Monolithic Zirconia

Japanese Dental Science Review 56 (2020) 1–23
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Japanese Dental Science Review

journal homepage: www.elsevier.com/locate/jdsr
Review Article
Strength and aging resistance of monolithic zirconia: an update to

current knowledge
Eleana Kontonasaki a,∗ , Panagiotis Giasimakopoulos b , Athanasios E. Rigos b
a
Department of Prosthodontics, Faculty of Dentistry, School of Health Sciences, Aristotle University of Thessaloniki, Greece
b
Dentist, Thessaloniki, Greece
a r t i c l e i n f o a b s t r a c t
Article history: New zirconia compositions with optimized esthetic properties have emerged due to the fast-growing
Received 20 May 2019 technology in zirconia manufacturing. However, the large variety of commercial products and synthesis
Received in revised form 2 August 2019 routes, make impossible to include all of them under the general term of “monolithic zirconia ceramics”.
Accepted 17 September 2019
Ultra- or high translucent monolithic formulations contain 3–8 mol% yttria, which results in materials
with completely different structure, optical and mechanical properties. The purpose of this study was to
Keywords:
provide an update to the current knowledge concerning monolithic zirconia and to review factors related
Monolithic zirconia ceramics
to strength and aging resistance. Factors such as composition, coloring procedures, sintering method
Strength
Aging
and temperature, may affect both strength and aging resistance to a more or less extend. A significant
reduction of mechanical properties has been correlated to high translucent zirconia formualtions while
regarding aging resistance, the findings are contradictory, necessitating more and thorough investigation.
Despite the obvious advantages of contemporary monolithic zirconia ceramics, further scientific evidence
is required that will eventually lead to the appropriate laboratory and clinical guidelines for their use.
Until then, a safe suggestion should be to utilize high-strength partially-stabilized zirconia for posterior
or long span restorations and fully-stabilized ultra-translucent zirconia for anterior single crowns and
short span fixed partial dentures.
© 2019 The Authors. Published by Elsevier Ltd on behalf of The Japanese Association for Dental
Science. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/
licenses/by-nc-nd/4.0/).
1. Introduction its strength. Specific processing conditions, environmental humid-

ity, stress and temperatures between 200–300 ◦ C may accelerate
Zirconia was suggested as the first candidate for full contour it [5,8–10]. Many experimental studies have shown that water
monolithic restorations due to its significant advantages, such as molecules can penetrate the zirconia structure when exposed to a
excellent mechanical properties, superior to those of other ceramic hygroscopic environment. The triatomic character of yttrium con-
systems, esthetic performance comparable to that of metal-ceramic tributes to the presence of several oxygen vacancies in the zirconia
restorations, radiopacity, low corrosion potential, good chemi- lattice, which facilitates the diffusion of water molecules into its
cal properties, volumetric stability and elastic modulus values mass [8]. The diffusion of water initially causes a lattice contraction
comparable to steel [1–6]. According to in-vitro studies, zirco- that will result in tensile stresses’ concentration on the surface of
nia restorations exhibit flexural or bending strength values of the zirconia grains resulting in the transformation of the tetragonal
900–1200 MPa and resistance to fracture of 9–10 MPa [7]. However, phase to monoclinic phase. The increase in volume, that accompa-
zirconia ceramics do suffer from low-temperature degradation nies the transformation of a tetragonal grain to monoclinic, causes
(LTD), also known as aging [8]. In particular, the spontaneous and surface uplifts (Fig. 1) and grain pull out. This causes microcracks,
progressive transformation of the tetragonal phase to monoclinic which facilitate further the access of the water molecules within
degrades the mechanical properties of the Y-TZP and, in particular, the internal grains and therefore the surface initial tetragonal to
monoclinic transformation progresses deeper and deeper into the
bulk of the material. As the microcracks grow and this process con-
tinues, the material fractures. Microstructural factors such as grain
∗ Corresponding author at: Laboratory of Prosthodontics, Department of Dentistry, size, percentage of stabilizer, residual stresses and manufacturing
Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR- imperfections may affect this phenomenon [10–12].
54124, Greece.
E-mail address: kont@dent.auth.gr (E. Kontonasaki).
https://doi.org/10.1016/j.jdsr.2019.09.002
1882-7616/© 2019 The Authors. Published by Elsevier Ltd on behalf of The Japanese Association for Dental Science. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
2 E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23
Fig. 1. AFM images showing increased roughness and surface uplifts (red arrows on the right image) of transformed 3Y-TZP zirconia grains after aging in autoclave for 10 h.
Although a remarkable number of studies investigating the urea, glycine, sucrose, glucose) or their mixtures are typically dis-
properties of zirconia ceramics currently exists, due to the fast solved in a solvent (i.e. water, hydrocarbons) with metal nitrate
growing of zirconia technology, new materials are released in the hydrates [20]. Two modes can be applied for the thermal treatment
dental market, which have not been adequately evaluated. Con- of the mixture. The first (volume combustion or thermal explosion)
sequently, the purpose of this paper was to provide an update involves a sequential thermal treatment in various stages and the
to the current knowledge concerning strength and aging resis- second (self-propagating combustion) the locally heating of a small
tance of monolithic zirconia ceramics, aiming at highlighting the portion of the reactive mixture to initiate an exothermic redox
advantages and weaknesses of conventional and newly-released reaction between nitrate ions and the fuel, which self-propagates
materials, through the data presented in recent literature. along with the rest of the volume in the form of a combustion
wave. It is a fast method for preparing multicomponent, crys-
talline, homogeneous, with high purity and narrow particle size
2. Factors affecting strength and aging resistance of
oxide nanopowders [21–23]. For mechanochemical processing, very
monolithic zirconia
pure oxide powders are mechanically mixed and milled before cal-
cination. The advantage of mechanochemical synthesis is that it
2.1. Synthesis of zirconia nanowpowder for dental restorations
does not require any additional chemicals, such as organic solvents,
however milling can result in contamination of the nanopowder,
The first step towards the fabrication of monolithic zirconia
coarser inhomogeneous product and destabilization of the tetrag-
restorations is the synthesis of the appropriate yttrium stabilized
onal zirconia through diffusion of yttrium towards the grain surface
zirconia nanopowder. Nanopowder should be of high purity and
[24,25]. The synthesis by chemical routes, is usually more expen-
with a narrow range of particle sizes, in order to yield densi-
sive than the mechanical methods, but offers a strict control of the
fied structures of the desired crystallography. The properties of
powder characteristics, provided that a very carefull consideration
the starting powders are controled by the method of their pro-
of all the specific synthesis variables is involved.
duction. In order to achieve higher densification, various methods
have been developed for synthesizing nanoscale zirconia. These
include co-precipitation, hydrothermal treatment, sol-gel, solu- 2.2. CAD/CAM milling
tion combustion synthesis, and mechanochemical processing. In
the co-precipitation method, the desired cations are dissolved in Monolithic and core zirconia frameworks are fabricated through
an aqueous solution where a chemical precipitant agent is added the CAD/CAM technology by milling commercially available blocks,
to cause the precipitation of metal hydroxides. The precipitated which can be either pre-sintered or fully sintered. Pre-sintered
powder is filtered, dried and calcined. By modifying the pH and blocks come from a fine grain or nanograin zirconia powder,
temperature of the solution nucleation and growth mechanisms synthesized as described in section 2.1., which is pressed to
can be controlled. Although it is a low-cost method, broad particle high-density compacts through cold isostatic pressing (CIP). Cold
size distribution and grain agglomeration are unavoidable [13–15]. isostatic pressing is the most common method for compact-
Hydrothermal treatment involves an initial co-precipitation, fol- ing ceramic powders. During cold-isostatic pressing, pressure is
lowed by heat treatment at high temperatures to obtain an applied at ambient temperature, gradually increasing from 50
anhydrous crystalline powder. It is a low cost, soft and ecological to 400–1000 MPa and transmitted uniformly on zirconia powder
method that allows good chemical homogeneity of the product. until the green compacts reach 40–60% of their theoretical den-
It can be combined with microwave (microwave-hydrothermal sity prior to sintering [26,27]. Factors enhancing the densification
route) to supply further heat for the reactions. Its drawbacks are and pore elimination during CIP are nano-sized powder particles,
the long processing time and agglomeration, which leads to low uniform particle size distribution, high specific surface area and
sinterability [16–18]. The sol-gel method is based on hydrolysis and low degree of agglomeration. CIP zirconia blocks require a rela-
condensation reactions of inorganic salts and metal-organic com- tively easier and faster milling procedure causing less wear of the
pounds that form a sol which is converted into a gel. The gel is machining tools but frameworks present a linear and non-uniform
then dried and thermally treated to obtain a homogenous nano- shrinkage of 20–25% during sintering [1,28] leading to non-uniform
powder. It is a low cost method, with relatively simple reaction internal fit of Y-TZP copings [28]. Fully sintered blocks are pre-
conditions, that if properly monitored can tailor the microstruc- pared by presintering zirconia compacts at temperatures below
ture and the chemical composition of the powder. Agglomeration 1500 ◦ C to reach a density of at least 95% of the theoretical den-
is also a drawback of this method. A modified, nonaqueous sol- sity. Following, hot isostatic pressing (HIP) is performed to increase
gel process has been recently proposed as a novel green method densification by applying high pressure (50–200 MPa) and high
for the preparation of highly dispersive 3 mol% yttria-stabilized temperature (400–2000 ◦ C) via an inert isostatic gas pressure (e.g.,
zirconia nanopowder with particle sizes of 15–25 nm [19]. In the argon or nitrogen). This process aims at eliminating sub-surface
solution combustion synthesis, different types of organic fuels (i.e. voids through a combination of plastic flow and diffusion. For
E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23 3
densification of zirconia ceramics the temperature is elevated at parency. This technique provides direct contact between heating
temperatures ∼100–200 ◦ C below its sintering temperature and for elements and samples, very rapid heating/cooling rates (several
optimally sintering “green bodies” with no open porosity a remark- hundreds of ◦ C min−1 ), and uniaxial mechanical pressure. Con-
able increase in strength can be achieved by HIP [29] along with a cerning yttrium stabilized zirconia, limited literature exists [47–49]
small increase in densification [30]. Due to their high hardness and but the results show that the material can reach very rapid den-
low machinability hard machining of HIP processes zirconia ceram- sification with no cracks, shape distortions or density gradients
ics is more time consuming, requires tougher cutting tools and in sintered samples with complex shapes and dimensions of cen-
has been correlated to increased roughness, plastic deformation, timeters [49]. However in-vitro studies are needed to evaluate the
surface damage, residual stresses’ development [31] and higher feasibility and effectiveness of this sintering method for monolithic
monoclinic phase transformation. The generated cracks, flaws and zirconia ceramics.
surface damage cannot be removed during the sintering process,
and thus can cause early failure under mechanical loading.
2.4. Coloring of monolithic zirconia
2.3. Sintering
For monolithic zirconia restorations, coloring can be achieved
either by using pre-colored blocks or by immersing white zirconia
Different sintering methods have been proposed for the densifi-
restorations in coloring liquid or brushing their surfaces with it.
cation of CIP zirconia blocks. In general, they include conventional,
Coloring liquids are solutions of metal oxides such as ferric chlo-
microwave [32] and spark plasma sintering [33].
ride, manganese chloride, cerium acetate, cerium chloride, bismuth
Conventional sintering of monolithic zirconia includes high
chloride, terbium (III) chloride, chromium (III) chloride, manganese
temperatures and long heating times, thus being a time and energy
(II) sulfate, etc. The effects of liquid-coloring on the properties of
consuming process. As it constitutes the most applied method of
zirconia have been investigated in a few studies. In regards to LTD,
sintering, various studies have shown that differences in sinter-
liquid coloring has not been correlated with phase transformation
ing parameters of zirconia can directly affect its microstructure
but on the other hand, higher resistance to LTD compared to uncol-
and properties, such as translucency, grain size, and biaxial flex-
ored control specimens has been reported [50,51]. However, the
ural strength [34,35]. A general trend is that as the sintering
mechanical properties of the liquid colored zirconia ceramics seem
temperature increases, translucency and grain size also increase
to be affected by the process. Although a few studies report no effect
[34–36], but conflicting evidence exists regarding its effect on
on flexural strength [52–54], there are a lot of studies emphasiz-
flexural strength. For core zirconia ceramics, an increase of sin-
ing that immersion in coloring liquid can have detrimental effects
tering temperature above 1550 ◦ C can cause a decrease in flexural
on its flexural and fracture strength, hardness and densification
strength [34], probably due to yttrium migration to the grain
[51,55]. Ban et al. [56] reported that in cases of liquids contain-
boundaries [37]. In the study of Ebeid et al. [36], who investigated
ing erbium (Er), and neodymium (Nd), both crystalline changes
various sintering times for monolithic zirconia, the authors con-
(presence of cubic phases) and decrease in mechanical properties
cluded that even at 1600 ◦ C the biaxial flexural strength was not
can occur, attributed to the stabilization of the ions in the crystal
affected. Similar were the results in a recent study by Sen et al.
lattice. Although significant t→m transformation is not recorded
[38], who investigated various monolithic zirconia ceramics. They
after aging, the increased grain size and open porosity attributed
reported an increase in translucency by the increase in temperature
to some coloring oxides after sintering may negatively affect both
through grain enlargement and reduction of grain boundaries that
the optical and mechanical properties [51].
act as scattering centers, but no effect on biaxial flexural strength.
Pre-coloring involves the synthesis of colored nanopowder by
Although translucency can be improved, larger grain size makes
incorporating metal oxides such as Fe2 O3 [57,58], Bi2 O3 [57], CeO2
the material more susceptible to transformation [39] which may
[59], Er2 O3 [59,60], MnO2 [61,62] and Pr6 O11 [60]. Doping oxides
jeopardize its mechanical performance.
in pre-colored zirconia may have a negative effect on its mechan-
Microwave sintering is a low cost and time-consuming method.
ical properties [60]. This comes as a result of the changes in the
Its main advantage is that heating takes place through molecular
crystal lattice that take place due to the replacement of a Zr ion
interactions with the applied electromagnetic field and effective
with a metal ion. Depending on the valence and the ionic radius
heating is achieved throughout the material [40] in significantly
of the metal ion that enters zirconia crystal lattice, formation of
less time. In this way, the temperature gradients within the
oxygen vacancies and changes in lattice dimension (expansion or
bulk of the material that are usually encountered during conven-
contraction) can occur [63], variously affecting both the mechani-
tional sintering are avoided [41], which is important especially
cal/physical properties and color characteristics of zirconia [64,65].
for large and geometrically complicated specimens, such as den-
By adding various amounts of Fe2 O3 -which is the most common
tal crowns. Almazdi et al. [42] compared density and flexural
oxide for zirconia coloring- into a 3 mol% Y2 O3 zirconia powder,
strength of specimens prepared from a commercial dental zirco-
Kao et al. [66] produced powders with varying combinations of red
nia, and reported that the microwave-sintered specimens had a
and yellow. Although the densification and sintering of the powders
more uniform grain size distribution and were more closely packed
were improved, the size of zirconia grains as well as the monoclinic
than conventionally sintered specimens. No statistically signifi-
content was increased along with Fe content, making it necessary
cant difference was observed in the fracture toughness of various
to reduce the total amount of the applied oxide [66].
dental zirconia ceramics sintered in microwave or conventional
ovens [43,44], suggesting that this method can be widely applied
alternatively to conventional sintering. Recently Kim et al. [45] 3. Strength of monolithic zirconia
reported that microwave-sintered pre-colored monolithic zirconia
ceramics exhibited similar color appearance and smoother surfaces Although dental zirconia is the strongest dental material in
compared to those conventionally sintered, but with reduced pro- terms of flexural strength and fracture resistance, during the last
cessing time and cost. few years, the translucency of zirconia ceramics has increased at the
Spark plasma sintering, or plasma-activated sintering or field- expense of strength, and translucent full-contour, monolithic zir-
assisted sintering technique (FAST), is a new promising method conia restorations have become increasingly popular as a result of
for very fast sintering leading to homogeneous and crack-free advances in CAD/CAM technology. There are 2 types of monolithic
microstructures [46] with very limited porosity and high trans- zirconia materials; opaque and translucent zirconia. Opaque zir-
4
Table 1
Studies investigating the strength of monolithic zirconia crowns. Studies are presented in ascending chronological order.
Authors Zirconia system Test type/Methodology Results

a
Beuer et al. (2012) [67] - Zirluna Fracture strength, molar crowns, loading in Higher strength of monolithic compared to
chewing simulator, crosshead-speed veneered zirconia
0.5 mm min−1 .
Zhang et al. (2012) [68] - Lava Chipping test (Vickers) on zirconia and Chipping resistance: glass-infiltrated
- In-Ceram Zirconia YZ glass-infiltrated monolithic zirconia molar monolithic zirconia crowns comparable to
crowns monolithic zirconia and significantly higher
compared to veneered zirconia crowns
Sun et al. (2014) [69] - Lava Frame (MZC) Axial load, molar crowns of varying occlusal MZC exhibited higher fracture loads than MLC,
thickness (0.6–1.5 mm), crosshead speed of LZC and MCC. The fracture resistance of MZC
0.5 mm min−1 . (1.0 mm) was equal to MCC. Doubling the
- IPS e.max Press (MLC) Cementation with resin cement monolithic zirconia core from 0.6 mm to
- Layered zirconia crowns (LZC) 1.5 mm increased the fracture resistance
- Metal ceramic crowns (MCC) system threefold.
E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

Nakamura et al. (2015) [70] - Lava Plus Fracture strength, molar crowns cemented to The occlusal thickness significantly affected
composite dies, crosshead-speed 0.5 mm min−1 the fracture load, but not the axial thickness.
Higher strength compared to monolithic
lithium disilicate crowns.
Zhang et al. (2016) [71] - Lava Plus Fracture strength, molar crowns cemented to The stiffer and stronger zirconia and lithium
composite dies, crosshead-speed 0.1 mm disilicate crowns afforded superior stress
min−1 . shielding of the tooth interior and inhibited
crack initiation
Sorrentino et al. (2016) [72] - Aadva Fracture test, axially loaded molar crowns of The occlusal thickness did not influence the
various thicknesses (0.5, 1, 1.5 and 2 mm), fracture resistance and the mode of failure of
crosshead speed 1 mm min−1 the restorations.
Schriwer et al. (2017) [73] Soft machined - Bruxzir Fracture strength, axially loaded premolar The hard-machined Y-TZP crowns had the best
- ICE Zirkon crowns from hard and soft machined zirconia margin quality and the highest load at fracture.
- DD Bio ZX2 ceramics, crosshead speed 0.5 mm min−1 The BX and the PZ group had statistically
−
NobelProcera significant weaker load at fracture than the
Hard machined: - Denzir Y-TZP other groups. Margin defects affected
- Denzir Mg-PSZ negatively the load at fracture.
Rohr et al. (2018) [74] - VITA YZ T Fracture strength, implant supported For uncemented crowns the initial fracture
monolithic crowns, crosshead speed initiated from the internal surface, for
1 mm min−1 cemented crowns from the loading point. VITA
- VITA In-Ceram AL VITABLOCS Crowns cemented with temporary, adhesive YZ T presented the highest flexural strength
- Mark II VITA ENAMIC dual-cured cements cement and self-adhesive and fracture strength. Increased compressive
- IPS e.max CAD dual-cured cement. strength of the cement was correlated to high
fracture toughness, but not for monolithic
zirconia.
Tsuyuki Y et al. (2018) [75] - Adamant, Tokyo, Japan Fracture strength, crosshead speed The presence of an occlusal groove decreased
1 mm min−1 . fracture strength but to a smaller degree when
Different types of abutments fabricated with resin cement was used. The use of glass
different depths of occlusal groove or ionomer cement was associated with lower
abscesnce of groove. Evaluation of the effects fracture strength.
of abutment morphology, crown thickness and
cement type.
Moilanen et al. (2018) [76] - PSZ Prettau Fracture strength, 45◦ angle to the long axis, Cementation of the crown on a titanium base
crosshead speed 1 mm/min. was correlated to higher fracture strength
- FSZ Prettau Anterior A titanium base on the implant surface was compared to direct cementation on the
evaluated with regard to its effect on the implant’s surface.
monolithic crown’s fracture strength.
a
The composition of the materials presented in this and all the tables in the manuscript are presented in Table 5.
Table 2
Studies investigating mechanical properties of monolithic zirconia specimens. Studies are presented in ascending chronological order.
Zhang et al. (2013) [106] Experimental monolithic zirconia Chipping (Vickers) and flexural strength (3- and 4- point Monolithic restorations exhibited superior
bending, specimens cemented on composite), crosshead fracture resistance relative to their
speed 1 mm min−1 porcelain-veneered counterparts and
higher resistance to failure than lithium
disilicate glass–ceramics
Basso et al. (2015) [108] - IPS e.max ZirCAD Flexural strength (3-point bending), monolithic and No significant differences between
trilayer (zirconia core, fusion glass, veneer) specimens, monolithic and trilayer structures
crosshead-speed 0.5 mm min−1 .

Sulaiman et al. (2015) [100] - Prettau (PSZ) Biaxial strength test (piston-on-three balls), Unstained PSZ had significantly higher
crosshead-speed 1 mm min−1 . strength than unstained FSZ. After staining
both had similar strength.
- Prettau, Anterior (FSZ)
Schatz et al. (2016) [114] - Ceramill Zolid (C) Biaxial, 3-point, and 4-point flexural strength testing, No significant difference among the
crosshead speed 1 mm min−1 different ceramics.
- Zenostar Zr (Z) The 4-point flexural strength testing shows
the lowest flexural strength data; biaxial
test method the highest.
- DD Bio ZX2
Tong et al. (2016) [97] - Zpex (High-Translucency) Fracture toughness test (edge chipping), Vickers hardness High-strength Y-TZP exhibited the best
test and flexural strength test (4-point bending) of and high-translucency the worst
specimens, crosshead-speed 0.1 mm min−1 . mechanical properties. The opposite was
for the translucency.
- TZ-3YS-E (High-Strength)
- TZ-3Y-E (High-Surface Area)
Vichi et al. (2016) [104] - IPS e.max Zir-CAD Flexural strength (3-point bending test), crosshead-speed The new “augmented translucency” TZPs
1 mm min−1 . (VITA In-Ceram YZ HT and inCoris TZI)
specimens showed higher translucency
and similar flexural strength than
“traditional” TZPs.
- inCoris ZI
- inCoris TZI
- In-Ceram YZ
- In-Ceram YZ HT
Zhang et al. (2016) [102] - TZ-3YE Flexural strength (4-point bending), crosshead speed Increasing the yttria content decreased the
1 mm min−1 , hardness (Vickers indentation), toughness fracture toughness and flexural strength
(Single-etchV-notch beam) but increased resistance to aging. The
addition of La2 O3 decreased the flexural
strength but did not influence hardness
and toughness.
- Zpex
- Zpex Smile
- Experimental monolithic 1
- Experimental monolithic 2
5
6
Table 2 (Continued)
Carrabba et al. (2017) [103] - Aadva Standard Translucency [ST] Flexural strength (3-point bending), crosshead-speed There was an inverse relationship between
1 mm min−1 . strength and translucency for the materials
tested. Addition of Al2 O3 and increased
yttria content strongly downgraded the
mechanical properties.
- Aadva Enamel Intensive [EI]
- Aadva Natural Translucency [NT]
Chougule et al. (2017) [112] Lava Flexural strength (3-point bending test), crosshead-speed Flexural strength was significantly higher
of 0.5 mm min−1 . after glazing but not after polishing.
Church et al. (2017) [64] BruXZir Shaded 16 Flexural strength (3-point bending), crosshead-speed of The flexural strength of highly translucent
1 mm min−1 . zirconia materials was significantly higher
than those of lithium disilicate. No
statistically significant differences among
the various monolithic ceramics were
recorded.

BruXZir HT
Lava Plus
inCoris TZI C
Elsaka et al. (2017) [98] - Ceramill Zolid FX Flexural strength (3-point bending test), crosshead-speed ZT monolithic zirconia revealed higher
0.5 mm min−1 , fracture toughness (3-point bending test), flexural strength and fracture toughness
crosshead speed 0.5 mm min−1 , Vickers hardness compared with CZF and PA
- Multilayer (CZF) CZF revealed higher hardness compared
with PA and ZT.
- Prettau Anterior (PA)
- Zenostar T (ZT)
Munoz et al. (2017) [99] - Prettau Anterior Biaxial flexural strength, crosshead-speed 1 mm min−1 Pretatu Anterior presented the lowest
strength which was significantly reduced
by mechanical and thermomechanical
cycling
- Prettau Hydrothermal degradation; mechanical cyclic load;
mechanical cyclic plus hydrothermal degradation (H + M);
non-treated specimens (control group).
- ICE Zirkon
Ozer et al. (2017) [110] - Pretau Biaxial flexural strength (piston-on-three balls strength), Statistically higher strength of the thicker
crosshead-speed 0.5 mm min−1 specimens, but both had higher than the
reported masticatory forces
Airborne-particle abrasion increased the
flexural strength of monolithic zirconia.
Grinding did not affect flexural strength if
subsequently polished
Disc specimens of 0.8 and 1.3 mm :
- untreated (control)
- airborne-particle abrasion
- grinding with a diamond rotary instrument followed by polishing.
Sulaiman et al. (2017) [101] - Prettau Flexural strength (3-point bending), crosshead-speed The strength of FSZ was approximately half
0.5 mm min−1 . that of PSZ. Staining enhanced the strength
of FSZ, with no effect on PSZ.
Airborne-particle abrasion lowered the
strength of FSZ, while enhanced that of
PSZ. Artificial aging had no effect on the
flexural strength of either.
- Prettau, Anterior
- ICE Zircon
Kumchai et al. (2018) [111] - inCoris TZI Flexural strength (3-point bending test), crosshead-speed Overglazing significantly decreased the
of 0.5 mm min−1 . flexural strength.
Table 2 (Continued)
- Prettau - heat treated (glazed with no paste) Heat treatment had no significant effect on
the flexural strength. There was no
significant difference in the flexural
strengths of different brands
- Zirlux FC - overglazed (use of glaze paste)
Two different glaze materials:
- Zirkonzahn glaze paste + liquid
- Zirlux FC glaze paste + liquid
Sakai et al. (2019) [109] - translucent TZP (Zpex, Tosoh) Biaxial flexural strength, Monolithic zirconia materials of Flexural strength was not affected

different tranclucencies were adhered and evaluated as a negatively.
method for more accurate colour simulation.
- high- translucency PSZ (ZpexSmile,
Tosoh)
Reis et al. (2019) [80] Vita In Ceram YZ Nano-indentation (hardness evaluation), pulse-echo Silica infiltration increased the hardness
(elastic modulus), scratch test but reduced the fracture toughness.
Adhesion of feldspathic porcelain to
non-infiltrated zirconia proved to be
stronger
- monolithic zirconia
- silica infiltrated monolithic zirconia(via
the sol-gel method)
- zirconia + feldspathic porcelain of two
thicknesses
- silica infiltrated zirconia + feldspathic
porcelain of two thicknesses
Juntavee et al. (2018) [96] Y-TZP, VITA YZ HT color® Flexural strength (3-point bending), crosshead speed Increasedsintering temperature and
1 mm min−1 prolonged sintering holding time was
correlated with higher flexural strength
Sintering at different temperatures: Sintered holding times:
- decreasing - shortening
- regular - regular
- increasing - prolonged
Yan et al. (2018) [107] dental zirconias (the Luxisse series) Flexural strength (piston-on-three balls) ceosshead speed The load-bearing capacity of the lithium
1 mm min− 1, specimens bonded to a dentin-like substrate disilicate ceramic presented higher values
than 5Y-TZP.
- 5Y-PSZ
- 4Y-PSZ
- 3Y- TZP (control)
IPS e.max CAD
Candido et al. (2018) [105] - Prettau Zircon Flexural strength (four-point bending) crosshead speed Flexural strength did not present
1 mm min−1 significant difference between monolithic
and conventional zirconia.
- ICE Zirkon Transluzent
- BloomZir
7
8
Table 2 (Continued)
Nishioka et al. (2018) [81] - Feldspathic ceramic (VITABLOCS Mark II) Flexural strength (piston-on-three balls) under water The highly translucent polycrystalline
(staircase approach :100,000 cycles at 10 Hz) zirconia can withstand a higher cyclic load
before failure
- Polymer-infiltrated ceramic network
(VITA Enamic)
- Zirconia-reinforced lithium silicate
glass-ceramic (VITA Suprinity)

- Lithium disilicate glass-ceramic (IPS
e.Max CAD)
- High translucent yttrium partially
stabilized tetragonal zirconia polycrystals
(Zirconia YZ HT)
Ozer et al. (2018) [86] Prettau Flexural strength (piston-on-three balls), crosshead speed 1.3 mm specimens presented significantly
0.5 mm min−1 (disks of thickness 0.8 mm and 1.3 mm) higher flexural strength. Airborne-particle
abrasion significantly increased the
flexural strength. Grinding and polishing
didn not affect the flexural strength
- airborne-particle abrasion, 50-mmAl2 O3 particles
(pressure of 400 kPa, distance of 10 mm)
- grinding with a diamond rotary instrument followed by
polishing
- control
Ebeid et al. (2018) [95] Bruxzir Biaxial flexural strength (piston-on-three balls), crosshead Surface treatment at the pre-sintered was
speed 0.5 mm min−1 correlated with higher flexural strength
- air-abrasion with Al2 O3 50 mm particles
- silica coating with 30 mm Rocatec soft particles
- control (no surface treatment)
- the surface treatments were performed either at the
pre-sintered stage or the post-sintered stage
Zucuni et al. (2017) [115] Zenostar blank Flexural strength (piston-on-three balls), fatigue tests -polishing after grinding is mandatory in
included 20,000 cycles and a frequency of 6 Hz order to avoid strength deterioration
- control - heat treatment is not a good alternative
to polishing
- grinding - polishing enhances fatigue
- polishing
- glazing
- heat treatment
- polishing + heat treatment
- polishing + glazing
conia offers significantly greater flexural strength and is indicated strength of monolithic zirconia crowns increased after treatment
for the posterior regions of the mouth, while translucent zirconia with polishing burs and polishing can reduce the monoclinic phase.
has the more natural esthetic appearance but lower mechanical Several studies have evaluated the fracture resistance of mono-
properties. The presence of cubic zirconia in translucent composi- lithic zirconia crowns retained by implants. According to Moilanen
tions is responsible for the enhanced optical properties; however, et al. [76], the fabrication technique of monolithic zirconia implant-
a significant reduction of the mechanical properties is a conse- retained crowns using a prefabricated titanium base led to crowns
quent drawback. The mechanical strength of monolithic zirconia with superior strength to static mechanical testing compared to
was evaluated in many studies, depicted in the following tables crowns fabricated directly on the implant surface. According to
(Tables 1 and 2). Rohr et al. [74], the use of resin cements with high compressive
Concerning fracture resistance of monolithic zirconia crowns, a strength was found to be correlated linearly to fracture resistance
clear superiority exists for full-contour monolithic crowns, even and flexural strength of implant-supported monolithic zirconia
if they are glass-infiltrated [68], compared to veneered bilayer crowns. Elshiyab et al. [90] proved that after 5 years equivalent
[67,77,78] and lithium disilicate crowns [69–71,79]. Reis et al. [80], chewing simulation, implant retained monolithic zirconia crowns
used the sol-gel method to infiltrate zirconia surfaces with silica survived, although their resistance to fracture had decreased.
in order to eliminate veneering ceramic delamination. This proce- The effect of grinding and polishing on monolithic zirconia
dure only enhanced the structural homogeneity and hardness of restorations has been evaluated by a few studies. In the study
monolithic zirconia, but it reduced its fracture toughness. of Khayat et al. [91], grinding was found to increase the sur-
After cyclic loading, high translucency tetragonal zirconia face roughness of monolithic zirconia and decrease the flexural
demonstrated the higher fatigue strength among a feldspathic strength. However, polishing after grinding leads to the preserva-
ceramic, a polymer-infiltrated ceramic network, a lithium dis- tion of the flexural strength. The authors suggest that monolithic
ilicate glass-ceramic and a zirconia-reinforced lithium silicate zirconia’s mechanical strength can be compromised when zirconia
glass-ceramic [81]. According to Pereira et al. [82], third generation surfaces are left rough leading to higher susceptibility to aging. The
ultra-translucent monolithic zirconia materials present no trans- monolithic zirconia ceramic evaluated was not compromised by
formation toughening when aged as well as significantly inferior grinding and low-temperature degradation and both thicknesses
mechanical properties. All fractures started from surface defects tested maintained acceptable mechanical strength [92]. Polishing
on the tensile surface. High-translucency monolithic zirconia has a after grinding was determined mandatory in order to prevent crack
reduced bi-axial flexural strength compared to conventional zirco- propagation and to enhance the material’s fatigue [93]. A 2nd gen-
nia, but it is appropriate for clinical us [83]. According to Camposilva eration zirconia ceramic was submitted to grinding and artificial
et al. [84], translucent zirconia presents significantly lower tough- aging to assess its fatigue strength and survival rates and it was
ness and strength compared to conventional zirconia ceramics and found that its properties were not compromised [94].
it should be considered carefully for clinical application. In order to evaluate sintering parameters for monolithic zir-
The occlusal thickness of the crown has shown to be correlated conia, specimens were submitted to air-borne particle abrasion
to fracture [69,70], as well as the presence of an occlusal groove and silica coating in the pre-sintered stage and this led to higher
[75]. Monolithic zirconia crowns cemented on abutments with an biaxial flexural strength. Thus, surface pre-treatment in the pre-
occlusal groove presented lower fracture resistance compared to sintered stage of monolithic zirconia might be beneficial to the
crowns cemented on abutments with flat occlusal surfaces [75]. final restoration’s strength [95]. Juntavee et al. [96] studied the
Sun et al. [69], reported a threefold increase from 0.6 to 1.5 mm, effect of sintering temperature and duration alterations and proved
but on the contrary, Sorrentino et al. [72] did not find any sig- that high sintering temperature combined with long sintering time
nificant correlation. It has recently been reported by Weigl et al. attribute higher flexural strength and hence translucent monolithic
[85], that monolithic zirconia crowns with a thickness of 0.5 mm zirconia restorations with higher strength.
ensure acceptable strength regardless of the type of cementation, Based on the majority of the studies included in Table 2, it can
following in-vitro cyclic loading to simulate the clinical function be concluded that high translucent specimens of zirconia ceramics
of the restoration. However, thickness of 0.2 mm was too low to with yttrium content >3 mol% present significantly lower strength
establish predictability, regardless of cement type. Ozer et al. [86] compared to the partial stabilized 3 mol% Y-TZP ones (Fig. 2)
suggest that thickness between 0.7 and 1.3 mm are ideal for the fab- [97–103]. However, translucent zirconia ceramics with 3 mol% Y-
rication of monolithic zirconia restorations and air-borne particle TZP presented similar strength compared to conventional 3 mol%
abrasion enhances the materials flexural strength, whereas grind- Y-TZP ceramics [64,104]. In addition, Candido et al. [105] reported
ing and polishing did not influence the material’s strength. Schriwer that the monolithic zirconia tested showed similar flexural strength
et al. [73] investigated the strength of hard machined versus soft to a conventional zirconia ceramic. All monolithic zirconia spec-
machined premolar crowns and resulted that the hard-machined imens presented higher strength compared to lithium disilicate
Y-TZP crowns had the best margin quality and the highest load ones [64,106], although this is not in agreement with a recent study
at fracture, pointing out the significance of good marginal fit for by Yan et al. [107] who reported that when bonded on a dentin-like
higher performance. Sarikaya et al. [87] reported that Bruxzir and substrate, lithium disilicate presented higher load-bearing capac-
Incoris TZI monolithic zirconia systems present acceptable resis- ity compared to an ultra-translucent 5Y-PSZ ceramic. Compared
tance to fracture for the fabrication of monolithic crowns when to veneered specimens one study reported higher strength for
tested at physiologic mastication forces. Overall, several studies bilayer [106] and another similar strength for trilayer specimens
have concluded that high translucency cubic zirconia presents [108]. Sakai et al. [109] reported that layering zirconia of various
significantly lower mechanical properties due to the absence of translucencies with resin cement between the layers is a method
transformation toughening mechanism and this can compromise that improves the optical properties of the restoration while main-
their use in clinical cases where high loads are applied [84,88]. An taining the flexural strength of the monolithic zirconia ceramic.
increase of yttrium oxide percentage in zirconia ceramics can lead Sulaiman et al. [100,101] investigated the effect of staining on
to a reduction of the mechanical strength, but only following arti- partially and fully stabilized zirconia specimens and reported a sig-
ficial aging [88]. However, even the high-translucency materials nificant increase of strength for fully stabilized monolithic zirconia
demonstrate fracture strength acceptable for clinical application ceramics. Air-borne particle abrasion had a positive effect on the
exceeding 3000 N [88]. According to Yin et al. [89], the fracture strength of partially stabilized but a detrimental effect to fully sta-
bilized zirconia specimens [100,110], while glazing had either no
Fig. 2. Graphical summary with the major findings of this review regarding strength and aging resistance of high translucency zirconia ceramics.
effect [111] or positive effect [112] on partially stabilized zirconia even after the significant amount of m-ZrO2 present on their surface
specimens. According to Nam et al. [113], glazing of translucent (Table 5).
monolithic zirconia plates led to a significant reduction in flexural Guilardi et al. [123] examined the effects of grinding and low
strength, whereas low-temperature degradation did not present temperature aging on flexural strength, roughness, and phase
any significant effects. transformation of Y-TZP ceramics. Grinding increased significantly
the characteristic strength and affected positively the material’s
3.1. Aging resistance sensitivity to the tetragonal to monoclinic phase transformation
during aging, a transformation which was less for the fine ground
Aging resistance of monolithic zirconia restorations is a fun- specimens. Exactly the same results came from the study of Pereira
damental property as the whole surface is exposed to aggressive et al. [124]. On the other side, Khayat et al. [91] reported that
oral conditions. The aging behavior of zirconia is generally inves- grinding alone can significantly increase roughness and make the
tigated through an accelerating aging test in an autoclave [116]. material more prone to aging, however they did not investigate
According to theoretical calculations, 1 h at 134 ◦ C corresponds to the effect of aging on the strength of rough grinded specimens.
3–4 years in-vivo. By this, 10 h of in-vitro aging, have theoretically Polishing after grinding, however, significantly reduced roughness.
the same effect as a restoration in the oral cavity for 30–40 years, Although boiling in artificial saliva for 7 days increased monoclinic
which is a more than sufficient lifespan for a fixed partial denture fraction from 2.4% to 21%, the increase was superficial and there
(FPD). Despite the criticism that this test does not correspond to was no reduction in strength, but in some ceramics, an increase
actual clinical conditions and that it may underestimate the actual was recorded instead [118]. The flexural strength was not affected
degradation of zirconia ceramics in the oral environment [117], it by the amount of monoclinic fraction on the surface. Dehestani
still remains an efficient method to estimate the long-term perfor- and Adolfsson [125] found no significant change in strength after
mance of these materials. Other tests include boiling in hot water immersion in boiling water up to 6 months, although a significant
or artificial saliva, mechanical cyclic loading, thermocycling, and amount of monoclinic fraction was recorded after 32 days (50% for
combinations of mechanical and thermal fatigue. 3 Y-TZP monolithic ceramics). On the recent study of Pereira et al.
Autoclave aging has been correlated to no significant change [82], three different translucencies of monolithic zirconia ceramics
in strength [84,118,119], as well as to significant decrease and were evaluated following autoclave aging at 134 ◦ C under pressure
increase depending on time of treatment, brand and composition of 2 bars pressure for 20 h and it was reported that the high translu-
[120,121] of the zirconia system investigated (Tables 3 and 4). cency system presented a significant increase in flexural strength
Comparing 3 mol% Y-TZP ceramics with translucent monolithic as well as increased monoclinic phase percentage, compared to
ceramics of higher yttrium amount [101,121,122], significantly the super- and ultra-translucency systems. Another recent study’s
higher resistance to aging degradation was recorded for the new findings, in which monolithic zirconia specimens were submitted
generation translucent ceramics, but only after prolonged aging to fatigue strength test, have shown that ground specimens pre-
[84,121]. This is not in agreement with Almansour et al. [83], whose sented higher fatigue strength, whereas ground specimens which
study found significant differences in several monolithic zirconia were submitted to autoclave aging presented lower percentages of
systems following shorter periods of aging. In a recent study [121], monoclinic phase [94]. This is in agreement with previous findings
the monoclinic phase fraction increased remarkably between 5 from Prado et al. [92].
and 50 h of aging, especially for Prettau and BruxZir, and less for Concerning the effect of steam autoclave aging on molar crowns’
Katana ML and Katana HT13. The aged specimens had a detectable strength, significant reduction of strength up to 50 h of autoclave
layer of transformed material which reached 6̃0 ␮m in Prettau and treatment has been reported [126] and no further reduction after-
BruxZir and less than 5 ␮m in Katana ML and HT13. Although sig- wards, while Leone et al. [127] reported significant reduction after
nificant differences were recorded, these exceedingly long periods 54 h of autoclave treatment only for the 3 mol% Y-TZP, and no
of accelerating autoclave treatment (usually after 10 h) are beyond change for the ultra high translucent zirconia, which however pre-
the clinical lifespan of a restoration. In the other three studies sented the lowest mechanical properties. On the other hand, in
[99,101,122] investigating the ultra-translucent Pretau Anterior other studies [120,128], no significant difference among various
zirconia, no significant differences in strength were recorded after brands of 3–5 mol% Y-TZP monolithic zirconia crowns was found,
8 h of steam autoclave treatment in two of the studies [101,122] even after 50 h of aging [120,126]. Although limited evidence exists
and significant reduction in one studies [99]. Similarly, no signifi- concerning ultra high translucent ceramics, they seem to present
cant change in strength was recorded in another study [84], neither a high resistance to degradation, but lower mechanical strength
for 3 mol% nor for 5.5 and >6 mol% translucent zirconia ceramics, [127].
Table 3
Studies investigating mechanical properties of monolithic zirconia specimens/crowns after hydrothermal aging (steam autoclave and boiled water/artificial saliva). Studies are presented in ascending chronological order.
Authors Zirconia system Test type /Aging test Flexural strength change m-ZrO2 content
Specimens
− 5.3 mol% Y2 O3
Alghazzawi et al. (2012) [118] Flexural strength No significant change Control = 2.4 ± 0.6%
(piston-on-three balls),
crosshead-speed 1 mm min−1
Boiled: 100 ◦ C, 7 days, artificial Aged = 21.0 ± 2.0%
saliva
- 3Y-TZP
Dehestani and Adolfsson (2013) Flexural strength (4-Point No significant change. 3Y-TZP Values cannot be extrapolated.
[125] Bending) containing materials showed the 12Ce-TZP: almost no change in
- 3Y-TZP/Al2 O3 Aging in water at 90 ◦ C for 2, 4, and highest strength m-ZrO2 , 10Ce-TZP: m-ZrO2 up to
- 12Ce-TZP/Al2 O3 6 months 90% and 3Y-TZP: m-ZrO2 5̃0% after
- 10Ce-TZP /Al2 O3 32 days.

All composites had
70/30 vol
zirconia/alumina
Adabo et al. (2015) [122] - ICE Zirkon Flexural strength No significant change No values are reported, however all
(piston-on-three balls), specimens presented increase
- Prettau Steam autoclave: 120 ◦ C, 2 kg/cm2 ,
- Prettau Anterior 8h
- Lava Plus (Lav)
Alghazzawi et al. (2015) [120] Flexural strength (3-point Coupons: N/A
bending), crosshead speed
0.5 mm min−1
- Argen HT (Arg) Steam autoclave: 134 ◦ C, 0.2 MPa, - increase for Arg, Zir and Zen
- Zirlux (zir) 50 hours - no significant change for Lav,
- BruxZir (Bru) Brux and DDB
- Zenostar (Zen)
- DDBioZX2 (DDB)
Pereira et al. (2016) [124] - Zirlux FC Flexural strength Significant increase of Before aging After aging
(piston-on-three balls), characteristic strength for control,
grinded specimens (diamond no significant change for the rest
burs, water cooling), crosshead
speed 1 mm min−1
Steam autoclave: 134 ◦ C, 2 bars, Control 0% 67.97%
20 h Fine grinded 9.49% 38.74%
Coarse grinded 9.66% 42.76%
- Zenostar
Stawarczyk et al. (2016) [119] Flexural strength (4-Point No significant change. All N/A
Bending), crosshead-speed monolithic showed lower flexural
1 mm min−1 strength values compared to the
- DD Bio ZX2 Steam autoclave: 134 ◦ C, 2.3 bars, 5 conventional zirconia.
- Ceramill Zolid h
- InCoris TZI
- Ceramill ZI
Flinn et al. (2017) [121] - Prettau Flexural strength (4-point Significant reduction only for Before aging (%) After aging for 200h (%)
bending), crosshead speed Prettau and BruxZir
0.5 mm min−1
- BruxZir Steam autoclave: 134 ◦ C, 0.2 Mpa, Prettau 2.90 ± 0.34% 76.1 ± 0.64%
- Katana HT13 5, 50, 100, 150, and 200 h BruxZir 2.69 ± 0.18% 76.0 ± 0.26%
- Katana ML Katana HT 4.6 ± 0.19% 35.8 ± 0.80%
Katana ML 3.57 ± 0.35% 33.2 ± 1.1%
11
12
Table 3 (Continued)
Guilardi et al. (2017) [123] - InCeram YZ Flexural strength No significant change. Grinding Before aging (%) After aging (%)
(piston-on-three balls), fine affected positively the material’s
and coarse grinded specimens aging sensitivity.
(diamond burs under water
cooling), crosshead speed
1 mm min−1

Steam autoclave: 134 ◦ C, 2bars, 20 Control 0 ± 0.0 76.1 ± 0.64
h Fine grinding 9.70 ± 0.89 24.42 ± 3.45
Coarse grinding 13.07 ± 1.5 40.94 ± 1.61
Khayat et al. (2017) [91] Tizian Blank Translucent Flexural strength Grinding significantly increased N/A
(piston-on-three balls), roughness and decreased strength.
crosshead-speed 0.5 mm min−1 Grinding and polishing had no
Steam autoclave: 134 ◦ C, significant effect on flexural
200 kPa, 3 h strength. Rough zirconia was more
Specimens were: prone to aging.
- grinded
- grinded and polished
(polishing kit 1)
- grinded and polished
(polishing kit 2)
- glazed
Munoz et al. (2017) [99] - Prettau Anterior Flexural strength Significant difference for Pretau Prettau Anterior Pretau ICE Zirkon
(piston-on-three balls), Anterior, but not for the others
- Prettau Steam autoclave: 134 ◦ C, 0.2 MPa, 0% 39.71% 24.89%
- ICE Zirkon 8h
Sulaiman et al. (2017) [101]- Prettau (PSZ) Flexural strength (3-point No significant effect of either FSZ or N/A
bending test), crosshead speed PSZ
0,5 mm min−1 .
- Prettau Anterior Steam autoclave: 125 ◦ C, 200 kPa,
(FSZ) 8h
- ICE Zircon (PSZ)
- Aadva ST
Camposilvan et al. (2018) [84] Flexural strength No significant change Arithmetic values cannot be
(piston-on-three balls) extrapolated from the graph. NT
- Aadva EI Steam autoclave: 134 ◦ C, 2 bar, 0, 2, and ML showed no transformation
- Aadva NT 6, 18, 54 h at all, while ST and EI presented
- Katana UT high amounts of m-ZrO2 (4̃5%)
Table 3 (Continued)
Crowns
Alghazzawi et al. (2015) [120] - Lava Plus (Lav) Fracture toughness, axially - no significant effect N/A
oriented molar crowns,
crosshead speed 0.5 mm min−1
-Argen HT (Arg) Steam autoclave: 134 ◦ C, 0.2 MPa,
- Zirlux (zir) 50 hours

- BruxZir (Bru)
- Zenostar (Zen)
- DDBioZX2 (DDB)
Nakamura et al. (2015) [126] Lava Plus Fracture toughness, axially Significant decrease up to 50 h 70% after 50 h of aging and no
oriented molar crowns, of aging and no change increase thereafter
crosshead speed 0.5 mm min−1 thereafter.
Combination of cycling loading Cycling loading had no effect on
(50, 300 N, 240,000 cycles, strength.
water) and autoclave
treatment for 100 h
Steam autoclave: 134 ◦ C,
0.2 Mpa, 0, 10, 50, 100 h
Bergamo et al. (2016) [128] - Ceramill Zolid Fracture test, molar crowns: No significant change Control: 4%
axial load, crosshead-speed
1 mm min−1
Steam autoclave: 122 ◦ C, 2 bars, Steam autoclave:
1h up to 4.5%
Leone et al. (2016) [127] - GC Initial Zr: Flexural strength Significant change for ST. The No values are reported, complete
(piston-on-three balls), presence of glaze had a protective absence of hydrothermal
crosshead-speed 1 mm min−1 effect. The mechanical properties degradation for UHT.
Ultra high steam autoclave 134 ◦ C, 2 bars, for of cubic crowns (UHT) were lower
translucency (UHT) 2, 6, 18 and 54 h than for tetragonal ones.
High translucency
(HT)
Standard
translucency (ST)
Prado et al. (2017) [92] Zirlux FC Flexural strength, crosshead Low temperature degradation led control group:
speed 1 mm min−1 to an increase in flexural strength 58.17%
Aging: Grinding with extra-fine ground samples:
diamond burs (grit size 30 ␮m) 9.25%
under constant water-cooling,
autoclave storage at 134 ◦ C / 2 bar /
20h
13
14
Table 3 (Continued)
ground + low
temperature
degradation: 16.13
Pereira et al. (2018) [82] Katana YSZ Flexural strength (piston-on-three No significant change for STML - Increase for ML
ceramics used: balls), crosshead-speed and UTML.
– ML/HT 1 mm min−1 , step stress fatigue Significant increase for ML. - No impact on STML and UTML
- STML approach, autoclave aging at 134 ◦ C

- UTML / 2 bars pressure/20 h
Almansour et al. (2018) [83] - Lava Plus HT Flexural strength (piston-on-three before: Ceramill ZI Not evaluated
balls), crosshead-speed (935.3 ± 47.1 MPa)>Copran Zr-i
0.5 mm min−1 , fatigue (chewing Monolithic HT
simulator with 250,000 cycles / (847.8 ± 20.7 MPa)>Lava Plus
frequency of 1.6 Hz / load of 200 N), (732.4 ± 25.5 MPa)>Ceramill
accelerated artificial aging at 3500 Zolid White (685.7 ± 32.6 MPa)
- Ceramill Zolid cycles (two water baths, 5 ◦ C and after: Copran Zr-i Monolithic HT
White HT 55 ◦ C. 60 sec per cycle in 5 ◦ C bath, (777.5 ± 21.2 MPa)>Ceramill ZI
- Copran Zr-i 10 sec to transfer samples to 55 ◦ C (668.0 ± 20.1 MPa)>Lava Plus
Monolith HT bath, 20 seconds in 55 ◦ C bath and (666.4 ± 21.1 MPa)>Ceramill Zolid
- Ceramill ZI-LT 10 seconds to transfer back to 5 ◦ C White (575.0 ± 36.3 MPa)
bath
Dapieve et al. (2018) [94] - Zirlux FC2 Flexural strength, step-stress Fatigue strength change: aging Before aging: Control Autoclaved
fatigue, 20 Hz and minimum increased the fatigue strength for samples: 56.75%, Ground + Autoclaved:
stress of 10 MPa, 5000 cycles ground groups, it did not affected 30.63%
under 200 MPa + incremental the as-sintered groups
steps of 25 MPa for 10,000
cycles from 400 MPa to
complete failure
- Ardent Aging protocol: Grinding with After: Control Autoclaved: 75.27%.
coarse diamond burs (#3101 G Ground + Autoclaved: 40.14%
– grit size 181 ␮m) in a
slow-speed motor under
constant water-cooling
(≈30 mL/min). Dry storage in
sealed vessel for 2 years (mean
temperature of 27 ◦ C and mean
humidity of 80% + autoclave
LTD / 134 ◦ C / 2 bar / 20 h
Table 4
Studies investigating mechanical properties of monolithic zirconia specimens/crowns after cycling loading, mechanical loading and various combinations of thermomechanical loading. Studies are presented in chronological
order.
Specimens
Salihoglu-Yener et al. -ZirkonZahn Flexural strength (piston-on-three balls), Significant decrease only of unglazed zirconia. N/A
(2015) [129] crosshead-speed 1 mm min−1 ZirkonZahn presented the highest strength
- Cercon Thermal cycling (0-control, 1000, 3000, 5000 with or without thermal cycling.
– Ceramill cycles, 5-55 ◦ C, water).
Stawarczyk et al. - Zenostar Flexural strength (4-Point Bending), No significant change. All monolithic showed N/A

(2016) [119] crosshead-speed 1 mm min−1 lower flexural strength values compared to the
- DD Bio ZX2 Chewing simulator (100 N for 1.2 million times conventional zirconia.
- Ceramill Zolid at 1.64 Hz)
- InCoris TZI
- Ceramill ZI
Munoz et al. (2017) [99] - Prettau Anterior Flexural strength (piston-on-three balls), Significant reduction after M and H + M for
crosshead-speed 1 mm min−1 Pretau Anterior. Significant reduction after M
- Prettau - mechanical cyclic load (M) for the rest. Anterior zirconia had the lowest
- ICE Zirkon - mechanical cyclic + hydrothermal (H + M) flexural strength
-non-treated specimens (C).
Crowns
Johansson et al. (2014) - Z-CAD HTL Flexural strength after thermocycling (5000 The fracture strength of high translucent Y-TZP N/A
[78] - NexxZr HT cycles, 5–55◦ , water), molar crowns, crowns is considerably higher than that of
- Z-CAD HTL-veneered crosshead-speed 0,025 mm min−1 . porcelain-veneered Y-TZP crown cores,
- NexxZr HT- veneered porcelain-veneered high translucent Y-TZP
- NexxZr HS-veneered crown cores and monolithic lithium disilicate
crowns.
Lameira et al. (2015) - Lava Plus for monolithic crowns Fracture strength, crowns (on bovine incisors) Monolithic crowns (polished and glazed) N/A
[77] - Lava Frame for bi-layer crowns after thermocycling (2,500, 000 cycles, 80 N, presented higher fracture strength than bilayer
37 ◦ C, artificial saliva) and loading in chewing veneered crowns. No difference between
simulator, crosshead-speed 0.5 mm min−1 . polished and glazed monolithic crowns.
Nordahl et al. (2015) - Lava Fracture toughness, 10◦ angulated molar Absence of non-aged specimens. There was no N/A
[131] crowns of varying thicknesses: 0.3, 0.5, 0.7, 1.0, difference in strength between crowns of high-
and 1.5 mm, crosshead-speed 0,025 mm min−1 or low-translucency. The load at fracture
- Lava Plus Thermocycling of crowns (5000 cycles, 6-55 ◦ C, decreased from thicker to thinner
water)
Bergamo et al. (2016) - Ceramill Zolid Fracture test, molar crowns,crosshead-speed No significant change Control: 4%
[128] 1 mm min−1
- Thermal fatigue (T): 104 cycles, 5–55 ◦ C Thermal fatigue:up to 4.5%
- Mechanical fatigue (M): 106 cycles, 70 N, Mechanical fatigue: up to
1.4-Hz, water, 37 ◦ C 8,9%
- Combination of M + T fatigue Combination of mechanical
and thermal fatigue: up to
8.3%
15
16
Table 4 (Continued)
Mitov et al. (2016) Zeno Zr Fracture toughness,molar crowns with various Autoclave + chewing simulation caused a N/A
[130] preparation designs (shoulderless, 0.4 mm and significant decrease of the fracture load for all
0.8 mm chamfer), crosshead speed groups, but thermocycling did not.
0.5 mm min−1 Circumferential shoulderless preparation had a
Steam autoclave 134 ◦ C, 2 bar, 3 h + chewing significantly higher fracture
simulation
Thermocycling 5–55 ◦ C, 5000 cycles, + chewing
simulation

Bankoglu et al. (2017) Incoris TZI Fracture toughness, molar crowns, Absence of non-aged specimens. The highest N/A
[132] crosshead-speed 0.5 mm min−1 . resistance was observed for zirconia crowns.
Thermal and mechanical cycling 5000 cycles, All specimens survived the mastication
5◦ -55 ◦ C, water simulation.
Mechanical loading 100 N, 12 × 105 cycles.
Sarıkaya et al. (2018) - Bruxzir Fracture strength, crosshead speed - No fractures during chewing simulation N/A
[87] 1 mm min−1 (crowns: force applied on buccal
and lingual cusps, FPDs: force applied on
occlusal connector area).
- Incoris TZI Aging: thermocycling (10,000 cycles /5–55 ◦ C / - Bruxzir crowns and FPDs presented
dwell time = 60 s / transfer time = 10 s, significantly higher fracture strength
compared to Incoris TZI
Dual axis chewing simulator with a total of - No significant difference in fracture strength
1,200,000 cycles. of crowns and FPDs fabricated from Bruxzir
Weigl et al. (2018) [85] Zirkon BioStar HT Fracture strength, crosshead speed 1 mm - All 0.5 mm crowns exceeded 900 N. N/A
min−1
Aging: chewing simulation (1,200,000 cycles, − 0.2 mm adhesively cemented control crowns
50 N, f = 1.6 Hz)) exceeded 900 N.
Thermal cycling (2 × 3000 between 5 ◦ C and
55 ◦ C, 2 minutes for each cycle)
Elshiyab et al. (2018) -Zenostar Zr Fracture strength, crosshead speed 1 mm - Monolithic lithium disilicate crowns N/A
[90] min−1 presented lower fracture strength compared to
monolithic zirconia
- IPS e.max- CAD Aging: fatigue by chewing simulation with 1.2 - All crowns presented a reduction in fracture
million cycles + thermal cycling at 5–55 ◦ C in strength following fatigue aging.
distilled water (5118 thermal cycles with 60 s
dwell time for each cycle, 15 s pause time).
Yin et al. [89](2019) A3 12 T, Liaoning Fracture strength, crosshead speed After polishing the crown presented higher Not calculated but
Upcera, Benxi, China 1 mm min−1 fracture strengths than after adjustment of observed in the
Different polishing protocols were evaluated. occlusal contact diffraction patterns
Cementation using resin cement. depending on the
Chewing simulation with cyclic loads between polishing method
2 and 300 N, frequency 1 Hz (100,000 cycles)
Table 4 (Continued)

Elsayed et al. (2019) - DD Bio ZX2 (3Y-TZP) Fracture strength, lower molar crowns with Significantly higher fracture strength was N/A
[88] minimum thickness 0.8 mm (buccal) and noted for 3Y-TZP compared to 5Y-TZP.
1.0 mm (occlusal, lingual, and approximal),
crosshead speed 0.5 mm min−1 .
- DD cubeX2 HS (4Y-TZP) chewing simulator for 1,200,000 (3Y-TZP > 4Y-TZP > 5Y-
- DD cubeX2 (5Y-TZP) cycles + simultaneous thermocycling between TZP)
5 ◦ C and 55 ◦ C. Vertical load of 49 N applied
2 mm buccal to the central fissure with a lateral
Fixed partial dentures movement of 0.3 mm towards the center
Preis et al. (2012) [133] - Cercon ht Fracture strength, 3-unit FDPs after thermal Similar strength of monolithic compared to
cycling, crosshead-speed 1 mm min−1 veneered zirconia
Alshahrani et al. (2017) - ICE Zirkon Translucent Fracture strength, cantilevered frameworks Increased occlusocervical thickness and N/A
[134] after thermal cycling, crosshead-speed decreased cantilever length allowed the
1 mm min−1 cantilever to withstand higher loads.
Villefort et al. (2017) In-Ceram YZ Fatigue limit after cycling loading The glass/silica infiltration techniques in the N/A
[135] Control group (CTL) (100,000cycles, 5 Hz frequency), 3-unit monolithic zirconia bridges significantly
Silica sol-gel group (SSG) posterior FDPs increased the fatigue limits compared with the
Glass-zirconia-glass group (GZG) glazed control group
Lopez-Suarez et al. Veneered FDPS: Fracture strength, 3-unit FPDs after loading in Comparable fracture resistance of monolithic N/A
(2017) [136] - Lava chewing simulator, crosshead-speed and veneered zirconia FDPs.
Monolithic FDPs: 1 mm min−1 .
- Lava Plus
17
Table 5
Commercial products listed in the studies included in the review, manufacturers and compositions.
Brand Manufacturer Composition (wt%) Source
Aadva Standard Translucency GC Tech, Leuven, Belgium 3 mol% Y-TZP: 94.8% ZrO2 , 3%Y2 O3 , 0.2%Al2 O3 Reference [103]
[ST]
Aadva Enamel Intensive [EI] GC Tech, Leuven, Belgium 3 mol% Y-TZP: 95%ZrO2 , 5%Y2 O3 , trace of Al2 O3 Reference [103]
Aadva Natural Translucency GC Tech, Leuven, Belgium 5.5 mol% Y-TZP: 91%ZrO2 , 9%Y2 O3 , trace of Reference [103]
[NT] Al2 O3
Argen HT Argen Corp, USA 5̃ mol% Y-TZP: ZrO2 >99%, Y2 O3 6.1 – 8.2%, HfO2 https://www.argen.com/store/
<5%, Al2 O3 <0.2% products/9164
BruXZir HT Glidewell laboratories, USA 3 mol% Y-TZP (No other details can be found) Reference [64]
BruxZir Prismatik Glidewell laboratories, USA 3 mol% Y-TZP (No other details can be found) Reference [73]
BruXZir Shaded 16 Glidewell laboratories, USA 3 mol% Y-TZP (No other details can be found) Reference [64]
Ceramill Amann Girrbach AG, 3 mol% Y-TZP: ZrO2 w% main component, Y2 O3 Reference [129]
Austria 4-6 w%, Al2 O3 0-1 w%, HfO2 1-5 w%
Ceramill ZI Amann Girrbach AG, 3 mol% Y-TZP: ZrO2 + HfO2 + Y2 O3 : > 99,0%, https://www.amanngirrbach.
Austria Y2 O3 : 4,5 – 5,6%, HfO2 : ≤ 5%, Al2 O3 : ≤ 0,5%, com/en/products/cadcam-
Other oxides: ≤ 1% material/ceramic/zolid-
zirconia/zi/
Ceramill Zolid Amann Girrbach AG, 3 mol% Y-TZP: ZrO2 + HfO2 + Y2 O3 > 99%, Y2 O3 : Reference [114]
Austria 4.5–5.6%, HfO2 < 5%,Al2 O3 < 0.5%
Ceramill Zolid FX –Multilayer Amann Girrbach AG, 5̃ mol% Y-TZP: ZrO2 + HfO2 + Y2 O3 ≥99%, Y2 O3 Reference [98]
Austria 8.5-9.5%, HfO2 <5%, Al2 O3 <0.5%, other
oxides<1%
Cercon DeguDent GmbH, Germany 3 mol% Y-TZP: ZrO2 (+HfO2 ) % main Reference [129]
component, Y2 O3 5 w%, Al2 O3 + SiO2 1 %, HfO2
2%
Cercon ht DeguDent GmbH, Germany 3 mol% Y-TZP: ZrO2 , Y2 O3 5 %, HfO2 < 3 %, Al2 O3 , http://www.degudent.com/
SiO2 < 1 % Communication and Service/
Download/Cercon/Download
Cercon.php
DD Bio ZX2 Dental Direkt GmbH, 3 mol% Y-TZP: ZrO2 + HfO2 + Y2 O3 > 99; Al2 O3 < Reference [114]
Germany 0.5; other oxides ≤ 1
Denzir Y-TZP Denzir AB, Sweden 3 mol% Y-TZP: ZrO2 + Y2 O3 + HfO2 + Reference [73]
Al2 O3 >99,95 wt%
Denzir Mg-PSZ Denzir AB, Sweden ZrO2 + MgO9̃9,95 wt% Reference [73]
Diazir Ivoclar Vivadent, 3 mol% Y-TZP (No other details can be found) Reference [137]
Lichtenstein
D max Natura Z-B2018 DMAX Co., Daegu, Korea 3 mol% Y-TZP (No other details could be found) http://www.dmax.biz/eng/
zirconia-block/block
properties.html
DDcubex2 Dental Direct Materials, ZrO2%+HfO2 > 90%,Y2O3 < 10%Al2O3 < 0.1%,other Reference [138]
Germany oxide<0.005%
GC Initial Zr GC Corp., Japan 3 mol% Y-TZP (No other details can be found) Reference [127]
ICE Zirkon Zirkonzahn, Italy 3 mol% Y-TZP: ZrO2 , Y2 O3 4–6%, Al2 O3 < 1% Reference [139,140]
SiO2 < 0.02%, Fe2 O3 < 0.01% Na2 O < 0.04%
ICE Zirkon Translucent Zirkonzahn, Italy 3 mol% Y-TZP: 4%-6% Y2 O3 , <1% Al2 O3 , < 0.02% Reference [139]
SiO2 ,< 0.01% Fe2 O3 , < 0.04% Na2 O
In-Ceram Zirconia YZ Vita Zahnfabrik, Bad 3 mol% Y-TZP: ZrO2 90.9 – 94.5%, Y2 O3 4 – 6%, Reference [141]
Sackingen, Germany HfO2 1.5 – 2.5%, Al2 O3 0 – 0.3% Er2 O3 0%, Fe2 O3
0 – 0.3%
In-Ceram zirconia YZ HT Vita Zahnfabrik, Bad 3 mol% Y-TZP: ZrO2 90.4 – 94.5%, Y2 O3 4 – 6%, Reference 2016 [141]
Sackingen, Germany HfO2 11.5 – 2.5%, Al2 O3 0 – 0.3%, Er2 O3 0 0 –
0.5%, Fe2 O3 0 – 0.3%
Incoris TZI Dentsply Sirona, USA 3 mol% Y-TZP: ZrO2 +HfO2 +Y2 O3 ≥ 99.0%, Y2 O3 Reference [104]
> 4.5 - ≤ 6.0%, Hf O2 ≤ 5%, Al2 O3 ≤ 0.04%, Other
oxides ≤ 1.1%
inCoris TZI C Dentsply Sirona, USA 3 mol% Y-TZP: ZrO2 +HfO2 +Y2 O3 ≥ 99.0%, Y2 O3 > http://manuals.sirona.com/en/
4.5 - ≤ 6.0%, HfO2 ≤ 5%, Al2 O3 ≤0.04%, Other digital-dentistry/cad-cam-
oxides≤ 1.1% materials/incoris-tzi-c.html
inCoris ZI Dentsply Sirona, USA 3 mol% Y-TZP: ZrO2 +HfO2 +Y2 O3 ≥ 99.0%, Y2 O3 Reference [104]
> 4.5 - ≤ 6.0%, Hf O2 ≤ 5%, Al2 O3 ≤ 0.5%, Fe2 O3 ≤
0.3%
IPS e.max ZirCAD Ivoclar Vivadent AG, 3 mol% Y-TZP: ZrO2 =87.0– 95.0%, Y2 O3 =4.0 – Reference [104]
Schaan, Liechtenstein 6.0, HfO2 =1.0 – 5.0%, Al2 O3 =0.0 – 1.0%
Katana HT13 KURARAY CO, LTD, Japan 5̃.5 mol% Y-TZP: Al2 O3 = 0.13 (0.10), Calculated by the authors in
Y2 O3 = 10.91 (0.73), ZrO2 = 86.50 (0.85), Reference [121]
HfO2 = 2.46 (0.26)
Katana ML KURARAY CO, LTD, Japan 5̃.5 mol% Y-TZP: Al2 O3 = 0.16 (0.10), Calculated by the authors in
Y2 O3 = 10.95 (0.29), ZrO2 = 86.21 (0.59), Reference [121]
HfO2 = 2.41 (0.27)
Katana ST KURARAY CO, LTD, Japan 88–93% ZrO2, 7–10% Y2 O3 , Other<2% Reference [142]
Katana UT KURARAY CO, LTD, Japan 5.4 mol% Y-TZP: Al2 O3 = 0.1 (0.1), Reference [143] Calculated by
Y2 O3 = 10.1(0.7), ZrO2 = 87.8 (0.7), HfO2 = 2 (0.1) the authors in Reference [144]
Katana UTML KURARAY CO, LTD, Japan 87–92% ZrO2 + HfO2 , 8–11% Y2 O3, other oxides https://www.bego.com/
0-2% fileadmin/user downloads/
Mediathek/Medical/en
Keramik/KATANA Zirconia/me
800369 0000 pp en.pdf
Table 5 (Continued)
Brand Manufacturer Composition (wt%) Source
Everest ZS KaVo Dental GmbH, 3 mol% Y-TZP (No other details can be found) Reference [145]
Germany
KZ-3YF type AC KCM, Nagoya, Japan 3% mol% Y-TZP: ZrO2 as main component, Y2 O3 http://www.kyoritsu-kcm.co.
5.4%, Al2 O3 0.25% jp/english/new material/new
material 01.html
Lava, Lava Frame 3M ESPE, USA 3 mol% Y-TZP (No other details could be found) http://www.lava-elite.com/
lava-classic-crowns-bridges.
shtml
Lava Plus al 3M ESPE, USA 3 mol% Y-TZP (No other details could be found) http://www.lava-elite.com/
lava-classic-crowns-bridges.
shtml
Lava TM Esthetic 3M ESPE, USA 5 mol% Y-TZP (No other details could be found) https://www.3m.com/3M/en
US/company-us/all-3m-
products/˜/3M-Lava-
Esthetic-Fluorescent-Full-
Contour-Zirconia-Disc/
?N=5002385+3291669973rt=rud
Nissin Dental Zirconia Blank Nissin-Metec China Co., 3% mol% Y-TZP: ZrO2 ≥99.0% Inorganic https://www.accessdata.fda.
Ltd., China Pigment (Fe2O3, Er2 O3 )≤ 1 gov/cdrh docs/pdf16/K160367.
pdf
NexxZr HS Sagemax Bioceramics, Inc., 3% mol% Y-TZP: ZrO2 +HfO2 +Y2 O3 = 99.1%, http://sagemax.com/portfolio-
Federal Way, WA Al2 O3 <0.3% item/nexxzr-s/
NexxZr HT Sagemax Bioceramics, Inc., 3 mol% Y-TZP: ZrO2 +HfO2 +Y2 O3 = 99.1%, Al2 O3 http://sagemax.com/portfolio-
Federal Way, WA <0.1% item/nexxzr-t/
Nobel Procera Nobel Biocare Services AG, 3 mol% Y-TZP: ZrO2 + Y2 O3 + HfO2 ≥ 99.0%, Reference [73]
Switzerland Y2 O3 > 4.5 to ≤6.0, HfO2 ≤ 5%, Al2 O3 ≤ 0.5%.
Other oxides ≤0.5%
Prettau Zirkonzahn, Italy 3 mol% Y-TZP: ZrO2 = main component, Reference [100]
Y2 O3 = 4 – 6 %, Al2 O3 < 1 %, SiO2 < 0.02 %, Fe2 O3 <
0.01 %, Na2 O< 0.04 %
Prettau, Anterior Zirkonzahn, Italy 8̃ mol% Y-TZP: ZrO2 = Main component, Y2 O3 < Reference [100]
12 %, Al2 O3 < 1 %, SiO2 <0.02 %, Fe2 O3 < 0.02 %
Tizian Blank Translucent Schutz Dental GmbH, 3 mol% Y-TZP: ZrO2 < 96%, yttrium oxide > 4%, Reference [146]
Germany HfO2 > 1%, Al2 O3 < 1%, SiO2 < 0.02%
TZ-3Y-E Tosoh Corporation, Tokyo, 3 mol% Y-TZP: 5.2% Y2 O3 , 0.25% Al2 O3, 5.2 ± 0.5 Reference [102] https://www.
Japan Y2 O3, < 5.0HfO2 , 0.1 0̃.4%, Al2 O3 , ≤ 0.02% SiO2 , tosoh.com/our-products/
≤ 0.01% Fe2 O3 , ≤0.04% Na2 O advanced-materials/zirconia-
powders
TZ-3YS-E Tosoh Corporation, Tokyo, 3 mol% Y-TZP: 5.2% Y2 O3 , 0.25% Al2 O3, 5.2 ± 0.5 https://www.tosoh.com/our-
Japan Y2 O3, < 5.0 HfO2 , 0.1 0̃.4% Al2 O3 , ≤ 0.02% SiO2 , products/advanced-materials/
≤ 0.01% Fe2 O3 , ≤0.06% Na2 O zirconia-powders
VITA YZ-HT Vita Zahnfabrik, Bad 3 mol% Y-TZP: ZrO2 90.4-94.5, + HfO2 + Y2 O3 4 VITA 10160 10160E YZ TWD EN V02
Säckingen, Germany -6, HfO2 1.5-2.5, Al2 O3 0-0.3, Er2 O5 0-0.5, screen en.pdf (www.vita-
Fe2 O3 0-0.3 zahnfabrik.com/en/)
VITA YZ-T Vita Zahnfabrik, Bad 3 mol% Y-TZP: ZrO2 90.4-94.5, + HfO2 + Y2 O3 4 VITA 10160 10160E YZ TWD EN V02
Säckingen, Germany -6, HfO2 1.5-2.5, Al2 O3 0-0.3, Fe2 O3 0-0.3 screen en.pdf (www.vita-
zahnfabrik.com/en/)
Zenostar Zr Wieland Dental + Technik 3 mol% Y-TZP: ZrO2 + HfO2 + Y2 O3 > 99; 4,5 < Reference [114]
GmbH & Co. KG, Germany Y2 O3 ≤6; HfO2 ≤ 5; Al2 O3 + other oxides ≤1
Zeno Zr Wieland Dental + Technik 3 mol% Y-TZP: (ZrO2 + HfO2 ) 94%, (Y2 O3 ) 5%, Reference [130]
GmbH & Co. KG, Germany (Al2 O3 ) <1%, other oxides <1%)
ZirkonZahn Steger, Ahrntal, Italy 3 mol% Y-TZP: ZrO2 (+HfO2 ) w% main Reference [129]
component, Y2 O3 4.955̃.26 w%, Al2 O3
0.150̃.35 w%, SiO2 0.02 w%, Fe2 O3 0.01 w%,
Na2 O 0.04 w%
ZirLuna ACF, Amberg, Germany 3 mol% Y-TZP (No other details can be found) Reference [67]
Zirlux Ardent Inc., Pentron 3 mol% Y-TZP: ZrO2 +HfO2 >94%, Y2 O3 <6 %, https://www.custom-milling.
Ceramics, USA HfO2 < 3 %, Al2 O3 < 0.5 % com/images/pdfs/materials/
Zirlux Full Contour Zirconia
Discs MSDS.pdf
Zirlux FC Ardent Inc., Pentron 3 mol% Y-TZP: ZrO2 +HfO2 :>94%, Y2 O3 : 5.35% ± https://www.zirlux.com/fc2/
Ceramics, USA 0.20, AL2 O3 : <0.1%, HfO2 : Typically <3.0%
ZirPremium ACUCERA, Korea 3 mol% Y-TZP (No other details could be found) http://www.buykorea.org/
product-details/zirpremium-
dental-cad-cam-blocks–
3039039.html
Zmatch Dentaim, Seoul, Korea 3 mol% Y-TZP : 94– 95% ZrO2 and HfO2 , Reference [147]
5 ± 0.2% Y2 O3 and 0.25% Al2 O3
Zpex Tosoh Corporation, Tokyo, 3 mol% Y-TZP: 5.2% Y2 O3 , 0.05% Al2 O3 Reference [102]
Japan
Zpex Smile Tosoh Corporation, Tokyo, 5̃ mol% Y-TZP: 9.35% Y2 O3 , 0.05% Al2 O3 Reference [102]
Japan
Z-CAD HTL Metoxit AG, Thayngen, 3 mol% Y-TZP: ZrO2 +HfO2 +Y2 O3 > 99.5%, http://www.metoxit.com/
Switzerland Y2 O3 = 5.2%, Al2 O3 = 0.05%, other oxides≤0.5%
Chewing simulator did not induce any significant alterations in constantly about their properties, the limitations in their applica-
the strength values of 3 mol% Y-TZ specimens, but all monolithic tion and their resistance to low-temperature degradation that will
zirconia materials presented lower values compared to the con- eventually reach to laboratory and clinical guidelines for their use.
ventional one [119]. In a recent study by Elsayed et al. [88], which However, monolithic zirconia ceramics include a group of materi-
evaluated the fracture strength of 3Y-TZP, 4Y-TZP and 5Y-TZP molar als with different properties and sound scientific knowledge should
crowns following chewing simulation with simultaneous thermo- guide the selection of the appropriate material in each clinical sit-
cycling, supports that crowns from zirconia with high Y2 O3 content uation.
presented higher fracture strength. On the contrary, significantly
higher decrease in strength after mechanical cyclic loading was
recorded for 8 mol% monolithic zirconia specimens, especially after Conflicts of interest
the combination of thermal and mechanical cycling [99]. In another
study, unglazed monolithic crowns presented the lowest strength None.
after thermal cycling in water [129]. In the opposite direction,
other studies report that thermal cycling alone does not decrease
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Japanese Dental Science Review 56 (2020) 1–23

Contents lists available at ScienceDirect

Japanese Dental Science Review

Strength and aging resistance of monolithic zirconia: an update to

1. Introduction its strength. Speciﬁc processing conditions, environmental humid-

Authors Zirconia system Test type/Methodology Results

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

Authors Zirconia system Test type/Methodology Results

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

Authors Zirconia system Test type/Methodology Results

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

Authors Zirconia system Test type/Methodology Results

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

Authors Zirconia system Test type/Methodology Results

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

E. Kontonasaki et al. / Japanese Dental Science Review 56 (2020) 1–23

Brand Manufacturer Composition (wt%) Source

Brand Manufacturer Composition (wt%) Source

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