Page 26 - CEREC Q3|2013

24 | cerecdoctors.com | quarter 3 | 2013
agreatadvantagetocerecdentistry
is taking complete control of our restora-
tions. For new users such as myself, this
is eye-opening as we realize what limita-
tions we created for our lab technicians
with poorly prepared teeth.
One of our biggest challenges is
proper occlusal reduction. We have
a great desire to be conservative and
preserve tooth structure, so there is a
tendency to under-reduce. Also, all of
us have experienced reducing a tooth
by 2 mm and being surprised to finish
with a restoration that is 1 mm thick.
The materials we work with are very
forgiving, and we often get away with
less-than-ideal restoration thickness,
but with the release of new materials
and recommendations it is a good idea
for new and experienced
CEREC dentists alike to
consider common pitfalls
that can lead to thinner
Avoiding Thin Restoration Pitfalls
Proper Reduction Leads to Successful Outcomes
c a s e s t u d y | | | b y M a r k D av i s , D . D . S .
the same effect. To illustrate this, I took
a Biocopy image of a tooth before prepa-
ration and designed the crown using
Biogeneric individual. After designing the
crown, I overlaid the Biogeneric image on
the crown proposal, used the Slice tool to
visualize the difference in fissure depth,
and measured it (Fig. 2).
If we are restoring such a tooth
without opening the bite, we should
consider limiting the anatomy we design
in our new restoration or increasing our
reduction. If we need to limit our reduc-
tion because of a short clinical crown or
close proximity to the pulp, we should
consider a Biogeneric Copy design. A
perfectly smooth and rounded prepara-
tion (no over-milling) with a Biogeneric
Copy design requires the least amount
of reduction (spacer thickness plus the
desired restoration thickness) (Fig. 3).
When we plan on a “high” margin with
short axial walls, we have a tendency to
restorations than we planned.
The following common pitfalls can
lead to thin restorations:
• Misunderstanding the relationship
between pre-existing anatomy and the
planned final restoration
• Failing to include a functional cusp
bevel with a “high” margin
• Rough prep or sharp line angles
• Misunderstanding spacer and occlusal
milling offset
I will briefly describe these pitfalls and
make a few recommendations.
We are usually planning crowns on
badly broken-down teeth with poor or
limited occlusal anatomy (Fig 1). If we
reduce a toothwith no central groove, and
plan on adding one in our final restora-
tion, we can lose 0.5 - 1.0mmof our reduc-
tion to the restoration of this anatomy.
Adding cusp height or inclines to a tooth
with advanced attrition/erosion will have
1 2
3 4
Fig. 1: Pre-op condition
Fig. 2: Rough prep
Fig. 3: Copy design thickness
Fig. 4: Over-milling