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26 | CERECDOCTORS.COM | QUARTER 4 | 2014
and margins must be sharp and clear in
order to capture an accurate digital scan.
By leaving a small retraction cord in the
sulcus throughout the scanning procedure,
dentists can help ensure that the tissue
stays retracted while limiting sulcular
fluids fromcontaminating the field.
Figure 4 shows the result of paying
careful attention to the margin. The
image is clean and sharp. Additionally,
the geometry of the preparation, which
minimizes sharp angles and emphasizes
smooth anatomical transitions, meets the
requirements specified for glass ceramic
restorations to optimize the performance
of the material.3 Despite best efforts, the
initial proposal developed by the soft-
ware revealed that the restoration would
be in hyper-occlusion (Fig. 5).
Clearance for morphologic form and
function is still necessary. If this were
done using a BioCopy design, this may
not have occurred given the preparation
was performed in congruence with the
anatomic contours of the original crown.
With a BioIndividual design, the soft-
ware will examine the adjacent teeth and
create a proposal based on them from the
software database. The software respects
occlusal thickness first and, if not within
the recommended parameter of 1,600 µm,
will add enough material to the
occlusal table to establish this 1,600 µm
parameter with the excess translated to
an occlusally “high” proposal. Rather
than struggling to balance thickness with
occlusion by altering the initially excellent
morphologic form or altering the antago-
nist, the CEREC software allows for easy
andexpedient remedy throughre-prepara-
tion, digitallytrimmingtheareare-prepped
on the digital model and re-scanning only
over the newly altered area.
This useful feature of the software
should encourage clinicians to put the
proper emphasis on the prep itself,
rather than trying to “design and grind”
around deficiently reduced areas which
may negatively affect the long-term
performance of the materials (Fig. 6).
After these steps were completed, the
software’s revised proposal then showed
a crown in proper occlusion that satis-
fied the minimal thickness parameters
of 1,600 µm (Fig. 7).
Once the design was completed, 3M
ESPE Lava Ultimate restorative was
chosen for this case. This patient exhibits
a pronounced level of parafunction, which
is reflected in the damaged veneering
material and adjacent teeth. Chairside
CAD/CAM dentists often prescribe high
strength lithium disilicates (e.g., e.max
CAD), and lithium silicates where “extra
strength” or increased fracture resis-
tance is desired. Lava Ultimate can offer
the similar fracture resistance with some
added benefits.4,5 The unique polymer/
ceramic technology offers high perfor-
mance and exceptional fracture resis-
tance by comparison to the feldspathic
glass materials. This includes resiliency
for a cushioning or shock absorber effect,
which could be useful for a patient with
damaging habits. Lava Ultimate can be
easily sustained through adjustment
or repair with conventional compos-
ites should chipping or breakage occur,
although monoblocks in general are
much less likely to do so. Reparability is a
nice feature should endodontic access be
required or to address recurrent caries.
Lastly, the ease of use of this material at
the chair is unmatched in terms of adjust-
ment and finishing by comparison to the
full-glass content ceramics.
After the crown finished milling, it
was removed from the milling chamber
and tried in the mouth in a dry-fit step.
The proximal contacts were assessed
and adjusted, the marginal fit verified
and the occlusion pre-adjusted. Occlusal
adjustments can be made before final
placement due to thematerial’s inherent
resiliency and less brittleness by
Fig. 4: Margination prior to proposal
calculation
Fig. 5: The initial proposal was the proper
thickness but in hyper-occlusion
Fig. 6: The preparation was altered
with a cut-out over the reduced area
and a subsequent re-scan
Fig. 7: The re-calculated proposal after
re-prep and re-scan
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6
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