Study: Dentsply Sirona’s Celtra® Duo (ZLS) Rates Highest Among Chairside CAD/CAM Materials in Fracture Toughness
York, PA (August 11, 2016) – A recent study revealed that Dentsply Sirona’s
Celtra Duo (ZLS) ranked highest in fracture toughness (KIC) when
compared with five different chairside CAD/CAM materials used for crown
fabrication. Conducted by the University of Toronto, the complete study report
entitled, “Fracture toughness of chairside CAD/CAM materials – Alternative
loading approach for compact tension test,” is published in the July 2016
edition of Dental Materials, the
official publication of The Academy of Dental Materials.
The study applied a
modified compact tension (CT) test in order to measure fracture toughness of
the group of restorative CAD/CAM materials that included both ceramics and
nanoceramic resin composite materials. Five different chairside CAD/CAM blocks
including VITA® Mark II, Lava™ Ultimate, VITA Enamic, IPS e.max CAD,
and Celtra Duo (ZLS) were tested. Means and standard deviations of fracture
toughness measured in MPa m1/2 for the materials are as follows:
· Celtra Duo (ZLS) (fired and unfired) – 2.65
(0.32), and 1.01 (0.15) respectively
· IPS e.max CAD (crystallized and
un-crystallized) – 1.88 (0.62), and 0.81 (0.25) respectively
· VITA Enamic – 1.02 (0.19)
· Lava Ultimate – 0.85 (0.21)
· VITA Mark II – 0.73 (0.13)
Celtra Duo (ZLS) and
e.max had the notably highest mean toughness values, with Celtra Duo (ZLS)
found to be higher than that of e.max. Both leading materials had a substantial
increase in fracture toughness after firing. Although the mean KIC values
of the tested materials varied considerably, none were able to reach the mean KIC
of natural dentin, previously reported at 3.08 MPa m1/2.
According to the
report, the difference in IPS e.max CAD and Celtra Duo (ZLS) fracture toughness
is most likely due to Celtra Duo’s (ZLS) composition. Celtra Duo (ZLS) is
mainly composed of 58% silica, lithium-metasilicate, -disilicate, and
-phosphate crystals, and 10% zirconia crystals in addition to other minor
ingredients. The highly-dispersed zirconia content is completely dissolved in a
glassy matrix and acts as a crystal nucleus. Zirconia-based ceramics are known
for their enhanced load resistance and fracture toughness compared to alumina-
or lithium-disilicate ceramics.
Dental restorations
must be extremely durable in order to resist damaging effects of a harsh oral
environment. Fracture toughness is an essential property of any material that
relates its resistance to crack propagation which imminently causes failure. A
restorative material with high fracture toughness shows better fracture
resistance and longevity as compared to materials with lower fracture
toughness. Moreover, during the CAD/CAM milling process, grinding of the blocks
creates micro-cracks and flaws that are routinely smoothed with polishing and
glazing.
To review a complete
version of the study, please refer to the July 2016 issue of Dental Materials or contact
855.723.5872.
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