orthodontics

2. IMPRESSION MATERIALS
AND TECHNIQUES IN
ORTHODONTICS
By,
Dr.Karan Purohit
M.S.R.D.C

3. CONTENTSCONTENTS
• INTRODUCTION.
• HISTORY
• IDEAL REQUISITES OF AN IMPRESSION MATERIAL
• CLASSIFICATION OF IMPRESSION MATERIALS AND TRAYS
• IMPRESSION MATERIALS- ALGINATE,AGAR AND SILICONES
• IMPRESSION TECHNIQUE
• IMPRESSION FOR CLEFT PALATE PATIENT
• IMPRESSION FOR MYOFUNCTIONAL APPLIANCES
• ORA SCANNER
• CONCLUSION
• REFERENCES

4. INTRODUCTION
•Impression materials are used to make an accurate replica
of oral tissues.
•The area involved may vary from a single tooth to the
whole dentition or an impression of an edentulous mouth.
•Usually the impression material is carried to the mouth in a
plastic state on a tray and removed from the mouth when
the material has set.
•The accuracy, detail and quality of the final replica is of
greatest importance.

5. • There are a wide range of impression materials
having its own advantages and disadvantages.
• When making impressions for orthodontic cast
the hard and soft tissues should be accurately
reproduced.
• The casts should include the teeth, palate and
the alveolar process to the base of vestibule and
to the floor of the mouth.

6. DENTAL IMPRESSION?
An imprint or a negative likeliness of the teeth and or
edentulous areas where the teeth have been removed, made
in a plastic material which becomes relatively hard or set
when it comes in contact with these tissues.
IMPRESSION MATERIAL ?
Any substance or combination of substances used for
making a negative reproduction or a replica of the oral
tissues

7. HISTORY
 PHILIP PFAFFS (1756) WAS THE FIRST TO DESCRIBE TAKING AN IMPRESSION OF
THE JAW .
 DELABARRE (1820) INTRODUCED THE IMPRESSION TRAY
 HARLES STENT (1857) A LONDON DENTIST TESTED A COMBINATION OF
DIFFERENT KINDS OF WAXES HARDENED AT ORAL TEMPERATURES, WHICH IS
STILL USED TODAY UNDER THE NAME OF STENTS COMPOSITION.
JOSEPH RICHARDSON (1860) SUGGESTED THE EARLY USE OF GUTTA PERCHA
FOR OBTAINING IMPRESSION BECAUSE OF ITS ELASTICITY
S. WILLIAM WILDING (1940) USED ALGIN AS DENTAL IMPRESSION MATERIAL
 S. L. PEARSON, (1955) LIVERPOOL UNIVERSITY DEVELOPED ELASTIC
IMPRESSION MATERIALS FROM SYNTHETIC RUBBER AND RESIN BASES.

8. In orthodontics, impression gives a negative reproduction of
the tissues and by filling it with dental stone or other model material
a positive cast is made that can be removed after model material has
set., which in turn are used for;
1. STUDY PURPOSE
2. FABRICATION OF APPLIANCES
3. MAINTAINING RECORDS

9. IDEAL REQUISITES OF AN IMPRESSION MATERIAL
• BE NON TOXIC TO THE TISSUES.
• SHOULD HAVE AN ADEQUATE SHELF LIFE .
• BE SUFFICIENTLY FLUID ON INSERTION TO GIVE
ACCURATE SURFACE DETAIL.
• HAVE PLEASANT TASTE, SMELL AND APPEARANCE .
• HAVE NO DIMENSIONSAL CHANGES EITHER IN OR OUT OF THE
MOUTH AT ALL NORMAL DEGREES OF TEMPERATURE AND HUMIDITY.

10. • SET OR HARDEN, AT OR NEAR MOUTH TEMPERATURE .
• IT SHOULD HAVE SUITABLE WORKING AND SETTING TIME.
•BE COMPATIBLE WITH DIE AND MODEL MATERIALS
• BE INEXPENSIVE

11. No impression material fulfills all these requirements
And the selection of the material best suited for a
particular Clinical situation and technique rests with
Dentists.

12. CLASSIFICATION OF THE
IMPRESSION MATERIALS BASED
ON:
SETTING
REACTION
THERMOPLASTIC THERMOSET
ELASTICITY ELASTIC INELASTIC
NATURE OF
THE SETTING
REACTION
REVERSIBLE IRREVERSIBLE
PRESSURE
EXERTED ON
THE TISSUE
MUCOCOMPRESSIVE MUCOSTATIC
DENTITION
STATUS
EDENTULOUS DENTULOUS

13. COLLOIDS
• They are the fourth state of matter because of their differences in
structure, constitution, and reactions .
•Particles size ranging from 1 to 200 nanometers.
• Colloid are Suspension of 2 phases
• Colloidal materials used for making impressions are either algin or
agar dissolved in water.
•Hence the name “HYDROCOLLOIDS”

14. Colloids , have two distinct phases
A dispersed phase + dispersion phase
LIQUID COLLOIDS ARE CALLED SOL
SOLID COLLOIDS ARE CALLED GEL

15. In orthodontics we require impression materials that are elastic
since we deal with dentulous patients
The most commonly employed materials include
I. Hydrocolloid – Agar Agar (reversible)
- Alginate (irreversible)
II. Elastomeric impression materials.

16. SYNERISIS
The process of synerisis may be explained as the squeezing of
water from between the polysaccharide chains. As a result of
which one may often observe a small droplets of water on the
surface of impression. Which results in shrinkage of the
impression.

17. IMBIBITION
In the presence of excess water the hydrocolloids may absorb
water by a process, which is opposite of synerisis that will
cause the separation of the polysaccharide chains and thus
causes the swelling of the impression.

18. IRREVERSIBLE HYDROCOLLOID
ALGINATE (ADA no 18)
At the end of 19th
century the chemist from Scotland noticed
that certain brown seaweed produced a mucous extraction that he
termed as ‘ALGIN’. Later S William wilding used this algin as
dental impression. This became the chief ingredient in our
popularly used dental ALGINATE, which is
A SODIUM SALT ANHYDRO-ß-D-MANURONIC ACID/
ALGINIC ACID

19. The factors causing its successful use as an impression material
include:
• Ease of manipulation
• Comfortable to the patients
• Relatively inexpensive not requiring elaborate armamentarium.
TYPES
TYPE I – RAPID OR FAST SETTING
TYPE II – NORMAL SETTING

20. APPLICATIOS OF ALGINATE
1.Most communally used for making impression for
orthodontic study models.
2.For duplicating models.

21. COMPOSITION
NO COMPOSITION FUNCTION %
I. Salt of Alginic acid Dissolves in water & reacts
with calcium ions
15%
II. Calcium sulphate Reacts with pottasium
alginate to form calcium
alginate
16%
III. Tri sodium
phosphate
Reacts in preference with
calcium sulphate - retarder
2%
IV. Pottasium Titanium Gypsum hardener 3%
V. Zinc oxide Filler 4%
VI. Diatomaceous earth Filler 60%
VII. Flavouring &
coloring agents
Makes the material more
palatable
TRACES

22. SETTING REACTION.
Soluble alginate reacts with the calcium sulphate resulting in the
formation of an insoluble calcium alginate.
This process occurs quite rapidly and thus would not allow sufficient
working time, so to compensate for this problem a water soluble salt
namely Tri-sodium phosphate is added to prolong the working time.
The basic idea behind adding this salt is to allow calcium sulphate to
initially react with tri-sodium phosphate in preference to the soluble
alginate

23. Properties
WORKING TIME ;-
for fast setting materials -1.25 to 2 min (mixing time-45 sec)
for regular setting times is - 2 to 4.5 min (m.t.-60 sec)

24. • Flexibility
A D A specification permits a range of 5% to 20% at a stress
of 1000 gmscm2 and most alginate have a typical value of 14%.
• Strength
The compressive strengths range from 5000 – 9000 gmscm².
The Tear strength vary from 380- 700 gmscm.
• Elasticity
highly elastic but less when compared to agar and about 97.3% elastic
recovery occurs.
The amount of permanent deformation is more as compare to agar.

25.  ACCURACY
• Alginates are sufficiently flexible to record fine detail in the mouth..
• During setting of the material it is important that the impression
should not be moved.
• The reaction is faster at higher temperature and so the material is
contact with the tissues sets first.
• Any pressure on the gel due to movement of the tray will set up
stresses within the materials which will distort the alginate after its
removal from the mouth.

26. • The material is sufficiently elastic to be withdrawn over undercuts;
occasionally tearing of the impression materials may occur with
serious undercuts.
• Alginate are not stable on storage because of evaporation
• Compatibility with plaster and stone can be good. Some alginates
give powdery surface on casts from dental stones.
• SHELF LIFE;-
• Short shelf life.Alginate impression material deteriorates rapidly at
elevated temperature and The material should be stored in cool dry
place.(not above 37c)

27. DIMENSION STABILITY
Alginate impression loses water by evaporation and shrinks on
standing in air
If it is placed in water it absorbs water and swells .Therefore, cast
should be poured immediately after making the impression.
If storage is unavoidable keeping in a humid temperature of 100%
results in least dimensional changes.
BIOLOGICAL PROPERTIES
Some of silica particles present in dust are of possible health
hazards.
Presently some manufacturers supply “Dust free” alginate.

28. • Inexpensive and hydrophillic (contact angle 37°)
• Easy to manipulate
• Displace blood and saliva and pour well with gypsum stone)
• Minimum requirement of equipments
• Accurate if proprely handled

29. Disadvantages of alginate
Low tear strength
Poorer reproduction of surface detail as compare
to agar
Not as dimensionally acccurate as medium and light body silicone.
Not dimensionally stable on storage due to syneresis and poured
immediately.(triethanolamine modified alginates more stable in long
life hermetically sealed bags impressions can be stored for 48 hrs)

31.  Zelgan (densply)
 W:P 57 ml : 22 g
 Mixing time 45 sec
 Manipulation time 60 sec
 Time in mouth 45 sec

32.  Dustless alginates:- Many materials have now been formulated which gives off
little or no dust particles, so avoiding dust inhalation. This can be achieved by
coating the material with a glycol
 Siliconised alginates:- Two pastes alginates have been developed, which
incorporate silicon polymer component. These materials have superior resistance
to tearing compared to unmodified alginates. However dimensional stability is
reported to be poor
 A combination reversible hydrocolloid / alginate impression technique has been
improved.

33. Modified alginates
Fluorides or silicofluorides to improve
surface of stone model(hexafluoro titanate
in alginoplast and xantalgin)
Chlorhexidine added to alginate powder
(hydrogum plus chlorhexidine) inactive
bacterial microorganism.
Mint and vanilla flavour (orthoprint,
formula 1) flavoured drops available(TOC)
Zhermack vanilla flavored orthoprint is
antinausea.

34.  ALGINATE KROMOPAN
• This material has ability to eliminate gagging.
• It is dimensionally stable upto 100 hrs.
• Unique three color change determines time for spatulating
,loading tray and insertion of impression.
• Colour change to indicate different stages of manipulation e.g
violet during spatulation, pink when loaded into tray and white
when ready to load in mouth .(kromopan 100,kromogel)

35. • The only one with physical working time adjustment.
• For every Personal Krono drop, added to a water measure (water
used to obtain the mixing), working time is lengthened of 20
seconds.
• Personal Krono is not a chemical retarder and therefore does not
alter Kromopan components' balance.
• The in-mouth setting speed remains unaltered.
• Personal Krono can be used in summer when the working time is
shorter due to high temperatures.
• The colour timing guide ensures that Kromopan is perfectly mixed
and that the insertion is perfectly timed.The in-mouth setting time is
30 seconds.

36. Orthoprint
5 Year Guarantee
Highly Elastic
Vanilla Flavor, that Works with Alginate Flavors too
Dust Free

37. Alginate Flavorings
•Creates great tasting alginate at an
economical low price
•Sugar free
•20 different flavors
Flavour Codes:
Banana (BAN), Blueberr y (BB), Bubble Gum (BG)
Cherr y (C), Cinnamon (CIN), Cola (COLA)
Fruit Punch (FP) ,Grape (G), Lemon (L)
Orange (O), Pina Colada (PC), Peppermint (PEP)
Pineapple (PIN), Raspberr y (R), Root Beer (RB)
Strawberr y (S), Chocolate (CHOC) ,Crème Caramel (CC)
Jamaica Java Cof fee (JJC), Watermelon (WM)

38.  It is essential that impression materials adhere firmly to the
impression trays.
 This can be achieved by either perforations or by the use of
adhesives. Adhesive solutions are needed for alginates,
polysulphides and silicones.
 Adhesives for alginates are solutions of resins in alcohol, they are
supplied in a bottle with a brush or an aerosol spray.
 Polysulphide adhesives are rubber solutions in acetone. Examples
of silicone adhesives are isopropylalcohol or amylacetone.

39. Tray adhesive for alginates
Come in liquid or aerosol presentation. Solvent is also
available for cleaning metal trays after use.
INDICATIONS
Fix Adhesive – Liquid and Fix Adhesive – Spray are tray adhesives for alginate
impression materials.
Fix Solvent is used to remove Fix Adhesives from the impression tray after
impression taking and casting.
CONTRAINDICATIONS
Use in patients or by persons with a known allergy to diethylenetriamine or any
other components of the products.
Kerr adhesive for silicones

40. IMPRESSION TRAYS
They are used to carry the impression material
to the mouth in its plastic state till it sets.

41. TRAYS
STOCK CUSTOM
PERFORATED NONPERFORTED
OTHER TRAYS
E.g – TRIPLE TRAY FOR BITE REGISTRATION

42. Disposable impression trays

43. Tuff Lock™ Disposable Impression Tray
A unique mechanical locking system eliminates the need
for spray adhesives
A clean, complete impression is assured
High sides provide excellent margin and gingival detail

44. Econo Lock™ Disposable Impression Tray
Specifically designed for Orthodontic use
Made from sturdy plastic that will insure an accurate,
distortion free impression

45. Prestige Rimlock Impression
Trays
Prestige 'Rimlock' Impression Trays
offer dentists the chance to produce
ideal impressions in a solid, non-
flexible tray, without the need to use
impression adhesives.
Rimlock trays incorporate a unique
'beaded' edge that retains the
impression material securely.
They are of high quality stainless steel
that is fully autoclavable

46.  MAXILLARY TRAY
• The tray must completely cover the tuberosity
• Must be 4mm wider than the most apical portion of the alveolar
process at the molar region.
• The tray must cover the anteriors with the incisors contacting the flat
portion of the tray about 4 mm from the raised palatal part of the
tray.
SELECTION OF IMPRESSION TRAY

47.  MANDIBULAR TRAY
• The tray should cover all the teeth as well as the retromolar pad
• The tray should be 4-6 mm wider than the buccal and lingual
portion of the anterior teeth
• It must be possible to center the tray
.

49.
MODIFICATION OF THE TRAY MAY BE DONE USING SOFT
OR MODELING WAX
• When the teeth are in extreme malposition or the arch is
abnormally shaped, soft wax may be added to the impression tray.
For example: to carry the impression material well up into the vestibule in Class II
Division 1
• In case where patients have high arched palates it is advisable to
place wax in relation to the palatal aspect of the tray to ensure
accurate recording of the palate and minimal wastage of the
material.

50. Upper and lower extend impression trays with motite
The wax has the added advantage of reducing the pressure of the
impression tray metal rim on the displaced tissue during the
Impression taking technique

51. PREPRATION OF THE PATIENT
• Explain the procedure to the patient in the simplest of terms so
that the patient is aware of the procedure and therefore the
fear of the unknown is over come.
•Seat the patient upright so as to prevent the gagging due to the
backward flow of the excess material into the throat.

52. • Advice the patient to breath through the nose and in case of
gagging try and distract the patient’s attention and ask the patient
to look down wards.
• Prior to making the impression it is advisable to ask the
patient to rinse the mouth with pre-impression mouth wash
cocktail
 Removes the debris
 Reduce the surface tension of the teeth and tissues.

53. • Practice the placement of the empty tray into the patient’s mouth
• Assume the correct operator positioning
 Maxillary impression - 11 o’ clock
 Mandibular impression - 7 o’ clock

54. MANIPULATION
The recommended water powder ratio should be used. In general it is 38 ml
of water per 16 gms of powder but slight variation can be presented
depending on the manufacturer. The weighed power is incorporated into the
water by carefully mixing with the spatula. Care should be taken to ensure
that air is not incorporated into the mix by spatulating the mix against the
side of the bowl while using the vigorous figure of 8 motion till a smooth
creamy mix is obtained.

55. SEQUENCES OF IMPRESSION MAKING
It is advisable to make mandibular impression
first as there is less chance of the patient to gag .This
allows the patient to become accustomed to the taste and
the feeling of the material in the mouth which in turn
reduces the chances of gagging while making an
impression of the maxillary arch.

56. SEATING THE IMPRESSION TRAY
MANDIBULAR IMPRESSION
• Operator position at 7 O’clock
• Patient seated such a way that the occlusal plane placed
parallel to the floor.
• Use the thumb and the index finger of the free hand to
retract the cheek.
• Grasp the handle of the tray and rotate the tray into the
mouth by using the front of the tray to deflect the other
cheek.

57. • Once inserted straighten the tray so that the tray is in line with the
patient’s midface .
• Note the position of the tray in relation to the anteriors.
• Using the index finger of both the hands press the tray downwards
lightly and evenly over the mandibular arch until resistance
is felt.

58. • Manipulate the patients cheeks and lips to create a more detailed
anatomy of the facial and vestibular area.
• Ask the patient to raise the tongue and then move it from side to side.
• Allow the material to set and then remove. Using a firm grip on the
tray handle, use a side ways lifting motion to remove the tray.

59. MAXILLARY IMPRESSION.
• Operator position at 11 O’clock position
• Patient seated such a way that the occlusal plane placed parallel
to the floor.
• A blob of material may be placed in the palatal vault of the patient
just behind the incisors, to eliminate the trapped air and to ensure the
faithful reproduction of palatal tissue
• Use the thumb and the index finger of the free hand to retract the
cheek.

60. Maxillary impression taking technique

61. • The tray is rotated into the mouth once again using the front of
the
tray to deflect the other cheek.
• Once inserted straighten the tray so that the tray is in line with the
patient’s mid face .
• Begin to apply light pressure upwards till the light resistance is
felt

62. • Initially seating the posterior region of the tray and subsequently the
anterior part of the tray allowing the material to flow over the molars.
• Retract the upper lip as the tray is seated. This allows the material to
flow and displace any air which might otherwise cause voids.
• Hold the tray in place till the material is set.
• To remove the impression , lift lips and cheek away with fingers to
break the seal ,grasp handle pull tray away from teeth with quick motion

63. Making impression for cleft palate patients(for
combined Prosthesis and orthodontic appliances)
Preliminary impression
If the registration of the entire cleft is desirable the stock tray modified
with modeling compound wax. extending posteriorly to the post
pharyngeal wall.
Fast setting irreversible hydrocolloid is used.

64. 1.If the patient is a child, heshe should be given the opportunity to
examine the tray.
2. The patient should have an early morning appointment.
3. The patient should have an empty stomach.
4. Topical anesthetic should be used on a child who has a severe gag
Reflex.
5. The tray should not be over loaded with the impression material.
excess material in the naso pharynx will increase the difficulty of
removing the impression without fracture.

65. 6. All oral perforations should be packed with the gauze that has
Been saturated with petroleum jelly.
Final impression- an acrylic resin tray is constructed over the
Diagnostic cast,

66. The patient is prepared in the same manner as for the
Preliminary impression , the final is then made with the irreversible
Hydrocolloid impression material.

67. IMPRESSION FOR A FUNCTIONAL APPLIANCE
Impression for functional appliance fabrication differ some what from
those for orthodontic diagnostic cast
1] Areas where appliance components will contact soft tissue must be clearly
delineated. Most appliances use contact with lingual mucosa to stimulate
forward posturing,The impression must include the alveolar process below the
lower molars if long lingual flanges are employed.

68. The impression must not stretch and excessively displace the soft
tissues in an area of contact with appliance.This is critical when
lip pads and buccal shields are planned. To much extension
of impression will result in pads and shield are too long and will
cause soft tissue irritation and ulceration when the appliance is
worn

69. DISINFECTING THE IMPRESSION
Disinfection of impression is a concern due to viral diseases such
as Hepatitis B,A I D S and herpes simplex
• Gently rinse the impression under the tap water to remove any
debris that may be retained in the impression.
• Gently shake the excess water.
• Spray the entire impression with an O.S.H.A. (occupational health
and safety administration) approved disinfecting solution.
OR

70. • May immerse the impression in a disinfectant such as :
gluteraldehyde solution
iodophors
1:10 dilution of sodium hypochlorite
synthetic phenols
• Rinse again

71. CRITERIA FOR ACCESSING THE IMPRESSION
• Lack of voids.
• No distortion , clear and distinct impression
• Adequately extended.
• Free of debris and extraneous material.
• Adequate details and all structure must be recorded.
• Stable material which is sufficiently attached to the tray.

73. CAUSES OF FAILURE
1. Grainy material •Improper mixing
•Prolong mixing
•Undue gelation
•Water : powder ratio too low
2. Tearing •Inadequate bulk
•Moisture contamination
•Premature removal from mouth
•Prolong mixing
3. External bubbles •Undue gelation, preventing flow
•Air incorporated during mixing

74. 4. Irregularly shaped voids •Moisture or debris on tissue
5. Rough and chalky stone
model
•Inadequate cleansing of
impression
•Excess water or potassium
sulfate solution left in
impression
•Premature removal of model
6. Distortion •Impression not poured
immediately
•Movement of tray during
gelation
•Premature removal from mouth

75. REVERSIBILE HYDROCOLLOIDS
AGAR-AGAR(ADA NO:-11)
This is a organic , hydrophilic colloid (polysaccharide)
extracted from certain type of sea weed. It is a sulfuric ester of a
linear polymer of galactose
The temperature at which the
LIQUIFACATION TEMPERATURE (700
– 1000
C)
GEL SOL
GELATION TEMPERATURE (370
– 500
C)

76. INGREDIENTS FUNCTION COMPOSITION %
1. AGAR BASIC
CONSTITUENT
13-17
2. BORATES STRENGTH 0.2-0.5
3. SULPHATES GYPSUM
HARDNER
1.0-2.0
4. WAX FILLER 0.5-1.0
5. THIXOTROPHIC
MATERIAL
THICKNERS 0.3-0.5
6. WATER REACTION
MEDIUM
BALANCE
7. ALKYL
BENZOATE
PRESERVATIVE 0.1%

77. THE MATERIAL
TYPES AVILABLE
The hydrocolloid is supplied in two forms:-
The more fluid “cartridge form” available for use in syringes.
the more viscous type used in trays
Special water cooled trays are used to rapidly cool the
material in the patients mouth

78. AGAR

79. WATER COOLED TRAYS

80. Properties
Permanent deformation-A D A specification requires that the
recovery from deformation be greater than 96.5% after the material
is compressed 20% for 1 sec
FLEXIBILITY- 4-15%
STRENGTH- 8000gmcm²
TEAR STRENGTH- 800-900gmcm
Compatibility with gypsum-more compatible with gypsum material
AGAR impression are best stored in 100% relative humidity if models
cannot prepared immediately
BIOCOMPATIBILITY
Thermal injury from reversible hydrocolloid as a result of improper
tempering or faulty equipment during impression making

81. DUPLICATING MATERIAL
Alginate and Agar –Agar may be used successfully as a
duplicating material. In this way multiple casts can be duplicated
from a single master cast, which may have been formed using some
other material. This process is essential in ones orthodontic practice
as it enables the use of one master cast to form several casts
subsequently.

82. 1. Grainy material •Inadequate boiling
•Storage temperature too low
•Storage time too long.
2. Separation of tray and
material.
•Water soaked layer of tray
material not removed
•Premature gelation
3. Tearing •Inadequate bulk
•Premature removal from
mouth
•Material partially gelled when
tray seated
4. External bubbles •Gelation of syringe material
preventing flow
CAUSES FOR FAILURE OF
IMPRESSION

83. 5. Irregularly shaped voids • Material too cool or grainy
6. Rough and chalky stone
model
•Inadequate cleansing of
impression
•Excess water or potassium
sulfate solution left in
impression
•Premature removal of die
7. Distortion •Impression not poured
immediately
•Movement of tray during
gelation
•Premature removal from mouth

84. NON AQUEOUS ELASTOMERIC IMPRESSION
MATERIAL (ADA no 19)
These materials are classified as synthetic
rubbers, developed to mimic natural rubber when it became
difficult to obtain during WORLD WAR II .They are liquid
polymers and can be converted to rubber at room temperature by
mixing with a suitable catalyst.

85. They undergo polymerization or cross linking by
condensation/addition reactions to produce a firm elastic solid.
CLASSIFICATION
• POLYSULFIDES
• SILICON POLYSILOXANES
CONDENSATION SILICON
ADDITION SILICON (VINYL
POLYSILOXANE)
• POLYETHER
•RECENTLY INTRODUCES LIGHT CURE POLYERHER
URETHANE DIMETHACRYLATE.

86. THEY ARE SUPPLIED IN FOUR CONSISTENCY
• LOW (SYRINGE/WASH)
• MEDIUM (REGULAR)
• HIGH (TRAY)
• PUTTY (VERY HIGH)

87. HIGH, MEDIUM AND LOW CONSISTENCIES ARE
SUPPLIED AS A PASTE IN TWO FORMS
• BASE
• ACCELARATOR / CATALYST
CATALYST SOME TIMES ALSO AVAILABLE AS LIQUID

88. MANIPULATION
Equal lengths of two pastes are dispensed on a paper
pad for normal mixes. Initial mixing is accomplished with
circular motion and final mixing to produce a mix free from
streaks is done with broad stroke of spatula. Mixing is readily
accomplished in 45 seconds. When catalyst is supplied in liquid
form a specific number of drops per unit length is indicated in
the instructions and mixing is accomplished in the manner
similar to the two paste system

90. ADVANTAGES :-
HIGHLY ACCURATE IMPRESSION
PLEASANT ODOUR AND TASTE
GOOD DIMENSIONAL STABILTY
TEAR STRENGHT IS GOOD
GOOD SHELF LIFE
DISADVANTAGES
SETTING TIMES IS SHORT MIXING SHOULD BE DONE
RAPIDLY
HIGHLY EXPENSIVE

91. FOR MAKING DIGITAL ORTHODONTIC
STUDY MODELS
The impression can be taken in a high quality
ALGINATE or
POLYVINYL SILICONE or POLYETHER material
 High quality alginate such as ORTHOPRINT is
taken in a rigid plastic
impression tray.
 The alginate impressions are sanitized, wrapped in a
paper
towel and Packaged in sealed plastic bags.
This ensures that impression will remain stable for 5
days

92. ORASCANER
It is a revolutionary new process. The orthodontist uses 3-D
images taken by the OraScanner™
to build a computer model of the
teeth. The OraScanner functions much like a video camera, taking
pictures of the teeth and sending them to the computer to build a
complete 3-D model

93. CONCLUSION
• One must not depend on a material to provide good
impressions.
• Any material is good and should be used till the
operator is familiar with its characteristics
• Selecting the impression material depends on the
convenience of the dentist and clinical situation.
ALL WE NEED IS AN ACCURATE IMPRESSION.

94. REFERENCES
I Anusavice
Philips science of dental materials XI Edition
2 Restorative dental materials X EDITION
By Robert G. Craig
3 Contemporary Orthodontics III Edition
By William R. Proffit
4 Removable appliance Fabrication
By Emil Witt, Dr Med. Dent
5 Hand book of Orthodontics IV Edition
By Robert E. Moyers

95. 7 Orthodontics for dental students
By T.C. White and J.H. Gardiner
8 Journal of Orthodontics Vol 31 Nov 4 Dec 2004 ISSN 1465-
3125 (AJODO)