1. There are various cavity designs for amalgam restorations depending on the location and extent of the dental caries. Cavity designs are classified based on the Black Classification system as Class I through Class VI cavities. 2. Key principles of tooth preparation for amalgam restorations include establishing an outline form that extends the cavity margins into sound tooth structure. The cavity should have a primary resistance form and features like cavosurface margins, reverse curves, and retention forms or locks to resist forces and retain the restoration. 3. Specific cavity preparations are described for different classes of cavities, including designs for single surface Class I cavities, multi-surface Class I cavities, various Class II cavity designs for proximal lesions

1. 1
VARIOUS CAVITY DESIGNS
FOR AMALGAM
RESTORATIONS
Dr. SV.SATISH
Professor & HOD
Dept of Conservative Dentistry & Endodontics
Navodaya Dental College

2. Nomenclature
2

3.  Cavity
3
Line angle Point angle
 Class l 8 4
 Class 2 11 6
 M O D 14 8
 Class l
l
l 6 3
 Class lV 11 6
 Class V 8 4

4. There are many angles in a cavity
prepared cavity such as:
4

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. Cavosurface margin
6

7. Cavity
7
 Simple cavity: only one tooth
surface is involved.
 Compound cavity: two surfaces
are involved.
 Complex cavity: three or more
surfaces are involved.

8. Simple
Compound 8

9. Classification of cavity
9
 G.V .Black classification
 Class l – pit and fissure restoration
on occlusalsurface of premolar and
-Restoration
molars
-Restoration on occlusaltw o thirds of facial and
lingual surfaces of molars
-Restoration on lingual surface of maxillary incisors

10.  Class ll –Restoration on proximal surfaces of
posterior teeth
 Class l
l
l- 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 occlusalcusp heights of
posterior teeth
10

11. 11

12. The four sizes of carious lesions
12
 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
w e akened to the extent that cusps or incisal
edges are split,
 Size 4. Extensive caries with bulk loss of tooth
structure has already occurred.

13. Principles of
tooth preparation
for amalgam
13

14. 14

15. Outline Form
15
 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.

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.  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.  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.  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. Primary Resistance Form
20

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. Cavosurface margin
22

23. Resistance form
23

24. Reverse curve

25. Primary retention form
25

26. Class l designs
26

27. Class l, design 1
27
 Caries penetration into dentin does
not exceed 0.5-1mm
 Width- I/4 intercuspal distance
 Low caries index

28. Molar outline
28
Premolar outline
General shape

29. Mesio distal cross section

30. • Pulpal Floor mesio-distally is flat and
perpendicular to the long axis of the tooth
30

31. 31

32. Pulpal floor of
32
Lower premolar

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

34. Mesiodistal cross section
34

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. Internal anatomy
36

37. Class l, design 4
Applied to molars involving their occlusal surfaces,the
grooved part of the facial or lingual surfaces
37

38. --Pulpal wall elevated occlusaly
--Use in mandibular first molar
38

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 m a rgins
 In occlusalcavity mesial
and distalm a rgins located at
Corresponding axialangles
 Gingivalm a rgins
 –gingivalthird of the facial
or lingual Surface
 Pulpal floor – internalboxes (mesialthird)
39

40. Mesio distal cross section
40

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 )
Gingivalm a rgin should extend to allow
Occlusalclearance of 1.5-3 m m from
Opposing teeth
41

42. Class l, Design 7
 Involves occlusal , facial and lingual surfaces of
molars and premolars
 Pins and posts are indicated
42

43. Class l, design 8
 Endodontically treated tooth
 Pulp chamber is retention form
43

44. 44

45. Out line form
45
• 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

46. Small cusps
Tensile stress
Compressive stress
Large cusps 46

47. Axial wall
47
Design features for the protection of mechanical integrity of
restoration

48. Reverse curve
48

49. 49

50. Class ll, Design 1
Conventional design
50
Indications
Moderate to large size proximal
Lesion with occlusal surface cavity
promotes the cavity width of cavity to
exceed 1/4 0f intercuspal distance

51. Proximal box
Inverted truncated shape
51

52. Tunnel preparation
52

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 anatom55y

56. Gingival margin
Middle third
56
Gingival third

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. Bucco-lingual
Cross section
58
Occlusal-gingival
Cross section

59. Class ll, Design 5
Part of proximal surface ,with a limited access area on facial
or lingual surface
1)Do not have dovetail
2) Have dovetail
Indications •: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. 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. Class ll, Design 7
ShapeA Shape B
(Combinations of class ll with class V )
ShapeA: junctions between the class ll and class V via, the
Proximal , crossing the axial angles
Shape B : via buccal / lingual groove
61

62. Class ll, Design 8
Two or more surfaces of an endodontically treated tooth
does not require post retention
62

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
63
G e neralprinciples are similar to class l
l
cavity
preparation but with emphasis laid on in
areas of preparation
1 esthetic concern
2 extension for access
3stress consideration enamel rod direction
Incisalaccess

64. Designs of cavity preparation at the distal slope of
the cuspid
64
Indications;
1The lesion does not involve or undermine the distal
slope of cupid
2bulky walls will remain, incisally, after removal of
Undermine tissues
3 the labials axial angle is intact
4the restoration will be directly loaded by vertical
forces

65. Internal anatomy ;
Axial convex
Depth - .5
from DEJ
Retention
points :
Depth 1 to
2 mm in
dentin
65

66. Class lV
Indications :
•Incisal angle is undermined
•Labial and lingual walls intact
Labio lingual cross section
66

67. Modifications
67

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. •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

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. 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
75

76. Class VI
76

77. Retention coves
77

78. Retention locks
78

79. Tooth preparation for pin amalgam
79

80. Pin location
80

81. Cavosurface angle
81

82. Enamel –amalgam junction
82