N AN O E X P R E S S Open Access
The Biocompatibility of Dental Graded
Nano-Glass-Zirconia Material After Aging
, Ruoyu Liu
, Xiangning Liu
, Xiaoli Feng
, Yanli Zhang
and Renfa Lai
A graded nano-glass/zirconia (G/Z) system has been developed via the infiltration of nano-glass into a nano-zirconia
surface, which is advantageous for robust core-veneer bonds. The aging issue is a key for yttrium-stabilized tetragonal
zirconia polycrystals (Y-TZPs), and therefore, it is necessary to evaluate the influence of aging degradation on the
biocompatibility of G/Z systems before their possible clinical application. Herein, such biocompatibility testing
was performed with human gingival fibroblasts (HGFs) seeded onto unaged/aged G/Z and Y-TZP for 2–72 h.
Assessments included an oral mucous membrane irritation test in conjunction with analyses of cell viability, cell
adhesion, and oxidative stress responses. Significant metabolic decreases in aged G/Z- and Y-TZP-treated cells
were observed at 72 h. G/Z did not elicit any significant differences in cell viability compared with Y-TZP over
72 h both before and after aging. The oxidative stress data for the aged G/Z- and Y-TZP-treated cells showed a
significant increase at 72 h. The G/Z specimens did not elicit any significant differences in ROS production compared
with Y-TZP over 72 h both before and after aging. The cell adhesion rates of both G/Z and Y-TZP increased significantly
after aging. The cell adhesion rates of G/Z and Y-TZP were not significantly different before and after aging. According
to the oral mucous membrane irritation test, scores for macroscopic and microscopic observations for both the aged
G/Z and unaged G/Z sides were 0, demonstrating no consequent irritation.
Conclusions: The excellent biocompatibility of G/Z indicates that it has potential for future clinical applications.
Keywords: Dental, Zirconia, Graded, Aging, Biocompatibility
Dental zirconia-based ceramics (e.g., 3 mol% yttrium-
stabilized tetragonal zirconia polycrystals (3Y-TZPs)) ex-
hibit excellent mechanical strength and superior fracture
resistance due to inherent transformation toughening
mechanisms, and they are widely utilized for the fabrica-
tion of prosthetic devices . Zirconia core materials are
usually coated with translucent veneering porcelain to
cover their opaque appearance. However, layered zirco-
nia restorations tend to fail; chipping and delamination
of the veneering ceramic have been reported as the most
frequent reason for the failure of zirconia-based restora-
tions [2, 3]. Chipping and delamination of the veneering
ceramic were reported to result from mismatches of the
thermal expansion coefficient and elastic modulus be-
tween the zirconia cores and veneering ceramics .
Consequently, in our previous study, we introduced a
new concept for the improvement of core-veneer bond-
ing by infiltrating a low modulus nano-sized glass with a
matching thermal expansion coefficient into the zirconia
surface sintered from nano-zirconia particles, thus pro-
ducing elastic graded nano-glass/zirconia (G/Z) systems.
The bond strengths of the G/Z systems to veneering
porcelains were demonstrated to be threefold higher
than those of conventional zirconia-based systems .
The aging of Y-TZP is well acknowledged. The aging
of Y-TZP can be induced by an oral environment, with
exposure to humidity, mechanical loading, and low
temperature, resulting in surface roughening, micro-
cracks, and Y-TZP particle release into the body [5, 6].
In the presence of humidity and low temperature, a tet-
ragonal to monoclinic (t-m) zirconia phase transformation
could be triggered. The crystal volumetric expansion re-
sults in localized stress and microcracking in the material
* Correspondence: firstname.lastname@example.org
Ting Sun and Ruoyu Liu are co-first authors.
Ting Sun and Ruoyu Liu contributed equally to this work.
Medical Center of Stomatology, The First Affiliated Hospital of Jinan
University, Guangzhou 510630, China
Full list of author information is available at the end of the article
© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
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Sun et al. Nanoscale Research Letters (2018) 13:61