Principles of cavity preparation accordi.ppt

1. Principles of cavity preparation according to GV
Black
PRESENTATION BY: MHD NASR EMAD ALMASRI
SUPERVISION BY : DR. SAFOH ALBONI

2. CAVITY PREPARATION
- Defined as 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, along
with normal form and function.

3. Objectives of Tooth Restorations
1- To restore form/function and
esthetics, if possible.
2- To promote maintenance of
integrity of hard and soft tissues of the
oral cavity.
3- To promote health and welfare of
patients.

4. Objectives of Cavity Preparation
1- To remove all defects and give necessary protection to the
pulp
2- To locate the margins of the restorations as conservatively
as possible
3- To form the cavity so that under the masticatory forces the
tooth and the restoration will not fracture and the restoration
will not be displaced
4- To allow for the esthetic and functional placement of a
restorative material

5. Definition of Cavity Preparation
- Mechanical alteration of a tooth to receive a restorative material which will return the
tooth and area to proper form, function, and esthetics.
- Preparation procedure includes all defective and friable tooth structure.

6. FACTORS AFFECTING CAVITY PREPARATION
1- GENERAL FACTORS : 2- PATIENTS FACTOR:
- Diagnosis - economic status
- Prevention - age
- Interception - choice of material
- preservation
- restoration

7. Principles of Cavity Preparation
1- Outline form.
2- Resistance form: resistant to tooth and restoration fracture and displacement
of restoration.
3- Retention form: prevent from dislodging of restoration.
4- Convenience form: access for caries removal, band insertion, etc.
5- Remove remaining carious lesions.
6- Finish margin of enamel walls.
7- Perform the toilet of the cavity.

8. INITIAL CAVITY PREPARATION
- extension & initial design of external walls of preparation at a specific limited depth,
provide access to cavity/ defect reach sound tooth structure, resist fracture of
restoration/ tooth, forces directed in long axis of tooth & retain restoration
- no deeper than 0.2mm into dentin -pit & fissure
- 0.2mm -0.8mm -smooth surface.

9. OUTLINE FORM & INITIAL DEPTH
- placing cavity margins in positions will occupy in final preparations except
enamel walls & margins.
- preparing initial depth of 0.2 -0.8mm pulpally of DEJ.

10. PRINCIPLES
1- friable / weakened enamel removed.
2- all faults included.
3- margins placed in position-good finishing of margins of restoration.
4- extension for prevention.
5- sufficient enamel & dentin to locate the pulpal & axial walls or prepn.
surfaces within 0.5mm from DEJ.

11. FACTORS
- extent of carious lesion, defect/ faulty restorations.
- esthetic considerations.
- occlusal relationships.
- adjacent tooth structure.
- cavosurface margin.

12. Principles of Cavity Preparation

13. 1- Outline form
1- Cover all carious lesions.
2- No extension for prevention.

14. PRIMARY RESISTANCE FORM
1- defined as the shape & placement of the cavity walls
best enables both restorations & the tooth to withstand,
without fracture , masticatory forces delivered in long axis
of tooth.
2- architectural form given to a tooth , which enables both
restoration & remaining tooth to resist structural failure
from occlusal loading stresses.

15. 2- Resistance form
1.Depth-0.5 mm below DEJ (about 1.5 mm from the deepest pit)
2.Flat floor
3.No unsupported enamel (undermined):
- Cavosurface margin: 90 degree.
- Angle of departure: 90 degree.
4.Slightly-rounded internal line angle.
5.Preserve marginal ridge if possible.

16. PRINCIPLES
utilize box shape with a flat floor
- restrict extension of external walls
- slight rounding of internal line angles -reduce stress
- cap weak cusps & envelope / include enough weakened tooth
- provide enough thickness of restorative material -prevent fracture
- major principle is that restoration should rest on flat sound tooth structure,
perpendicular to occlusal forces directed parallel to the long axis of tooth

17. FEATURES
- relatively flat floors.
- box shape.
-includes weakened tooth structures.
- preservation of cusps & marginal ridges.
- rounded internal line angles.
- adequate thickness of restorative materials.
- seats on sound dentin peripheral to excavation of infected
dentin.
-reduction of cusps for capping.

18. Flat Floor
Relatively parallel to the cusp tips

19. Cavosurface Margin

20. Undermined Enamel or Overhanged Enamel
Cavity preparation -> walls of cavity should be parallel to
directions of enamel rods as much as possible.

21. Retention form
- shape / form of prepared cavity that resists displacement / removal of
restoration from tipping/ lifting forces.
defined as a form given to tooth prepn.,especially its detailed anatomy &
general shape, which enables the restoration, that will accommodate, to avoid
being lodged by masticatory loading.
- intra coronal-inside a cavity prepn, within the tooth.
- extra coronalon prepn. surface, replacing reduced ext. tooth.

22. Retention form
1.Box form
2.Convergence to occlusal surface (small undercut)
3.Retentive groove
4.Pins and slots
5.Dovetail
6.Acid etching (for resin composite restorations)

23. Retention form
1- Box form
2- Convergence to occlusal surface (small undercut)

24. Retention form
3- Dovetail

25. Retention form
Retentive groove
Pins

26. Retention Slot & Pin

27. Convenience form
•Convenience form : shape/ form of cavity that provide
adequate observation & accessibility.
•ease of operation in preparing & restoring the cavity.

28. FINAL CAVITY PREPARATION
Removal of any remaining enamel pit / fissure &/ or infected dentin &
/ old restorative material, if indicated.
it is elimination of any infected carious tooth structure / faulty restoration
within the tooth after initial cavity preparation

29. FINAL CAVITY PREPARATION
-caries left in pulpal / axial floor excavated
-0.75-1mm of dentin cover the pulp
-when affects esthetically
-weakened tooth-given retention
-secondary caries , if present
-periphery of old resto.mate. not intact

30. PULP PROTECTION
-pulpal injury, due to:
1- heat generated while cutting
2- resto.mat.with good thermal conductivity
3- chemicals from resto.mate.
4- Galvanic currents
5- microleakage
- placement of cavity liners / bases/varnish–not a step
- it is the step in adapting the preparation for receiving the final restorative material
- mechanical, chemical & thermal protection of pulp

31. SECONDARY RESISTANCE & RETENTION
FORM
TWO TYPES:
- MECHANICAL FEATURES
- CAVITY WALL CONDITIONING

32. SECONDARY RESISTANCE & RETENTION FORM
- Mechanical featuresretention locks
1- grooves & coves
2- skirts
3- beveled enamel margins
4- pins amalgapins
5- slots
Cavity wall conditioning features
1- enamel, dentinal wall conditioning
2- for bonded restorations

33. FINISHING THE EXTERNAL WALLS OF CAVITY
PREPARATION
- further development when indicated, of a specific cavosurface design & degree
of smoothness that produces maximum effectiveness of restorative material
being used.
-to create best marginal seal bet.resto.mate.& tooth.
-to afford smooth marginal jn.
-provide maxi.strength of both tooth & resto.

34. Concepts behind conservative restorations
1.Remove minimum tooth structure required for convenience form
2.Caries removal
3.Access, carving and finishing margins
4.Retention and resistance form

35. False conservatism
1.Insufficient convenience form
2.Leaving unsupported enamel
3.Insufficient reduction for restoration strength

36. Advantages
1.Reduced risk of pulpal and perio involvement
2. Improved esthetics
3. Less risk of margin and tooth fracture

37. The End