Synthesis, mechanical properties and bioactivity of nanostructured zirconia

Implant deformation and implant-abutment fracture resistance after standardized artificial aging: An in vitro study

BACKGROUND AND PURPOSE

Zirconia abutments have been widely adopted in clinical implant practice. The unique mechanical properties of zirconia may significantly affect the long-term prognosis of implant treatments. The purpose of this study was to investigate the influence of abutment material on implant deformation and fracture resistance of internal conical connection implant-abutment complexes of two diameters after standardized artificial aging.

MATERIALS AND METHODS

Thirty original abutments (one-piece titanium, one-piece zirconia, zirconia with alloy base) with two diameters (regular, narrow) were connected to internal conical connection implants and subjected to a standardized artificial aging process consisting of thermal cycling and mechanical cyclic loading. Microcomputed tomography (μCT) scans of implant bodies were performed before and after aging. 3-dimensional images of implant bodies were generated from the μCT scans and aligned for before and after aging to calculate the volumetric deformation amount. Finally, fracture resistance was measured using a mechanical static loading test for the surviving aged and 30 brand-new specimens.

RESULTS

All specimens survived artificial aging. No significant difference in implant deformation was found in the regular groups (p = 0.095). In narrow groups, the one-piece zirconia group showed significantly less deformation (p < 0.0001). For fracture resistance, no significant decrease was observed after aging in any group (p > 0.05). One-piece zirconia abutments showed significantly lower strength than the other two materials for both diameters (p < 0.0001).

CONCLUSIONS

In the regular diameter system, abutment material had no significant influence on the tested mechanical property degradation after simulated long-term oral use. The mechanical performance of narrow diameter one-piece zirconia abutments differed from the other two materials. For optimal performance, one-piece zirconia abutments should be adopted only in anterior regions.

Strategies to improve bioactive and antibacterial properties of polyetheretherketone (PEEK) for use as orthopedic implants

Polyetheretherketone (PEEK) has gradually become the mainstream material for preparing orthopedic implants due to its similar elastic modulus to human bone, high strength, excellent wear resistance, radiolucency, and biocompatibility. Since the 1990s, PEEK has increasingly been used in orthopedics. Yet, the widespread application of PEEK is limited by its bio-inertness, hydrophobicity, and susceptibility to microbial infections. Further enhancing the osteogenic properties of PEEK-based implants remains a difficult task. This article reviews some modification methods of PEEK in the last five years, including surface modification of PEEK or incorporating materials into the PEEK matrix. For surface modification, PEEK can be modified by chemical treatment, physical treatment, or surface coating with bioactive substances. For PEEK composite material, adding bioactive filler into PEEK through the melting blending method or 3D printing technology can increase the biological activity of PEEK. In addition, some modification methods such as sulfonation treatment of PEEK or grafting antibacterial substances on PEEK can enhance the antibacterial performance of PEEK. These strategies aim to improve the bioactive and antibacterial properties of the modified PEEK. The researchers believe that these modifications could provide valuable guidance on the future design of PEEK orthopedic implants.

Preparation of Zirconium Hydrogen Phosphate Coatings on Sandblasted/Acid-Etched Titanium for Enhancing Its Osteoinductivity and Friction/Corrosion Resistance

Background

Sandblasted/acid-etched titanium (SLA-Ti) implants are widely used for dental implant restoration in edentulous patients. However, the poor osteoinductivity and the large amount of Ti particles/ions released due to friction or corrosion will affect its long-term success rate.

Purpose

Various zirconium hydrogen phosphate (ZrP) coatings were prepared on SLA-Ti surface to enhance its friction/corrosion resistance and osteoinduction.

Methods

The mixture of ZrCl₄ and H₃PO₄ was first coated on SLA-Ti and then calcined at 450°C for 5 min to form ZrP coatings. In addition to a series of physiochemical characterization such as morphology, roughness, wettability, and chemical composition, their capability of anti-friction and anti-corrosion were further evaluated by friction-wear test and by potential scanning. The viability and osteogenic differentiation of MC3T3-E1 cells on different substrates were investigated via MTT, mineralization and PCR assays.

Results

The characterization results showed that there were no significant changes in the morphology, roughness and wettability of ZrP-modified samples (SLA-ZrP0.5 and SLA-ZrP0.7) compared with SLA group. The results of electrochemical corrosion displayed that both SLA-ZrP0.5 and SLA-ZrP0.7 (especially the latter) had better corrosion resistance than SLA in normal saline and serum-containing medium. SLA-ZrP0.7 also exhibited the best friction resistance and great potential to enhance the spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells.

Conclusion

We determined that SLA-ZrP0.7 had excellent comprehensive properties including anti-corrosion, anti-friction and osteoinduction, which made it have a promising clinical application in dental implant restoration.

Designing of Co0.5Ni0.5GaxFe2-xO4 (0.0 ≤ x ≤ 1.0) Microspheres via Hydrothermal Approach and Their Selective Inhibition on the Growth of Cancerous and Fungal Cells

The current study offers an efficient design of novel nanoparticle microspheres (MCs) using a hydrothermal approach. The Co0.5Ni0.5GaxFe2-xO4 (0.0 ≤ x ≤ 1.0) MCs were prepared by engineering the elements, such as cobalt (Co), nickel (Ni), iron (Fe), and gallium (Ga). There was a significant variation in MCs' physical structure and surface morphology, which was evaluated using energy dispersive X-ray analysis (EDX), X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HR-TEM), and scanning electron microscope (SEM). The anti-proliferative activity of MCs was examined by MTT assay and DAPI staining using human colorectal carcinoma cells (HCT-116), human cervical cancer cells (HeLa), and a non-cancerous cell line-human embryonic kidney cells (HEK-293). Post 72 h treatment, MCs caused a dose dependent inhibition of growth and proliferation of HCT-116 and HeLa cells. Conversely, no cytotoxic effect was observed on HEK-293 cells. The anti-fungal action was assessed by the colony forming units (CFU) technique and SEM, resulting in the survival rate of Candida albicans as 20%, with severe morphogenesis, on treatment with MCs x = 1.0. These findings suggest that newly engineered microspheres have the potential for pharmaceutical importance, in terms of infectious diseases and anti-cancer therapy.

Effect of nanostructured zirconium dioxide incorporation in an experimental adhesive resin

OBJECTIVES

The aim of this study was to evaluate the influence of nanostructured zirconium dioxide incorporation in an experimental adhesive resin.

METHODS

ZrO₂ particles were characterized by X-ray diffraction (XRD), micro-Raman spectroscopy and Brunauer-Emmett-Teller (B.E.T). Experimental adhesive resins were formulated with 0, 0.5, 1, 4.8, and 9.1% ZrO₂ in weight. The adhesives were evaluated based on degree of conversion (DC), radiopacity, softening in solvent and microtensile bond strength (μTBS) 24 h and after 1 year of aging. Mineral deposition at the hybrid layer was assessed with micro-Raman spectroscopy at the baseline and after 14 days.

RESULTS

XRD showed monoclinic and tetragonal phases of ZrO_2.particles. B.E.T data revealed a surface area of 37.41 m²/g, and typical chemical groups were shown on the Raman spectra_. The addition of ZrO₂ did not influence the radiopacity. The addition of 4.8% and 9.1 wt.% ZrO₂ showed higher initial hardness with increased softening in solvent (P < 0.05) and promoted mineral deposition at the dentin interface. DC was significantly increased in the group with 1% ZrO₂ (P < 0.05). The μTBS test showed difference on the group with 9.1 wt.% of ZrO₂, with a significant reduction after aging.

CONCLUSION

The incorporation of ZrO₂ promoted mineral deposition on the adhesive interface and the addition of 1 wt.% caused a significant increase on the DC without compromising the other physicochemical characteristics, which may prove promising for the development of new dental adhesive systems.

CLINICAL RELEVANCE

The mineral deposition on the hybrid layer can result in a longer stability of the adhesive, thus delaying the hydrolytic degradation.

rBMSC and bacterial responses to isoelastic carbon fiber-reinforced poly(ether-ether-ketone) modified by zirconium implantation

PEEK-based biomaterials have great potential applications as hard tissue substitutes in bone tissue engineering. However, inherent bio-inert properties limited their clinical use. In order to improve the bioactivity, in this work, zirconium ions were implanted into the carbon fiber-reinforced PEEK (CFR-PEEK) using plasma immersion ion implantation (PIII) technology. Surface morphologies and chemical compositions of Zr-PIII treated samples were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), respectively. The results indicated that nanostructures and ZrO₂ nanoparticles were formed on the surface of CFR-PEEK after Zr-PIII. Mechanical tests revealed that nanohardness, elastic modulus, and elastic resistance increased after implantation, especially for the elastic modulus with a maximum value of about 14 GPa, which is much close to that of human natural bone. In vitro cellular experiments showed that Zr-PIII treated samples enhanced the initial adhesion of rBMSCs, spreading and proliferation significantly. Moreover, the heightened ALP activity, collagen secretion, and extracellular matrix mineralization suggested that Zr-PIII treatment could greatly lead to an up-regulated osteogenic differentiation of rBMSCs on CFR-PEEK. In addition, antibacterial properties were also investigated and the results showed that Zr-PIII treated CFR-PEEK with nanostructures exhibited obvious antibacterial activity against S. aureus but no effect on E. coli.

Calcium Silicate-Based Cements Associated with Micro- and Nanoparticle Radiopacifiers: Physicochemical Properties and Bioactivity

Objective. The aim of this study was to evaluate the physicochemical properties and bioactivity of two formulations of calcium silicate-based cements containing additives (CSCM) or resin (CSCR), associated with radiopacifying agents zirconium oxide (ZrO2) and niobium oxide (Nb2O5) as micro- and nanoparticles; calcium tungstate (CaWO4); and bismuth oxide (Bi2O3). MTA Angelus was used as control. Methods. Surface features and bioactivity were evaluated by scanning electron microscopy and the chemical composition by energy dispersive X-ray spectrometry (EDS-X). Results. CSCM and CSCR presented larger particle sizes than MTA. Hydroxyapatite deposits were found on the surface of some materials, especially when associated with the radiopacifier with ZrO2 nanoparticles. All the cements presented calcium, silicon, and aluminum in their composition. Conclusion. Both calcium silicate-based cements presented composition and bioactivity similar to MTA when associated with the radiopacifiers evaluated.