Impressions

IMPRESSION MAKING
(IN COMPLETE
DENTURES)
DR ZURYATI AB GHANI
BDS (WALES), Grad Dip Clin Dent
(Adelaide), Doctor in Clinical Dentistry
(prosthodontics), Adelaide, FRACDS
17.06.2007

Impressions
• An impression – an imprint produced
by ‘the pressure of one thing upon or
into the surface of another’
• Active rather than passive role
• Making rather than taking
• Flawed impressions account for the
majority of denture problems

Categories
• Primary impressions
• Conventional techniques
• Template techniques
• Definitive/secondary impressions
• Conventional techniques
• Selective pressure techniques
• Functional techniques
• Reline and rebases techniques

PRIMARY IMPRESSION
• Definition-an impression made for the purpose
of diagnosis or for the construction of a tray

Tray selection for primary
inpression
• stock trays (for edentulous ridge)
• metal or plastic, perforated or non
perforated
• 2-33 mm clearance between stock
tray and ridge
• tray should extend over tuberosity
and hamular notch

Materials for primary
impression
• Relatively high viscosity materials
• Alginate – used with perforated trays
(metal or plastic)
• Compound – used in with non
perforated trays

Primary impression
• Upper
Sit patient upright
‣ Stand on one side and behind the patient (Your elbows
level with patient’s s upper jaw)
‣ Evert upper lip
‣ Hold the loaded tray inferior and anterior to the incisive
papilla
‣ Insert the tray upwards and backwards to fill, first of all,
the labial sulcus, , then left and right sulci before the palatal
area is pressed into position
‣ Ensure the material record the right and left sulci
‣ Borders definition- ask pt to suck down into tray, move
mandible side to side and then open wide.

Primary impression
• Lower
Sit patient upright with your elbows level with
patient’s s lower jaw.
‣ Stand to one side and in front of the patient
‣ Rotate the tray within the pt’s s mouth in a
horizontal plane until it is in the center of
residual ridge and press the loaded tray
‣ The labial, right and left sulci in turn being
everted to permit the impression material to fill
the functional width of the sulci
‣ ask pt to raise tongue, then border mould.

• Once the material has set, the tray is
removed in one motion
• Mark the borders of the custom tray to
be made.
• Pour up impression

Secondary or definitive
impression
• Definition
‣ Should record the entire functional denture-
bearing area to ensure maximum support,
retention and stability for the denture during use
• Primary purpose
‣ To record accurately the tissues of the denture
bearing areas, in addition to recording the
functional width and depth of the sulci

Special trays
• Close fitting tray
• 2mm even thickness
• Smooth
• Rigid material ( eg. Cold cure acrylic)
• 2mm short of sulcus
• 45° handle

2°impression (Conventional
technique)
• Disinfect the trays
• Check for adequate extension (antero-
posteriorly and bucco-lingually)
• Use pressure indicating paste
• Correct under extension with tracing compound
• Trim the tray if over extended
• Apply tracing compound to the posterior
aspect of the upper tray to produce a
posterior seal

Secondary impression
making
• Upper and lower arches- follow
primary impression taking
• Materials – Zinc oxide eugenol
(material of choice)
- Polyether
- Polyvinylsiloxane (PVS)

Anatomical landmarks of
importance
• Upper arch
• Lower arch

Salient anatomical features of
denture bearing areas

The Incisive Papilla
• Soft tissue pad
• Covering the incisive canal

The Incisive Papilla
• Nerves and blood vessels supplying
the anterior part of the palatal mucosa
• Position – relatively constant following
the extraction of the natural teeth
• Useful guide when placing artificial
teeth as the labial surface of the upper
anterior teeth is usually 8-10mm 8 10mm in
front of the centre of the papilla

Palatine Fovea/fovea
Palatinae
• Two orifices (small depressions in the
mucosal surface) one each side of the
midline
• About 2mm posterior to the vibrating
line
• Act as collecting ducts for a group of
minor palatine salivary glands

Vibrating Line
• Imaginary line across the posterior part of
the palate marking the division between the
movable and immovable tissues of the soft
palate
• Junction of the hard and soft palate
• This line should lie in the soft palate
• The posterior border of the denture usually
finishes on the compressible tissue 1-2mm 1
posterior to the vibrating line. It must cover
to the tuberosities and extend to the
hamular notches.

Freanum
• A narrow fibrous submucosal
membrane bridging the buccal, , labial,
or lingual sulcus
• This picture shows an upper
impression with a depression created
by a buccal freanum

Retromolar Pad
• Triangular soft tissue elevation distal to
the third molars
• Important for denture support and
preventing distal denture displacement
• Bounded by tendons and raphes of
muscles.
• Denture base should extend only one
half to two third of the retromolar pad

THANK YOU
Some of the materials are
courtesy of Dr Adam
Husein

References
1. Nallaswamy D. (2003). Textbook
of Prosthodontics. Jaypee brothers
medical publishers (p) LTD. New Delhi
2. Some illustration are courtesy Dr
Adam Husein