Table 1. Flexural strength and Fracture toughness of different ceramics; modified according to (Raigrodski AJ. Contemporary
materials and technologies for all-ceramic fixed partial dentures: a review of the literature. J Prosthet Dent. 2004;92(6):557-
562; Aurelio IL, et al. Extended glaze firing improves flexural strength of a glass ceramic. Dent Mater. 2015;31(12):e316-324;
Drummond JL, et al. Fracture surface examination of dental ceramics using fractal analysis. Dent Mater. 2005;21(6):586-589).
Material
Flexural strength (MPa)
Fracture toughness KIC(MPa/m1/2)
Leucite reinforced 140-210 1.2-2.0
Lithium disilicate reinforced 300-400 2.8-3.5
Zirconia oxide (Y-TZP) 900-1200 9-10
PARTIAL CERAMIC CROWNS. ESTHETIC AND TISSUE CONSERVATIVE
RESTORATIONS – PART I: POSTERIOR TEETH
Figure 6. Overview of dental ceramic materials.
ZrO 2 have been introduced as an alternative material
for the fabrication of single unit ceramic restorations
which have to be adhesively luted. Restorations can
be fabricated either labside (Celtra, Celtra Press;
Suprinity) or CAD/CAM chairside (Celtra Duo, with
an optional sintering step). Zircon oxide reinforced
lithium silicate ceramics exhibit good mechanical
properties and are translucent. Little clinical
experience, however, exists with this ceramic for
PCCs yet, and therefore this class of ceramics is not
further covered in this review.
Oxide ceramics show low translucency compared
to silicate ceramics but much better mechanical
properties, which is due to the high amount of
crystals. 18 Both, adhesive and conventional luting
is possible. Adhesive luting, however, needs
special ceramic pretreatment. 18 Today, monolithic
restorations can be fabricated from zircon dioxide
ceramics, but the range of indication rather covers
crowns, bridges and more complex restorations
than partial ceramic crowns. Therefore, this class of
ceramics will not be addressed in this review.
Recently, materials named “Hybrid ceramics” have
been marketed. These are, however, basically resin-
based composites and/or contain methacrylate
Stomatology Edu Journal
monomers. Therefore, the term “hybrid ceramic”
may be misleading. These materials are industrially
manufactured and must be processed by CAD/
CAM techniques. They include heavily particle filled
resins (i.e. resin based composites) cured at high
temperature/pressure (e.g. Lava Ultimate, 3M or
Cerasmart, GC) or a resin interpenetrating network
(IPN) in a porous ceramic structure (e.g. Enamic,
Vita). The latter material contains 86 wt.% feldspatic
ceramic, which is infiltrated with resins (14 wt.%
polymers). It has a strength of 144,4 MPa, 20 like glass
ceramic (Mark II) but lower than lithium disilicate and
a lower elastic modulus compared to other ceramics
ranging between enamel and dentin. 20 Adhesive
luting is required for these materials. Other similar
materials are being marketed. For this group of
materials little clinical experience for PCCs exists for
the time being.
Processing methods
Initially, (feldspatic) ceramics were processed by
sintering or - in the 80s of last century - by casting
(e.g. Dicor). The method was based on impression
taking and further processing in a dental laboratory.
However, mechanical properties of the resulting
restorations were limited and especially for the
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