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Functional impression in RPD
- 1. FUNCTIONAL IMPRESSION IN RPD BY – ENISHA AGARWAL BATCH-D ROLL NO. 38
- 2. ANATOMIC FORM • Anatomic form is the surface contour of ridge when it is not under any occlusal load • The surface of the residual ridge at rest • Anatomical impression record the tissue in anatomical form • Recorded with soft impression materials like ZOE and Plaster of Paris
- 3. FUNCTIONAL IMPRESSION • These impression are recorded under functional load, that is tissue surface is recorded in compressed form • As soft tissues are recorded in compressed form ,denture will not exert additional stress on abutment teeth during functional loading • So occlusal load can be evenly distributed between soft tissues and abutment teeth • These are required only to record edentulous saddles • Note – these impressions are indicated for tooth supporting partial dentures • For distal extension bases (class 1and 2) mainly in mandibular arch and long span anterior edentulous ridge (class 4)
- 4. IMPRESSION MAKING FOR KENNEDY’S TOOTH SUPPORTED PARTIAL DENTURE. • Conventional anatomic impression are made. • The procedure for impression making is similar to procedures described for making a diagnostic impression. • A small quantity of alginate is spread over the prepared tooth surfaces before placing the tray material. • After making the impression,it is gently wash under water to clear the saliva and debris. • The cast should be poured within 12 min. after impression making.
- 5. IMPRESSION MAKING FOR DISTAL EXTENSION BASES: • Support for distal extension denture is obtained from both the teeth and the tissues. • Factors influencing the support of a distal extension base: • Contour and quality of residual ridge. • Extent of residual ridge coverage by denture base. • Type and accuracy of the impression. • Accuracy and fit of the denture base. • Design of the partial denture frame work. • Total occlusal load applied.
- 6. PHYSIOLOGICAL OR FUNCTIONAL DUAL IMPRESSIONS • One anatomical impression is made of the entire ridge and one physiological or functional impression is made on the edentulous portion. • The functional impression is made by applying occlusal load on impression tray and tissues are displaced during impression making.
- 7. The common techniques employed to record a physiological dual impression are: • McLean’s technique. • Hindle’s modification of Mclean’s technique. • Functional relining method. • Fluid wax technique.
- 8. MCLEAN’S PHYSIOLOGIC IMPRESSION • Principle: • Two impressions are made in this procedure. • A functional impression of the edentulous ridge is made. The second impression is made over the functional impression and it records the remaining structures in their anatomic form . • The second impression is also known as the pick up impression because it covers, and pick up the functional impression (first impression) along with itself.
- 9. PROCEDURE • A custom made impression tray is fabricated over the edentulous areas of the preliminary cast. • A spacer is not adapted because we intend to record only the supporting tissues • Occlusal rims are made on the custom tray. (required to bite on )
- 10. • The tray loaded with the impression material is inserted into a patient mouth and the patient is asked to close on the occlusal rims built over the tray • when patient occludes on rims, the tissues under the tray are compressed and impression is recorded. • After making the impression the custom tray should not be removed from the mouth. • An alginate over-impression(this impression is made over the existing impression)is made using a large stock trays.
- 11. • When over-impression is removed, the functional master impression comes along with it. Since the alginate over impression carries the functional impression along with it, it is called pick up impression. • Finger pressure should be applied on the stock tray while making over impression so that custom tray is pushed towards tissue while making overimpression • A cast is poured into the impression. This will reproduce the teeth in the anatomical form and the tissues in functional form.
- 12. • The supporting tissues may not be as compressed as they were while making the functional impression, this can lead to errors ( as biting force is not equal to finger pressure) • Small quantity of alginate between the occlusal rim of the custom tray and the over-impression stock tray. • This alginate may act like a buffer and prevent the transfer of the entire load (finger pressure) applied on the stock tray to the special tray. DISADVANTAGES
- 13. HINDLE’S MODIFICATION OF MCLEAN’S TECHNIQUE Principle- it is similar to Mclean’s technique. Hindle modified Mclean’s technique to overcome the disadvantages • Procedure – Special tray with an occlusal rim is fabricated using the primary cast. The special tray should have stoppers to avoid excessive pressure on tissues. • It records the supporting tissues under rest • Special tray with the impression is left untouched in the patient’s mouth. • A special stock tray with large holes is used to make over impression • While making the over impression clinician should apply steady constant pressure by placing his fingers into the holes till the alginates sets completely
- 15. ILL EFFECTS PRODUCED BY MC LEAN AND HINDLE’S METHODS • Dentures made using functional impressions will constantly pressurise the soft tissues. • Constant pressure from the denture will stimulate osteoprogenitor cells to form osteoclast which resorb bone.
- 16. • Constant pressure from the denture can produce ischemia. Ischemia can produce bone resorption via various chemical mediators that stimulate osteoclasts. • Dentures made using functional impressions get occlusally displaced at rest due to tissue rebounce. This may lead to premature contacts.
- 17. FUNCTIONAL RELINING METHOD • Principle • In this method, an anatomical master impression of all the oral structures is made • Two casts are made from this anatomical impression, one is the master cast and the other is the refractory cast. • The framework of the partial denture is fabricated using the refractory cast. • This framework is verified in the patient’s mouth and directly used as a special tray to record functional impression • The master cast is altered according to functional impression made on tissue surface of framework
- 18. PROCEDURE • Partial denture framework is constructed on the cast made from a single anatomic impression: first master impression. • Master cast is made from the anatomical impression. The master cast is duplicated and a refractory cast is made. • A framework is fabricated using the refractory cast. • Ash no.7 soft metal spacer which was adapted on cast before constructing framework should be removed before making impression • Next the framework is tried on patient’s mouth • A functional impression is made on the tissue surface of the framework: second master impression. Hence this technique is categorized as a dual impression.
- 19. • The functional impression is made with low fusing modelling plastic. • The material is added in flowing consistency onto tissue surface of framework • Sufficient pressure is applied during impression making to ensure compression of tissues • The function of modeling plastic is to act like a tray for ZOE paste • the modeling plastic at the border of framework are resoftened to do border modelling
- 20. • After recording the tissues with modelling plastic it is trimmed to provide space for ZOE impression paste • the modelling plastic at borders is reduced by 1mm and modelling plastic at the crest of the ridge is removed to its entire thickness • After reducing modelling plastic the final impression is made with ZOE impression paste. If undercuts are present. Light bodied polysulfide or silicone rubber can be used
- 21. • Patient should keep his mouth partially opened position because- • In this position movements of cheek and tongue are in best control • The relationship between partial denture framework and teeth can be observed
- 22. ADVANTAGES • Improves the fit of the denture after bone resorption. • The tissue surface of the metal framework can be relined after insertion. DISADVANTAGES • Difficult to maintain the relationship of the framework to the abutment teeth while making the impression. • Occlusion is usually affected due to the addition of a new layer to the tissue surface of the denture base
- 23. FLUID WAX FUNCTIONAL IMPRESSION • Principle • In this technique, a framework is fabricated using the anatomical impression. The framework is modified into a special tray. A fluid wax functional impression is made using the special tray. • Uses • Reline the tissue surface of an existing RPD. • Correct the distal extension edentulous ridge of the original master cast.
- 24. OBJECTIVES • To obtain maximum extension of the peripheral borders of the denture without interfering with movable tissues • To record stress bearing areas in functional form. • To record the non stress bearing areas in anatomic form. • It is an open mouth technique and displacement of tissues under occlusal load is reduced Materials used: • Iowa wax • Korrecta wax
- 25. PROCEDURE • Fabricating the special tray • Framework is positioned on the master cast. • Outline of tray is drawn in the master cast made from the anatomical impression. • Cast coated with separating medium • A spacer is adapted over the crest of the edentulous ridge using a single layer of the base plate wax. • Framework is placed over the spacer.
- 26. • Autopolymerising resin is mixed and adapted over the framework along the length of the ridge and excess material is removed with sharp knife before resin hardens
- 27. • Borders of the cured resin tray should be trimmed according to the outline. • Relief holes can be prepared along the crest of the ridge and retromolar pad to allow the escape of excess impression material.
- 28. IMPRESSION MAKING • Wax is softened in a water bath at 51-54C. It is then painted evenly on the tissue surface of impression tray with a brush. Wax should be painted in excess near the borders to record the sulcus. • Tray is seated and held with three fingers. • The cheeks are then pulled over the borders of the tray to record the buccal vestibule. • The patient is asked to force his tongue against cheeks to record sublingual borders and against anterior teeth to record distolingual extensions
- 29. • Pt should keep mouth half open for 5 min to ensure cooling and hardening of wax • When the wax hardens, the framework special tray is removed and impression is examined. • The wax surface that contacted the tissues appear glossy and the other areas will appear dull. • Additional wax is painted over the dull areas and the procedure is repeated until glossy borders are obtained. • Each time wax impression is inserted in mouth Operator must wait for 5 mins before impression removal • The impression should be placed in the mouth finally for 12 minutes and then cast is poured
- 30. SELECTIVE PRESSURE FUNCTIONAL DUAL IMPRESSION TECHNIQUE • In this technique one anatomical impression and one selective pressure functional impression is made. A master cast is prepared from the anatomical impression and is later altered according to the selective pressure functional impression. • Advantage • It equalizes the stress acting on the abutment teeth and the soft tissues. • The rate of ridge resorption is reduced because relieving areas that cannot withstand any load are not stressed.
- 31. PROCEDURE • Special tray is fabricated on master cast made from an anatomical impression • The tray is fabricated without a wax spacer • Tissue surface of special tray is trimmed with burs to provide adequate relief • The impression material ( preferably ZOE ) is loaded on prepared special tray and inserted into patient’s mouth • Patient is advised to keep his mouth open • The impression is recorded under finger pressure • Only the stress bearing areas will be compressed during impression making
- 32. BLATTERFEIN’S TECHNIQUE FOR IMPRESSION MAKING SEMI PRECISION AND PRECISION PARTIAL DENTURES • Here an algniate impression is made and cast is poured • Baseplate wax is adapted over the teeth region on the cast • Second layer of wax is then adapted over the complete cast • Windows are cut in wax to provide for tissue stops • An acrylic plate is fabricated • The impression is made using polyether and then master cast is poured
- 33. TWO STAGE IMPRESSION FOR DISTAL EXTENSION REMOVABLE PARTIAL DENTURES BY -ROBERTOVON AND KRAMMER • Here the impression area is divided into tooth zone and tissue zone respectively • A spacer is adapted over entire cast and custom tray is fabricated • A tube is attached in the tooth zone • First the spacer is removed from tissue zone and ZOE impression is made of tissue zone • Next the spacer is removed from the tooth zone and irreversible hydrocolloid material is injected into the tubes attached to the tray near tooth zone Alginate zoe
- 34. CLYDE D LEACH’S TECHNIQUE FOR MAXILLARY RPD • Outline is marked on maxillary cast for fabrication of resin tray • The tray is fabricated and multiple perforations are made • An impression is made of palatal tissues • A special tray with stops is then used to make an over impression over the resin tray impression
- 35. SINGLE TRAY DUAL IMPRESSION TECHNIQUE BY JOSEPH A RUPANO • In this technique a spacer is adapted over the tooth region • A special tray is made with an opening around the teeth region • Border moulding and impression is made of edentulous region • Occlusal rims are fabricated over tray to record a functional impression • A final pick up impression is made over teeth region and excess material flows out through the perforations
- 36. MODIFIED APPROACH FOR MANDIBULAR DISTAL EXTENSION RPD BY-SONI PRASAD • A polyvinyl siloxane impression is made of mandibular arch and master cast is poured • The metal framework is fabricated and verified • Wax try-in is verified and denture is processed and inserted • During insertion, a soft liner is placed after 2 days post insertion • It is worn for period of 1 week and permanent relining is done • The final denture is then dileverd
- 37. SIMPLIFIED IMPRESSION TECHNIQUE FOR DISTAL EXTENSION RPD BY ELIE DAOU • It is same as hindel’s technique except that impression compound is used to fabricate occlusal rims instead of wax.
- 38. Thank you