Functional impression in RPD

These impressions are recorded under functional load, that is tissue surface is recorded in compressed form

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 Principl e- 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

14. 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.

15. 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.

16. 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

17. 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.

18. 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

19. 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

20. 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

21. 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

22. 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.

23. 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

24. 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.

25. 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

26. 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.

27. 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

28. 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

29. 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.

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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.

37. Thank you