PROSTHODONTICS: RECORDING OF SECONDARY IMPRESSION.pptx

RECORDING OF SECONDARY
IMPRESSION
H.O.TIMOTHY

Outline
• Introduction
• Definition
• Principles of Impression Making
• Recording of Secondary Impression

Introduction
• The impression is made during the
impression visit and provides the clinician
with the opportunity to confirm the
diagnosis of oral conditions.

“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

Good impressions are basic to the fabrication
of a well fitting denture. An impression
should fulfill MM Devan’s dictum.
“It is perpetual preservation of what already
exists and not the meticulous replacement of
what is missing.”

Definition
 Oxford Advanced Dictionary defines Impression as an ‘imprint produced
by the pressure of one thing upon or into the surface of another.’
 An impression is an imprint or negative likeness of the teeth or of
edentulous areas where the teeth have been removed which becomes
relatively hard or set when in contact with the oral tissues.
 The Objectives of Impression Making is to obtain the following in the
final denture:
- Support
- Stability
- Retention
- Aesthetics
- Preservation of remaining oral structures.

Principles of Impression
1 . The oral tissues must be healthy.
2. Impression should include all the basal seat
within the limits of health and function of the
supporting and limiting structures.
3. The borders must be in harmony with the
anatomical and physiological limitations of the oral
structures.
4. Physiological type of border moulding should be
performed.
5. Sufficient space should be provided within the
impression trays for the selected impression material.

Principles (cont.)
6 Impression must be removed from the
mouth without damaging the mucosa.
7 Selective pressure should be applied on the
basal seat during impression making.
8 A guiding mechanism should be provided for
correct positioning of the tray within the mouth.
9 The tray and impression material should be
made of dimensionally stable materials.
10 The external shape of the impression should
be similar to the external form of complete
denture.

Secondary Impression Making
This is a clinical procedure in complete denture
fabrication done to prepare a master cast.
It is a very important step as it should record the denture
bearing area in great detail and also record the muscular
peripheral tissues in function.
The procedure makes use of a custom or special tray
prepared from the master cast.
The borders of the tray should end 2mm short of the
peripheral structures.
The tray can be made of auto-polymerizing resin or
reinforced shellac base plate

Cont’d.
Once the tray is ready, the peripheral
structures are recorded by a procedure called
Border moulding or Peripheral tracing
which involves the use of tracing
compounds or elastomers.
The lips, cheeks and other muscles are
stimulated passively by the clinician to
record the length and width of the vestibule.

Cont’d.
The impression material chosen for the
secondary impression should be of low
viscosity to record the structures accurately.
Loading excess material to the tray may lead
to an overextended impression.
The material of choice are Zinc oxide
Eugenol Impression paste and medium-
bodied elastomeric impression materials.

Recording the Secondary Impression.
Secondary impression involves four steps:
 Making the special tray.
 Special tray preparation
 Border moulding.
 Making the impression.

Special tray preparation
The special tray to be used must be reduced
through out its borders to 2-3 mm short of the
functional depth of the sulcus in the primary cast.
This is because primary impressions are usually
over extended.
Border moulding is defined as the shaping of the
border areas of an impression tray by functional or
manual manipulation of the tissue adjacent to the
borders to duplicate the contour and size of the
vestibule

Border Moulding the Maxillary
Special tray
 Soften the modeling plastic impression compound over the
alcohol torch flame, and place it over the border of the tray.
 After tempering in water bath at 70 F, border mould it in the
mouth.
 In the region of labial sulcus, the upper lip is elevated and
extended out and then pulled downward and inward.
 Re-soften the compound and repeat this procedure to establish
proper border moulding.
 In the region of buccal frenum, the cheek is elevated and then
pulled outward ,downward and inward .
 Move the cheek backward and forward to simulate movement
of buccal frenum as in function during eating and smiling

Border Moulding the Maxillary
Special tray Cont’d.
 The posterior buccal flange at the tuberosity region is border
molded when the cheek is extended outward, downward and
inward.
 With the tray in place, have the patient open mouth widely and
move the jaw laterally to establish the width of the sulcus.
 Place strip of softened compound at the posterior border of the
custom tray and seat it firmly in the mouth.
 Mark vibrating line and post palatal seal area with indelible
pencil
 Seat the tray again firmly in the mouth for the indelible pencil
mark to be transferred to the tray . Remove excess of modeling
compound.

Making Final Maxillary Impression.
The mixed impression material is placed on the
tray with borders covered.
Seat the tray in the mouth and border mould
in the posterior region and then in the anterior
region.
Do not load the tray with excess material.

Border moulding mandibular
special tray
 Start border moulding
(1) beginning with labial flange .
(2) buccal flanges,
(3) finally lingual flanges.
 In the region of labial sulcus, the lower lip is lifted outward, upward and
inward.
 The buccal flange must not extend lateral to external oblique ridge
 The disto buccal flange must record the masseter groove and the superior
border of retromolar pad.
 In the region of buccal frenum, the cheek is lifted outward, upward inward,
backward and forward to simulate the movement of buccal frenum.
 Record masseter groove by instructing the patient to exert closing force and
the dentist exerting a downward pressure on the tray.

Border Moulding Mandibular
Special Tray
The lingual flange is border moulded in 5 steps
 Step 1.The extension of anterior lingual flange of the tray is limited by the lingual
frenum and sublingual folds, and is 2mm short of the tissues
 Step 2. Place the softened modelling compound on the border of the tray extending
between premylohyoid fossa. Instruct the patient to protrude the tongue to establish
the length of the sulcus. The compound is re-softened and placed again in the mouth
and the patient is instructed to push the tongue forcefully against the palate to
determine the thickness of the flange.
 Step 3. Modelling compound is added to the lingual borders from premylohyoid
fossae posteriorly on both sides .After placing the tray in the mouth, instruct the
patient to protrude the tongue. This procedure establishes the length of the sulcus.

Border Moulding Mandibular
Special Tray Cont.
 Step 4.Repeat step 3 and have the patient move the tongue laterally and touch the
corners of the mouth. Remove the wax spacer from the tray
 Step 5.Add modelling compound on the distal end of the lingual flange of the tray.
Place the tray in the mouth and have the patient protrude the tongue to activate the
superior constrictor of the pharynx muscles
(1) that support the retromylohyoid curtain and pterygomandibular raphe
Instruct the patient to forcefully close the mouth .The resulting contraction of
the medial pterygoid muscles
(2) limits the retromylohyoid area.

Border moulding the lingual flange.

Final Rubber Base Impression.
Place the tray with impression material in patients
mouth. Manipulate lips and cheeks.
Have the patient move the tongue and keep it in
protruded position till the impression sets.

PROSTHODONTICS: RECORDING OF SECONDARY IMPRESSION.pptx

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