impression procedures

IMPRESSION procedures FOR

Removable partial denturetheoptimalsmile.wix.com

By:Ahmed Ali Abbas

INTRODUCTIONAn impression is defined as a negative

likeness of the teeth and/or edentulous areas where the teeth have been removed, made in a plastic material which becomes relatively hard while in contact with these tissues

MATERIALS AVAILABLE FOR MAKING IMPRESSION

Reversible hydrocolloids (agar-agar)Irreversible hydrocolloids (Alginate)Elastomeric impression materials

STEPS IN IMPRESSION MAKINGPosition of patient & dentistTray selectionMixing the material & loading into the

trayImpression making & removalInspecting, cleaning & disinfecting the

impression

POSITION OF PATIENT & DENTISTDentist should stand & patient should sit uprightOcclusal plane should be parallel to the floorMAXILLARY IMPRESSION- dentist should

stand at the right rear of the patientMANDIBULAR IMPRESSION- dentist should

stand at the right front of the patient

Mandibular impressionMaxillary impression

IMPRESSION TRAY SELECTIONStock trays for dentulous & partially edentulous arches are of 3 types:

Rimlock traysPerforated metal traysPlastic disposable trays

MIXING IMPRESSION MATERIAL

Bowel Spatula Scoop and Measuring jar

REMOVAL OF IMPRESSION FROM MOUTH

Clinically the initial set of alginate is determined by loss of surface tackiness

Release seal by retracting lips & cheekThen impression is removed by a sudden

jerk

INSPECT THE IMPRESSION FOR DEFECtS

Mandibular impressionMaxillary impression

IMPRESSION TECHNIQUESMc LEAN’S PHYSIOLOGIC IMPRESSIONFLUID WAX FUNCTIONAL IMPRESSIONSELECTIVED PRESSURE IMPRESSION

Mc LEAN’S PHYSIOLOGIC IMPRESSIONProcedure

A custom impression tray is constructed over a preliminary cast

Functional impression of distal extension ridge is made. Patient applies some biting force with occlusion rims

Then an Alginate impression is made with the 1st impression held in it’s functional position with finger pressure

FLUID WAX FUNCTIONAL IMPRESSIONMake an anatomic impression of the arch using

alginateFabricate a refractory cast using this impressionFabricate the partial denture framework over the

refractory cast

Draw the outline of the denture baseCast is coated with separating mediumWax Spacer is adapted over the crest of

the edentulous ridge

Framework is placed over the spacerAuto-polymerizing resin is mixed to dough

stage and is adapted and contoured over the framework along the length of the ridge

Borders of the tray are trimmed

SELECTIVED PRESSURE IMPRESSION• More force are applied to areas that can absorb

stress without adverse response & protect that areas that is least able to absorb force

• Stress bearing areas are the buccal shelf area & the lingual slopes of residual ridge stress bearing areas

• The denture base made from this impression will be closely adapted to & in firm contact with the tissues in buccal shelf area

CONCLUSION

An accurate impression is vital for the success of a cast partial denture. So proper selection of material, impression technique and the skill of the dentist plays a key role in the success of the overall treatment.

REFRENCEMc Cracken’s Removable Partial ProsthodonticsREMOVABLE PARTIAL PROSTHODONTICS-STEWART’S 4TH EDISION

THANK YOU