Theories of impression making

theories of impression making

1. THEORIES OF IMPRESSION MAKING Dr. Shweta Pandey PG 1 st yr Govt College Of Dentistry

2. CONTENTS 2

3. INTRODUCTION 1

4. 4 The beginning of good denture starts with making of a good impression ,so a good impression is stepping stone . SO WHY WE NEED IMPRESSIONS????? Impression procedure is simply a means of recording the details of basal seat area so that a stone replica can be poured, because without such a replica, trial plates and the final denture can not be formed . COMPLETE DENTURE IMPRESSION A complete denture impression is a negative registration of the entire denture bearing, stabilizing and border seal areas present in the edentulous mouth. (GPT-9)

5. HISTORY 2

6. 6 1 3 5 4 2 Era of Accuracy Closed mouth impression 1600-1844 Before 1600 complete denture replacement were not made 1845-1900 Basic principles of impression making 1900-1929 1930-1950 Anatomy of denture bearing area and muscle physiology is recognized 1950-2009 Emphasis on biological factors affecting impression

7. 1951 BOUCHER 7 IMPRE SSION TECHNIQUE AMOUNT OF PRESSURE EXERTED LANDMARK ANATOMIC ARBITA RARY OPEN CLOSE MOUTH POSITION SELECTIVE P R ESSURE PRESSURE NON PRESSURE NEGETIVE PRESSURE

8. PRINCIPLES OF IMPRESSION MAKING 3

9. 9 1.The impression should extend to include the entire basal seat. 2. The border must be in harmony with the anatomical and physiological limitations of the structures. 3. Space for the final impression material within the impression tray. 4. Physiological type of border molding procedure performed (dentist/patient under the guidance of the dentist). 5. Selective pressure on the basal seat during impression making 6. The impression must be removed without damage to mucous membrane. 7. A guiding mechanism is provided for correct positioning of the tray. 8. Tray and impression material should be dimensionally stable. 9. External shape is similar to external form of the complete denture.

10. OBJECTIVES OF IMPRESSION MAKING 4

11. 11

12. THEORIES OF IMPRESSION MAKING 5

13. 13

14. 14 MINIMAL PRESSURE THEORY

15. KEY FEATURES 15 Technique demand that a metal base be used rather then dimensionally unstable acrylic. ( GOLD ) Interfacial surface tension as the only important retentive mechanism in complete denture. Did not use conventional flanges because these did not resist vertical displacement. Dykins (1947) recommended a short lingual flange to resist lateral displacement .

16. TECHNIQUE 16

17. 17 IGNORES value of dissipating masticatory forces over the largest possible basal seat. Mucostatic denture minimized the retentive role of musculature. FISH 1948

18. MODIFIED MUCOSTATIC IMPRESSION TECHNIQUE GERBER (1977) refuted theory that the retention of complete denture could be provided only with tissue topography. Impression is taken under very little pressure. No muscle movement by patient. Clinician forms border tissue using his hand. 18

19. 19 MUCOCOMPRESS IVE THEORY

20. TECHNIQUE 20

21. 21 IGNORES Denture are in actual occlusal contact for only a relatively short period of time and the constant pressure, even if equal, may overstress the tissue.

22. 22 S ELECTIVE PRESSURE THEORY

23. TECHNIQUE 23

24. 24 KEEP IN MIND

25. MYOSTATIC IMPRESSION THEORY 25 The concept was introduced by John P. Frush(1960) for the BPS Denture

26. 26 DYNAMIC IMPRESSION THEORY Dynamic Impression is a functional and physiological impression technique.

27. TECHNIQUE (Method 1) 27

28. TECHNIQUE (Method 2 & 3) 28 Old lower denture can be used as an individual tray when opposing natural or artificial teeth are present. “Stops” are built to a height that will re-establish the correct vertical relationship. The denture must be perforated and completely dry . Material is placed directly in the oral cavity, the denture base is filled with impression material, and the impression is made Denture is first processed on the basis of a conventional impression. Thickness of the final impression material will be critically thin and irreversible hydrocolloid cannot be used. Principles of this third method can also be applied to dentures that are several months or years old and are lacking in retention and stability, provided that the vertical dimension of occlusion has remained adequate.

29. ADVANTAGES 29 Avoidance of the dislocating effect of the muscles on improperly formed denture borders. Complete utilization of the possibilities of active and passive tissue fixation of the denture. TURBYFILL DENTURES ARE MADE BY THIS TECHNIQUE

30. Impression technique in compromised situation 6

31. IMPRESSION TECHNIQUES TO MANAGE RESORBED MANDIBULAR RIDGES Conventional Functional Elastomeric 31 Admix Is Cocktail All green Flange Technique Modified Functional Is t dange.

32. IMPRESSION TECHNIQUES FOR FLABBY RIDGES Window Technique Modified Fluid Wax Cage Technique 32

33. MODIFICATIONS IN FOR LIMITED MOUTH OPENING 33 Hydrocolloid primary impression using sectional plastic stock tray. (Baker et al)

34. IMPRESSION TECHNIQUE FOR NEUTRAL ZONE 34 The term neutral zone concept was coined by Beresin and Schiesser in 1976 . It is that region where forces imposed by the tongue directed outward are neutralized by inwardly directed forces originating from the cheeks and lips during normal neuromuscular function. The neutral zone achieves 2 important objectives 1. Teeth do not interfere with normal muscle function. 2. Normal oral and perioral muscle activity imparts force against the complete dentures that serves to stabilize and retain the prostheses rather than cause denture displacement.

35. TECHNIQUE 35

36. MODIFICATIONS IN IMPRESSION MAKING IN SOME DISEASES 36

37. 37 IMPRESSION TECHNIQUES FOR PATIENT WITH GAG REFLEX

38. GENERAL MANAGEMENT AND USEFUL TIPS 38

39. SUMMARY & CONCLUSION 7

40. The main objective of impression making is to construct dentures, having maximum retention and stability, without causing any damage to the supporting structures. Dentists should be able to modify his technique to cope with the conditions of the basal tissues as presented by each patient. Thus, it is the responsibility of the dentist, to select the best possible procedures, based on sound knowledge, for achieving the best possible results for the patient. 40

41. 41 "Ideal impression must be in the mind of the dentist before it is in his hand. He must literally make the impression rather than take it" - M.M. Devan

42. 42 Dynamic Impression Methods J. Prosth . Den Nov- dec 1965 COMPLETE DENTURE PROSTHODONTICS Planning And Decision Making 2ND EDITION YASEMIN K. O`zkan Textbook Of Prosthodontics Deepak Nallaswamy 2 nd Edition Complete Denture Prosthodontics, John J Sharry 3rd Edition Bernard Levin, Impression For Complete Denture A Systematic Review Of Impression Technique For Convention Complete Denture J Indian Prosthodontic Soc. 2010 Complete Denture Prosthodontcs John J. Manappalli Boucher Co (1951) A Critical Analysis Of Mid-century Impression Techniques For Complete Dentures. J Prosthet Dent Prosthetic Treatment For Edentulous Patients Zarb – Bolender , 12 th Edition REFERENCES