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IMPRESSION MATERIALS AND PROCEDURES

IMPRESSION MATERIALS

A. Rigid Materials

Set to a rigid consistency.

Recording tooth and tissue details accurately.

Cannot be remoed !rom the mouth "ithout !racture and reassembly.

#. Plaster o! Paris

o $sed !or abutment castings and co%ings in the !abrication o! !i&ed

restorations.

o Record ma&illomandobular relationshi%s.

'. Metallic O&ide Paste

o Not used as a %rimary im%ression materials.

(. Thermo%lastic Materials

(ecome %lastic at higher tem%eratures and resume their original !orm "hen

cooled.

Cannot record minute details accurately because they undergo %ermanent

distortion during "ithdra"al !rom tooth and tissue undercuts.#. Modeling Plastic

o A secondary im%ression material to record edentulous ridges in remoable

%artial denture !abrication.

'. Im%ression )a&es and Natural ResinsC. Elastic Materials

#. Reersible *ydrocolloidsused !or !i&ed restorations.

'. Irreersible *ydrocolloids used !or ma+ing diagnostic casts, orthodontic

treatment casts, and master casts !or remoable %artial denture %rocedures.

-. Marca%tan Rubberbase Im%ression Materials

/. Polyether Im%ression Materials

o Polysul!ide and Silicone Materials.

o 0ood accuracy in clinical ealuation.

o Much shorter "or+ing and setting time.

1. Silicone Im%ression Materials

o More accurate and easier to use than the other elastic im%ression materials.

o *ae less %olymeri2ation shrin+age, lo" distortion, !ast recoery !rom

de!ormation, and moderately high tear strength.

IMPRESSION O3 T*E PARTIALL4 E5ENT$LO$S ARC*ES

An im%ression o! the %artially edentulous arch must record accurately the anatomic !orm

o! the teeth and surrounding tissue.

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Materials that could be %ermanently de!ormed by remoal !rom tooth or tissue undercuts

should not be used.

The thermo%lastic im%ression materials and metallic o&ide %astes are there!ore e&cluded

!or recording the anatomic !orm o! the dental arch.

Rubberbase materials that are highly crosslin+ed should not be used "hen large or

multi%le undercuts are %resent because these materials "ill be sub6ected to considerable

distortion u%on "ithdra"al.

Plaster o! Paris and modeling %lastic are ca%able o! recording tissue detail accurately, but

they must be sectioned !or remoal and subse7uently reassembled, "hich o!ten leads to

%ermanent de!ormation.

Ste%byste% Procedure !or Ma+ing a *ydrocolloid Im%ression#. Select a suitable, sterili2ed, %er!orated or rim loc+ im%ression tray that is large enough to

%roide a / to 1mm thic+ness o! the im%ression material bet"een the teeth and tissue,and the tray.

'. (uild u% the %alatal %ortion o! the ma&illary im%ression tray "ith "a& or modeling %lastic

to ensure een distribution o! the im%ression material and to %reent the material !rom

slum%ing a"ay !rom the %alatal sur!ace.

-. The lingual !lange o! the mandibular tray may need to be lengthened "ith "a& in the

retromylohyoid area or to be e&tended %osteriorly./. Place the %atient in an u%right %osition.

1. )hen irreersible hydrocolloid is used, %lace the measured amount o! "ater in a clean,

dry, rubber mi&ing bo"l. Add the correct measure %o"der and stir ra%idly against the side

o! the bo"l.

8. Place the material in the tray, aoid entra%%ing air.9. Place the im%ression material.

:. *old the tray !or - minutes "ith light !inger %ressure oer the le!t and right %remolar

areas.;. Remoe the im%ression 7uic+ly in line "ith the long a&is o! the teeth to %reent tearing or

other distortion.

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