This document discusses different types of crown preparations including full metal crowns, metal-ceramic crowns, and all-ceramic crowns. For full metal crowns, extensive tooth reduction is required due to their high retentiveness. Metal-ceramic crowns provide better aesthetics than full metal crowns but still require significant tooth reduction. All-ceramic crowns are the most conservative preparation and provide excellent aesthetics but have less strength than other options. Proper preparation is critical for all-ceramic crowns to withstand occlusal forces. The document outlines the armamentarium, steps, and criteria for preparing teeth for each of these crown types.

1. Dr Ishani Sharma
MDS 1st
Year
Paedodontics

2. Contents
Preparations for full veneer crowns
- Full metal crown preparation
- Anterior metal ceramic crowns and posterior
metal ceramic crowns
- All ceramic crowns

3. Definition
Preparation: The selected form given to
a natural tooth when it is reduced by
instrumentation to receive a prosthesis,
guided by clinical circumstances and
physical properties of the material.

4. Types
 Complete Crown / Full Veneer Crown:
A restoration that covers the entire
coronal tooth surfaces (mesial, distal,
facial, lingual and occlusal)
 Partial veneer crown: A restoration that
restores all but one coronal surface of a
tooth or dental implant abutment, usually
not covering the facial surface(GPT-8)

5. Full metal crowns

6. Full metal crowns
Used where the break down of tooth structure is
severe to the extent that has been described in
operative dentistry as “the final attempt to
preserve the tooth”
Most retentive of veneer preparations

7. Indications
Extensive destruction from caries
Endodontically treated tooth
Existing restoration that needs the use of a more
conservative restoration
Necessity for maximum retention
Minor correction of malinclinations
Recontouring of axial surfaces.
Provide contour to receive removable appliances
Correction of occlusal plane

8. Contraindications
Less than maximum retention necessary
Aesthetics

9. Advantages
Strong
High retentive qualities
Easy to obtain adequate resistance form
Option to modify form and occlusion

10. Disadvantages
Removal of large amount of tooth structure
Adverse effects on tissue
Vitality testing not easily feasible
Display of metal

11. Preparation

12. Armamentarium
Tapered carbide bur- for occlusal guiding grooves.
Narrow round-tipped tapered diamond (regular grit)
(0.8mm)- for occlusal reduction , axial alignment
grooves, axial reduction, chamfer prep
Wide round tipped tapered diamond (fine grit) (1.2
mm)- for finishing

13. Step by step procedure
Guiding grooves for occlusal reduction:-
Tapered carbide is recommended.
Place depth groove holes app 1mm deep in central,
mesial, and distal fossa and connect them.
Guiding grooves in buccal and lingual developmental
grooves
Place a functional cusp bevel
Depth – 0.8 mm for central groove & nonfunctional
cusp, 1.3 mm for functional cusp

14. Occlusal reduction :- by 2 steps
Half occlusal surface is reduced first and other half
can be maintained as reference
Minimum clearence of 1.5 mm on functional cusp and
1mm on nonfunctional cusp.

15. Axial reduction :-
 place 3 alignment groove on each buccal and lingual
wall with narrow round end tapered diamond.
The bur should be parallel to proposed path of
withdrawal of restoration.
 diamond bur with 6 degree taper is used and
identical axial taper will result in preparation.

16. The remaining islands of tooth structure between
alignment grooves are removed while the chamfer
margin is placed.
Place cervical chamfer of app 0.5 mm width.
Finishing – with fine grit carbide bur.
Round off all line angles.

18. Chamfer and seating grooves

19. Features of full metal crown
preparation

20. Metal ceramic crowns

21. Metal-ceramic crowns (PFM)
Use grew with the development of first
commercially successful porcelain/gold alloy by
Weinstein etal in 1950s.
Ceramic layer bonded to a thin cast metal coping
that fits over the tooth preparation
Greater strength than all ceramic crowns

22. Indications
Aesthetics
If porcelain-jacket crown is contraindicated
Contraindication
Large pulp chamber
Intact buccal wall
When more conservative retainer is technically
feasible

23. Advantages
Superior aesthetics
retentive

24. Disadvantage
Removal of substantial tooth structure
Subject to fracture because porcelain is brittle
Shade selection can be difficult
Inferior aesthetic compared to all ceramic
Expensive

25. Preparation

26. Armamentarium
Round tipped rotary diamonds (regular grit for buccal
reduction, fine grit for finishing)
Foot ball or wheel shaped diamonds ( for lingual
reduction)
Flat end tapered ( for shoulder prepration)
Finishing stones
Hatchet and chisel

27. Steps of prepration
Guiding grooves:-
 place 3 depth grooves- centre, mesiofacial and
distofacial line angles.
Place in 2 planes- the cervical portion is parallel to
long axis of tooth, for incisal (occlusal) follows
normal facial contour.
1.3 mm deep

28. Incisal (occlusal)reduction:-
Bur – tapered round tipped diamond bur.
Criteria – 1.2 to 1.5mm reduction for the metal and
porcelain.

29. Labial reduction guide grooves ( two plane):-
Bur – tapered- round tipped diamond bur
Criteria- 1.2- 1.5mm reduction for metal and
porcelain.
Labial reduction ( two plane):-
Bur – tapered flat- tipped diamond

30. Axial reduction:-
Bur – tapered round tipped diamond
Lingual reduction:-
Bur – football shaped diamond
Criteria- 1mm clearance .

31. Finishing of shoulder (or beveled shoulder):-
Bur – tapered flat tipped bur , hand instrument
Criteria – extend 1mm lingual to proximal contact
area.
Finishing :-
Bur – tapered round tipped diamond or carbide bur
Criteria – round off all line angles

33. Metal-ceramic crowns

34. Radial shoulder

35. Features of metal ceramic
preparation

36. Metal ceramic preparation for
posteriors

38. Posterior metal-ceramic crowns

40. All ceramic crowns

41. Indications:
1. High aesthetic requirement
2. Incisal egde reasonably intact
3. Endodontically treated teeth
4. Considerable proximal caries
5. Favourable distribution of occlusal load.

42. Contraindications:
1. When superior strength is needed
2. Insufficient coronal tooth structure
3. Thin teeth faciolingually
4. Unfavourable distribution of occlusal load.

43. Advantages:
1. Excellent aesthetic
2. Good tissue response
3. More conservative of facial wall

44. Disadvantages:
1. Less strength.
2. Proper preparation extremely critical.
3. Brittle nature of material.
4. Expensive

45. Preparation

46. Depth grooves for the incisal reduction:-
Bur – tapered diamond
Criteria – 1.3 mm deep to allow the for additional
reduction during finishing, perpendicular to the long
axis of opposing tooth.

47. Incisal reduction :-
Bur – tapered diamond
Criteria – clearance 1.5 mm
Depth grooves for the facial reduction:-
Bur – tapered diamond
Criteria – 0.8mm needed for the additional reduction
during finishing.

48. Facial reduction:-
Bur- tapered diamond
Criteria – reduction of 1mm is needed
Depth grooves and lingual reduction:-
Bur –tapered and football-shaped diamonds
Criteria – initial depth 0.8mm , recreate the concave
configuration (avoid stress)

49. Depth grooves for cingulum reduction:-
Burs – tapered diamond
Criteria – parallel to cervical aspect of facial
preparation.
- 1mm reduction
- shoulder follows free gingival margin

50. Lingual shoulder preparation:-
Bur – square-tipped diamond
Criteria – shoulder 1mm wide , 90 degree cavosurface
angle.
Finishing :-
Bur – fine grit diamond or carbide
Criteria- all surfaces smooth and continous
- no unsupported enamel
- 90 degree cavosurface angle

51. Preparation:

52. Features of all-ceramic crowns

54. Thank you.