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ON THE
SUBJECT OF CERAMIC RESTORATIONS:
1) What
is Empress 2?
The Empress
2 system is comprised of two new ceramic materials. The framework material
is composed of lithium disilicate, and a fluorapatite ceramic used in
the the layering phase of the fabrication of the restorations. Empress
2 material provides strength and esthetics for single-unit crowns and
three-unit bridges. The original Empress continues to be indicated for
esthetic inlays, onlays, veneers, and single unit anterior crowns, where
less reduction is necessary for ideal esthetics.
2) What
preparation requirements are needed for Empress 2 posterior crowns?
For full
coverage restorations, posterior crown preparations should have:
a) 1.5-2.0
mm occlusal reduction; at least 2.0 in opposing tooth contact areas
such cusps and fossae.
b) 1.5
mm axial reduction with a 4-8 degree of taper.
c) 1.0
mm reduction at the gingival margin.
d) Butt
joint margin with a flat-ended tapered diamond bur yielding a shoulder
of at least 1.0 mm.
e) Remaining
coronal tooth length of at least 4 mms.
3) What
are the Empress 2 preparation requirements for a three-unit bridge?
For three-unit
bridges:
a) The
pontic span must not exceed 11 mm on the anterior and 9 mm on a posterior
bridge (about the width of the maxillary 1st premolar).
b) The
connector dimensions between pontic and abutments must be at least 4
mm by 4 mm for the anterior and 5 mm (occlusal-gingival height) by 4
mm for the posterior.
c) Posterior
abutments are prepared in the same way as the single posterior crown
(see above).
d) Anterior
abutments are prepared similar to single unit Empress anterior crowns
(see below), except that a 2.0 mm reduction is needed on the incisal.
4) What
are the anterior single crown preparation guidlelines for an Empress restoration?
For full
coverage single-unit anterior crowns, the preparation should have:
a) 1.0-1.5
mm facial reduction.
b) 1.5-2.0
mm incisal reduction.
c) 1.0-1.5
mm reduction at the gingival margin with a butt joint margin.
d) 1.5-2.0
mm lingual contact clearance achieved with a football shaped diamond.
e) Rounded
internal line angles.
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