Gtc 4 - Impressions & Retraction Cord (Ppsg Lectures)

7/28/2019 Gtc 4 - Impressions & Retraction Cord (Ppsg Lectures)

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FIXED PROSTHODONTICS

DR. ERWAN SUGIATNO

DR HARYO M.DIPOYONO

PUSAT PENGAJIAN SAINS PERGIGIAN

UNIVERSITI SAINS MALAYSIA


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IMPRESSIONS

An impression is an imprint or negative

likeness.

It is made by placing some soft, semi fluid

material in the mouth and allowing the

material to set.

The impression must be handled properly

until it is poured up in a gypsum product.


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An impression for a cast restoration should

meet the following requirements :

1. It should be an exact duplication of the

prepared tooth2. Other teeth and tissue adjacent to the

prepared tooth must be accurately

reproduced3. It must be free of bubbles


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Custom resin tray

Custom resin tray have been utilized in

elastomeric impression techniques

because these material are more accurate

in uniform, thin layer of 2to 3 mm.

The custom tray must be rigid, and it

should have stops on the occlusal

surfaces of the teeth to orient the tray

properly when it is seated in the mouth.


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Armamentarium :

1. Diagnostic casts

2. Autopolimerizing acrylic resin

3. Measuring vial for monomer4. Measuring scoop for polymer

5. Waxed paper cup

6. Spatula

7. Baseplate wax


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8. Aluminum foil

9. Laboratory knife with no. 25 blade

10. Bunsen burner11. Matches

12. Arbor bands

13. Adhesive for impression material used


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Construction of custom tray : Heat a sheet of baseplate wax in a flame until it is

softened Fold it in half and place it on the diagnostic cast of

the arch to be restored.

Adapt it to the cast and trim any excess thatextends more than 2 to 3 mm beyond the necks ofthe teeth.

Cut a 3 x 3 mm hole through the wax over

posterior teeth on both sides of the arch and inthe incisor area.

The tray resin will touch the teeth in these areas,

forming solid stops for the tray.


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On the side where the prepared tooth is situated,

the stop should be distal to the preparation.

Mix the resin in the waxed paper cup, using onemeasure of powder and one vial of liquid.

As soon as it is pliable and will not stick to yourfingers, form it into a rod that is approximatelythe length of the dental arch (molar to molar,around the incisor).

Flatten it out to form an oblong shape about 2.5

cm wide and 5.0 cm thick. Leave some extra bulk in the middle.


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Cutouts for stops(arrows) in the spacers

for fabrication of a

custom impression tray

Tray resin ready for

adaption to the cast


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Make sure that the tray does not extend beyondthe trimmed distal border of the cast in theretromolar area.

The bulk left in the middle of the tray should beused to shape a horizontal handle in the middleand a narrow ledge or wing on either side of it.

The wings can be used to get better leverage onthe tray for removal from the mouth.

Allow the resin to polymerize.

Paint the inside of the tray with a thin, uniformcoat of adhesive, using the one specified for theimpression material being used.


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Finished custom impression

tray with a handle in front

and wings on the side tofacilitate removal

Inside of the tray is painted

with adhesive

To achieve maximum adhesion of the impression

material to the tray, allow it to dry for a minimum

of 15 minutes.


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Gingival retraction

It is essential that gingival tissue be healthy and

free of inflammation before cast restorations arebegun.

To start tooth preparations in the face of

untreated gingivitis makes the task more difficultand seriously compromises the chances for

succes.

Because the marginal fit of a restoration isessential in preventing recurrent caries and

gingival iritation, the finish line of the tooth

preparation must be reproduced in the

impression.


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Armamentarium :

1. Evacuator (saliva ejector)

2. Scissors

3. Cotton pliers4. Mouth mirror

5. Explorer

6. Fisher Ultrapak Packer (small)

7. DE plastic filling instrument IPPA


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8. Cotton rolls

9. Retraction cord

10. Hemodent liquid11. Dappen dish

12. Cotton pellets

13. 2 x 2 gauze sponges


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Retraction procedure :

Form the cord into a U and loop it around theprepared tooth.

Hold the cord between the thumb andforefinger, and apply slight tension in an apicaldirection.

Gently slip the cord between the tooth and thegingiva in the mesial interproximal area with aFisher packing instrument or a DE plasticinstrument IPPA.

Once the cord has been tucked in on the mesial,use the instrument to lightly secure it in thedistal interproximal area.


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A loop of retraction cord isformed around the tooth and held

with the thumb and forefinger

Placement of the retraction cord is

begun by pushing it into the

sulcus on the mesial surface of the

tooth (A). It should also be tackedlightly into the distal crevice (B)

to hold the cord in position while

it is being placed.

h f h h ld b l d


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The tip of the instrument should be inclinedslightly toward the area where the cord hasalready been placed.

If the tip of the instrument is inclined awayfrom the area in which the cord has beenplaced, the cord may be displaced and pull

out.

Gently press apically on the cord with theinstrument, directing the tip slightly toward

the tooth.

Slide the cord gingivally along thepreparation until the finish lineis felt.

Then ush the cord into the crevice.


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As the cord is being placed

subgingivally, the instrument must be

pushed slightly toward the area already

tucked into place (A). If the force of

the instrument is directed away from

the area previously packed, the cord

already packed will be pulled out (B)

The instrument must be angledslightly, toward the root to facilitate

the subgingival placement of the

cord.


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If the instrument is directed totally in anapical direction, the cord will rebound of

the gingiva and roll out of the sulcus.

If cord persists in rebounding from aparticularly tight area of the sulcus, do not

apply greater force. Instead, maintain gentle force for a longer

time, if it still rebounds, change to a smalleror more pliable cord.

Pack all but the last 2.0 or 3.0 mm of cord.


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If the instrument is held parallel

to the long axis of the tooth, theretraction cord will be pushed

against the wall of the gingival

crevice, and it will rebound.

Placement of the distal end

of the cord is continued until

it overlaps the mesial. The

force of the instrument must

be directed toward the cord

previously packed.

Ti t ti h ld b d fi l b t


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Tissue retraction should be done firmly butgently, so that the cord will rest at the finish line.

Heavy-handed operators can traumatize the

tissue, create gingival problem, and jeopardizethe longevity oh the restoration that they place.

Do not over pack.

Placement of the retraction cord in the sulcus :

A, correct; B, incorrect.


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Impression materials(polysulfide):

Polysulfide is an elastomer that is known as

mercaptan, thiokol, or simply as rubber base. The impression material is packaged in two tubes

: a base and an accelerator.

The base contains a liquid polysulfide polymermixed with an inert filler.

The accelerator, which is usually lead dioxidemixed with small amounts of sulfur and oil, acts

as an oxidation initiator on terminal thiol groupson the polymer.


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Armamentarium :1. Polysulfide impression kit (regular base and

accelerator)

2. Polysulfide impression kit (light base andaccelerator)

3. Adhesive (butyl rubber cement)

4. Two disposable mixing pads

5. Two stiff spatulas

6. Syringe with disposable tip

7. Two 2 x 2 inch gauze sponges

8. Alcohol

9. Custom resin tray


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Impression Making With Polysulfide :

Try the custom tray in the mouth to make sure itfits without impinging on the prepared tooth.

Insert the retraction cord and place a large gauze

pack in the mouth.

The following steps require an assistant : On one

disposable mixing pad squeeze aout 4.0 cm each

of light (syringe) base and accelerator. On second

pad place 12.5 cm strips of regular (tray) base

and accelerator.

Th i t t h ld t t i i th t


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The assistant should start mixing the traymaterial on one pad 30 seconds before theoperator begins mixing the syringe material on

the other. Pick up the dark accelerator on the spatula and

incorporate it into the white base.

Holding the spatula flat against the pad, mix witha back-and-forth motion, pressing hard againstthe pad.

Change directions often to produce a smooth,

homogenous mixture. Be careful not to incorporate bubbles.

Do not take more than 1 monute to mix it.


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Mixing is started with the dark

accelerator.

The mixture should be free

of streaks and bubbles.

Fold a sheet previously removed from the

mixing pad in half and then fold it to

make a cone. Open it up and wipe the syringe material

from the spatula onto the crease.


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Fully extended mixing pad sheet. The sheet is folded in half

The sheet is folded to form a cone Impression material is wiped on the crease

Fold the cone over


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Fold the cone over.

Squeeze the syringe material from the cone intothe back end of the syringe.

Insert the plunger and express all the air from thesyringe.

In a second method of loading the syringe, the

back end of the syringe is brought in contact withthe pad, and quick, closely spaced sweeps of thesyrunge will fill it, with a minimum of materialspilled.


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The paper is refolded to form cone again. The cone is inserted into the syringe

The plunger is placed into the syringe Scraping the back end across themixing pad to scoop up material.

Remove the 2 x 2 gauze squares from the


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Remove the 2 x 2 gauze squares from thepatients mouth.

Be sure that the retraction cord is slightly damp

before removing it from the sulcus. Immediately inject polysulfide syringe material

into the sulcus.

Use an air syringe to direct a stream of air againstthe material to spread it evenly over the surfaceof the preparation and drive it into small detailsuch as grooves and boxes.

Impression material is also forced morecompletely into the gingival crevice.


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Impression material is

injected into the sulcus

An air syringe is used to

drive the impression

material into the sulcus and

preparation detail.


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Seat the tray slowly until the stops hold the traysolidly in one position.

The tray should be held with light pressure for 8to 10 minutes without movement.

The set of the material can be tested with a bluntinstrument.

After the material has polymerized, theimpression is removed.

The wings on the sides of the tray can be used for

added leverage in this task.


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Wings on either side of the tray (arrows) are grasped

to remove the impression from the mouth.


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Soal midterm

Pasien kehilangan 3 dan2 RA kanan .

1.buat design GTC porselein fused metal

2.gigi mana sebagai abutment 3.jenis preparasi gigi abutment

4.bagaimana hukum Ante diterapkan pd

pemilihan gigi abutment tsb

5.jenis pendak yg sdr pakai

Gtc 4 - Impressions & Retraction Cord (Ppsg Lectures)

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