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12 | cerecdoctors.com | quarter 2 | 2013
dental ceramics and resin-based
composites are presented within a
simplifying framework, allowing for
facile understanding of their develop-
ment, composition and indications. This
simplifying framework is then used to
explore what is known about the clinical
performance of both materials. In the
case of CAD/CAMceramics, we have the
best and longest clinically studied mate-
rials in the history of dentistry. From this
rich clinical evidence come well-based
indications for specific commercial
systems. Resin-based materials perform
clinically no better whether fabricated
in a laboratory, by the manufacturer or
directly intraorally, and are inferior
to ceramics with respect to wear,
fracture and loss of restorations.
There is no new class of material
termed a “resin nano ceramic,” as just a
few years back there was no new class
of material termed a “polyglass” – both
derive from marketing minds, not mate-
rials science.
Confused about CAD/CAM
materials?
Essentially, CAD/CAM ceramics can
be predominantly glassy, particle-filled
glasses or polycrystalline with no glass
content. Polycrystalline ceramics can
be of alumina, zirconia or even combi-
nations of the two. Ceramic parts can
be machined fully sintered or partially
sintered from data sets derived from
scans of patients, impressions or patterns
that are either net-shaped
or over-sized. Ceramic
parts can be mono-layer or
bi-layer, and either can be
CAD/CAM Materials
in Dentistry
An In-depth Look at theMake-up of Chairside Restorations
M at e r i a l s | | | b y J . R o b e r t K e l ly, D . D . S . , M . S . , D M e d S c
Background Concepts
in Materials Science
There are two quite useful concepts
that help demystify dental materials by
providing a structure within which to
organize thinking. First, there are only
three main classes of dental ceramics:
1) predominantly glassy materials; 2)
particle-filled glasses, and; 3) polycrys-
talline ceramics.1-3 Defining character-
istics will be provided for each of these
ceramic types, as they are represented in
madeusingautomatedsystems. Ceramics
can be further characterized by translu-
cency, grain-size, wear-kindness, shade,
polish-ability and sensitivity to mois-
ture. Along with resin-based composites,
ceramics are correctly thought of as being
composites, but resin-based composites
(even highly filled nano-particle ones)
are not correctly characterized as being
ceramics. Now, if this clears things up for
you, then read no further – if not, then
welcome aboard!
Fig. 1: Ceramic classifications
Fig. 2: Ceramic composition
1
2