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CERECDOCTORS.COM
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QUARTER 4
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2014
ips e.max cad (ivoclar) was intro-
duced in 2006
as a lithium disilicate
CAD/CAM material with two to three
times the flexural strength of other
available chairside ceramic materials.
The improved flexural strength of the
lithium disilicate was a strong influence
in making this the most popular chair-
side CAD/CAMmaterial. The significant
increase in flexural strength is purported
to afford the opportunity to either adhe-
sivelybondthematerial to the toothprep-
aration or use a conventional cement.
Many clinicians prefer conventional
cementation techniques since they
are generally easier and more efficient
than adhesive bonding techniques to
deliver restorations. The obvious ques-
tion is: does the enhanced strength of
the lithium disilicate material predict-
ably allow for conventional cementation
instead of adhesive bonding?
One early in vitro study compared the
fracture strength of crowns made of feld-
spathic porcelain (Vita Mark II/Vident),
leucite-reinforced ceramic (ProCAD/
Ivoclar) and lithium disilicate (e.max
CAD/Ivoclar) cemented to composite dies.
Fifteen crowns fabricated from of each
type of material were cemented using a
conventional cement (zinc phosphate
cement), and 15 crowns fabricated from
each type of material were etched with
hydrofluoric acid and cemented using
an adhesive resin cement
(Panavia 21). All the crowns
were loaded laterally on the
occlusal surface to simulate
Adhesive Bonding or
Conventional Cement … Does
It Matter for Lithium Disilicate?
To Bond or Not to Bond?
C A S E S T U D Y
| | |
B Y D E N N I S J . FA S B I N D E R , D . D . S . , A . B . G . D .
fracturethantheothertwotypesofcrowns.
This study supports the concept that
adhesive cements significantly improve
the fracture resistance of ceramic mate-
rials compared to conventional cement.
Another in vitro study compared the
effect of using a conventional cement
and an adhesive cement on the fracture
resistance of thin-walled copings of
0.4 mm thick.
Crowns of YTZP-zirconia, lithium
occlusal loading, and the force required to
initiate the fractureaswell as thecomplete
fracture loadwere recorded.
For all three types of crowns, the load
to initiate a fracture was greater with the
use of the adhesive cement compared to a
conventional cement, indicatingadhesively
cemented crowns were statistically more
resistant to fracture. When the final frac-
ture load was compared, lithium disilicate
crowns were more resistant to complete
Fig. 1: Pre-op view of teeth #3 and #4
with fractured restorations
Fig. 2: Full crown preparations
for emaxCAD crowns #3 and #4
Fig. 3: Post-op view of crowns
Fig. 4: Post-op facial view of crowns
Fig. 5: Two-year post-op view of crowns
Fig. 6: Two-year post-op view of occlusal
function crowns
Fig. 7: Five-year post-op view of crowns
Fig. 8: Five-year post-op view of occlusal
function crowns
Fig. 9: Five-year facial post-op view
of crowns
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