Principles and technique of tooth preparation for a molar to receive a full veneer cast metal crown

1. TOOTH PREPARATION IN FPD
DR. AAMIR GODIL
DEPARTMENT OF PROSTHODONTICS
M.A.R.D.C.

2. QUICK
RECAP
TOOTH PREPARATION FOR FPD
BIO- MECHANICAL PRINCIPLES OF TOOTH PREPARATION
MARGIN GEOMETRIES
MARGIN INDICATIONS

3. PRINCIPLES OF TOOTH PREPARATION
The principles of tooth preparation may be
divided into three broad categories:
1. Biologic considerations:
which affect the health of the oral tissues
2. Mechanical considerations:
which affect the integrity and durability of
the restoration
3. Esthetic considerations:
which affect the appearance of the patient
Contemporary fixed prosthodontics. Stephen Rosenstiel, Martin Land, Junhei Fujimoto- 5th edition (2015)

4. MARGIN GEOMETRY
Chamfer Shoulder Sloped Shoulder
Knife EdgeFeather Edge
Radial Shoulder
Shoulder with Bevel

5. MARGIN GEOMETRY

6. ALL METAL CROWN
FULL VENEER CROWN FOR MOLAR

7. PREPARATION DESIGN
ALLMETALPREPARATION
Margin geometry: Chamfer
Margin placement: Supragingival/ equigingival
Occlusal reduction:
Non-functional cusp- 1 mm
Functional cusp- 1.5 mm
Axial reduction:
Near margins: 0.5 mm
Occluso-axially: 0.8- 1.0 mm
Retentive features:
Grooves, pinholes

8. BIOMECHANICAL CONSIDERATIONS
BIOLOGICAL CONSIDERATIONS
1. Prevention of damage
 Pulp
 Periodontium
2. Conservative preparation
 Cast metal restoration
 Minimal taper
 Avoidance of over contour
3.
Margin placement and
adaptation
 Supragingival
 Well flushed
4. Harmonious occlusion and prevention of tooth fracture

9. BIOMECHANICAL CONSIDERATIONS
MECHANICAL CONSIDERATIONS
1. Retention form
 Taper: ~6 degrees
 Prevention of undercuts
 Optimal surface area of preparation
 Retentive luting agent
2. Resistance form
 Adequate taper and height: width ratio
 Pinholes/ grooves/ boxes
 Choice of luting agent
3.
Prevention of
deformation
 Adequate tooth preparation
 Alloy selection: Noble/ base metal
 Margin placement and geometry

10. BIOMECHANICAL CONSIDERATIONS
ESTHETIC CONSIDERATIONS
1. Metal vs PFM/ all ceramic × Compromised esthetics
2. Acrylic facing/ porcelain facing × Less conservative
3. Partial coverage × Not applicable

11. ARMAMENTARIUM
Armamentarium for the complete cast crown preparation

12. ARMAMENTARIUM
Torpedo bur

13. OVERVIEW

14. OVERVIEW

15. OVERVIEW

16. STEPS IN TOOTH PREPARATION
Occlusal guiding
grooves
Occlusal reduction Alignment grooves for
axial reduction
Axial reduction

17. STEPS IN TOOTH PREPARATION
Breaking proximal contact Retentive grooves Finishing of the preparation

18. OCCLUSAL GUIDING GROOVES
Burs for occlusal planar
reduction: round-end tapered
Round ended diamond bur used
to prepare depth grooves
Depth can be gauged with the
diameter of the diamond point
Occlusal depth grooves: 1.0-1.5 mm

19. OCCLUSAL REDUCTION
1.0-1.5 mm enamel chisel can be
used for assessment of depth
grooves
Cuspal contours are followed and
tooth morphology is maintained
Functional cusp bevel: round end
tapered bur

20. ALIGNMENT GROOVES: AXIAL REDUCTION
AND FUNCTIONAL CUSP BEVEL
Depth grooves for axial reduction using round end tapered bur
Functional cusp bevel given at 1.5 mm depth at an angle of 45 degrees

21. ASSESSMENT OF OCCLUSAL CLEARANCE
A small piece of utility wax used for assessment of occlusal clearance
Translucent areas are indicative of inadequate preparation

22. AXIAL REDUCTION
Facial and lingual reduction using torpedo diamond bur
The reduction is done as facially and lingually as possible, without nicking the adjacent tooth

23. AXIAL REDUCTION
Facial and lingual axial preparation and formation of proximal “lip”

24. BREAKING PROXIMAL TOOTH CONTACT
Proximal contact broken with thin needle shaped point

25. PROXIMAL PREPARATION
Proximal axial preparation continued with torpedo diamond point

26. FINISHING
Finishing done with small grit diamond bur or carbide bur

27. FINISHING AND RETENTIVE GROOVES
Additional grooves placed on mid-buccal surface to aid in retention

28. FINAL PREPARATION
Final preparation of mandibular
molar of full veneer metal crown
Schematic
representation

29. THANK YOU