EFFECT OF SURFACE TREATMENT PROTOCOLS OF ZIRCONIUM DIOXIDE MULTILAYER RESTORATIONS ON FUNCTIONAL PROPERTIES OF THE HUMAN ORAL MUCOSA STROMAL CELLS.

Aim - to study the effect of protocols of surface treatment of zirconium dioxide multilayer restorations on the functional properties of stromal cells of the human oral mucosa using molecular biological methods. For all experiments, identical standardized specimens of different types of zirconia with a diameter of 10 mm and a height of 1 mm were used. These types included Katana (Kuraray Noritake Dental, Tokyo, Japan) HTML (control) UTML, STML and ZirCAD Prime (Ivoclar Vivadent). DMEM/F12 growth medium (Paneco, Russian Federation) with addition of fetal calf serum (Gibco, USA) up to 10% and penicillin-streptomycin (Paneco, Russian Federation) up to 1% was used in the experiment. Cells were detached from the culture substrate with trypsin-EDTA solution (Paneco, RF) and their number and viability were assessed using an automatic counter TC-20 (Bio-Rad, USA). For repopulation, samples were transferred into wells of a 96-well culture plate (1 sample in 1 well) and cell suspension was layered at the rate of 12.5 thousand or 25 thousand live cells per well. After 48 hours, the cytotoxic properties of the tested samples were evaluated in vitro. According to the results of MTT test we can conclude that samples of ZirCad Prime and Katana UTML groups do not show cytotoxic properties (score "0" on the cytotoxicity scale according to GOST R ISO 10993-5-2009 "National Standard of the Russian Federation. Medical devices. Evaluation of biological effect of medical devices. Part 5. Studies on cytotoxicity: in vitro methods"). The samples of Katana STML group samples were slightly reduced compared to the control (about 12%), nevertheless, these samples can also be considered non-cytotoxic. Analyzing the direct contact with the material in all samples, a good occupancy of the material by cells was observed, in particular, the polished surface prevailed over the glazed one, however, this difference is not statistically significant. Analysis of human oral stromal cells to zirconium dioxide showed no statistically significant effect of different surface treatment protocols. However, the number of fibroblasts prevailed on the polished surface.

Comparative study of effective antibiofilm activity of beneficial microbes-mediated zirconia nanoparticles.

In the present study, beneficial microbes-mediated zirconia nanoparticles were prepared using endophytic bacteria isolated from the seed of Terminalia chebula which were evaluated on inhibition of bacterial adherence and promotion to exhibit antibiofilm properties. The structure and distribution of the zirconia nanoparticles were examined through SEM (Scanning Electron Microscopy), EDS (Energy-Dispersive X-Ray spectroscopy), and XRD (X-ray diffraction analysis), which reveal the distribution of the particles. The morphology of biogenic zirconia nanoparticles was monoclinic and cubic. The formation of zirconia particle was confirmed using UV spectrum and the functional groups were intensified in FTIR (Fourier-transform infrared spectroscopy). The antibiofilm activity of the synthesized nanoparticles was tested in oral pathogens that cause biofilm by membrane integrity and leads to periodontal associated disease. The results showed that the particles had a significant effect on biofilm removal caused by oral pathogens. For determined concentration, the cytotoxicity of the endophytic bacterial facilitated zirconia nanoparticle (Zr NPs) was examined in HGF (Human gingival fibroblast cell line).

Ultrasmall zirconium carbide nanodots for synergistic photothermal-radiotherapy of glioma.

Glioma is characterized by highly invasive, progressive, and lethal features. In addition, conventional treatments have been poorly effective in treating glioma. To overcome this challenge, synergistic therapies combining radiotherapy (RT) with photothermal therapy (PTT) have been proposed and extensively explored as a highly feasible cancer treatment strategy. Herein, ultrasmall zirconium carbide (ZrC) nanodots were successfully synthesized with high near-infrared absorption and strong photon attenuation for synergistic PTT-RT of glioma. ZrC-PVP nanodots with an average size of approximately 4.36 nm were prepared by the liquid exfoliation method and modified with the surfactant polyvinylpyrrolidone (PVP), with a satisfactory absorption and photothermal conversion efficiency (53.4%) in the near-infrared region. Furthermore, ZrC-PVP nanodots can also act as radiosensitizers to kill residual tumor cells after mild PTT due to their excellent photon attenuating ability, thus achieving a significant synergistic therapeutic effect by combining RT and PTT. Most importantly, both in vitro and in vivo experimental results further validate the high biosafety of ZrC-PVP NDs at the injected dose. This work systematically evaluates the feasibility of ZrC-PVP NDs for glioma treatment and provides evidence of the application of zirconium-based nanomaterials in photothermal radiotherapy.

Biosynthesis of zirconium nanoparticles (ZrO2 NPs) by Phyllanthus niruri extract: Characterization and its photocatalytic dye degradation activity.

The present study focused on microwave assisted synthesis of zirconium nanoparticles (ZrO2NPs) using leaf extract of Phyllanthus niruri as ecofriendly approach and assessed its antimicrobial and bioremediation efficiency. Visual color transition from yellow to brown indicates the formation of ZrO2NPs which was further substantiated by UV-Visible absorption peak at 300 nm. Dynamic Light Scattering (DLS) analysis revealed that the average particle size of ZrO2NPs as 121.5 nm with negative zeta potential of -22.6 mv. Scanning electron microscopic analysis showed spherical shaped nanoparticles with an average size of 125.4 nm. Results of photocatalytic studies revealed that ZrO2NPs exhibited 74%, 62% and 57%, dye degradation for methyl red, methyl orange, and methyl blue respectively. Antimicrobial studies depicted that ZrO2NPs exhibited bactericidal activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Aspergillus niger at dose of 200 µg/mL. Overall results of the present study revealed biogenic synthesis of ZrO2 NPs with potent bioremediation and antimicrobial properties.

Inflammatory responses to metal oxide ceramic nanopowders.

Ceramic orthopaedic implants are increasingly popular due to the need for robust total joint replacement implants that have a high success rate long-term and do not induce biological responses in patients. This study was designed to investigate the biological effects of ceramic nanopowders containing aluminium oxide or zirconium oxide to activate the human macrophage THP-1 cell line. In vitro investigation of pro-inflammatory gene expression and chemokine secretion was performed studied using RT-qPCR and ELISA, respectively. TLR4 inhibition, using a small-molecule inhibitor, was used to determine whether ceramic-mediated inflammation occurs in a similar manner to that of metals such as cobalt. THP-1 macrophages were primed with ceramics or LPS and then treated with ATP or ceramics, respectively, to determine whether these nanopowders are involved in the priming or activation of the NLRP3 inflammasome through IL-1ß secretion. Cells treated with ceramics significantly increased pro-inflammatory gene expression and protein secretion which was attenuated through TLR4 blockade. Addition of ATP to cells following ceramic treatment significantly increased IL-1ß secretion. Therefore, we identify the ability of ceramic metal oxides to cause a pro-inflammatory phenotype in THP-1 macrophages and propose the mechanism by which this occurs is primarily via the TLR4 pathway which contributes to inflammasome signalling.

In vitro effects of photobiomodulation applied to gingival fibroblasts cultured on titanium and zirconia surfaces and exposed to LPS from Escherichia coli.

Photobiomodulation (PBM) therapy is used to stimulate cell proliferation and metabolism, as well as reduce inflammatory cytokine synthesis, which plays a main role in the long-term stability of implants. This study assessed the response of gingival fibroblasts cultured on titanium (Ti) and zirconia (ZrO2), submitted to PBM and exposed to lipopolysaccharide (LPS). Cells seeded on Ti and ZrO2 were irradiated (InGaAsP; 780 nm, 25 mW) 3 times, using 0.5, 1.5, and 3.0 J/cm2 doses, and exposed to Escherichia coli LPS (1 µg/mL). After 24 h, cell viability (alamarBlue, n = 8), interleukin 6 (IL-6) and 8 (IL-8) synthesis (ELISA, n = 6), and IL-6 and vascular endothelial growth factor (VEGF) gene expression (qPCR, n = 5) were assessed and statistically analyzed (one-way ANOVA, α = 0.05). Cell morphology was evaluated by fluorescence microscopy. Increased cell viability occurred in all groups cultured on Ti compared with that of the control, except for cells exposed to LPS. Fibroblasts cultured on ZrO2 and LPS-exposed exhibited reduced viability. PBM at 3.0 J/cm2 and 1.5 J/cm2 downregulated the IL-6 synthesis by fibroblasts seeded on Ti and ZrO2, as well as IL-8 synthesis by cells seeded on ZrO2. Fibroblasts seeded on both surfaces and LPS-exposed showed increased IL-6 gene expression; however, this activity was downregulated when fibroblasts were irradiated at 3.0 J/cm2. Enhanced VEGF gene expression by cells seeded on Ti and laser-irradiated (3.0 J/cm2). Distinct patterns of cytoskeleton occurred in laser-irradiated cells exposed to LPS. Specific parameters of PBM can biomodulate the inflammatory response of fibroblasts seeded on Ti or ZrO2 and exposed to LPS.

Multifunctional and flexible ZrO2-coated EGaIn nanoparticles for photothermal therapy.

With extensive investigations involving liquid metals (LMs), Ga-based LMs have attracted increasing attention from biomedical researchers because of their good biocompatibility, ideal fluidity, and high thermal conductivity. LMs employed in cancer treatment suffer from high surface tension, thereby yielding unstable nanoparticles (NPs). Here, ZrO2 is coated onto LM NPs to form a stable core-shell nanostructure. In particular, LM NPs coated with ZrO2 and modified by PEG (LM@pZrO2 NPs) still maintain favorable flexibility, which is beneficial for cellular uptake. With regard to the photothermal properties of LM, LM@pZrO2 NPs rapidly warm up and emit the requisite amount of heat under NIR laser radiation. It is confirmed that LM@pZrO2 NPs are more effectively internalized by cells and are beneficial for tumor photothermal therapy. This research provides a coating strategy to fabricate a stable and flexible core-shell LM nanostructure, making it a promising vehicle for nanotheranostics.

Magnetic Targeting of Nanotheranostics Enhances Cerenkov Radiation-Induced Photodynamic Therapy.

The interaction between radionuclides and nanomaterials could generate Cerenkov radiation (CR) for CR-induced photodynamic therapy (PDT) without requirement of external light excitation. However, the relatively weak CR interaction leaves clinicians uncertain about the benefits of this new type of PDT. Therefore, a novel strategy to amplify the therapeutic effect of CR-induced PDT is imminently required to overcome the disadvantages of traditional nanoparticulate PDT such as tissue penetration limitation, external light dependence, and low tumor accumulation of photosensitizers. Herein, magnetic nanoparticles (MNPs) with 89Zr radiolabeling and porphyrin molecules (TCPP) surface modification (i.e., 89Zr-MNP/TCPP) were synthesized for CR-induced PDT with magnetic targeting tumor delivery. As a novel strategy to break the depth and light dependence of traditional PDT, these 89Zr-MNP/TCPP exhibited high tumor accumulation under the presence of an external magnetic field, contributing to excellent tumor photodynamic therapeutic effect together with fluorescence, Cerenkov luminescence (CL), and Cerenkov resonance energy transfer (CRET) multimodal imaging to monitor the therapeutic process. The present study provides a major step forward in photodynamic therapy by developing an advanced phototherapy tool of magnetism-enhanced CR-induced PDT for effective targeting and treatment of tumors.

Seaweed Sargassum wightii mediated preparation of zirconia (ZrO2) nanoparticles and their antibacterial activity against gram positive and gram negative bacteria.

In the present study, a facile and green combustion method has been optimized for the synthesis of zirconia (ZrO2) nanoparticles using marine brown alga (seaweed), Sargassum wightii (S. wightii). Structural, optical and photoluminescence properties of the prepared ZrO2 nanoparticles were studied using XRD, FTIR, HR-TEM, UV-vis and PL spectroscopy. The average grain size of the nanoparticles calculated from the XRD pattern was around 4.8 nm which exhibits tetragonal structure. TEM results showed that the synthesized nanoparticles were uniformly monodispersed without aggregation. Formation of zirconia nanoparticles were confirmed by FTIR studies. The PL spectra exhibit broad emission peaks at the interface of UV and visible regions which can be assigned to the ionized oxygen vacancy in the material. Antibacterial activity of the synthesized zirconia nanoparticles was studied against gram positive and gram negative bacterial strains using agar well diffusion method. The prepared zirconia nanoparticles show significant antibacterial effect against Bacillus subtilis, Escherichia coli and Salmonella typhi due to their large surface area by their nanosize.

Investigation the impact of ZTA addition on the properties of nano biogenic hydroxyapatite.

The target of the recent study is to achieve a significant inexpensive and eco-friendly way for getting ZTA/HA composites, based on the nano-HA derived from the eggshell biogenic source. Combining simultaneously the porous structure; which is considered as a bone formation key, with developed mechanical properties and adequate biocompatibility, is another purpose of this study. Furthermore, the impact of ZTA addition from 10-30 mass-%, fabricated by uniaxial pressing and sintering at 1200-1300 °C for 2 h, on the physical and mechanical properties, microstructure and phase composition of ZTA/HA composite bodies was investigated. The results demonstrated that the increasing of ZTA content increases the bodies' apparent porosity and decreases the bulk density due to the decomposition of HA into ß-TCP. Where the formation of ß-TCP possessed the predominant impact on the mechanical properties of the sintered ZTA/HA composites. ICP, SEM, EDX and thin film XRD results of composites containing 20 mass-% ZTA affirmed the excellent bioactivity of the bodies.

Surface modification using the biomimetic method in alumina-zirconia porous ceramics obtained by the replica method.

The modification of biomaterials approved by the Food and Drug Administration could be an alternative to reduce the period of use in humans. Porous bioceramics are widely used as support structures for bone formation and repair. This composite has essential characteristics for an implant, including good mechanical properties, high chemical stability, biocompatibility and adequate aesthetic appearance. Here, three-dimensional porous scaffolds of Al2 O3 containing 5% by volume of ZrO2 were produced by the replica method. These scaffolds had their surfaces chemically treated with phosphoric acid and were coated with calcium phosphate using the biomimetic method simulated body fluid (SBF, 5×) for 14 days. The scaffolds, before and after biomimetic coating, were characterized mechanically, morphologically and structurally by axial compression tests, scanning electron microscopy, microtomography, apparent porosity, X-ray diffractometry, near-infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, energy dispersive X-ray spectroscopy and reactivity. The in vitro cell viability and formation of mineralization nodules were used to identify the potential for bone regeneration. The produced scaffols after immersion in SBF were able to induce the nodules formation. These characteristics are advantaged by the formation of different phases of calcium phosphates on the material surface in a reduced incubation period. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2615-2624, 2018.

Sub-surface assessment of hydrothermal ageing in zirconia-containing femoral heads for hip joint applications.

Zirconia-based materials have been used in orthopaedics since the 1980s, with large success, mainly thanks to transformation toughening. On the other hand, their main drawback is their potential sensitivity to hydrothermal ageing, i.e. tetragonal to monoclinic phase transformation on their surface in the presence of water. Hydrothermal ageing may result in roughness increase and microcracking of the surface. In this article the hydrothermal ageing behaviour of three medical-grade zirconia-based materials is assessed at high temperature and extrapolated to room or body temperature. The degradation is also characterized by FIB/SEM nano-tomography to better assess sub-surface evolutions. In both zirconia and alumina-toughened zirconia (ATZ), ageing results in the presence of a homogenous transformed layer of constant thickness whose growth rate is about 8 times slower in ATZ than in zirconia. Microcracking occurs in the entire transformed layer in zirconia, but was much less relevant in ATZ. Zirconia-toughened alumina (ZTA) is much less prone to ageing. In ZTA ageing results in a thin transformed layer in which the monoclinic fraction decreases with depth. No microcracking was observed in ZTA. STATEMENT OF SIGNIFICANCE: This article details the microstructural evolution of the surface of three zirconia-based ceramics when exposed to water (hydrothermal ageing), and establishes a time-temperature equivalences of these evolutions. It shows that different zirconia-alumina composites do not degrade the same way: zirconia and alumina-toughened zirconia present a homogeneous degraded zone of constant thickness, whereas zirconia-toughened-alumina presents a gradient of transformation. These new findings will help understanding better the hydrothermal degradation of zirconia based materials, and in particular will facilitate a better prediction of the durability of zirconia-based devices such as orthopaedic implants and dental devices (implants, crowns, abutments…).

Hollow mesoporous zirconia delivery system for biomineralization precursors.

Strategies based on the combination of nanocarrier delivery systems and scaffolds provide bone tissue engineering scaffolds with multifunctional capability. Zirconia, a biocompatible ceramic commonly used in orthopedic and dental implants, was used to synthesize hollow mesoporous nanocapsules for loading, storage and sustained release of a novel polyamine-stabilized liquid precursor phase of amorphous calcium phosphate (PAH-ACP) for collagen biomineralization and bone marrow stromal cells osteoinduction. Hollow mesoporous zirconia (hmZrO2) nanocapsules loaded with biomimetic precursors exhibited pH-sensitive release capability and good biocompatibility. The PAH-ACP released from loaded hmZrO2 still retained the ability to infiltrate and mineralize collagen fibrils as well as exhibited osteoinductivity. A collagen scaffold blended with PAH-ACP@hmZrO2 supplement and stem cells may be a promising tool for bone tissue engineering. STATEMENT OF SIGNIFICANCE: The advent of nanotechnology has catalyzed the development of bone tissue engineering strategies based on the combination of nanocarrier delivery systems and scaffolds, which provide distinct advantages, including the possibilities of sustained release and protection of the bioactive agents, site-specific pharmacological effects and reduction of side effects. Herein, hollow mesoporous zirconia (hmZrO2) nanocapsules with pH-sensitive capacity were synthesized for loading, storage and sustained release of a novel polyamine-stabilized liquid precursor phase of ACP (PAH-ACP). The loaded nanocapsules show good biocompatibility and demonstrate bioactivities for collagen biomineralization and bone marrow stromal cells osteoinduction. Our results may offer a promising tool for designing bone tissue engineering "cocktail therapy" involving seeding scaffolds with biomineralization precursors loaded hmZrO2 supplement and stem cells.

Bioactivity of NANOZR Induced by Alkali Treatment.

In recent years, zirconia has been a recognized implant material in clinical dentistry. In the present study, we investigated the performance of an alkali-modified ceria-stabilized tetragonal ZrO2 polycrystalline ceramic-based nanostructured zirconia/alumina composite (NANOZR) implant by assessing surface morphology and composition, wettability, bovine serum albumin adsorption rate, rat bone marrow (RBM) cell attachment, and capacity for inducing bone differentiation. NANOZR surfaces without and with alkali treatment served as the control and test groups, respectively. RBM cells were seeded in a microplate with the implant and cultured in osteogenic differentiation medium, and their differentiation was evaluated by measuring alkaline phosphatase (ALP) activity, osteocalcin (OCN) production, calcium deposition, and osteogenic gene expression. The alkali-treated NANOZR surface increased ALP activity, OCN production, calcium deposition, and osteogenesis-related gene expression in attached RBM cells. These data suggest that alkali treatment enhances the osteogenesis-inducing capacity of NANOZR implants and may therefore improve their biointegration into alveolar bone.

Effect of Nanofeatured Topography on Ceria-Stabilized Zirconia/Alumina Nanocomposite on Osteogenesis and Osseointegration.

PURPOSE: The objective of this study was to evaluate the osteogenic and osseointegration capability of the Ce-tetragonal zirconia polycrystal (TZP)-based nanostructured zirconia/alumina composite (Ce-TZP/Al2O3) that was treated with hydrofluoric acid (HF). MATERIALS AND METHODS: Osteogenic MC3T3-E1 cells were cultured on acid-etched titanium (AETi) disks and Ce-TZP/Al2O3 disks without HF treatment (Zr[0%]), with 4% HF treatment (Zr[4%]), or with 55% HF treatment (Zr[55%]) for 24 hours, and biologic responses were compared among four conditions in vitro. Miniature implants of AETi and Zr(55%) were surgically placed in the femora of rats. Osseointegration was evaluated by a biomechanical push-in test after 2 and 4 weeks of healing. RESULTS: The surface of Zr(55%) rendered nanofeatured topography with a greater surface area and roughness, and extensive geographical undercut as ceria-zirconia crystal disappeared from the superficial layer and was similar to the surface morphology of biomineralized matrices. Culture studies showed that the attachment, proliferation, spread, and functional phenotypes of osteogenic cells, such as alkaline phosphatase activity and bone-related gene expression, were remarkably increased on the Zr(55%) surface. The strength of osseointegration measured using the biomechanical push-in test in a rat model was stronger for Zr(55%) implants than for AETi implants by 1.6 fold. CONCLUSION: The nanostructured Ce-TZP/ Al2O3 surface substantially enhanced the osteogenic response in vitro and the osseointegration capability in vivo, which suggest its potential clinical application as a novel implant material.

Reconciling in vivo and in vitro kinetics of the polymorphic transformation in zirconia-toughened alumina for hip joints: III. Molecular scale mechanisms.

Understanding the intrinsic reason(s) for the enhanced tetragonal to monoclinic (t→m) polymorphic phase transformation observed on metal-stained surfaces of zirconia-toughened alumina (ZTA) requires detailed knowledge of off-stoichiometry reactions at the molecular scale. In this context, knowledge of the mechanism(s) for oxygen vacancy creation or annihilation at the material surface is a necessary prerequisite. The crucial aspect of the surface destabilization phenomenon, namely the availability of electrons and holes that allow for vacancy creation/annihilation, is elucidated in this paper. Metal-enhanced alterations of the oxygen sublattice in both Al2O3 and ZrO2 of the ZTA composite play a decisive role in accelerating the polymorphic transformation. According to spectroscopic evidences obtained through nanometer-scale analyses, enhanced annihilation of oxygen vacancies triggers polymorphic transformation in ZrO2 near the metal stain, while the overall Al2O3 lattice tends to dehydroxylate by forming oxygen vacancies. A mechanism for chemically driven "reactive metastability" is suggested, which results in accelerating the polymorphic transformation. The Al2O3 matrix is found to play a key-role in the ZrO2 transformation process, with unambiguous confirmation of oxygen and hydrogen transport at the material surface. It is postulated that this transport is mediated by migration of dissociated O and H elements at the surface of the stained transition metal as they become readily available by the thermally activated surrounding.

Effects of grain refinement on the biocorrosion and in vitro bioactivity of magnesium.

Magnesium is a new class of biodegradable metals potentially suitable for bone fracture fixation due to its suitable mechanical properties, high degradability and biocompatibility. However, rapid corrosion and loss in mechanical strength under physiological conditions render it unsuitable for load-bearing applications. In the present study, grain refinement was implemented to control bio-corrosion demonstrating improved in vitro bioactivity of magnesium. Pure commercial magnesium was grain refined using different amounts of zirconium (0.25 and 1.0 wt.%). Corrosion behavior was studied by potentiodynamic polarization (PDP) and mass loss immersion tests demonstrating corrosion rate decrease with grain size reduction. In vitro biocompatibility tests conducted by MC3T3-E1 pre-osteoblast cells and measured by DNA quantification demonstrate significant increase in cell proliferation for Mg-1 wt.% Zr at day 5. Similarly, alkaline phosphatase (ALP) activity was higher for grain refined Mg. Alloys were also tested for ability to support osteoclast differentiation using RAW264.7 monocytes with receptor activator of nuclear factor kappa-ß ligand (RANKL) supplemented cell culture. Osteoclast differentiation process was observed to be severely restricted for smaller grained Mg. Overall, the results indicate grain refinement to be useful not only for improving corrosion resistance of Mg implants for bone fixation devices but also potentially modulate bone regeneration around the implant.

Synthesis of uranyl(II), vanadyl(II) and zirconyl urate complexes, spectral, thermal and biological studies.

Three urate chelations were obtained when uric acid was reacted with UO2(CH3COO)2H2O, VOSO4·XH2O and ZrOCl2·XH2O salts with neutralized with 0.1 M NaOH aqueous media. The 1:2 metal-to-ligand complexes [(UO2)2(C5H2N4O3)2](H2O), [(ZrO)2(H2O)2(C5H2N4O3)2] and [VO((C5H3N4O3)2] were characterized by elemental analyses, molar conductivity, (infrared, Raman and UV-vis) spectra, effective magnetic moment in Bohr magnetons, and thermal analysis (TG/DTG). The urate ligand coordinates as mononegative bidentate donor towards the mononuclear central vanadium atom and coordinated as binegative tetradentate mode towards the binuclear dioxouranium and zirconyl centers. The antibacterial activity of the metal complexes were tested against some kind of bacteria and fungi strains and compared with uric acid. The ligand, ZrO(II) and UO2(II) complex showed a week potential degradation on calf thymus DNA, whereas VO(II) complex slightly degraded the DNA.

An alumina toughened zirconia composite for dental implant application: in vivo animal results.

Ceramic materials are widely used for biomedical applications because of their remarkable biological and mechanical properties. Composites made of alumina and zirconia are particularly interesting owing to their higher toughness with respect to the monolithic materials. On this basis, the present study is focused on the in vivo behavior of alumina toughened zirconia (ATZ) dental implants treated with a hydrothermal process. A minipig model was implemented to assess the bone healing through histology and mRNA expression at different time points (8, 14, 28, and 56 days). The novel ATZ implant was compared to a titanium clinical standard. The implants were analyzed in terms of microstructure and surface roughness before in vivo tests. The most interesting result deals with a statistically significant higher digital histology index for ATZ implants with respect to titanium standard at 56 days, which is an unprecedented finding, to the authors' knowledge. Even if further investigations are needed before proposing the clinical use in humans, the tested material proved to be a promising candidate among the possible ceramic dental implants.

Effects of fly ash and boric acid on Y2O3-stabilized tetragonal ZrO2 dispersed with MgAl2O4: An experimental study on rat subcutaneous tissue.

The aim of this study was to evaluate the subcutaneous tissue reaction around zirconia-based materials. Forty-eight male Wistar Albino rats were used in this study. Disk-shaped (1mm height and 5mm diameter) samples composed of 67% spinel (MgAl2O4), 27% tetragonal zirconia polycrystal, 4% (m/m) fly ash and 2% (m/m) boric acid were inserted into dorsal muscles of rats. After 1, 4, 8 and 16 weeks, the animals were sacrificed and zirconia materials were removed with the surrounding tissue. Tissue sections were made with a microtome and then stained with hematoxylin and eosin. Sections were evaluated for the intensity of inflammation. Additionally, the somatic and visceral lymph nodes were evaluated. Data were submitted to one-way analysis of variance (ANOVA) and Tukey HSD tests at a significant level of p < 0.05. There were statistically significant differences between mean inflammatory scores in different experimental periods (p <0.05). In addition, the inflammatory reaction decreased over time. The tested materials had no damaging effect on the rat lymph nodes and did not have a toxic action on the internal organs. Therefore, zirconia polycrystal tested in the present study may offer a promising treatment alternative after further mechanical and biological studies are performed.