DR. TAJamMUL AHMED
a.tajammul@gmail.com
aLL CERAMIC CROWN
PREPARATION
INTRODUCTION
The all ceramic crown differs from other ceramic veneer
restorations because it’s not cast in gold or some other metal
It is capable of producing the best cosmetic effect of all dental
restoration.
However since it is entirely made of ceramic, a brittle
substance, it is more susceptible to fracture.
A lot of recent advances have improved the properties of
dental porcelain.
Indications
High esthetic requirement.
Incisal edge reasonably intact.
Endodontically treated teeth with post-and –cores.
Favourable distribution of occlusal load.
Contraindications
When superior strength is warranted and metal-ceramic
crown is more appropriate.
Significant caries with insufficient coronal tooth structure
for support.
Thin teeth faciolingually.
Unfavourable distribution of occlusal load.
Advantages
Excellent esthetics
Good tissue response even for subgingival margins.
Slightly more conservative of facial wall than metal
ceramic
Disadvantages:
Reduced strength compared to metal ceramic crown.
Proper preparation extremely critical
least conservative preparations
Brittle nature of material
PORCELAIN JACKET CROWN PREPARATION
Depth orientation grooves:
A flat end tapered diamond bur is used.
Bur is first aligned with the incisal portion of
the facial surface and two vertical cuts are
made
Three similar grooves are made maintaining
the same instrument parallel to the gingival
segment of the facial surface.
Two incisal orientation grooves 2.0 mm deep
are made.
Incisal reduction:
A flat end tapered diamond is
used to reduce the incisal edge
by 2.0 mm keeping the plane of
the reduced surface parallel to
the former incisal edge.
A round wheel diamond may
also be used for incisal
reduction.
Facial reduction, incisal half:
A flat end tapered diamond
is used to remove the tooth
structure remaining between
the orientation groove in the
incisal portion of the facial
surface.
Facial reduction, gingival half:
A flat end tapered diamond is used
to reduce the gingival segment and
extend well into the proximal
surface.
Extend the facial reduction through
the proximal surfaces with the flat
end tapered diamond producing a
shoulder in the process.
Lingual reduction:
A small round diamond with a
head 1.4 mm in diameter is
used to make four depth
orientation cuts. A small round
wheel diamond is used to
create a concave surface over
the lingual surface of the
tooth incisal to the cingulum.
Lingual axial reduction:
A flat end tapered diamond is
employed for axial reduction
to prepare the vertical lingual
wall. Blend the reduction of
each axial surface with that on
the adjacent axial surface.
Axial finishing:
No: 171 bur is used to
smooth the axial surfaces
and to round all distinct
positive angles on the
preparation.
Shoulder finishing:
No: 957 bur is used for
preparing a smoothly cut
shoulder perpendicular to the
line of force or to the long axis
of the tooth.
The features of all ceramic crowns preparation for a
porcelain jacket crown on an anterior tooth and the
function served by each.
POSTERIOR ALL CERAMIC CROWN PREPARATION
Occlusal reduction:
A large round end tapered diamond is
used to place depth orientation grooves on
triangular ridges and major grooves.
The final occlusal reduction should be 1.5
mm to 2.0 mm deep.
Remove the tooth structure remaining
between the depth-orientation grooves
with the large round-end tapered diamond.
Functional cusp bevel:
The large round end tapered
diamond is used to produce
depth orientation grooves in the
facial incline of the facial cusp.
A minimum of 1.5 mm of
clearance is necessary.
Facial and lingual axial
reduction:
The flat end tapered diamond is
used to obtain axial reduction
ranging from 1.0 to 1.5 mm by
making depth orientation
grooves and removing the tooth
structure between them. The
axial reductions are carried out
as far as possible into the
proximal embrasures.
Complete axial reduction:
A short needle diamond is used
to begin the proximal axial
reduction without touching the
adjacent tooth. The axial
reduction interproximally is
complete by running the flat end
tapered diamond.
Preparation finishing:
Flat end tapered carbide
bur is used to finish the
axial surfaces and the
functional cusp bevel.
The features of a cast ceramic crown preparation for an all
ceramic crown on a posterior tooth and the function
served by each.
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