this presentation includes various techniques used while taking impressions in dental practice.

1. PRESENTED BY:PRESENTED BY:
DR MEENAL ATHARKAR
MDS
DEPT OF ENDO AND CONS

2.  Based on the position of the mouth
 Open mouth technique
 Closed mouth technique (functional impression )
 Based on the pressure applied
 Positive pressure
 Negative pressure
 Selective pressure technique

3.  Based on the mixing technique
 Double mix
 Heavy-light body technique
 Putty wash technique
 One stage – simultaneous
 Two stage – relief channel
- 2mm spacer technique- 2mm spacer technique
 Single mix or monophase technique
 According to the tray used
 Custom tray impressions
 Stock tray impressions

4.  The light body material is injected from the filled syringe
within and around the tooth preparation.
 The tray filled with heavy body material is inserted in the
mouth and seated over the syringe material.mouth and seated over the syringe material.
 The two materials bond together on setting.
 Most commonly used with custom tray.

6.  Advantages
 Over comes the polymerization shrinkage of the light
body material
 Margins duplicated in light body
 Disadvantages
 Use of custom tray
 An assistant required for mixing the material -
tray/syringe simultaneously
 Margins duplicated in heavy body in case of excess
pressure

7.  Medium viscosity of polyether and addition silicones used
in a stock tray
 Only one mix is made, part of the material placed in the
tray and another portion placed in the syringe for injectiontray and another portion placed in the syringe for injection
in the cavity preparation or on prepared teeth
 Success of this technique depends on the pseudoplastic
behavior of these two materials

8.  Advantages
 Reduced wastage of the material
 Less time consumption
 Avoids the time involved in fabrication of custom tray
 Disadvantages
 Relatively high viscosity and reduced flow of the
monophase materials, makes their injection onto the
preparation more difficult to control -increased incidence
of surface voids

10.  Light body material syringed on to the preparation
while the putty material loaded in a stock tray is
simultaneously inserted into the mouth.simultaneously inserted into the mouth.

12.  Advantages
 Reduced chair side time
 Disadvantages
 Absolute lack of control in the bulk of wash
material.
 By mixing putty, syringe material simultaneously, By mixing putty, syringe material simultaneously,
setting distortion of putty included in over all
distortion of impression.
 Possibility of margins duplicated in putty medium
 Tendency of bubbles to be formed and occluded in
the set impression

13.  Pre-operative putty impression is made intra orally
 In the area where the teeth are to be prepared
impression material is removed or channels prepared
using putty cutter instrumentusing putty cutter instrument
 The impression is then relined with low viscosity
material

15.  Advantages
 Impression can be captured with the wash materials
 Disadvantages
 To confine the wash material to area of relieved impression
 If entire area is washed - creates hydraulic displacement of If entire area is washed - creates hydraulic displacement of
putty impression resulting in smaller dies

16.  2 mm thickness wax spacer is prepared on a diagnostic
cast, occlusal stops are provided on non-functional
cusps
 A putty impression is made with a stock tray resulting
in a putty custom tray with 2mm space for the washin a putty custom tray with 2mm space for the wash
material
 Putty custom tray is then washed with light body
material

18.  Advantages
 Wash stage carried out after the putty has set and
contracted.
 Controlled wash bulk compensates for this contraction
with minimal dimensional change.
 Disadvantages
 Extra chair side time
 Extra material

19.  This technique was used to salvage an impression of
multiple preparations when there were only vague
margins on one or two preparations that were not
adequately replicated in the impression.adequately replicated in the impression.
 Copper tube is prepared that extends 1 mm beyond
the finish line.

21.  Top one - third of copper tube filled with impression
compound and sealed on the preparation.
 2 mm of compound was removed from the impressed
occlusal surface for the rubber base.
 Disadvantages Disadvantages
 Can cause damage to the attachment apparatus
 Time consuming

22.  This technique captures the prepared teeth, the opposing
arch and the occlusal articulation in maximumarch and the occlusal articulation in maximum
intercuspation (MIP) simultaneously .

23.  Indications
 Used with a maximum of two prepared teeth
 Unprepared stops anterior and posterior to the prepared
teeth should be present
 Used only with patients that have existing anterior guidance Used only with patients that have existing anterior guidance
 Must be able to close completely in maximum intercuspation
position with the impression tray in place

24.  Contraindications
 Presence of third molars
 Rapidly ascending ramus
 Excess soft tissue distal to the molars

25.  Advantages
 Accurate recording of the MIP
 Eliminates any mandibular flexure that might be
associated with opening
 Disadvantages Disadvantages
 Complicated laboratory procedure

26.  Impressions of multiple prepared teeth due to inherent
limits in working time and difficulties maintaining
moisture control
 Arch is broken down into segments of two prepared teeth
Custom tray prepared for each segment with 1mm of wax Custom tray prepared for each segment with 1mm of wax
relief, trays should extend 3 mm past the gingival margin

27.  Low viscosity material is loaded into the syringe as
well as the segmental tray, and then an impression
made.
 Procedure repeated with each segment.
 Finally an over impression is made using a stock tray.
UsesUses
 When moisture control is difficult in specific patients.
 When making simultaneously impressions of implants
and prepared teeth.

28.  Indicated when multiple dowel cores are required or when
radicular attachments are to be used
 A 25 gauge local anaesthetic needles - vent to allow air to
escape as the impression material is injected into the canal
space
 Needle is gradually removed while the low viscosity
materials is injected into the canal
 Plastic impression dowel coated with adhesive is inserted
into the canal
 Procedure is repeated with multiple dowels and finally an
over impression is made

30.  Elastomers are strong enough to reproduce a pinhole
without tearing
 However to ovoid bubbles
 Cement tube : the tube filled with impression material is
squeezed into each pinhole, making sure no air is trapped by
inserting and removing an explorer into the materialinserting and removing an explorer into the material
 Lentulospirals : rotated slowly along the sides of the pin-
hole
 Reversible hydrocolloid - special nylon bristles are used
to register the pin hole

31.  It is the electro deposition of metals (silver, copper) on
the surface of the impression to improve the abrasion
resistance of gypsum
 Advantages
 Increased hardness of the die
 Excellent abrasion resistance
Die is so strong that wax patterns & gold castings can be Die is so strong that wax patterns & gold castings can be
burnished with little distortion or damage to the die
 Disadvantages
 Toxicity of cyanide baths
 Time required to prepare the die
 Expense of labor and materials
 Limited control of die accuracy

32. DISINFECTION OF IMPRESSION
 The dental impression is one of the ways by which
pathogens can leave the operatory and spread their risk
abroad .
The impression must be rendered harmless before The impression must be rendered harmless before
being passed on to another person who will work with it
or with the gypsum cast made from it, outside the dental
operatory .

33.  Chemical disinfectants used for this purpose
 Chlorine compounds
 Synthetic phenolic compounds
 Glutaraldehydes
 Iodophors
Phenolic/ alcoholic combinations Phenolic/ alcoholic combinations

34. MaterialMaterial MethodMethod DisinfectantDisinfectant
AlginateAlginate
AgarAgar--agaragar
Disinfectant with shortDisinfectant with short--
term exposure timeterm exposure time
(<10min )(<10min )
Chlorine compounds orChlorine compounds or
iodophorsiodophors
PolysulfidePolysulfide
SiliconeSilicone
Immersion time shouldImmersion time should
not exceed thenot exceed the
recommended pouringrecommended pouring
Glutaraldehydes,Glutaraldehydes,
Chlorine compounds,Chlorine compounds,
iodophors, phenolicsiodophors, phenolics
SiliconeSilicone
recommended pouringrecommended pouring
timetime
iodophors, phenolicsiodophors, phenolics
PolyetherPolyether Disinfectant with shortDisinfectant with short--
term exposure timeterm exposure time
(<10min )(<10min )
Chlorine compounds orChlorine compounds or
iodophorsiodophors

35.  An alternative method for the hydrophilic materials:
 Disinfectant can be sprayed on the impression - wrapped in
a disinfectant soaked paper towel and placed in sealed
plastic bag for 10 min.
 Long immersion time may cause the surfactant in
hydrophilic PVS to leach out and render the impression
less hydrophilic.less hydrophilic.

36.  Ultraviolet treatment - effective against Candida
organisms, and there was no adverse effect on either
dimensional change or surface roughness of impression
materials
 Disadvantages - cannot kill micro organisms that are
shadowed from the emission
 UV light unit should be designed in such a way, that the
impression rotates on the table and unit surrounded by
mirror

37.  Sent well cleaned (rinsed) and undisinfected in a
biohazard-labeled, heat sealed plastic bag
OROR
 Debride, clean (rinse) and adequately disinfect it, place
it in a sealed transport bag labeled with the precautions
taken

39. The ability to record consistently good impressions is
both a science and an art.
Impression techniques, methods and materials are
evolving and changing but underlying principles andevolving and changing but underlying principles and
fundamentals remain constant.
An ideal impression must be in the mind of the dentist
before it can be in his hand. It is this knowledge and
experience that enables a dentist to create desirable results

40.  Philip’s science of Dental Materials – Eleventh Edition.
Anusavice
 Restorative Dental Materials - Eleventh Edition. Robert
G. Craig
 Fundamentals of Fixed Prosthodontics - Third Edition.
Shillingburg
 Contemporary Fixed Prosthodontics - Second Edition.
Roseinsteil Art and Science of Operative Dentistry -
Fourth Edition. Sturdevant