Impressions

kck.usm.my

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