ORTHODONTIC IMPRESSION

1. ALGINATE IMPRESSION
DR. MD. ISHTIAQ HASAN
FCPS TRAINEE
DEPT OF ORTHODONTICS
DHAKA DENTAL COLLEGE

3. SEATING OF THE PATIENT
The pt should be seated upright in a comfortable position with
the head resting firmly on the head rest
Chair height and position is adjusted to a comfortable
working position for the dentist.

4. For maxillary impression:
The pt is seated in a upright position.
Gravity affect the position of the oral tissues. Since the
major part of the appliance use in upright position , the
impression is made in this position.
If reclining position is used , then there is a danger of
impression material flowing down the palate , causing
discomfort or gagging , which can hamper impression
procedure.
Gagging is most easily controlled in the upright position.
The operator stands behind and to the right side of patient.

5. Position for mandibular impression:
The mandibular impression also made with
upright position.
Unlike maxillary impression , the operator
stands infront and right side of the patient.

6. SELECTING THE STOCK TRAY:
The tray is selected according to the size of
the arches.
There should be a space of at leat 6 mm
between the sides of tray and mucosa.
Posteriorly it should extend upto and cover
the palatal seal area in the maxilla and the
retromolar pad in the mandible.

7. PATIENT PREPAEATION:
Trial helps to prepare the pt.
Relax the pt
Pt is educated about the impression
procedure
Pt is asked to perform various movement
required to mold the impression.
Trial are performed with the tray in the
mouth

8. MODIFICATION OF THE STOCK
TRAY:
The borders of the stock tray can be lined with a
strip of boxing wax to create a rimlock that helps
confine the material.
An adhesive can be painted on the tray to help
retain the alginate.
In the case of deep palatal vault , alginate may not
record the deeper portion. The palatal portion can
be built up with wax.
The tray can be extended when necessary with
wax.

9. TAKING MAXILLARY IMPRESSION
Alginate mixed and loaded in tray.
Some material take in hand and applied on
the palate to reduce air entrapment.
The loaded tray insert into mouth , right
post corner first , while retracting the left
cheek and rotated into position over the
ridge.
Next the lip is retracted and labial frenum is
used as guide to align the midline of the
tray.

10. The tray is pressed upward and backward.
The index fingure is placed in the first molar
region.
Using alternate pressure , the tray is pressed until
the posterior part contact the post palatal seal area.
After seating , the tray is supported by finger on
the middle of the tray and a limited and gentle
border molding is carried out.
Care should be taken to minimize the flow of the
material to the throat.

11. TAKING MANDIBULAR IMPRESSION:
Mix alginate and loads in tray.
Some alginate can be placed in the
retromolar sulcus before inserting the
loaded tray.
One corner of the tray is inserted into
mouth. Meanwhile opposite corner of the
mouth is retracted with a mirror and the tray
is rotated into position over the teeth.
The pt is instructed to raise the tongue and
position it slightly forward. This ensure that
the tongue does not get trapped beneath
lingual borders of tray.

12. COMMON MISTAKES:
 Improper tray position is very common.
In upper impression ,tray Is brought too close to
the labial surface and posteriorly the tray may
deviate too much to either right or left side
causing exposure of the tray.
 Large voids may be observed in different area of
important. Frequently seen in palatal region .
 Gagging can occur if excess material has been
loaded in the posterior part of tray.

13.  Separation of tray is occationally seen. If
this happen , repeat the imp.
Tray retention can be increased by—
Having more number of holes
Having rimlock
Use tray adhesive

15. MIXING:
Mixing ratio of powder and water is 15 gm
of powder mixed with 40 ml of water.
Correct ratio is important.

16. Spatulation:
First mix slowly to make all he powder wet.
Then mix vigorously by using a figure of 8
method.
Mixing time is 1 min
At the end of it, the mix must be smooth ,
homogenous and creamy.

17. REMOVAL OF THE TRAY
• Remove the tray with sudden pull.
Permanent deformation is more in alginate.
Permanent deformation is less if the set
impression is removed from mouth quickly

18.  After removal of the tray fom th mouth , rinse in
cold running water.
 Shake of excess water and cast should be done as
soon as possible , preferably within an hour .
 If it is not possible , cover it with wet cloth , put it
in polythene bag and sealed it. This step is
necessary to prevent synersis which may cause
shrinksage.

19. DISINFECTION:
 At first , wash with running water.
 Then spraying sodium hypochloride or
glutaraldihyde for 10 min.

20. SEQUENCE OF BORDER MOLDING:
Anatomic region Tissue that
influence
How to active
Labial flange i.Mentalis muscle
ii.Incisive labi
inferioris
iii.Orbicularis oris
i.Hand massage and
manipulate the
lip side to side
motion
ii.Instruct the pt to
evert the lower
lip
Labial frenum Labial frenum &
its associatd
connective
tissue fibres
Lower lip is lifted
outward , upward &
inward and then
massage the lip with
side to side motion.
Manibular border molding

21. • Buccal frenum Buccal frenum The cheek is lifted outward ,
upward , then inward & the
mold the cheek in antero-posterior
direction.
Massetric notch Masseter muscle Instruct the pt to close his
jaw against downward
pressure from the operator
thumb in the region of molar.
Distal extension
area
Pterigomanibular
raphe
Retromolar pad
Ask the pt to open his mouth
wide
Lingual frrenum
and sublingual
flange
Lingual frenum &
its intrinsic
connective tissue
fibres
i.Pt is asked to wipe his lower
lip side to side with the
tongue tip
ii.Pt is asked to push his tongue
forcefully against his front
part of palate

22. Mylohyoid portion of
lingual flange
i.Mylohyoid muscle
ii.Mylohyoid ridge & the
medial body of
mandible
i.To mold lingual flange ,
instruct the pt to
bring the tongue in
contact with left
cheek.
ii.The left lingual flange
is mold similarly
by contacting the
right buccal
mucosa.
iii.Pt is asked to protrude
the tongue, this
determine the
length of the flange
in this region
Buccal External obligue Manually manipulate the
cheek with fingure
pressure upon the denture
border I an ant-post
direction.

24. Maxillary border molding:
Buccal frenum & buccal fange Buccal frenum associated
with connective tissue
fibres of facial expression
In the region of buccal
frenum , the cheek is
pulled , then outward ,
downward , inward and
finally forward and
backward.
Labial frenum and labial
flange
Labial flange The upper lip is lifted
up ,then outward ,
downward and inward.
Coonoid process area Coronoid process, Fibres
of temporal muscle
attached to coronoid
process

25. • Mixing time: 60 sec
• Working time: 2 min

26. Synersis
loss of water , as a result shrink.
Due to synersis , material exudates some
acidic substance come out on the surface of
the material and this acidic substances are
retarder to model material as plaster of
paris.

27. Inbibition
• Absorb water and swell.

28. How to prevent synersis
 Pour immediately
 Wash in running water to wash away acid
& saliva from surface
 If need to keep long time , should cover
with damp but not wet cotton
 Use fixers or hardening solution ( solution
of k-lam , sol of NaCl , sol of KCl)

29. • Can we use plain tray for alginate
impression?
No,
because Na-alginate act as a separating media
and it cannot stick to plain tray.

30. • How we take alginate impression with plain
tray?
Plain tray need to be lined by sticky wax or
lined with adhesive paste.

31. IMPRESSION WITH PT OF
EXCESSIVE SALIVATION:
Imp field keep dry by placing cotton rolls in
upper buccal sulcus to block parotid duct ,
in floor of the mouth to control sub-mandibular
and sub-maxillary duct which
are remove before tray loads.
Use saliva ejector
Use anti-sialogue.

32. TAKING IMPRESSION OF HYPERACTIVE GAGGING PATIENT
1.REDUCTION OF STIMULI:
 Avoid thick tray
 Avoid oversized tray specially post palatal region
 Avoiding loading excess material specially post palatal area
 Pt sit upright leaning slightly forward with head tilted slightly
downward ,sothat material cannot go to throat.
 Use fast setting alginate
 Use saliva ejector.
2.DISTRACTION TECHNIQUE:
 Talking & engage pt to some topic of his special interest
 Ressurance
 Distract pt by asking him to breath deeply through nose
 hypnosis

34. 3.PROGRESSIEVE DESENSITIZATION:
 Use in case of severe gaggers
 Pt is introduced to minimal stimuli which he can tolerate. Gradually
stimuli is increase until pt is able to tolerate impression procedure. As
a example , pt is asked to practice with marble. Gradually the numbers
of marble increase.
 Impression tray is handed over to the pt & allowed to take home &
practice in front of mirror everyday.
4.MEDICINE:
 ANTIHISTAMINE
 SEDATIVE
 TRANQUILIZER
 ANTIEMETIC
 LA GEL
 CNS DEPRESSANT