and the impression is
thus suitable for the electroformed die technique

56. ARMAMENTARIUM
▪Baseplate wax
▪0.025-mm (0.001-inch) tin or aluminum foil
▪ Scalpel
▪ Scissors
▪ Waxing instrument

57. STEP BY STEP: AUTOPOLYMERIZING
RESIN
1. Using a pencil, mark the border of the tray
on the diagnostic cast approximately 5 mm
apically from the crest of the free gingiva (less
for the more rigid impression materials).

59. 2. Adapt a wax or other suitable spacer to the
diagnostic cast. Two layers of baseplate wax
result in a combined thickness of approximately
2.5 mm (the sheets should be measured with a
thickness gauge because wax thicknesses
vary).

63. 3. Soften the wax by carefully heating it
over a Bunsen burner or in hot water.
Overheating may melt it and produce an
undesirable thin spot. Only light pressure
should be applied.

64. 4. After the second sheet of wax has been
applied, trim it back until the pencil line is
just visible.
This creates the space needed for the
impression material.

65. Three stops are needed in the tray to maintain even
space for the impression material in the oral cavity.
These are placed on nonfunctional cusps of teeth
that are not to be prepared
If all teeth are involved, a larger soft tissue stop can
be placed on the crest of the alveolar ridge or in the
center of the hard palate.

68. 5. Because the wax may melt from the
polymerization heat of the material, apply a layer
of tin or aluminum foil over the wax to prevent it
from contaminating the inside of the tray.

70. 6. Mix auto-polymerizing acrylic resin
according to the manufacturer’s
recommendations.
The use of vinyl gloves is recommended to
prevent the development of sensitivity to the
monomer.

71. 7. After the resin is mixed, set it aside
until it is doughy (with the consistency of
putty).

72. 8. Gently adapt the resin to the cast.
A handle made from the excess resin can be
attached at this time. If working time is unavailable,
it can also be attached later with a separate second
mix of acrylic resin.
Buccal ridges, which are helpful with impression
removal, can also be added

74. 9. After the material has
polymerized, remove it from
the cast and trim it with an
acrylic-trimming bur where the
indentation made by the wax
ledge is visible.
All rough edges should be
rounded to prevent soft tissue
trauma.

75. 10. If necessary, fill defects in the stops with
additional resin, wetting the set tray material
with monomer to ensure a good bond. To
prevent the material from lifting up, maintain
some pressure during this phase.

76. STEP-BY-STEP PROCEDURE:
PHOTOPOLYMERIZED RESIN
Follow steps 1 to 5 as for the auto-
polymerizing technique……

77. 6. Remove
photopolymerized
tray material sheets
from their lightproof
packaging and
adapt them to the
relieved cast.

78. Adapt small pieces in the areas of the stops first, to
make sure they are filled completely Two sheets are
needed to make each tray and should be cut as
shown.

79. Carefully adapt the large piece of material
to the cast, being careful not to extend the
material beyond the scribed borders

80. Use a blade to trim the excess material away from
the cast.
Adapt the material with gloved fingers until the
pieces blend together and no seams are visible.
Do not press hard; otherwise, the material will be
deformed and thinned; this weakens the tray.

81. 7. Shape and attach a handle by molding
excess material. Blend it into the tray material.
Use a paper clip to support the handle
material by adapting the material around it.

83. 8. Position the cast in
the polymerization
unit for
approximately 2
minutes

84. Remove the cast from the polymerization unit, separate the
tray from the cast, and remove the softened wax spacer
and the foil barrier.

85. Paint the tray with
the air-barrier
coating provided by
the manufacturer.

86. 9. Return the cast to the polymerization unit
and polymerize in accordance with the time
recommended by the manufacturer.
Remove the tray, and scrub it clean under warm
running water.

87. 10. Clean the tray,
and trim as for the
auto-polymerizing
resin tray. Add
additional resin as
needed.

88. EVALUATION OF THE TRAY
1) Rigid, with a consistent thickness of 2 to 3 mm.
2) Extend about 3 to 5 mm cervical to the gingival margins
3) Shaped to allow muscle attachments.
4) Stable on the cast with stops that can maintain an
impression thickness of 2 or 3 mm.
5) Smooth, with no sharp edges.
6) The handle should be sturdy and shaped to fit between
the patient’s lips.

90. To avoid distortion from continued
polymerization of the resin, the tray should be
made at least 9 hours before its use.
When a tray is needed more urgently, it can be
placed in boiling water for 5 minutes and
allowed to cool to room temperature. A light-
polymerized tray can also be made

91. IMPRESSION
MATERIALS

92. IMPRESSION MATERIALS
In historical order:
•Reversible Hydrocolloid (Agar-Agar)
•Irreversible Hydrocolloid (Alginate)
•Polysulfide
•Condensation Silicone
•Polyether
•Addition Silicone

93. FACTORS AFFECTING CHOICE OF IMPRESSION
MATERIAL
•Is the impression going to be stored
•Stock tray vs. custom tray
•Material of dye manufacture
•Impression technique

94. REVERSIBLE
HYDROCOLLOID
Conditioning equipment:
Liquefaction
Storage
Tempering

95. REVERSIBLE HYDROCOLLOID
Step-by Step:
1) Selection correct size of
water-cooling system tray
2)Place prefabricates stops
to prevent overseating and
increase retention
3) Placement of retraction
cord

96. REVERSIBLE
HYDROCOLLOID
4) Fill the tray
with heavy
bodied
impression
material

97. REVERSIBLE
HYDROCOLLOID
5) Apply wash material
in the area of the
preparation and one
adjacent tooth

98. REVERSIBLE
HYDROCOLLOID:
6) Place the tray in the
tempering time for the
specified time

99. REVERSIBLE
HYDROCOLLOID
7) Removal
of retraction
cord

100. REVERSIBLE
HYDROCOLLOID
8) Hydrocolloid
material placed in
patients mouth prior
to insertion of the
tray.

101. REVERSIBLE
HYDROCOLLOID
9) Remove tray from
the tempering bath
and place in the
patient’s mouth for
sufficient amount of
time

102. REVERSIBLE
HYDROCOLLOID
10) Inspect impression
11)Pour in type
IV or V stone

103. ELASTOMERIC IMPRESSION: HEAVY-LIGHT COMINATION
TECHNIQUE
1) The tray is coated
with the proper
adhesive material
2) The adhesive is
left to dry for the
specified time frame
3) Retraction cord is
placed intra-orally.

104. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
4) Equal amounts of base and
catalyst are dispensed onto the
mixing pads.
Two separate mixing pads are
used:
One for the syringe material
and the other for the tray
material
Fig. showing the Syringe
material (Light)

105. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
5) The light-bodied
material for the syringe is
mixed
(catalyst of polysulfide is
picked up first because
base is too sticky and will
not be mixed if picked
up first)

106. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
6) Continue to mix
until a uniform,
homogenous mix is
obtained.

107. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
7) Place the material
into the syringe as
shown in the
photograph.
(The syringe may
also be loaded from
the other side)

108. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
8)Simultaneous mixing of the heavy bodied material placed in

109. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
9) Remove retraction cord
and dry the preparation.
10) Inject the light bodied
material around the
margins of the restoration
starting from the distal
mesially to prevent the
entrapment of air bubbles
in the mixture resulting
from dropping of the mix
mesiodistally.

110. ELASTOMERIC IMPRESSION: HEAVY-LIGHT
COMINATION TECHNIQUE
11) Seating of the
tray containing the
Heavy bodied
material over the
injected light
bodied material
and
immobilization till
full setting

111. ELASTOMERS: SINGLE VISCOSITY TECHNIQUE
Use of single medium viscosity material in both the syringe and tray.
Higher viscosity and reduced working time compared to the double
viscosity tech.

112. PUTTY WASH: SINGLE STAGE TECHNIQUE

113. PUTTY WASH: TWO STAGE TECHNIQUE
Putty is placed in the
impression tray after
being manipulated
independently for 20
seconds then kneaded
with the catalyst.

114. PUTTY WASH TECHNIQUE: TWO STAGE
•Place a spacer over the
putty material and insert
into patient’s mouth.
•Remove spacer after setting
of the material.
•Place light bodied material
in the tray after removal of
undercuts and excess putty.
•Pour within 1 hour

115. PUTTY WASH TECHNIQUE: TWO STAGED (VIDEO)

116. AUTO-
MIXING:
MAINLY
ADDITION
SILICONE

117. INSPECTION OF IMPRESSION
1) Presence of a continuous cuff of
material all around
2) No voids or discontinuities.
3) No streaks of base or catalyst
present.

118. THANK YOU!