tOOTH PREPARATION OF ALL CERAMIC CROWNS

1. TOOTHPREPARATION OF
ALLCERAMICCROWNS Nasreena K
Final Year
Part2

2. CONTENTS
1. Introduction
2. Tooth preparation for Maxillary Central Incisor
3. Methods Of Reduction
4. Incisal Reduction
5. Labial Reduction
6. Lingual Reduction
7. Proximal Reduction
8. Finishing
9. Advantages & Disadvantages
10. Indication & Contraindication
11. Conclusion
12. References

3. INTRODUCTION
● All ceramic crowns can create some of the most aesthetically
pleasing restoration available today.
● Using a Non metal substructure allows light to be transmitted
through the crown, closely replicating the translucency of a natural
tooth.
● An all ceramic crown also promote good tissue response, and only mild
reduction of the facial surface is required.
● However significant reduction is necessary on lingual and proximal
surfaces.

4. Tooth preparation for Maxillary Central
Incisor

5. Armamentarium
• Hand piece
• Flat-end tapered diamond
• No. 6 round bur
• Small wheel diamond
• Flat-end tapering fissure bur
• End-cutting diamond
• Binangle chisel
• Baseplate wax sheet - 2mm thick

6. METHODS OF REDUCTION
I. Incisal Reduction
II. Labial Reduction
III.Lingual Reduction
a. Lingual axial reduction
b. Lingual fossa reduction
IV. Proximal Reduction

7. 1.INCISAL REDUCTION
Depth of preparation: 2 mm.
Rotary instrument: Flat-end tapering diamond.

8. PROCEDURE
•Depth cuts are placed on the
incisal edge perpendicular to the
direction of loading by the
mandibular teeth. They are
normally placed at mid-incisal
and at the junction of each
proximal surface.

9. •The remaining tooth structure
is then removed maintaining the
same angulation

11. 2.LABIAL REDUCTION
Depth of preparation: 1.5 mm.
Rotary instrument: Flat-end tapering diamond.

12. •The surface is prepared by placing
depth orientation grooves/depth
cuts 1.2 mm deep which after
finishing will produce a depth of
1.5mm. This is done by sinking the
entire flat-end tapering diamond or
appropriate diameter into the tooth.
They are placed in two planes –

13. ● one set within the gingival half is
parallel to long axis or gingival
half of labial surface and the
incisal portion to follow the
labial/facial contour.
● The remaining tooth structure
between the depth cuts is then
removed using the flat-end
tapering diamond and preparation
extended to the facioproximal line
angle.

14. •A shoulder finish line is
produced by the flat-end tapered
diamond.
•Preparation should parallel the
gingival contour to avoid cutting
ofinterdental papilla and
excessive extension into the
gingival crevice.
Supragingival/equigingival
margins are preferred.

16. 3.LINGUAL REDUCTION
a.Lingual axial reduction
Depth of preparation: 1.5 mm.
Rotary instrument: Flat-end tapering diamond.

17. PROCEDURE
•This prepares the cervical
portion of the lingual surface. It
should be parallel to the path of
insertion and should produce a
taper of 3–5° with the cervical
portion of the labial surface.

18. •Maintaining this angle, a
flat-end tapering diamond is
used to prepare the surface
producing a shoulder finish line
and this is extended proximally
to meet the labial preparation
•A shoulder finish line is
recommended as the lingual
surface is covered by ceramic.
This is then converted to ‘radial
shoulder’ while finishing.

19. b.Lingual Fossa Reduction
Depth of preparation: 1.5 mm.
Rotary instrument: No. 6 round bur and wheel
diamond/football diamond.

20. •Depth cuts like pot holes are
placed on the lingual fossa with
a No. 6 round bur which has a
diameter of 1.8 mm. With this
depth cuts of approximately 1
mm are produced, which after
finishing will give the required
depth.
PROCEDURE

21. •The remaining tooth structure
is removed with a wheel
diamond or a football diamond.
•The clearance is checked
using baseplate wax of 2 mm
thickness, as described for
complete metal crown
preparation.

22. 4.PROXIMAL REDUCTION
Depth of preparation: 1.5 mm.
Rotary instrument: Long thin tapering diamond/long
needle diamond
and flat-end tapering diamond.

23. PROCEDURE
•Long thin tapering diamond is used
to provide access through the
proximal surface. The access is
prepared using a ‘vertical sawing
motion’ in an incisogingival direction.
•The axial preparation is now
continued onto the proximal surface
using the flat-end tapering diamond
which will produce the shoulder. A
taper of 3–5° is produced by the
reduced proximal surfaces.

24. 5.FINISHING
● Axial surface is finished using a flat-end tapering fissure bur.
● The shoulder is finished with an end-cutting diamond where the sides are
noncutting and smooth and only the tip has fine diamonds stones
● A heavy chamfer finish line can also be given instead of the shoulder
finishline for all-ceramic crowns .
● In that case, a 3 mm diameter round-end tapering diamond is used for the
axial reductions.and the same is finished with a fine grit chamfer
diamond/torpedo bur.

28. ADVANTAGES
● Translucency and light transmission
● Excellent tissue response
● Subgingival placement avoided
● Reduced risk for overcontouring.
● Reduced thermal conductivity
● No allergic potential
● Superior to metal with respect to corrosion,
galvanise and biocompatibility.

29. DISADVANTAGES
•Strength still not comparable to metal-ceramic
restoration
•Long term performance using fixed partial denture no
available data yet.
•Proper tooth preparation design is critical to ensure
mechanical success.
•More knowledge required in choosing appropriate
material.

30. INDICATIONS
● Indicated for inlays, onlays, veneers, anterior and
posterior crowns
● •Anterior three unit fixed partial dentures.

31. CONTRAINDICATIONS
● Occlusal clearance after tooth preperation is less
than o. 8mm.
● Thin teeth labiolingually.
● Deep bite with lingual wear facets.
● Bruxism and parafunctional activity.

32. CONCLUSION
● The removal of all morphological form of the tooth is a radical
treatment & restoring it properly can be difficult.
● The full veneer crown is a restoration that replaces lost tooth
structures and imparts some measures of structural support
to the tooth.
● Hence one must be able to judge correctly the type of
restoration required for each individual tooth and try to
follow the guidelines for the respective
tooth preparation.

33. REFERENCES
•Fundamentals of fixed prosthodontics-4th edition
shillingburg, sather, Wilson, Cain, Mitchell et al.
•Textbook of Prosthodontics, Second Edition. V
Rangarajan, TV Padmanabhan.
•Textbook of Prosthodontics, Second Edition, Deepak
Nallaswamy.