The document discusses the fundamentals of tooth preparation for restorations. It describes the objectives and stages of cavity preparation, including initial and final preparation stages. The initial stage involves outlining the cavity margins, forming primary resistance and retention, and convenience. The final stage includes removing infected dentin, pulp protection, secondary resistance/retention forms, finishing external walls, and cleaning/inspecting. The goal is to mechanically alter the tooth to receive restorative materials while preserving tooth structure and function.

1. FUNDAMENTALS IN TOOTH
PREPARATION
Dr. Maneesh Ahamed MDS
Senior Lecturer
Dept. Of Conservative Dentistry & Endodontics
Royal Dental College

2. Mechanical alteration of defective injured or diseased tooth to receive a restorative
material that reestablishes a healthy state for the tooth, including esthetic corrections
where indicated and normal form and function

3. Objectives of Cavity Preparation
Remove all defects
and give the
necessary protection
to pulp.
1
Locate the margins as
conservatively as
possible.
2
Form the cavity so
that both the
restoration and tooth
can withstand the
load of mastication.
3
Allow for the esthetic
and functional
placement of a
restorative material.
4

4. CAVITY DESIGN
FEATURES
Walls
Angles
Floor
 Line angles
 Point angles

7. STAGES AND STEPS
IN CAVITY
PREPARATION
• Initial cavity preparation
• Final cavity preparation

8. 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

9. 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: Cleaning,
inspecting and
sealing

10. 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

11. 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 to
0.8mm pulpally of the dentinoenamel junction

14. 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
• Margins of the preparation will be located on finishable,
self cleansing area.

15. 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.

16. 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.​

17. 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

18. PRIMARY RESISTANCE
FORM
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 tooth.

19. • 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
FEATURES

21. 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

22. PRIMARY
RETENTION
FORM
The shape or form of the prepared cavity that resists
displacement or removal of the restoration from
tipping or lifting forces.​

23. The dovetail 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.​

24. FOR COMPOSITE RESTORATION:​
A mechanical bond between the
material ​and conditioned, prepared
tooth structure.​

25. 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

26. CONVENIENCE
FORM

27. FINAL CAVITY
PREPARATION STAGE​

28. 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: Cleaning,
inspecting and
sealing

29. Removal of any
remaining
infected dentin
if indicated

30. 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: Cleaning,
inspecting and
sealing

31. PULP PROTECTION​
Using liners or bases to protect the pulp
or to aid pulpal recovery or both.

33. 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: Cleaning,
inspecting and
sealing

34. SECONDARY
RESISTANCE
AND
RETENTION
FORMS
Complex cavity preparations require
additional resistance and retention form.
The exception being those preparations that
are very conservative.

38. 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: Cleaning,
inspecting and
sealing

39. FINISHING THE
EXTERNAL WALLS
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.​

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

44. 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: Cleaning,
inspecting and
sealing

45. FINAL
PROCEDURES​
• Cleaning
• Inspecting
• Varnishing
• Conditioning