ALGINATE IMPRESSION

MD. ISHTIAQ HASAN

FCPS TRAINEE

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.

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.

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.

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.

PATIENT PREPAEATION:

Trial helps to prepare the pt.Relax the ptPt 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

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.

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.

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.

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.

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.

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

MIXING:

Mixing ratio of powder and water is 15 gm of powder mixed with 40 ml of water.

Correct ratio is important.

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.

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

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.

DISINFECTION:

At first , wash with running water. Then spraying sodium hypochloride or

glutaraldihyde for 10 min.

SEQUENCE OF BORDER MOLDING:

Anatomic region Tissue that influence

How to active

Labial flange i.Mentalis muscleii.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

• 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 rapheRetromolar 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

Mylohyoid portion of lingual flange

i.Mylohyoid muscleii.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.

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

• Mixing time: 60 sec

• Working time: 2 min

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.

Inbibition

• Absorb water and swell.

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)

• Can we use plain tray for alginate impression?

No,

because Na-alginate act as a separating media and it cannot stick to plain tray.

• How we take alginate impression with plain tray?

Plain tray need to be lined by sticky wax or lined with adhesive paste.

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.

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

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