amalgam cavity designs

1. Cavity Designs For Amalgam
Restoration
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2. Nomenclature
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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
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4. There are many angles in a cavity
prepared cavity such as:
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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.
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6. Cavosurface margin
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7. Cavity
 Simple cavity: only one tooth
surface is involved.
 Compound cavity: two surfaces
are involved.
 Complex cavity: three or more
surfaces are involved.
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8. Simple
Compound 8

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
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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
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11. Class 1
Class 2
Class 1
Class 2
Class 3
Class 4
Class 5
Class 6
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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.
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13. Principles of
tooth preparation
for amalgam
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14. 14

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.
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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
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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
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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
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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.
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20. Primary Resistance Form
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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.
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22. Cavosurface margin
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23. Resistance form
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24. Reverse curve
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25. Primary retention form
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26. Class l designs
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27. Class l, design 1
 Caries penetration into dentin does
not exceed 0.5-1mm
 Width- I/4 intercuspal distance
 Low caries index
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28. Molar outline Premolar outline
General shape
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29. Mesio distal cross section
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30. •Pulpal Floor mesio-distally is flat and
perpendicular to the long axis of the tooth
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31. 31

32. Pulpal floor of
Lower premolar
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33. Class l, design 2
Indication ; caries cones in dentin extend 1mm or more
from the DEJ
Pulpal floors have different levels 33

34. Mesiodistal cross section
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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
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36. Internal anatomy
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37. Class l, design 4
Applied to molars involving their occlusal surfaces,the
grooved part of the facial or lingual surfaces
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38. --Pulpal wall elevated occlusaly
--Use in mandibular first molar
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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)
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40. Mesio distal cross section
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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
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42. Class l, Design 7
 Involves occlusal , facial and lingual surfaces of
molars and premolars
 Pins and posts are indicated
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43. Class l, design 8
 Endodontically treated tooth
 Pulp chamber is retention form
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44. 44

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
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46. Small cusps
Tensile stress
Compressive stress
Large cusps 46

47. Axial wall
Design features for the protection of mechanical integrity of
restoration
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48. Reverse curve
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49. 49

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
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51. Proximal box
Inverted truncated shape
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52. Tunnel preparation
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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. Bucco lingually
Mesiodistally 54

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. Gingival margin
Middle third Gingival third
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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
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58. Bucco-lingual
Cross section
Occlusal-gingival
Cross section
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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
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60. Class ll, Design 6
The occlusal ,proximal and part of the facial or lingual
surfaces
Indications ; Cusp is missing
Badly broken down teeth
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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 )
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62. Class ll, Design 8
Two or more surfaces of an endodontically treated tooth
does not require post retention
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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
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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
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65. Internal anatomy ;
Axial convex
Depth - .5
from DEJ
Retention
points :
Depth 1 to
2 mm in
dentin
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66. Class lV
Indications :
•Incisal angle is undermined
•Labial and lingual walls intact
Labio lingual cross section
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67. Modifications
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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
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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
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70. 70

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
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72. Mesio distal
Occluso gingival 72

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. Class V Design 4
Multiple lesions in gingival third with sound tooth
structure separating them
General shape 74

75. Class V Design 5
Internal
anatomy
Involves bifurcation or part of it
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76. Class VI
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77. Retention coves
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78. Retention locks
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79. Tooth preparation for pin amalgam
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80. Pin location
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81. Cavosurface angle
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82. Enamel –amalgam junction
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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!
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