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09.amalgam cavity designs

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amalgam cavity designs

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09.amalgam cavity designs

  1. 1. Cavity Designs For Amalgam Restoration 1
  2. 2. Nomenclature 2
  3. 3.  Cavity Line angle Point angle  Class l 8 4  Class 2 11 6  MOD 14 8  Class lll 6 3  Class lV 11 6  Class V 8 4 3
  4. 4. There are many angles in a cavity prepared cavity such as: 4
  5. 5. Cavosurface angle This refers to the angle of the tooth structure formed by the junction of a prepared wall and the external tooth surface. 5
  6. 6. Cavosurface margin 6
  7. 7. Cavity  Simple cavity: only one tooth surface is involved.  Compound cavity: two surfaces are involved.  Complex cavity: three or more surfaces are involved. 7
  8. 8. Simple Compound 8
  9. 9. Classification of cavity  G.V .Black classification  Class l – pit and fissure restoration -Restoration on occlusal surface of premolar and molars -Restoration on occlusal two thirds of facial and lingual surfaces of molars -Restoration on lingual surface of maxillary incisors 9
  10. 10.  Class ll –Restoration on proximal surfaces of posterior teeth  Class lll - Restoration on proximal surfaces of anterior teeth that do not involve the incisal angle  Class lV -Restoration on proximal surfaces of anterior teeth that do involve the incisal angle  Class V – Restorations on the gingival third of the facial or lingual surfaces of all teeth  Class Vl – Restoration on the incisal edge of anterior teeth or the occlusal cusp heights of posterior teeth 10
  11. 11. Class 1 Class 2 Class 1 Class 2 Class 3 Class 4 Class 5 Class 6 11
  12. 12. The four sizes of carious lesions  Size 1. Minimal involvement of dentine just beyond treatment by remineralization alone.  Size 2. Moderate involvement of dentine. sound,. That is, the remaining tooth structure is sufficiently strong to support the restoration .  Size 3. The cavity is enlarged beyond moderate.The remaining tooth structure is weakened to the extent that cusps or incisal edges are split,  Size 4. Extensive caries with bulk loss of tooth structure has already occurred. 12
  13. 13. Principles of tooth preparation for amalgam 13
  14. 14. 14
  15. 15. Outline Form  means extending the preparation margins to the place they will occupy in the final preparation  Removal of all carious and defective pits and fissures to healthy tooth structure  Removal of all unsupported enamel rods  To avoid ending preparation margins in high stress areas like cusp tip and crest of the ridges  Placing margins on sound tooth structure. 15
  16. 16. Steps  establish the external outline form to extend all margins into sound tooth tissue.  Maintain the initial depth of 1.5 mm, this is approximately one-half of the length of the cutting bur. should be, at least 0.2 to 0.5 mm in dentin to provide adequate strength to resist fracture due to occlusal forces 16
  17. 17.  Extend the margin mesially and distally but do not involve marginal ridges. These walls should have dovetail shape to provide retention to the restoration 17
  18. 18.  While working towards mesial and distal surface, orient the bur towards respective marginal ridge. This will result in slight divergence of mesial and distal walls which helps to provide dentinal support for marginal ridges 18
  19. 19.  The isthmus width should be as narrow as possible  The deep pit and fissure defects less than 0.5 mm apart should be included within the outline form.  The external outline form should have smooth curves, straight lines and rounded angles. All unsupported and demineralized enamel should be removed. 19
  20. 20. Primary Resistance Form 20
  21. 21.  The shape given to a prepared tooth cavity imparting strength and durability to the masticatory dislodging forces of a dental restoration and remaining tooth structure. 21
  22. 22. Cavosurface margin 22
  23. 23. Resistance form 23
  24. 24. Reverse curve 24
  25. 25. Primary retention form 25
  26. 26. Class l designs 26
  27. 27. Class l, design 1  Caries penetration into dentin does not exceed 0.5-1mm  Width- I/4 intercuspal distance  Low caries index 27
  28. 28. Molar outline Premolar outline General shape 28
  29. 29. Mesio distal cross section 29
  30. 30. •Pulpal Floor mesio-distally is flat and perpendicular to the long axis of the tooth 30
  31. 31. 31
  32. 32. Pulpal floor of Lower premolar 32
  33. 33. Class l, design 2 Indication ; caries cones in dentin extend 1mm or more from the DEJ Pulpal floors have different levels 33
  34. 34. Mesiodistal cross section 34
  35. 35. Class l, design 3 Indication ; in occlusal one to two thirds of facial and lingual surfaces of molars and on lingual surfaces of anterior teeth General shape 35
  36. 36. Internal anatomy 36
  37. 37. Class l, design 4 Applied to molars involving their occlusal surfaces,the grooved part of the facial or lingual surfaces 37
  38. 38. --Pulpal wall elevated occlusaly --Use in mandibular first molar 38
  39. 39. Class l, design 5 : Indications  Occlusal surface, most of the facial or lingual surface involved  Occlusal surface is not conducive to retention of restoration  Location of margins  In occlusal cavity mesial and distal margins located at Corresponding axial angles  Gingival margins  –gingival third of the facial or lingual Surface  Pulpal floor – internal boxes (mesial third) 39
  40. 40. Mesio distal cross section 40
  41. 41. Class l, design 6 : Includes occlusal surfaces of molars or premolars as well as portion of facial, proximal or lingual surface in form of a table of an entire cusp or section of cusp (marginal ridges ) Gingival margin should extend to allow Occlusal clearance of 1.5-3 mm from Opposing teeth 41
  42. 42. Class l, Design 7  Involves occlusal , facial and lingual surfaces of molars and premolars  Pins and posts are indicated 42
  43. 43. Class l, design 8  Endodontically treated tooth  Pulp chamber is retention form 43
  44. 44. 44
  45. 45. Out line form • Extent of caries • Extent for convenience • Location of gingiva • Convexity of proximal surface • Location and extent of contact areas Resistance form Occlusal loading and its effects 45
  46. 46. Small cusps Tensile stress Compressive stress Large cusps 46
  47. 47. Axial wall Design features for the protection of mechanical integrity of restoration 47
  48. 48. Reverse curve 48
  49. 49. 49
  50. 50. Class ll, Design 1 Moderate to large size proximal Lesion with occlusal surface cavity promotes the cavity width of cavity to exceed 1/4 0f intercuspal distance Conventional design Indications 50
  51. 51. Proximal box Inverted truncated shape 51
  52. 52. Tunnel preparation 52
  53. 53. Class ll, Design 2 (moderate design ) Indications •Moderate to small sized proximal lesions •In stress concentration area •Width not exceeding 1/4 of intercuspal distance General shape width 53
  54. 54. Bucco lingually Mesiodistally 54
  55. 55. Class ll, Design 3 (conservative design ) • Involves primarily proximal surface and very limited part of occlusal Surface, not extending beyond adjacent triangular fossa •Sound occlusal crossing ridges •Minimal loading areas General shape Internal anatomy55
  56. 56. Gingival margin Middle third Gingival third 56
  57. 57. Class ll, Design 4 (Simple design ) •Proximal surface only •Indications; Decay restricted to contacting or proximal surface without undermining marginal ridges Diastema or adjacent tooth is missing 57
  58. 58. Bucco-lingual Cross section Occlusal-gingival Cross section 58
  59. 59. Class ll, Design 5 Part of proximal surface ,with a limited access area on facial or lingual surface Indications : 1)Do not have dovetail 2) Have dovetail •1)Preparation will have 4 surrounding walls •small proximal lesions •Marginal ridge intact •Does not involve contact area 2) Preparation will not have surrounding walls •medium proximal lesion 59
  60. 60. Class ll, Design 6 The occlusal ,proximal and part of the facial or lingual surfaces Indications ; Cusp is missing Badly broken down teeth 60
  61. 61. Class ll, Design 7 Shape A : junctions between the class ll and class V via, the Proximal , crossing the axial angles Shape B : via buccal / lingual groove Shape A Shape B (Combinations of class ll with class V ) 61
  62. 62. Class ll, Design 8 Two or more surfaces of an endodontically treated tooth does not require post retention 62
  63. 63. Class lll Amalgam is usually not indicated for anterior teeth due to its esthetic , but distal surface of the cuspid is a unique location General principles are similar to class ll cavity preparation but with emphasis laid on in areas of preparation 1 esthetic concern 2 extension for access 3 stress consideration enamel rod direction Incisal access 63
  64. 64. Designs of cavity preparation at the distal slope of the cuspid Indications; 1 The lesion does not involve or undermine the distal slope of cupid 2 bulky walls will remain, incisally, after removal of Undermine tissues 3 the labials axial angle is intact 4 the restoration will be directly loaded by vertical forces 64
  65. 65. Internal anatomy ; Axial convex Depth - .5 from DEJ Retention points : Depth 1 to 2 mm in dentin 65
  66. 66. Class lV Indications : •Incisal angle is undermined •Labial and lingual walls intact Labio lingual cross section 66
  67. 67. Modifications 67
  68. 68. Class V cavity Involvement :smooth surfaces apical to height of contour on facial and lingual surfaces of all teeth eg ; erosion, abrasion , hypoplasia, aplasia  Resistance and retention  To minimize the effects of displacing forces forces grooves occlusal and gingival walls are essential - cementum completely removed - Gingival margins follow the curvature of the furcation 68
  69. 69. •lesion are confined to gingival third of the facisal or lingual third of the facial or lingual surface - axial angles intact - no furcation involvement Class V design 1 69
  70. 70. 70
  71. 71. Class V ,design 2  Lesions on facial or lingual gingival third have involved axial angle  Lesion on facial or lingual gingival third are apical to contact area General shape Mesiodistal cross section 71
  72. 72. Mesio distal Occluso gingival 72
  73. 73. Class V Design 3 Indications; Lesion on gingival third facially or linguallly is continuous with isolated decalcifications or lesions occlusal to height of contour Bilateral extension 73
  74. 74. Class V Design 4 Multiple lesions in gingival third with sound tooth structure separating them General shape 74
  75. 75. Class V Design 5 Internal anatomy Involves bifurcation or part of it 75
  76. 76. Class VI 76
  77. 77. Retention coves 77
  78. 78. Retention locks 78
  79. 79. Tooth preparation for pin amalgam 79
  80. 80. Pin location 80
  81. 81. Cavosurface angle 81
  82. 82. Enamel –amalgam junction 82
  83. 83. Conclusion Although composite resins and crown and bridge restorative dental techniques receive much attention, amalgam will continue to be the most extensively used restorative material for many years to come . If it is used with care in minimal cavities, the restoration, the tooth and the occlusion will all last longer! 83

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