Surveying and Designing in Cast Partial Denture
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- 3. The best way to cure most of the ills of partial denture prosthesis is to anticipate the troubles which may be encountered & to change the conditions so that they never happen. There is no way more sure of accomplishing this than by …..Intelligent use of the Surveying & Principles of Design. 3
- 4. Department of Prosthodontics VSPM Dental College, Nagpur
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- 6. Until 1918s most RPD were designed and constructed by time honored method of “eye balling”. A prosthesis made on the basis of educated guesses. The turning point in the partial denture construction from guess work based on clinical experience to scientifically based procedure was the appearance of dental surveyors in 1918 6
- 7. Dr.A.J.Fortunati is thought to be first person to employ a mechanical device to determine the relative parallelism of tooth surfaces. Boston in 1918 has demonstrated a method for charting correct clasp placement by using a parallelometer. First such instrument to be produced commercially was NEYS instrument. 7
- 8. Basically two types of surveying methods Surveying by using parallelometer- used commonly Optical surveying by using light beams- rare in practice 8
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- 10. NEED FOR SURVEYING FOR RPD…?? 10
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- 12. CAST SURVEYOR The cast surveyor is an instrument by means of which these principles may be applied Dr. A. J. Fortunati is thought to be the person to employ a mechanical device to determine the relative parallelism of the tooth surfaces 12
- 13. DENTAL MODEL SURVEYOR The dental model surveyor is essentially a parallelometer, an instrument used to determine the relative parallelism of surfaces of teeth or other areas on a cast of the jaw. The Ney instrument was made available in 1923, it remains most widely used surveyor in dental field. There are other surveyors in the market today, but in the long run they accomplish the same purpose. Jelenko’s is the second most widely used. 13
- 15. Parts of Surveyor a. Platform b. Vertical arm c. Horizontal arm d. Movable vertical part e. Cast holder 15
- 19. Wax knife 19
- 20. Chisel 20
- 21. What are the types of surveyors? Types of Surveyors 1. Ney Surveyor 2. Jelenko Surveyor 3. Williams Surveyor 4. Retentoscope Surveyor 5. A 2000 – Buchnann Surveyor 6. Micro analyzor 7. Stress – O-Graph 8. Optical surveyor 9. Computerized surveyor 10.Intra Oral Surveyor 21
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- 23. Ney Surveyor Jelenko Surveyor 1. Horizontal arm is fixed 1. Horizontal arm is movable 2. Vertical arm is retained by friction 2. Vertical arm is spring mounted 3. The shaft remains in any vertical position until again it is moved 3.Vertical arm when released returns to its original position. It should be held against spring tension 4. Cast table is moved around surveyor platform 4.Cast table is fixed with the magnet in the surveyor platform Differences 23
- 24. THE OBJECTIVE IN SURVEYING The objective in surveying procedure is to reveal to the designer those physical characteristics of the mouth which favor the design of a successful prosthesis. 24
- 25. Surveying of the study cast will identify the structures that will need to be modified in order to make possible a design of the prosthesis that a. Can be easily inserted and removed by the patient. b. contribute optimally to appearance c. resist unseating forces to a reasonable degree d. create no undesirable food traps THE OBJECTIVE IN SURVEYING 25
- 26. The degree of success achieved will depend upon the designer’s judicious management and correlation of four factors. 1. Retentive undercuts 2. Interferences 3. Esthetic consideration 4. Guiding plane surfaces 26
- 27. When these four factors have been assessed, the path of insertion can be decided and design of the prosthesis established 27
- 28. It should be remembered that when a laboratory technician receives a cast from a dentist on which he is to construct a removable partial denture , there is nothing the technician can do but accept that cast as it is. He cannot alter the slope of the stone teeth to improve the position of the height of contour.He cannot cut away the bony exostosis. It is essential that dentist use the surveyor before planning the treatment for the patient. 28
- 29. THE SURVEY LINE OR THE HEIGHT OF CONTOUR - It is the greatest circumference of a tooth in a given horizontal plane. - The significance of the survey line is that any rigid, nonflexible part of the prosthesis must be designed to lie above the survey line and only flexible part may be designed to go below it. 29
- 30. DE VAN 1935 used some clarifying terms to describe retention. He referred to the surface of a tooth that is occlusal to the height of contour as SUPRA BULGE and surface inclining cervically as INFRA BULGE. 30
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- 32. BLATTERFEIN’S CLASSIFICATION OF SURVEY LINES. 32
- 33. 1) High survey line 2) Medium survey line 3) Low survey line 4) Diagonal survey line NZ FZ NZ FZ NZ FZ NZ FZ 33
- 34. Surveying Diagnostic Cast Surveying Master Cast Auxiliary Uses USES OF DENTAL SURVEYOR 34
- 35. SURVEYING THE DIAGNOSTIC & MASTER CAST 1. To determine the most desirable path of placement that will eliminate or minimize interference to placement and removal. 2. To identify proximal tooth surfaces that are or need to be made parallel so that they act as guiding planes during placement and removal. 3. To determine whether tooth and bony areas of interference will need to be eliminated surgically or by selecting a different path of placement. 35
- 36. 4.To locate and measure areas of the teeth that may be used for the retention. 5.To determine the most suitable path of placement that will permit locating retainers and artificial tooth to the best esthetic advantage. 6.To permit an accurate charting of the mouth preparations to be made. 36
- 37. 7.To delineate the height of contour on abutment teeth. 8.To record cast position in relation to the selected path of placement for future reference. 37
- 38. SURVEYING PROCEDURE Two stages I. Preliminary analysis of the diagnostic cast 1. determine the most advantageous path of insertion. 2. to decide upon various types of mouth preparation that will be required 38
- 39. II. Definitive design 1. Guidelines are drawn 2. Undercuts are measured and marked 3. Soft tissue undercuts are delineated 4. Design of the framework is outlined on the cast 39
- 40. PRELIMINARY ANALYSIS 1. Evaluating the claspability of potential abutment ( Retentive undercut ) 40
- 41. 2. Interferences Interferences can be dealt with 1.Elimination 2.Alteration 3.Avoidance 4.Exploitation 41
- 42. A. Soft tissue obstacles 1. Mylohyoid ridge 42
- 43. 2.Mental ridge of the mandible 43
- 44. 3. Alveolar ridge with severe labial undercut 44
- 48. The surveyor can be used to determine the best means of correlating the path of insertion of the prosthesis with the slope of the undercut. 48
- 49. PRELIMINARY ANALYSIS B. Hard tissue obstacles Migrated, tipped and rotated teeth may be found anywhere in either jaw and may interfere with the ideal design of the prosthesis 49
- 50. 1.Lingually inclined mandibular teeth 50
- 51. 2. Maxillary molars and bicuspids, which tip buccally 51
- 52. PRELIMINARY ANALYSIS 1.The metal must be concealed without compromising support and stability of the prosthesis 2. Artificial anterior teeth must be placed in most natural position. 3. Esthetics 52
- 53. The surveyor is used to locate existing or potential surfaces of the teeth that can be converted to guiding planes by selective grinding. Guiding plane does not need to be more than 2 or 3 mm in occluso-gingival height. 4.Guiding planes 53
- 54. TRIPODING Methods a. Tissue surface indexing b. Art portion indexing a b 54
- 55. C. CEMENTED PIN TECHNIQUE JOHN G. KNAPP ET AL (1979) The third method of locating cast is using thin retentive pins. The pins are placed in the desirable place to re-orient the cast in the surveyor. 55
- 56. Contouring of wax pattern Survey ceramic veneer restoration Handpiece holder attached to the surveyor ( drill press) AUXILIARY USES OF SURVEYOR 56
- 57. Milling of cast crownTapered fissure bur used to cut Internal rests in wax pattern AUXILIARY USES OF SURVEYOR 57
- 58. STEP BY STEP PROCEDURE 58
- 59. Examine the occluded diagnostic casts. 59
- 60. Indicate the proposed rest areas by short vertical lines on the cast below the tooth with black pencil. 60
- 61. Indicate by outlining in red any cuspal relief that will be needed to provide adequate occlusal clearance for rest spaces. 61
- 62. Examine the lingual aspect of the occluded casts for adequate space for cingulum rests, indirect retainers. Use black pencil for marking. 62
- 63. Place the cast on the cast holder at horizontal tilt. Examine the teeth to be clapsed for favorable retentive undercuts as well as the shape and contour of the proposed abutment teeth. 63
- 64. If the shape and contour of these teeth necessitate recontouring indicate the location and extent of proposed alteration with red crayon pencil. Determine the most favorable tilt of the cast that will permit convent and proper placement of clasps,minor connectors anterior teeth, and denture base areas. 64
- 65. CAST TILTING. 65
- 66. Tilting is changing the position of the cast, which thus changes the long axis of each tooth on the cast relative to the horizontal plane. 66
- 67. Change in the tilt then changes the position of survey line and location and extent of the undercut. 67
- 68. Tilting is used to obtain the most favorable path of insertion. Tilting is used to increase the desirable undercuts and to decrease undesirable undercuts. 68
- 69. Through tilting, it is possible to increase the undercuts on side of the tooth while decrease them on other side of the tooth. 69
- 70. standard reference position 0 degree tilt TYPES OF TILT 70
- 71. Path of insertion is straight downwards. 71
- 72. Path of insertion is upward and backwards. 72
- 73. Path of insertion is upward and forward. 73
- 74. The ultimate goal in the partial denture service is that it has to go to the place smoothly over the teeth and soft tissue. It has to function as it was planned. And it has to remain in the place by resisting the dislodging forces. 74
- 75. SUMMARY 75
- 76. Proper placement and contour of the components of design can be achieved only through an adequate survey and well planned mouth preparation. The components of RPD must be selected to control stress to the abutment teeth and tissues caused by forces of occlusion and movements of distal extension bases. Alterations in design may be dictated by the dentists’ prudent judgment. Compromising with the ideal principles in the location and design of components may jeopardize the potential success of the prosthesis. 76
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- 82. PHILOSOPHY OF DESIGN Physiologic basing Broad stress distribution Stress equalization 82
- 83. Stress director : A device that allows movement between denture base & direct retainer- (intra- coronal / extra-coronal) . Stress Equalization 83
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- 85. a movable joint b/w direct retainer & denture base e.g. hinge, ball & socket a flexible connection b/w direct retainer & denture base. e.g. split major connector, movable joint 85 Types Of Stress Directors
- 86. - Preserved alveolar support of abutment - Minimal requirement of direct retention - Massaging effect on soft tissues. - Complicated design - Tends to Fracture - Difficult to repair - Reduced indirect retention - Both vertical & horizontal forces- concentrated- resorption Disadvantages 86 Advantages
- 87. PHYSIOLOGIC BASING soft tissue is recorded in its functioning form by functional impression or relining before denture delivery 87
- 88. Disadvantages: Compresses soft tissues at rest Premature contacts Decreased indirect retention- tissue re-bounce at rest. Denture not well stabilized against lateral forces. Advantages : Intermittent base movement - physiologically stimulating effect on bone and soft tissue reduces frequency of reline or rebase the prosthesis Simplicity of design and construction Minimal retention is used 88
- 89. BROAD STRESS DISTRIBUTION Snowshoe Effect 89
- 90. Advantages Forces distributed over larger area (teeth & mucosa) Multiple clasp assemblies: support periodontally weak tooth. easier and less expensive to make. Lateral forces may be distributed over as many teeth as possible Rigid components minimize rotational movements and provide excellent horizontal stabilization . These partial denture do not require frequent relining or rebasing. 90 Disadvantages Less comfortable Difficult to maintain oral hygiene
- 91. ESSENTIALS OF PARTIAL DENTURE DESIGN. 1st step : ‘..to determine how partial denture is supported.’ 91
- 92. Tooth supported Periodontal health Crown- root morphologies Crown : root Location of tooth in arch Relationship of tooth – other support units Opposing dentition. 92
- 93. Quality of residual ridge – mucosa Extent covered by denture base Type & accuracy – impression registration Accuracy of denture base Design – components of partial denture framework Anticipated occlusal load Tooth & Tissue Supported 93
- 94. 2nd step : ‘..to connect the tooth & tissue support units.’ - Major & minor connectors 3rd step : ‘..to determine how partial denture will be retained.’ 94
- 95. 4th step : ‘..to connect retention units to support units.’ 5th step : ‘..to outline and join edentulous area to established design components.’ 95
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- 97. COLOR CODING Present system uses : acrylic metal tripod marks, areas on teeth that will be prepared , relieved or contoured rest seats survey lines, soft tissue under cuts ,other information 97
- 99. STEPS IN DESIGNING 1) Examining and occluding diagnostic casts : 99
- 100. 2) Mark areas of rest seats and to be reshaped 100
- 101. 3) SURVEYING : 101
- 102. 4) Rest seats 5) Denture base
- 103. 7) The major & minor connectors 103
- 104. 8) Tissue stops 104
- 105. 9) Retentive elements 10) Reciprocal elements
- 106. Completed design
- 107. KENNEDY’S CLASS I PARTIAL DENTURE DESIGN 107
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- 109. Distobuccal undercut: T or half T clasp Mesiobuccal undercut: wrought wire clasp 109
- 111. IMPORTANCE OF INDIRECT RETAINERS 111
- 112. KENNEDY’S CLASS II PARTIAL DENTURE DESIGN 112
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- 114. KENNEDY’S CLASS III PARTIAL DENTURE DESIGN 114
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- 116. KENNEDY’S CLASS IV PARTIAL DENTURE DESIGN 116
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- 118. CLASS IV 1.The movement of this type of RPD and resulting stresses transmitted to the abutment are unlike the pattern seen in any other type of prosthesis. 2. Esthetic placement of teeth may necessitate their placement anterior to the crest of residual ridge resulting in potential tilting leverages. Shorter the edentulous area , less will be the harmful leverages. 3. Strategic clasp position should be used 118
- 119. 4. Quadrilateral configuration with anterior clasp placed anterior and posterior clasp placed as far posterior as possible, would be the ideal. 5. Major connector should be rigid and broad coverage should be used in maxillary arch. 6. A functional type of impression - if the edentulous area is extensive CLASS IV 119
- 120. Aesthetics critical Rotational forces can be minimized by retaining serviceable teeth Use of labial flange – retention Indirect retention- not required if ideal quadrilateral configuration is followed. 120
- 121. Successful RPD Sound clinical judgment Laboratory Support Patient’s Co-operation Knowledge of principles of design 121
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- 124. DESIGNING-KENNEDY CLASS III PARTIAL DENTURE Applegate sub-divided Kennedy class III into 3 groups acc. to clinical conditions and type of treatment required : Group A: saddles are short , abutment are healthy minimum of bone loss around their roots Group B: abutments not able to support & provide bracing, saddle is long bone resorption around abutment teeth Group C: saddle exceptionally long , abutment unable to provide any support 124