Operative dentistry involves the diagnosis and treatment of tooth defects without full coverage restorations. The objectives of cavity preparation are to remove defects, locate conservative margins, withstand forces of chewing, and allow for esthetic/functional restorations. Factors like pulpal/periodontal status, dental anatomy, patient factors, and restorative materials influence tooth preparation. Cavity preparation involves initial and final stages, including outline form, resistance form, retention form, convenience form, infected dentin removal, pulp protection, and finishing. Proper cavity preparation is essential for restoring teeth effectively.

1. FUNDAMENTALS IN
TOOTH PREPARATION

2. Definition of Operative
Dentistry
Operative dentistry is the ART and
SCIENCE of the diagnosis, treatment,
prognosis of defects of teeth which do not
require full coverage restorations for
correction, such treatments should results
in the restoration of proper tooth form,
function, and esthetics while maintaining
the physiologic integrity of the teeth in
harmonious relationship with adjacent
hard and soft tissue, all of which enhance
the general health and welfare of the
patient.

3. Objectives of Cavity
Preparation
 Remove all defects and give the necessary
protection to pulp.
 Locate the margins as conservatively as
possible.
 Form the cavity so that both the restoration
and tooth can withstand the load of
mastication.
 Allow for the esthetic and functional
placement of a restorative material.

4. Need of Restoration
 Caries
 Malformed, discolored or fractured teeth
 Restoration replacement

5. Factors affecting tooth preparation
1. General Factors
 Pulpal & periodontal status
 Occlusal relationship
2.Dental anatomy
 Direction of enamel rods
 Thichness of enamel /dentin
 Size and positionof pulp
 Relationship of tooth to its supporting tissues

6. 3.Patient factors
 Age
 Esthetic consideration
 Economic status
 Patients with high risk caries
4.Affected & infected Dentine
5. Restorative material factors

7.  Cavity preparation
 Matrix application
 Preparation of materials
 Insertion and carving of materials
 Finishing and Polishing
Approach of Operative. cont…..

8. Cavity Preparation
The mechanical alteration of a
defective, injured, or diseased tooth in
order to best receive a restorative
material which will re-establish a
healthy state for the tooth including
esthetic corrections where indicated,
along with normal form and function.

9. Cavity Structure
 walls
 angles
 Floor

10. Classification of cavity
 Class I
 Class II
 Class III
 Class IV
 Class V
 Class VI
—G.V.Black in 1908

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

12. Class 1
Class 2
Class 1
Class 2
Class 3
Class 4
Class 5
Class 6

13. Stages and Steps in Cavity preparation
•Initial cavity preparation stage
•Final cavity preparation stage

14. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

15. FINAL CAVITY PREPARATION
STAGE
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

16. Outline Form and Initial Depth
Definition:
placing the cavity margins in the positions
they will occupy in the final preparation.
preparing an initial depth of 0.2~0.8 mm
pulpally of the dentinoenamel junction
position or normal root surface position.

17. Maxillary Class Ⅰ outline form

18. Mandibular Class Ⅰ outline form

19. Maxillary Class Ⅱ outline form

20. Mandibular Class Ⅱ outline form

21. Common Error

23. Outline Form and Initial Depth
Principles:
all friable and/or weakened enamel should be
removed
all faults should be included
all margins should be placed in a position to
afford good finishing of
the margins of the restoration.
Margins of the preparation will be located on
finishable, self –cleansing area.

24. Outline Form and Initial Depth
Features:
preserving cuspal strength
preserving marginal ridge strength
minimizing facio-lingual extension
using enameloplasty
connecting two close faults or cavities
restricting the depth of the preparation into
dentin.

25. Auxillary Factors
 Conservation
 Adjacent enamel cracks or decalcification
could be involved in the preparation.
 Type of restorative material.
 Extension for access.
 anatomy and alignment.
 If possible, no margins will be in occlusion
with opposing teeth.
 Esthetics

29. Outline Form and Initial Depth for pit and
fissure cavities
Controlled by three factors
1- Extension to which enamel has been involved
by caries.
2- Extension to achieve sound and smooth
margins.
3- Limited bur depth while extending the
preparaton

30. Rules
 Capping of cusp should be done when cavity
extension is two-third from central fissure to cuspal
eminence.
 Include all fissures that cannot be eliminated by
enameloplasty.
 Restrict the depth.
 Join two lesions if they are less than 0.5 mm apart.

31. Outline Form and Initial Depth for
smooth surface cavities
 Extension of cavity.
 Sufficient access.
 Depth.
 Sufficient clearance with adjacent tooth.

32. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

33. Primary Resistance Form
Definition:
The shape and placement of the cavity walls
that best enable both the restoration and the
tooth to withstand, without fracture,
masticatory forces delivered principally in the
long axis of the the tooth.

34. Primary Resistance Form
Principles:
To utilize the box shape with a relatively flat floor to
resist occlusal loading by virtue of being at right angles
to mastication force.
To restrict the extension of the external walls (keep as
small as possible) to allow strong cusp and ridge areas
to remain with sufficient dentin support.

35. Primary Resistance
Form
Principles:
To have a slight rounding of internal line angles to
reduce stress concentration in tooth structure;
The presence of sharp internal line angles in
GOLD FOIL resist the movement of the
restoration
Sharp internal line and point angles in dentin
serve as convenient “starting” points for
compacting of direct gold.
To provide enough thickness of restorative
material to prevent its fracture under load.

36. Primary Resistance Form
Feature:
Box shape
Relatively flat floors
Inclusion of weakened tooth structure
Preservation of cusps and marginal ridges
Rounded internal line angles
Adequate thickness of restorative materials
Reduction of cusps for capping if indicated

37. Primary Resistance cont….
 Designing the outline form so that minimal
of restoration is exposed to occlusal stress.
 Seat on sound dentin.

38. Vale Experiments
 1 MR at 1/4th ICD -10% Loss of FR
 2 MR at 1/4th ICD - 15% Loss of FR
 1 MR at 1/3th ICD -30% Loss of FR
 2 MR at 1/3th ICD -35% Loss of FR
 1 MR at 1/2 of ICD -40% Loss of FR
 2 MR at ½ of ICD -45% Loss of FR

40. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

41. Primary Retention Form
Definition:
The shape or form of the prepared cavity
that resists displacement or removal of the
restoration from tipping or lifting forces.

42. Primary Retention Form
Principles: depending on the
materials
Amalgam restoration:
developing external cavity walls that
converge occlusally and dovetail design

43. The devotail design provide retention form
to the occlusal portion of the cavity.
The occlusal convergence of the walls offers
retention in the proximal portion of the cavity
against displacement occlusally.

45. Primary Retention Form
Principles: depending on the
materials
Composite restoration:
a mechanical bond between the material
and conditioned, prepared tooth structure.

46. Dentin etched with 32% phosphoric acid Collagen
exposed by the acid.

47. FIG
Bonding of resin to dentin, using a "total-etch" technique

48. 16 Bonding to dentin using a self-etching primer.

49. Scanning electron micrograph of the transition between
composite resin (C) adhesive (A), adhesive-hybrid layer
(H), and hybrid layer-dentin.

50. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

51. Convenience Form
Conception:
The shape or form of the cavity that
provides for adequate observation,
accessibility, and ease of operation in
preparing and restoring the cavity.

52. Convenience Form
Principles:
 Allow access for caries removal
 Allow access for restoration placement
 Allow access to margins for finishing,
evaluation and cleaning

53. Convenience Form

54. Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

55. Removal of any remaining infected dentin if
indicated
Definition:
The elimination of any infected carious
tooth structure or faulty restorative material
left in the tooth after initial cavity
preparation.

56. Removal of dentinal caries using round burs and spoon
excavators

57. Pulp protection
 Using liners or bases to protect the pulp or
to aid pulpal recovery or both.
 If the infected dentin more than 2 mm
deeper from the initial pulpal or axial wall
then a Liner is indicated.

62. Final cavity preparation stage…..
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

63. Secondary resistance and retention
forms
 Most compound and complex cavity preparations
require additional resistance and retention form.
 The exception being those preparations that are very
conservative.

64. Secondary resistance and retention
forms
Mechanical forms
Cavity wall conditioning form

65. Mechnical form:
 Proximal locks
 Proximal slots

66. Proximal locks

69. Slot on gingival wall

70. Final cavity preparation stage….
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Finishing external walls
Step 9 Final procedures

71. Finishing the external walls
Definition:
Finishing the preparation walls is the
further development of a specific
cavosurface design and degree of
smoothness that produces the maximum
effectiveness of the restorative material
being used.

72. Finishing the external walls
Objectives:
 To create the best marginal seal possible
between the restorative material and tooth
structure;
 To afford a smooth marginal junction;
 To provide maximum strength of both the
tooth and the restorative material at and
near the margin.

73. The strongest enamel margin is that margin which
is composed of full-length enamel rods that are
supported on the cavity side by shorter enamel
rods, all of which extend to sound dentin.

74. Finishing the external walls
The design of the cavosurface angle
The degree of smoothness of the wall

75. The design of the cavosurface angle depending
on the material:
 Amalgam: 90°
 Composite: beveling 30°~ 40°

79. Final cavity preparation stage……..
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

80. Final procedures
 cleaning
 inspecting
 varnishing
 conditioning

83. Multiple Choice Questions
Q.1. In cavity prepartion cavo-surface margin will
be a junction between :
a) Cavity wall/floor and adjacent tooth surface.
b) Cavity wall and floor.
c) Floor of the occlusal box and aproximal box
d) Axial wall and occlusal floor.

84.  Q.2 Toilet of the cavity is:
 a) Removal of debris by washing with water
 b) Removal of debris by cold air
 c) Removal of debris by hot air
 d) Washing the cavity with water.

85.  Q.3 Most common fracture seen in amalgam
restoration at:
 a) Cavosurface margin.
 b) Contact area
 c) Isthmus area
 d) Proximal box

86.  Q 4 G. V Black concluded that following area
of tooth surface are relatively non-
selfcleansing:
 A) Pit and fissures
 B) Tips and cusps
 C) Fossa
 D) Marginal ridge

87.  Q.5 Class III amalgam restorations areusualy
prepared on:
 a) Distal surface of anterior teeth
 b) Mesial surface of canine
 c) Distal surface of canine
 c) Mesial and distal surface of all teeth.