CERECDoctors.com-Q2-2017 - page 26

24 | CERECDOCTORS.COM | QUARTER 2 | 2017
C A S E S T U D Y | | | B Y D A N I E L J . P O T I C N Y, D . D . S .
the beauty of in-office cad/cam is, as they say, “one and done.” Offering this service to patients lets you deliver a final
restoration in a single appointment; and the patient is out of the chair in a reasonable amount of time. Clinicians who have
pursued this technology aim to deliver restorations that they would be proud to have in their own mouths, and they have an
abundance of milling materials to select from to achieve this goal.
Tooth-Preserving Alternative
To Full-Coverage Crowns
Better Serving Patients Using AdvancedMaterials and CAD/CAMDentistry
To ensure long-term success of any CAD/CAM restoration, it is
imperative to not only choose the correct material for the situa-
tion at hand, but to choose a treatment plan that allows maximum
retention of natural tooth structure all while following proper
preparation guidelines.
At a time when patients expect highly esthetic outcomes, full-
coverage crowns might be what many clinicians first think of when
considering the capabilities of in-office CAD/CAM. However, clini-
cians have a responsibility to consider minimally destructive tech-
niques that offer equally esthetic results — such as partial-coverage
indirect restorations. Restoring a tooth with a full-coverage crown,
including strong all-zirconia crowns, means creating a preparation
that requires significant removal ofhealthy toothstructure toachieve
proper form.1 When presented with a situation where a crown or an
inlay/onlay would be equally acceptable, partial-coverage options
not only save valuable tooth structure,2 but can be easier for the clini-
cian to finish, as they typically do not require esthetic characteriza-
tion. When properly prepared and placed, tooth-colored inlays and
onlays can be as predictable as full-coverage restorative options.3
For any CAD/CAM restoration, being a full crown or inlay/onlay,
the form of the prepared teeth and the amount of tooth structure
removed are important contributors to the mechanical, biologic
and esthetic success of the restoration. Therefore, it’s important
to pay particular attention to clinical guidelines for optimizing
success. For partial coverage situations, preservation of tooth struc-
ture is about more than simply avoiding excessive destruction. It
requires specific attention to design that will reinforce and protect
the remaining enamel and dentin. It is the author’s opinion that the
preparation is the most important aspect to ensure success. The
geometry should follow principles for proper support based on the
material selected, and burs should be carefully selected to mimic
the geometry of the preparation.
Another consideration with supragingival partial-coverage rest-
orations is selecting a material with superior edge quality and good
marginal adaptation. Glasses, as we know, can be brittle, and tend to
chip and chunk slightly duringmilling with in-office systems.4 These
chips are often very small and may not dramatically affect clinical
performance but, if an alternative exists that can deliver better edge
quality andbettermarginal adaptation, it is certainlyworthexploring.
Furthermore, placement of a glass restoration does not leave the
clinicianmanyoptionsotherthantotalreplacementifthereisarecur-
rent problem with the tooth in the future. These materials have no
real way of being repaired. Especially today, withmany patients aged
50 and older who are prescribed multiple medications, dry mouth
is a significant issue. Dry mouth leaves these patients highly suscep-
tible to decay, and so the clinician must give thought to selecting a
material that offers serviceability. In such cases, serviceabilitymeans
the capability to address a margin discrepancy or plaque accumu-
lation, and easily seal the margin again without compromising the
tooth or potentially having to replace the entire restoration.
Composite restorations can of course be repaired, but polym-
erization shrinkage is a major concern when these materials are
used. Avoidance of polymerization shrinkage requires techniques
like layering, cross layering or the sandwich technique of using a
flowable composite underneath the denser universal composite.
All of thesemethods of ameliorating the drawbacks of thematerial
are time consuming and can be technique-sensitive.
ADVANTAGES OF NEW MATERIAL CLASSES
In the author’s experience, a new class of material has helped
address some of these clinical issues. 3M Lava Ultimate Restor-
ative is a resin nanoceramic that takes the favorable attributes
of a composite and combines them with the known esthetics
and durability of a glass material. Because this material is less
brittle than glass, it comes out of the mill with better edge quality,
enabling an excellent marginal adaptation. This is made possible