Altered casts technique

dentistry: functional impressions in cast partial dentures

1. ALTERED CAST TECHNIQUE By Dr. Saili Chandavarkar MDS II 1

2. CONTENTS Introduction Support of distal extension based partial denture Concept of functional impression Need of functional impression Indication for functional impression Objectives of functional impression 2

3. CONTENTS Factors influencing support of distal extension base Materials used for functional impression Impression methods Altered Cast Technique Modifications of altered cast technique 3

4. SUPPORT OF DISTAL EXTENSION BASED PARTIAL DENTURE A minor support comes from the abutment teeth The major support comes from elastic fibrous connective tissue pad overlying the alveolar process Residual ridge: It is the remnant of the alveolar process together with the fibrous connective tissue covering (& included structures) in an edentulous area of the dental arch. 4

5. ACCORDING TO THE METHOD OF IMPRESSION MAKING 5

6. ANATOMIC FORM The surface of the residual ridge at rest. It is the shape of the ridge before functional load is applied. 6

7. 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

8. 8 Anatomic or Resting form Supporting or Functional form McCracken’s Removable Partial Prosthodontics 3 rd edition

9. 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

10. HISTORY Applegate used impression wax to load functionally the residual ridge Hindel felt that 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 10

11. HISTORY Kramer & Singer used a double impression technique based on load distribution by Hindel McCracken concluded that a functional technique should be used when constructing mandibular distal extension based partial denture 11

12. NEED OF FUNCTIONAL IMPRESSION The displaceability of the mucosa of residual ridge is not uniform. The need of functional impression arises in cases of distal extension based partial denture. Some mouth does not exhibit significant difference in anatomical and functional form of ridge. Short span distal extension bases. 12

13. INDICATIONS FOR FUNCTIONAL IMPRESSION Mandibular distal extension partial dentures – Only a limited ridge area can be used as a stress bearing site. Mainly Kennedy’s class I & II edentulous arches. 13

14. OBJECTIVES OF FUNCTIONAL IMPRESSION ( O.C. Applegate) To obtain the maximum area of coverage Traumatic impact on any area must be avoided At rest there must be no islands of ischemia Under work loads all areas must receive massage stimuli. 14

15. Factors influencing the support of distal extension base Contour & Quality of residual ridge 15 McCracken’s Removable Partial Prosthodontics

16. Extent of residual ridge coverage by the denture base 16 McCracken’s Removable Partial Prosthodontics

17. Type & Accuracy of impression registration 17 McCracken’s Removable Partial Prosthodontics

18. Accuracy of fit of denture base 18 McCracken’s Removable Partial Prosthodontics

19. Design of partial denture framework 19 McCracken’s Removable Partial Prosthodontics

20. Total Occlusal load applied 20 McCracken’s Removable Partial Prosthodontics

21. IMPRESSION MATERIALS 21 ANATOMIC IMPRESSIONS IRREVERSIBLE HYDROCOLLOID ELASTOMERIC IMPRESSION MATERIALS REVERSIBLE HYDROCOLLOID FUNCTIONAL IMPRESSIONS FLUID WAXES METALLIC PASTES ELASTOMERIC IMPRESSION MATERIALS SOFT RELINERS

22. METHODS OF FUNCTIONAL IMPRESSION 22

23. The master cast may be altered to accommodate the new ridge impression it is referred as Altered Cast Technique Or Corrected Cast Impression Technique 23

24. McLean’s Physiologic Method 24 Clinical Removable Partial Prosthodontics – Stewart. 3 rd edition

25. Custom tray over a preliminary cast 25

26. 26 Custom tray over a preliminary cast

27. Occlusal rim over a distal extension base is made 27

28. 28 Functional impression of extension area under occlusal load

29. Hydrocolloid impression over the first impression made under finger pressure. 29

30. McLean’s Physiologic Method Finger pressure not equal to biting pressure Alginate between stock tray and occlusal rim acts as buffer. May not transfer entire load to special tray. 30 Disadvantages-

31. Hindel’s Modification First anatomic impression in alginate is made Acrylic resin tray over saddle area is prepared Impression of saddle area is made in zinc oxide eugenol paste without pressure Super impression is made with a modified tray applying finger pressure. 31 Clinical Removable Partial Prosthodontics – Stewart. 3 rd edition

32. 32 Hindel’s special tray with holes to apply pressure

33. 33 HINDLE’S FINGER LOADING

34. 34 HINDLE’S FINGER LOADING Tissues are in constant stage of compression Ischemia and bone resorption Premature contacts at rest. Disadvantage

35. Functional Reline Method 35 Clinical Removable Partial Prosthodontics – Stewart. 3 rd edition

36. Layer of relief given 36

37. The denture is processed & fitted in the mouth in customary manner, except that the relief metal is left in place. 37 It should be worn for a trial period of a week & all needed adjustments are done

38. The relief metal is stripped off from the acrylic. 38

39. low fusing modeling compound is added in increments 39

40. Border molding done. 40

41. 1 mm Modeling plastic is removed from the intaglio surface. 41

42. I mpression made using one of the corrective materials : fluid wax, Zinc-oxide Eugenol pastes or any elastomeric impression material. 42

43. Functional Reline Method Disadvantage – a ) Occlusion may be altered slightly by reline procedures & may require adjustments b) There remains a fine line of demarcation between the newly added & old resin of the denture 43

44. FLUID WAX TECHNIQUE 44 Clinical Removable Partial Prosthodontics – Stewart. 3 rd edition

45. FLUID WAX TECHNIQUE The most frequently used waxes are – Korrecta wax no. 4 - Dr. O.C.& S.G. Applegate at University of Michigan IOWA wax - Developed by Dr.Smith at University of IOWA Korrecta wax no. 4 is slightly more fluid than IOWA wax 45

46. The armantarium for fluid wax technique. (51- 54 degree Celsius) 46

47. Undercuts eliminated using baseplate wax 47

48. Separating medium applied to the cast. 48

49. Framework seated on the cast. 49

50. Tray material adapted 1-2 mm relief between residual ridge and intaglio surface of tray. 50 Excess material removed. Tray border smoothed using laboratory bur. Should be 2 mm short of border extension required.

51. Fluid wax painted onto the intaglio surface of tray (1 -2 mm) A ssembly seated in patients mouth.(5 -7 mins) 51

52. Completed impression. Check for proper tissue contact.(final insertion for 12 mins) 52

53. FLUID WAX TECHNIQUE The finished impression must be handled carefully & the new cast poured as soon as the wax is fragile & subject to distortion 53

54. SELECTIVE TISSUE PLACEMENT IMPRESSION METHOD 54

55. SELECTIVE TISSUE PLACEMENT IMPRESSION METHOD The technique attempts to direct more force to those portions of ridge able to absorb stress without adverse response & to protect the areas of ridge which are least able to absorb forces. 55

56. Framework tried on the cast Tray outline marked for extension 56 McCracken’s Removable Partial Prosthodontics

57. Framework with tray fabricated on it with holes on its ridge. 57 McCracken’s Removable Partial Prosthodontics

58. Areas in which relief is to be provided is marked 58 Tray is being relieved before the final impression is made Clinical Removable Partial Prosthodontics – Stewart. 3 rd edition

59. Acrylic resin impression trays with holes Framework with tray tried in patient’s mouth Functional impression made 59

60. ALTERED CAST TECHNIQUE Altered cast \oˆ l#terd ka˘ st \: a final cast that is revised in part before processing a denture base—called also corrected cast, modified cast Altered cast partial denture impression \oˆ l#terd ka˘ st pa¨r#shal de˘n#cher ı˘m-pre˘sh#an \: a negative likeness of a portion or portions of the edentulous denture bearing area(s) made independent of and after the initial impression of the natural teeth. This technique employs an impression tray(s) attached to the removable dental prosthesis framework or its likeness 60

61. Also known as Corrected cast or Split cast Technique. It is mainly a modification of functional impression through laboratory procedure. Functional impression for this technique can be made using any of the above mentioned materials and techniques. 61 ALTERED CAST TECHNIQUE Robert J. Leupold And Frank J. Kratochvil: An Altered-cast Procedure To Improve Tissue Support For Removable Partial Dentures . J Prosthet Dent 1965:672-679

62. Functional impression made Final impression 62 McCracken’s Removable Partial Prosthodontics 12thedition

63. Edentulous area cut from the master cast 63

64. Framework with attached impression seated on the master cast It is imperative that all the rests occupy their proper position on the cast 64

65. Assembly from underside of the cast Peripheral borders of the impression are protected with utility wax & the assembly wrapped with boxing wax 65

66. The newly obtained altered cast with newly added stone 66

67. Alternate techniques 67

68. Alternate technique to separate the edentulous cast 68

69. 69 Boxed elastomeric final impression in which edentulous ridges have been separated with contoured baseplate wax (A arrows) and sealed to anatomic contour of impression at base. Triangular wax bars (B arrows) are attached to make dovetails (three separate compartments of impression). Izharul Haque Ansari : A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

70. 70 Mix of properly proportioned dental stone vibrated into three compartments of impression. Impression must be overfilled to make solid base to prevent premature separation Izharul Haque Ansari : A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

71. 71 Master east ready for duplication. Three to 5 mm thick base (line shown by arrow) below level of separating wax to prevent premature separation while cast is handled to make the framework. Izharul Haque Ansari : A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

72. 72 Base of the cast has been trimmed to line shown by arrows in previous dgm and cast is ready for immersion in boiling slurry water. Portions of old cast may require trimming (arrow) before new impression is poured Izharul Haque Ansari : A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

73. 73 View from bottom of master cast after base has been trimmed to expose separating wax and wax dovetails. Izharul Haque Ansari : A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

74. 74 Edentulous portions separated from rest of master cast when removed from boiling clear slurry water. Appearance of dovetails for additional retention for dental stone. Izharul Haque Ansari : A new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made. J Prosthet Dent 1994;72:666-9.

75. Alternate boxing technique 75 Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

76. 76 Replacement of impression and framework on master cast after removal of edentulous distal extension areas of cast. Framework is luted to master cast with sticky wax. Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

77. 77 Protection of teeth in master cast with irreversible hydrocolloid. Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

78. 78 Immersion of master cast and frame assembly within supporting base. Framework with corrected impression is seated into a plaster mix contained bv wax boxing sheet. Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

79. Make a support base mix with an Accu -Dent (Buellton, Calif.) water measure. Mix 2 parts (26 mL ) cornstarch (Argo Cornstarch, Best Foods Div, CPC International Inc, Englewood Cliffs, N.J.), 1 part (13 mL ) fine pumice, and 1 part (13 mL ) plaster. Mix the dry powders and add to 115 mL water. Pour the material into a denture flask. Let set for 15 minutes. Pour a base with a compatible stone to that of the master cast, filling up the denture flask. Once set, remove from flask. Separate master cast from the supporting base and irreversible hydrocolloid (this supporting base is easy to remove with one’s fingers). Trim the cast to the desired dimensions 79 Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20

80. Mix 50% cornstarch (Argo Cornstarch, Best Foods Div. C.P.C. International Inc., Englewood Cliffs, N.J.) and 50% white modeling plaster by volume with water to a creamy consistency. Pour this into the boxing wax form . Place the impression in the mixture. Allow the mixture to set for 10 minutes. Remove and save the boxing wax. Seal the previously used boxing wax to the trimmed base leaving at least 20 mm from the top of the boxing wax to the highest point on the impression. Soak the master cast in slurry water for 5 minutes. Pour the cast using the same stone as the original master cast. No separating medium is needed When the stone is set, remove the boxing wax and place the cast in a water bath of 110” F to facilitate removal of the plaster/cornstarch mixture and the Framework. Separate the plaster/cornstarch mixture with plaster pliers and your fingers. 80 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

81. 81 Boxing wax placed around plaster base and cast leaving at least 20 mm from top of wax to highest point on impression. Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

82. Completed altered cast. 82 Completed altered cast. Leila Jahangiri , Patrick Mascarenhas and Donald Kitzis : A simple technique for boxing impressions for fabrication of altered casts. J Prosthet Dent 2001;85:519-20 Kevin D. Plummer: Technique for boxing an altered cast impression. J Prosthet Dent 1982;47:573-575

83. Alternative to altered cast technique 83 Ming- Sheh Chen, W.A. Eichhold , Chao-Chin Chien and D.A. Curtis : An altered-cast impression technique that eliminates conventional cast dissecting and impression boxing. J Prosthet Dent 1987;57:471-474

84. 84 Ming- Sheh Chen, W.A. Eichhold , Chao-Chin Chien and D.A. Curtis : An altered-cast impression technique that eliminates conventional cast dissecting and impression boxing. J Prosthet Dent 1987;57:471-474 Tissue surface of final impression. Note excess rubber base impression material has been trimmed to internal finish line (arrows) of metal framework. Lingual surface of custom tray. Most of excess final impression material has been trimmed. Only 3 mm of impression material is left over and above border flange . This residual final impression material is later used as a guide to develop ledge of an irreversible hydrocolloid land.

85. 85 Tissue surface of distal-extension irreversible hydrocolloid pickup impression. Irreversible hydrocolloid is purposely overextended 3 to 5 mm around distal-extension region.

86. 86 Irreversible hydrocolloid pickup impression after trimming is completed. Note a land of irreversible hydrocolloid impression material that is 3 mm in width and 3 mm below crest of border flange. It shows relationship between final impression, irreversible hydrocolloid land, and stock metal tray.

87. 87 Tissue surface of final impression is surrounded by a uniform land of irreversible hydrocolloid .

88. 88 Tissue surface of pickup impression. Note wax blockout (arrows) of all undesirable mechanical undercuts. There is no blockout of major connectors, rests, and reciprocal clasp arms

89. 89 Master cast obtained by this method. Note uniform stone land transition in distal-extension regions.

90. Alternative to altered cast technique 90 Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61

91. 91 Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61 Aluminum foil and two sheets of baseplate wax over diagnostic cast before tray fabrication.

92. 92 Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61 Custom tray fabricated with extensions reduced 2 mm short of vestibule.

93. 93 Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61 Custom tray with softened modeling compound reseated on diagnostic cast . Modeling compound over residual ridges shaped appropriately before intraoral placement.

94. 94 Herman B. Dumbrigue and Josephine F. Esquivel: Selective-pressure single impression procedure for tooth-mucosa–supported removable partial dentures. J Prosthet Dent 1998;80:259-61 Border molding procedure completed.

95. Trial of metal framework,altered cast technique and interocclusal record in one appointment 95

96. Technique 1 Richard Bauman and James DeBoer : A modification of the altered cast technique. J Prosthet Dent 1982;47:212-213 96 A custom tray was fabricated over the metal framework in the edentulous portion. A wax occlusal rim was fabricated over the custom tray

97. 97 Border molding is completed. Final impression is completed in material of choice Richard Bauman and James DeBoer : A modification of the altered cast technique. J Prosthet Dent 1982;47:212-213

98. 98 Richard Bauman and James DeBoer : A modification of the altered cast technique. J Prosthet Dent 1982;47:212-213 Interocclusal record is made by placing low fusing modelling compound o ver the wax rim to record the interocclusal relationship

99. 99 Richard Bauman and James DeBoer : A modification of the altered cast technique. J Prosthet Dent 1982;47:212-213 An over impression of the entire assembly in irreversible hydrocolloid

100. Technique 2 Lih-Shou Lay,Wing -Hong Lai and Chen- Tsye Wu : Making the framework try-in, altered-cast impression, andocclusal registration in one appointment. J Prosthet Dent 1996;75:446-8. 100

101. 101 Wax used to block out undercuts around framework over edentulous portion of cast. Autopolymerizing acrylic resin tray material formed over edentulous ridge portion of framework. Trays detached from framework. Custom-made trays attached to framework with acrylic resin.

102. 102 Index grooves on occlusal surface of trays. Jaw relation record (yellow) made in mouth with framework and record base in place. Altered cast poured without removal of jaw registration material.

103. 103 Technique 3 U. Santana-Penín and J. Gil Lozano: An accurate method for occlusal registration and altered-cast impression for removable partial dentures during the same visit as the framework try-in. J Prosthet Dent 1998;80:615-8 .

104. 104 Light-cured acrylic resin tray formed over edentulous ridge portion of framework. Holes are made in tray to allow resin columns to be built up through it. Position of holes can be marked with pencil so that it is clear where to locate bases of columns (arrows). U. Santana-Penín and J. Gil Lozano: An accurate method for occlusal registration and altered-cast impression for removable partial dentures during the same visit as the framework try-in. J Prosthet Dent 1998;80:615-8 .

105. 105 Acrylic resin trays (with holes for resin columns) detached from framework Framework in mouth showing 1 inch resin column built up as jaw relation index.

106. 106 Acrylic resin tray in position on framework after building up resin column (a) that acts as jaw relation index. In addition, stone index beneath major connector (b) will facilitate accurate repositioning of framework on altered cast . Framework in mouth showing 1 resin column built up as jaw relation index.

107. 107 Completed impression seated on cast from which edentulous ridges have been removed. Impression is boxed, in this case with plasticine .

108. 108 Finished altered master cast, with impression and jaw relation indexes (arrows) in place. Resin columns are used to relate mandibular cast to previously mounted maxillary cast, and are attached to lower arm of articulator with stone.

109. 109 Richard P. Frank et al : Clinical Outcome Of Altered Cast Impression Procedure Compared With Use Of A One Piece Cast J Prosthet dent 2004;91:468-76 Altered cast procedure does not offer significant advantages over one piece cast if the following standards are met : Complete extension of impression Use of magnification to adjust and ensure complete seating of the framework. Coverage of retromolar pad and buccal shelf area by the base 92

110. REFERENCES Essential of Removable partial denture –Applegate Removable Partial Prosthodontics – Miller Partial dentures – Osborne & Lamiae Advanced removable partial dentures – Brudvik Clinical dental prosthetics – Fenn , Liddelow and Gimson’s 110

111. REFERENCES Treatment of partially edentulous patients – Louis Boucher J.Pros.Dent. July,2004 :volume 24;number1 J.Pros.Dent May – June 1992 : Volume 15;number 3 111