11.Special Impression Procedures For TooTH-Tissue-Supported removable Partial dentures.pptx

Impressions

1. Special Impression Procedures For TooTH -Tissue-Supported removable Partial dentures GUIDED BY- PRESENTED BY- Dr. ASHISTARU SAHA Dr. POOJA AGRAWAL Dr. SUDHEER ARUNACHALAM Dr. TUSHAR TANWANI Dr. ANUPAM PURWAR Dr. NEHA NAVLANI Dr. RUCHI GUPTA Dr. SUDEEPTI SONI

2. CONTENT Introduction Impression methods McLean physiologic impression Functional reline method Fluid wax functional impression Selected pressure impression Corrected cast procedure Other techniques Conclusion References

3. Introduction Impression - A negative likeness or copy in reverse of the surface of an object; An imprint of the teeth and adjacent structures for use in dentistry. (GPT 9)

4. BASED ON METHOD OF IMPRESSION MAKING-

5. ANATOMICAL FORM- The surface of the residual ridge at rest. It is the shape of the ridge before functional load is applied . 

6. FUNCTIONAL FORM- It means the shape of the residual ridge tissue when it is functioning to support the denture base. It is the shape of the ridge after functional load is applied .

7. Impression materials Anatomic impressions- Irreversible hydrocolloid Elastomeric impression material Reversible hydrocolloid Functional impressions- Fluid wax Metallic paste Soft liners Elastomeric impression material (Light body)

8. CONCEPT OF FUNCTIONAL IMPRESSION- The term functional impression means recording the functional form of the residual ridge tissue & to obtain uniformity of support when the functional load is applied.

9. Initially   APPLEGATE -Impression wax to load functionally the residual ridge. HINDEL -Free end denture base under masticatory load should be related to metal framework when it is seated. HOLMES -Used four different materials with altered cast technique. LEUPOLD & KRATOCHVIL -Used zinc-oxide eugenol paste to record the shape of residual ridges. Leupold RJ, A comparative study of impression procedures for distal extension removable partial dentures. J Prosthet Dent 1966; 16:708. 20

10. KRAMER & SINGER -Used a double impression technique based on load distribution by hindel . MCCRACKEN -Functional technique should be used when constructing mandibular distal extension based partial denture. Leupold RJ, A comparative study of impression procedures for distal extension removable partial dentures. J Prosthet Dent 1966; 16:708. 20

11. Need of functional impression The displaceability of the mucosa of residual ridge is not uniform. In cases of distal extension based partial denture. Short span distal extension bases.  

12. INDICATIONS FOR FUNCTIONAL IMPRESSION Mandibular distal extension partial dentures Mainly kennedy’s class I & II edentulous arches.  

13. FACTORS INFLUENCING SUPPORT OF DISTAL EXTENSION BASE Contour and quality of residual ridge

14. Extent of residual ridge coverage by the denture base

15. Type and accuracy of impression registration

16. Accuracy of fit of denture base- Support of distal extension denture base is enhanced by intimacy of contact of the tissue surface of the base and the tissue that covers the residual ridge.

17. Design of partial denture framework

18. Total occlusal load applied The number of artificial teeth, the width of their occlusal surfaces and their occlusal efficiency influence the total occlusal load applied to the removable partial denture.

19. Methods of functional impression Physiologic impression Selected pressure impression McLean’s Method Hindle’s modification Functional relining Fluid wax

20. PHYSIOLOGIC IMPRESSION TECHNIQUES record the ridge portion of the cast in its functional form by placing an occlusal load on the impression tray during the impression procedure.

21. SELECTED PRESSURE TECHNIQUE- This technique is intended to equalize the support between the abutments and the soft tissues and to direct forces to the portions of the ridge that are most capable of withstanding such forces. This is accomplished by relieving the tray in some areas while allowing the impression tray to contact the ridge in other areas.

22. CORRECTED CAST OR ALTERED CAST PROCEDURE- In fluid wax technique and selected pressure technique, an impression of the edentulous ridge is made using an impression tray attached to the framework. The master cast is altered to accommodate the secondary impression, and a corrected cast is generated.

23. MCLEAN PHYSIOLOGIC IMPRESSION- The need for physiologic impressions was first proposed by McLean and others. They realized the need for recording the tissues of the residual ridge in a functional form while capturing the remaining teeth in the anatomic form. As a result, they developed a dual impression technique.

24. The McLean technique employs a custom tray for distal extension areas A functional impression is completed using an appropriate impression material. The impression is removed from the oral cavity and examined. If acceptable, the functional impression is repositioned in the mouth. An alginate "over-impression" is made while applying pressure to the previously completed functional impression. The resultant two-piece impression relates the functional form of the posterior ridges to the anatomic form of the remaining teeth.

25. Disadvantage- The practitioners could not produce the same functional displacement generated by occlusal forces.

26. MODIFICATION BY HINDLES- Impression is made with a modified tray applying finger pressure.

27. HINDLE’S FINGER LOADING

28. Disadvantages - Tissues are in constant stage of compression. Ischemia and bone resorption

29. FUNCTIONAL RELINE METHOD- This technique consists of adding a new surface to the intaglio of the denture base. The procedure may be accomplished before the insertion of the partial denture, or it may be done at a later date if denture becomes ill fitting.

30. A metal spacer may be placed on the dental cast to provide space for a functional reline After the denture base has been processed, the metal spacer is removed.

31. Heated modeling plastic is carefully applied to the intaglio of the denture base. Completed border moulding

32. 1 mm modeling plastic is removed from The Intaglio surface and final impression is made with zinc-oxide eugenol or light body Polysulphide rubber base.

33. Disadvantages- Failure to maintain the correct relationship between the framework and the abutment teeth during the impression procedure. Failure to achieve accurate occlusal contact following the reline procedure.

34. FLUID WAX FUNCTIONAL IMPRESSION- The fluid wax impression may be used to make a reline impression for an existing partial denture or to correct the edentulous ridge portion of a master cast. The term fluid wax is used to denote waxes that are firm at room temperature and have ability to flow at mouth temperature. Eg - Iowa wax, developed by Dr Smith at university of Iowa Korrecta wax No 4, developed by Dr O.C. and S.G. Applegate at university of Michigan

35. The Armamentarium for Fluid wax technique includes the wax itself, a stiff brush, a water bath and a container for confining the wax

36. Undercuts that would interfere with removal of the tray are eliminated using baseplate wax . An appropriate separating medium is applied to the cast.

37. The framework is seated on the cast Tray material is adapted to the metal struts and dental cast using finger pressure

38. Excess material is trimmed using a surgical scalpel or similar instrument. Following polymerization, the tray material is smoothed using a laboratory bur

39. Fluid wax painted onto the intaglio Surface of tray (1-2 mm) Completed impression. Check for Proper tissue contact

40. SELECTED PRESSURE IMPRESSION TECHNIQUE- The selected pressure impression attempts to direct more force to those portions of the ridge able to absorb stress and to protect the areas of the ridge least able to absorb stress. To accomplish this, the intaglio surface of the tray is selectively relieved.

41. The mandibular impression tray is selectively reduced at the ridge crest. This provides additional room for impression material and minimizes displacement of the soft tissues . Holes may be placed in the tray to further minimize the pressures generated during impression procedures .

42. Altered cast technique A final cast that is revised in part before processing a denture base—called also corrected cast, modified cast. Broken line indicates the proposed cast modifications for a bilateral corrected cast process. The master cast following modification

43. Properly border-molded impression tray Completed rubber base impression

44. Framework-impression assembly is properly seated on modified master cast. The assembly is inverted in preparation for rimming and boxing procedures.

45. Utility wax is used to rim the impression. The utility wax should be located 2 to 3 mm from impression borders and should ex- tend peripherally 3 to 4 mm. Boxing wax is added to form a watertight vertical wall. When this has been accomplished, freshly mixed dental stone is introduced. After the stone has gained sufficient strength, the corrected cast is recovered and Trimmed.

46. Rapuano JA. Single tray dual-impression technique for distal extension partial dentures. J Prosthet Dent,1970,24:41-46. Fig 1.The anterior teeth on the diagnostic casr are blocked out with three to four layer of asbestos paper. Fig. 2. The cold-curing resin is adapted on the diagnostic cast to form the custom tray. Fig. 3. An opening has been made around the teeth in the resin custom tray. Serial perfora ~ tions surrounding the teeth allow the impression material to be attached to the tray. Fig. 4. The custom tray is seated in the patient’s mouth. Note the accessibility of the teeth.

47. Fig. 5. The border of the tray has been molded to be in harmony with the movements of the surrounding tissues. Fig. 6. A zinc oxide and eugenol impression is made of the residual ridges. Fig. 7. The final impression of the residual ridges is completed. Fig. 8. An occlusion rim is constructed on the resin tray containing the final impression of the residual ridges.

48. Fig 9.The maxillary and mandibular occlusion rims are in contact at the vertical dimension of occlusion. The mandible is in centric relation. The anterior part of the maxillary occhuion rim has been removed so that the irreversible hydrocolloid can be forced through the opening in the tray while the residual ridges arc resisting occlusal forces. Fig. 10. Irreversible hydrocolloid impression material has been forced through the opening in the tray. Fig. 11. The single-tray dual-material impression is completed. Fig. 12. A cIoseup view of the two materials just distal to the abutment tooth shows that the tissue is under occlusal load.

49. The master cast has been recovered from the final impression.

50. Diagnostic cast is outlined for autopolymerizing acrylic resin tray. Acrylic resin tray is completed, perforated, and ready for try-in. Leach CD, Donovan TE. Impression technique for maxillary removable partial dentures. J Prosthet Dent, 1983,50:283-286.

51. Impression of palatal tissue is completed with a zinc oxide- eugenol wash. Impression of palatal tissue is trimmed and a wax stop is placed in preparation for overimpression .

52. Syringe impression material is carefully injected around palatal impression, teeth, and rest seats Final overimpression with palatal impression in place

53. Crosscut section of final overimpression taken in reversible hydrocolloid illustrates overall impression technique. Each layer of material is identified in diagrammatic view. 1 = Cast representing patient’s maxillary anatomy; 2 = zinc oxide- eugenol paste; 3 = acrylic resin tray with perforations; 4 = syringe impression material; 5 = wax stop; 6 = overimpression body material; and 7 = reversible hydrocolloid water-cooled tray.

54. CONCLUSION There are different techniques for recording impression in tooth-tissue supported partial denture. Knowledge of all techniques is must to select appropriate impression technique according to clinical condition.

55. REFERENCES Stewart’s Removable partial prosthodontics . Fourth edition. Quintessence publication. McCracken’s Removable partial prosthodontics . Eleventh edition. Elsevier publication. Leupold RJ, A comparative study of impression procedures for distal extension removable partial dentures. J Prosthet Dent 1966; 16:708-20. Leach CD, Donovan TE. Impression technique for maxillary removable partial dentures. J Prosthet Dent, 1983,50:283-286. Rapuano JA. Single tray dual-impression technique for distal extension partial dentures. J Prosthet Dent,1970,24:41-46.