112391_CEREC 2015 Q4 - page 44

42 | CERECDOCTORS.COM | QUARTER 4 | 2015
therefore increasing the chances for periodontal problems and
recurrent decay.
Finishing facial, lingual as well as cervical embrasure areas of
ceramic materials is generally a delicate job. The often-preferred
diamond disk should not be utilized to contour the embrasures of
lithiumdisilicateFPD, as itsusemay result inpredetermined fracture
points that may propagate through the connector area increasing
the risk of fractures. The clinician must resort to fine diamond burs
C A S E S T U D Y | | | B Y G I S E L E F. N E I VA , D . D . S . , M . S . , M . S .
the introduction of the 32 mm lithiumdisilicate block (e.max cad by ivoclar) (Fig. 1) in 2013 expanded the appli-
cations of chairside CAD/CAM restorations to include multiple unit designs. This provided an opportunity for dentists to
explore a completely new restoration modality using the CEREC system.
Chairside Lithium Disilicate
Fixed Partial Dentures
Customized Esthetics in a Single Firing
Patients today are naturally attracted to digital restoration
workflows because they allow for single-unit restorations to be
conveniently completed in one appointment, and without the
need for impressions, temporary restorations or their inherited
issues. Thanks to recent advances in CEREC software and the
advent of the 32mm lithium disilicate blocks (IPS e.max CAD by
Ivoclar Vivadent), it is possible to use a similar process to complete
anterior, three-unit fixed-partial dentures (FPDs).
Even though a same-day FPDcan be obtained, the patient would
have to wait 60-80 minutes before the restoration would be ready
for trial fitting and adhesive cementation. The processing time
may appear extensive at first; however, it includes CAD design,
CAM milling, custom shade application, and crystallization and
glazing of the lithium disilicate material.
Alternatively, simple modifications to the CERECworkflow can
enable patients to get a next-day permanent anterior FPD. The
patient would leave with a CAD/CAM acrylic temporary FPD that
could be milled and delivered much faster, and it would closely
resemble the final product (Fig. 2).
When designed and fabricated within manufacturer’s specifica-
tions, the chairside three-unit FPDs are strong and accurate. The
flexural strength of IPS e.max CAD material has been tested to
be 150MPa in its pre-crystallized state, to a final 360MPa flexural
strength after crystallization.
However, as with any all-ceramic, multiple-unit restoration,
the critical aspect lies on the size of the connection between
the abutments and the pontic. Ivoclar recommends a 16 mm2
connector for ideal strength, with preference to the height of
the connector being equal or greater than its width. This may
present a technical limitation when designing three-unit FPDs
for short clinical crowns. Similarly, designing a large and yet
natural-looking connector may be esthetically challenging —
especially at the central incisor area where the contacts are
shaped like inverted teardrops.
Often it’s necessary to over-
bulkmarginal ridges and lingual
proximal embrasures to assure
appropriate connector thick-
ness (Fig. 3). Special care should
be taken to avoid extending
the connector too close to the
prepared margins of the abut-
ments, as this would poten-
tially create an area of compro-
mised access for oral hygiene,
Fig. 1: 32 mm IPS e.max
CAD block
Fig. 2: Telio CAD FPD