Zirconium oxide: analysis of MG63 osteoblast-like cell response by means of a microarray technology

Ultrathin ALD Coatings of Zr and V Oxides on Anodic TiO2 Nanotube Layers: Comparison of the Osteoblast Cell Growth

The current study investigates and compares the biological effects of ultrathin conformal coatings of zirconium dioxide (ZrO2) and vanadium pentoxide (V2O5) on osteoblastic MG-63 cells grown on TiO2 nanotube layers (TNTs). Coatings were achieved by the atomic layer deposition (ALD) technique. TNTs with average tube diameters of 15, 30, and 100 nm were fabricated on Ti substrates (via electrochemical anodization) and were used as primary substrates for the study. The MG-63 cell growth and proliferation after 48 h of incubation on hybrid TNTs/ZrO2 and TNTs/V2O5 surfaces was evaluated in comparison to the uncoated TNTs of each diameter. The density of viable MG-63 cells was assessed for all the TNT surfaces, along with the cell morphology and the spreading behavior (i.e., the cell length). The ultrathin coatings retained the original morphology of the TNTs but changed the surface chemical composition, wettability, and cell behavior, whose interplay is the subject of the present investigation. These findings offer interesting views on the influence of the composition of biomedical implant surfaces, triggered by ALD ultrathin coatings on them. The outcomes of this work shed light on the assessment of the biocompatibility of the two different ALD coatings.

Evaluation of zirconia ceramics fabricated through DLP 3d printing process for dental applications

Zirconia ceramics are versatile materials with remarkable properties such as a high thermal resistance, high fracture strength, and low thermal conductivity. They are chemically inert and highly wear- and corrosion-resistant, making them ideal for a wide range of applications in the aerospace, automotive, and biomedical fields. In dentistry, zirconia ceramics are used for veneers, crowns, bridges, and implants because of their biocompatibility. Despite the various benefits of zirconia ceramics, they are difficult to process because of their high hardness and brittleness. Additive manufacturing (AM) has proven to be a viable alternative to conventional fabrication processes, particularly for the processing of difficult-to-cut materials. AM of ceramics has gained significant attention in recent years because of its flexibility and ability to produce customized geometries rapidly and economically. In this study, the digital light processing (DLP) technique was employed to 3D print yttria-stabilized zirconia. The fabricated zirconia was evaluated and characterized for use in dental applications. Thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) were performed on the green body to assess the decomposition of the additives in the slurry and determine the debinding temperatures. The as-built parts were subjected to debinding and sintering to obtain fully dense zirconia parts. The parts tended to shrink after sintering; therefore, the shrinkage ratios were evaluated and found to be 1.2817, 1.2900, and 1.3388 in the x-, y-, and z-directions, respectively. The average density after sintering was 6.031 g/cc. The flexural strength determined using four-point bending tests was 451.876 MPa, and the tensile and compressive strengths were 143 MPa and 298.4 MPa, respectively.

Nanoscale osseointegration of zirconia evaluated from the interfacial structure between ceria-stabilized tetragonal zirconia and cell-induced hydroxyapatite

BACKGROUND

The osseointegration of zirconia implants has been evaluated based on their implant fixture bonding with the alveolar bone at the optical microscopic level. Achieving nano-level bonding between zirconia and bone apatite is crucial for superior osseointegration; however, only a few studies have investigated nanoscale bonding. This review outlines zirconia osseointegration, including surface modification, and presents an evaluation of nanoscale zirconia-apatite bonding and its structure.

HIGHLIGHT

Assuming osseointegration, the cells produced calcium salts on a ceria-stabilized zirconia substrate. We analyzed the interface between calcium salts and zirconia substrates using transmission electron microscopy and found that 1) the cell-induced calcium salts were bone-like apatite and 2) direct nanoscale bonding was observed between the bone-like apatite and zirconia crystals without any special modifications of the zirconia surface.

CONCLUSION

Structural affinity exists between bone apatite and zirconia crystals. Apatite formation can be induced by the zirconia surface. Zirconia bonds directly with apatite, indicating superior osseointegration in vivo.

Atomic Layer Deposition of Zirconia on Titanium Implants Improves Osseointegration in Rabbit Bones

Purpose

Atomic layer deposition (ALD) is a method that can deposit zirconia uniformly on an atomic basis. The effect of deposited zirconia on titanium implants using ALD was evaluated in vivo.

Methods

Machined titanium implants (MTIs) were used as the Control. MTIs treated by sandblasting with large grit and acid etching (SA) and MTIs deposited with zirconia using ALD are referred to as Groups S and Z, respectively. Twelve implants were prepared for each group. Six rabbits were used as experimental animals. To evaluate the osteogenesis and osteocyte aspects around the implants, radiological and histological analyses were performed. The bone-to-implant contact (BIC) ratio was measured and statistically analyzed to evaluate the osseointegration capabilities.

Results

In the micro-CT analysis, more radiopaque bone tissues were observed around the implants in Groups S and Z. Histological observation found that Groups S and Z had more and denser mature bone tissues around the implants in the cortical bone area. Many new and mature bone tissues were also observed in the medullary cavity area. For the BIC ratio, Groups S and Z were significantly higher than the Control in the cortical bone area (P < 0.017), but there was no significant difference between Groups S and Z.

Conclusion

MTIs deposited with zirconia using ALD (Group Z) radiologically and histologically showed more mature bone formation and activated osteocytes compared with MTIs (Control). Group Z also had a significantly higher BIC ratio than the Control. Within the limitations of this study, depositing zirconia on the surface of MTIs using ALD can improve osseointegration in vivo.

A study on mechanical and tribological properties of eco-friendly synthesized ZrO2-doped borosilicate glasses

The research article aims to investigate the mechanical and tribological characteristics of bioactive glass specimens comprising 31B2O3-20SiO2-24.5Na2O-(24.5-x) CaO and xZrO2 (mol%). This glass system was partially derived from bio-waste, with varying concentrations of Zirconia (ZrO2) represented x (x = 0, 1, 3, and 5). The specimens were fabricated using the traditional melt-quench method. Mechanical studies like hardness and compressive strength were measured using Vickers hardness tester and universal tensile machine respectively, while a pin-on-disk tribometer was used to analyze the tribological characteristics. All the specimens were soaked in SBF for a week to assess in-vitro bioactivity. The research findings indicate that Zirconia inclusion resulted in a significant reduction in the intensity of hydroxyapatite peaks of FTIR and XRD spectra, suggesting a decrease in bioactivity. However, it concurrently resulted in increased glass hardness, with the highest value (∼7.55 GPa) observed in the BSG-5 glass sample. Similarly, compressive strength results demonstrated maximum strength in BSG-5 glass specimen, with a value of approximately ∼132 MPa. Moreover, the tribological properties of the glass system were enhanced, evident from the reduced coefficient of friction and specific wear rate. Notably, the BSG-5 glass specimen exhibited the least wear coefficient of 0.018 mm3/N-m at a track radius of 40 mm and a load of 15N. These findings were further supported by SEM images of the worn-out ZrO2-Doped Borosilicate Glass surface. Overall, the results suggest that the addition of Zirconia to borosilicate glass holds promise for improving its mechanical and tribological characteristics. However, this enhancement comes at the expense of its bioactivity. Consequently, the modified glass system presents a cost effective viable option for various applications, particularly in load-bearing and dental applications.

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.

Biocompatibility of ZrO2 vs. Y-TZP Alloys: Influence of Their Composition and Surface Topography

The osseointegration of implants is defined as the direct anatomical and functional connection between neoformed living bone and the surface of a supporting implant. The biological compatibility of implants depends on various parameters, such as the nature of the material, chemical composition, surface topography, chemistry and loading, surface treatment, and physical and mechanical properties. In this context, the objective of this study is to evaluate the biocompatibility of rough (Ra = 1 µm) and smooth (Ra = 0 µm) surface conditions of yttria–zirconia (Y-TZP) discs compared to pure zirconia (ZrO₂) discs by combining a classical toxicological test, morphological observations by SEM, and a transcriptomic analysis on an in vitro model of human Saos-2 bone cells. Similar cell proliferation rates were observed between ZrO₂ and Y-TZP discs and control cells, regardless of the surface topography, at up to 96 h of exposure. Dense cell matting was similarly observed on the surfaces of both materials. Interestingly, only 110 transcripts were differentially expressed across the human transcriptome, consistent with the excellent biocompatibility of Y-TZP reported in the literature. These deregulated transcripts are mainly involved in two pathways, the first being related to “mineral uptake” and the second being the “immune response”. These observations suggest that Y-TZP is an interesting candidate for application in implantology.

Advancing dental implants: Bioactive and therapeutic modifications of zirconia

Zirconium-based implants have gained popularity in the dental implant field owing to their corrosion resistance and biocompatibility, attributed to the formation of a native zirconia (ZrO₂) film. However, enhanced bioactivity and local therapy from such implants are desirable to enable the earlier establishment and improved long-term maintenance of implant integration, especially in compromised patient conditions. As a result, surface modification of zirconium-based implants have been performed using various physical, chemical and biological techniques at the macro-, micro-, and nano-scales. In this extensive review, we discuss and detail the development of Zr implants covering the spectrum from past and present advancements to future perspectives, arriving at the next generation of highly bioactive and therapeutic nano-engineered Zr-based implants. The review provides in-depth knowledge of the bioactive/therapeutic value of surface modification of Zr implants in dental implant applications focusing on clinical translation.

3D-Printed Polymer-Infiltrated Ceramic Network with Biocompatible Adhesive to Potentiate Dental Implant Applications

The aim of this work was to prepare and characterize polymer-ceramic composite material for dental applications, which must resist fracture and wear under extreme forces. It must also be compatible with the hostile environment of the oral cavity. The most common restorative and biocompatible copolymer, 2,2-bis(p-(2'-2-hydroxy-3'-methacryloxypropoxy)phenyl)propane and triethyleneglycol dimethacrylate, was combined with 3D-printed yttria-stabilized tetragonal zirconia scaffolds with a 50% infill. The proper scaffold deposition and morphology of samples with 50% zirconia infill were studied by means of X-ray computed microtomography and scanning electron microscopy. Samples that were infiltrated with copolymer were observed under compression stress, and the structure's failure was recorded using an Infrared Vic 2DTM camera, in comparison with empty scaffolds. The biocompatibility of the composite material was ascertained with an MG-63 cell viability assay. The microtomography proves the homogeneous distribution of pores throughout the whole sample, whereas the presence of the biocompatible copolymer among the ceramic filaments, referred to as a polymer-infiltrated ceramic network (PICN), results in a safety "damper", preventing crack propagation and securing the desired material flexibility, as observed by an infrared camera in real time. The study represents a challenge for future dental implant applications, demonstrating that it is possible to combine the fast robocasting of ceramic paste and covalent bonding of polymer adhesive for hybrid material stabilization.

Metal-based nanoparticles for bone tissue engineering

Tissue is vital to the organization of multicellular organisms, because it creates the different organs and provides the main scaffold for body shape. The quest for effective methods to allow tissue regeneration and create scaffolds for new tissue growth has intensified in recent years. Tissue engineering has recently used some promising alternatives to existing conventional scaffold materials, many of which have been derived from nanotechnology. One important example of these is metal nanoparticles. The purpose of this review is to cover novel tissue engineering methods, paying special attention to those based on the use of metal-based nanoparticles. The unique physiochemical properties of metal nanoparticles, such as antibacterial effects, shape memory phenomenon, low cytotoxicity, stimulation of the proliferation process, good mechanical and tensile strength, acceptable biocompatibility, significant osteogenic potential, and ability to regulate cell growth pathways, suggest that they can perform as novel types of scaffolds for bone tissue engineering. The basic principles of various nanoparticle-based composites and scaffolds are discussed in this review. The merits and demerits of these particles are critically discussed, and their importance in bone tissue engineering is highlighted.

Influence of Implant Material and Surface on Differentiation and Proliferation of Human Adipose-Derived Stromal Cells

For the guided regeneration of periimplant hard and soft tissues, human adipose-derived stromal cells (hADSC) seem to be a promising source for mesenchymal stromal cells. For this, the proliferation and differentiation of hADSC were evaluated on titanium and zirconia dental implants with different surface treatments. Results were compared to edaphic cells as human osteoblasts (hOB) and human gingival fibroblasts (HGF). Primary cells were cultured on (1) titanium implants with a polished surface (Ti-PT), (2) sandblasted and acid-etched titanium (Ti-SLA), (3) sandblasted and alkaline etched zirconia (ZrO₂-ZLA) and (4) machined zirconia (ZrO₂-M). The cell proliferation and differentiation on osteogenic lineage were assessed after 1, 7 and 14 days. Statistical analysis was performed by one-way ANOVA and a modified Levene test with a statistical significance at p = 0.05. PostHoc tests were performed by Bonferroni-Holm. Zirconia dental implants with rough surface (ZrO₂-ZLA) showed the highest proliferation rates (p = 0.048). The osteogenic differentiation occurred early for zirconia and later for titanium implants, and it was enhanced for rough surfaces in comparison to polished/machined surfaces. Zirconia was more effective to promote the proliferation and differentiation of hADSCs in comparison to titanium. Rough surfaces were able to improve the biological response for both zirconia and titanium.

Zirconia-Based Biomaterials for Hard Tissue Reconstruction

Implantable biomaterials are increasingly important in the practice of modern medicine, including fixative, replacement, and regeneration therapies, for reconstruction of hard tissues in patients with pathologic osseous and dental conditions. A number of newly developed advanced biomaterials have been introduced as promising candidates for tissue reconstruction. Among these, zirconia-based biomaterials have gained attention as a biomaterial for hard tissue reconstruction due to superior mechanical properties and good chemical and biological compatibilities. This review summarizes the types of zirconia, advantages of zirconia-based biomaterials for hard tissue reconstruction including bone and dental tissues, responses of tissue and cells to zirconia, and surface modifications for enhanced bioactivity of zirconia. Current and future applications of zirconia-based biomaterials for bone and dental reconstruction, ie, medical implanted devices, dental prostheses, and biocompatible osteogenic scaffolds, are also discussed.

Genome-wide functional analysis on the molecular mechanism of specifically biosynthesized fluorescence Eu complex

Fluorescence imaging as an attractive diagnostic technique is widely employed for early diagnosis of cancer. Self-biosynthesized fluorescent Eu complex in situ in Hela cells have realized specifically and accurately fluorescence imaging for cancer cells. But the molecular mechanism of the in situ biosynthesized process is still unclear. In order to reveal this mechanism, we have investigated whole-genome expression profiles with cDNA microarray, incubated with Eu solution in Hela cells for 24 h. Methylthiazoltetrazolium (MTT) assay and laser confocal fluorescence microscopy study showed the low cytotoxicity and specifically fluorescence imaging of Eu complex in Hela cells. It is observed that 563 up-regulated genes and 274 down-regulated genes were differentially expressed. Meanwhile, quantitative RT-PCR was utilized to measure the expression of some important genes, which validated the results of microarray data analysis. Besides, GO analysis showed that a wide range of differential expression functional genes involved in three groups, including cellular component, molecular function and cellular biological process. It was evident that some important biological pathways were apparently affected through KEGG pathway analysis, including focal adhesion pathway and PI3K (phosphatidylinositol 3' -kinase)-Akt signaling pathway, which can influence glycolytic metabolism and NAD(P)H-oxidases metabolic pathway.

Biomechanical and histological evaluation of the osseointegration capacity of two types of zirconia implant

The purpose of this study was to evaluate the biomechanical and histological behavior of a ceria-stabilized zirconia-alumina nanocomposite (NanoZr) in comparison with that of 3 mol% yttria-stabilized tetragonal zirconia polycrystalline (3Y-TZP) in Sprague Dawley rats. Cylindrical NanoZr and 3Y-TZP implants (diameter 1 mm, length 2 mm) were used. Implant-surface morphology and surface roughness were determined by scanning white-light interferometry and scanning electron microscopy, respectively. The cylindrical zirconia implants were placed at the distal edge of the femur of Sprague Dawley rats. At weeks 2, 4, and 8, the interfacial shear strength between implant and bone was measured by push-in test. Histological analysis was performed using hard-tissue sections. Bone-implant contact (BIC), the thickness of new bone around the implant within the bone marrow area, and osteoclast numbers were evaluated. The average surface roughness of 3Y-TZP (Sa 0.788 μm) was significantly higher than that of NanoZr (Sa 0.559 μm). The shear strengths of 3Y-TZP and NanoZr were similar at 2 weeks, but at 4 and 8 weeks the shear strength of NanoZr was higher than that of 3Y-TZP. The average BIC values within the bone marrow area for 3Y-TZP and NanoZr were 25.26% and 31.51% at 2 weeks, 46.78% and 38% at 4 weeks, and 47.88% and 56.81% at 8 weeks, respectively. The average BIC values within the cortical area were 38.86% and 58.42% at 2 weeks, 66.82% and 57.74% at 4 weeks, and 79.91% and 78.97% at 8 weeks, respectively. The mean BIC value did not differ significantly between the two zirconia materials at any time point. The NanoZr implants were biocompatible, capable of establishing close BIC, and may be preferred for metal-free dental implants.

Comparison of surface modified zirconia implants with commercially available zirconium and titanium implants: a histological study in pigs

INTRODUCTION

New biomaterials and their various surface modifications should undergo in vitro and in vivo evaluation before clinical trials. The objective of our in vivo study was to evaluate the biocompatibility of newly created zirconium implant surfaces after implantation in the lower jaw of pigs and compare the osseointegration of these dental implants with commercially available zirconium and titanium implants.

MATERIALS AND METHODS

After a healing period of 12 weeks, a histological analysis of the soft and hard tissues and a histomorphometric analysis of the bone-implant contact (BIC) were performed.

RESULTS

The implant surfaces showed an intimate connection to the adjacent bone for all tested implants. The 3 newly created zirconium implant surfaces achieved a BIC of 45% on average in comparison with a BIC of 56% from the reference zirconium implants and 35% from titanium implants. Furthermore, the new zirconium implants had a better attachment to gingival and bone tissues in the range of implant necks as compared with the reference implants.

CONCLUSION

The results suggest that the new implants comparably osseointegrate within the healing period, and they have a good in vivo biocompatibility.

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.

Zirconium ions up-regulate the BMP/SMAD signaling pathway and promote the proliferation and differentiation of human osteoblasts

Zirconium (Zr) is an element commonly used in dental and orthopedic implants either as zirconia (ZrO2) or in metal alloys. It can also be incorporated into calcium silicate-based ceramics. However, the effects of in vitro culture of human osteoblasts (HOBs) with soluble ionic forms of Zr have not been determined. In this study, primary culture of human osteoblasts was conducted in the presence of medium containing either ZrCl4 or Zirconium (IV) oxynitrate (ZrO(NO3)2) at concentrations of 0, 5, 50 and 500 µM, and osteoblast proliferation, differentiation and calcium deposition were assessed. Incubation of human osteoblast cultures with Zr ions increased the proliferation of human osteoblasts and also gene expression of genetic markers of osteoblast differentiation. In 21 and 28 day cultures, Zr ions at concentrations of 50 and 500 µM increased the deposition of calcium phosphate. In addition, the gene expression of BMP2 and BMP receptors was increased in response to culture with Zr ions and this was associated with increased phosphorylation of SMAD1/5. Moreover, Noggin suppressed osteogenic gene expression in HOBs co-treated with Zr ions. In conclusion, Zr ions appear able to induce both the proliferation and the differentiation of primary human osteoblasts. This is associated with up-regulation of BMP2 expression and activation of BMP signaling suggesting this action is, at least in part, mediated by BMP signaling.

Zirconium ions up-regulate the BMP/SMAD signaling pathway and promote the proliferation and differentiation of human osteoblasts

Zirconium (Zr) is an element commonly used in dental and orthopedic implants either as zirconia (ZrO2) or in metal alloys. It can also be incorporated into calcium silicate-based ceramics. However, the effects of in vitro culture of human osteoblasts (HOBs) with soluble ionic forms of Zr have not been determined. In this study, primary culture of human osteoblasts was conducted in the presence of medium containing either ZrCl4 or Zirconium (IV) oxynitrate (ZrO(NO3)2) at concentrations of 0, 5, 50 and 500 µM, and osteoblast proliferation, differentiation and calcium deposition were assessed. Incubation of human osteoblast cultures with Zr ions increased the proliferation of human osteoblasts and also gene expression of genetic markers of osteoblast differentiation. In 21 and 28 day cultures, Zr ions at concentrations of 50 and 500 µM increased the deposition of calcium phosphate. In addition, the gene expression of BMP2 and BMP receptors was increased in response to culture with Zr ions and this was associated with increased phosphorylation of SMAD1/5. Moreover, Noggin suppressed osteogenic gene expression in HOBs co-treated with Zr ions. In conclusion, Zr ions appear able to induce both the proliferation and the differentiation of primary human osteoblasts. This is associated with up-regulation of BMP2 expression and activation of BMP signaling suggesting this action is, at least in part, mediated by BMP signaling.

Microstructured zirconia surfaces modulate osteogenic marker genes in human primary osteoblasts

In dentistry, zirconia has been used since the early 1990s for endodontic posts, more recently for implant abutments and frameworks for fixed dental prostheses. Zirconia is biocompatible and mechanically strong enough to serve as implant material for oral implants. Although several zirconia implant systems are available, currently the scientific and clinical data for zirconia implants are not sufficient to recommend them for routine clinical use. Here the influence of microstructured yttria-stabilized zirconia (YZ) on human primary osteoblast (HOB) behavior was determined. YZ surfaces were treated by sandblasting (YZ-S), acid etching (YZ-SE) and additionally heat treatment (YZ-SEH). Morphological changes of HOB were determined by scanning electron microscopy. Actin cytoskeleton was investigated by laser scanning microscopy and analyzed by novel actin quantification software. Differentiation of HOB was determined by real time RT-PCR. Improved mechanical interlocking of primary HOB into the porous microstructure of the acid etched and additionally heat treated YZ-surfaces correlates with drastically increased osteocalcin (OCN) gene expression. In particular, OCN was considerably elevated in primary HOB after 3 days on YZ-SE (13-fold) as well as YZ-SEH (12-fold) surfaces. Shorter actin filaments without any favored orientation on YZ-SE and YZ-SEH surfaces are associated with higher roughness (Ra) values. Topographically modified yttria-stabilized zirconia is a likely material for dental implants with cell stimulating properties achieving or actually exceeding those of titanium.

An Overview of Zirconia Dental Implants: Basic Properties and Clinical Application of Three Cases

Due to the possible aesthetic problems of titanium implants, the developments in ceramic implant materials are increasing. Natural tooth colored ceramic implants may be an alternative to overcome aesthetic problems. The purpose of this article is to give information about the basic properties of dental zirconia implants and present 3 cases treated with two-piece zirconia implants. Two-piece zirconia dental implants, 4.0 mm diameter and 11.5 mm in length, were inserted into maxillary incisor region. They were left for 6 months to osseointegrate. Panoramic and periapical radiographs were obtained and examined for bone-implant osseointegration. During the follow-up period the patients were satisfied with their prosthesis and no complication was observed.

An overview of recent advances in designing orthopedic and craniofacial implants

Great deal of research is still going on in the field of orthopedic and craniofacial implant development to resolve various issues being faced by the industry today. Despite several disadvantages of the metallic implants, they continue to be used, primarily because of their superior mechanical properties. In order to minimize the harmful effects of the metallic implants and its by-products, several modifications are being made to these materials, for instance nickel-free stainless steel, cobalt-chromium and titanium alloys are being introduced to eliminate the toxic effects of nickel being released from the alloys, introduce metallic implants with lower modulus, reduce the cost of these alloys by replacing rare elements with less expensive elements etc. New alloys like tantalum, niobium, zirconium, and magnesium are receiving attention given their satisfying mechanical and biological properties. Non-oxide ceramics like silicon nitride and silicon carbide are being currently developed as a promising implant material possessing a combination of properties such as good wear and corrosion resistance, increased ductility, good fracture and creep resistance, and relatively high hardness in comparison to alumina. Polymer/magnesium composites are being developed to improve mechanical properties as well as retain polymer's property of degradation. Recent advances in orthobiologics are proving interesting as well. This paper thus deals with the latest improvements being made to the existing implant materials and includes new materials being introduced in the field of biomaterials.

Surface modification of zirconium by anodisation as material for permanent implants: in vitro and in vivo study

The potential use of anodised zirconium as permanent implant has been investigated. Zirconium was anodised at constant potential between 3 and 30 V in H(3)PO(4). Electrochemical assays were conducted in simulated body fluid solution (SBF) in order to evaluate the effect of the surface oxide on the corrosion resistance in vitro after 30 days of immersion. The rupture potential increases when increasing thickness of the anodic surface film. The increase in the barrier effect when increasing anodising potential is also verified by EIS. Anodisation in H(3)PO(4) proved to increase the apatite formation capability of zirconium in a single step. In vivo bone formation was also analysed by implanting the modified materials in Wistar rats. Anodised Zr presents higher corrosion resistance in SBF in all the studied immersion times when compared with non anodised Zr. Additionally, in vivo experiments evidence bone generation and growth in contact with zirconium implants both in the as-received and anodised condition.

Bottom-up engineering of the surface roughness of nanostructured cubic zirconia to control cell adhesion

Nanostructured cubic zirconia is a strategic material for biomedical applications since it combines superior structural and optical properties with a nanoscale morphology able to control cell adhesion and proliferation. We produced nanostructured cubic zirconia thin films at room temperature by supersonic cluster beam deposition of nanoparticles produced in the gas phase. Precise control of film roughness at the nanoscale is obtained by operating in a ballistic deposition regime. This allows one to study the influence of nanoroughness on cell adhesion, while keeping the surface chemistry constant. We evaluated cell adhesion on nanostructured zirconia with an osteoblast-like cell line using confocal laser scanning microscopy for detailed morphological and cytoskeleton studies. We demonstrated that the organization of cytoskeleton and focal adhesion formation can be controlled by varying the evolution of surface nanoroughness.

Molecular and genomic approach for understanding the gene-environment interaction between Nrf2 deficiency and carcinogenic nickel-induced DNA damage

Nickel (II) is a toxic and carcinogenic metal which induces a redox imbalance following oxidative stress. Nuclear factor erythroid-2 related factor 2 (Nrf2) is a redox factor that regulates oxidation/reduction status and consequently mediates cytoprotective responses against exposure to environmental toxicants. In this study, we investigated the protective roles of the Nrf2 gene against oxidative stress and DNA damage induced by nickel at sub-lethal doses. Under nickel exposure conditions, we detected significantly increased intracellular ROS generation, in addition to higher amounts of DNA damage using comet assay and γ-H2AX immunofluorescence staining in Nrf2 lacking cells, as compared to Nrf2 wild-type cells. In addition, we attempted to identify potential nickel and Nrf2-responsive targets and the relevant pathway. The genomic expression data were analyzed using microarray for the selection of synergistic effect-related genes by Nrf2 knockdown under nickel treatment. In particular, altered expressions of 6 upregulated genes (CAV1, FOSL2, MICA, PIM2, RUNX1 and SLC7A6) and 4 downregulated genes (APLP1, CLSPN, PCAF and PRAME) were confirmed by qRT-PCR. Additionally, using bioinformatics tool, we found that these genes functioned principally in a variety of molecular processes, including oxidative stress response, necrosis, DNA repair and cell survival. Thus, we describe the potential biomarkers regarded as molecular candidates for Nrf2-related cellular protection against nickel exposure. In conclusion, these findings indicate that Nrf2 is an important factor with a protective role in the suppression of mutagenicity and carcinogenicity by environmental nickel exposure in terms of gene-environment interaction.

Anatase-based implants nanocoating on stem cells derived from adipose tissue

PURPOSE

The aim of this study was to investigate the effect of a new anatase coating with antibacterial properties (Bactercline anatase coating [BAC]) on dental implants in the commitment of stem cells derived from adipose tissue to osteoblasts.

MATERIALS AND METHODS

Using real-time reverse transcription polymerase chain reaction, the quantitative expression of specific genes, such as transcriptional factors (runx2 and sp7), bone-related genes (spp1, col1a1, col3a1, alpl, and fosl1), and mesenchymal stem cells marker (eng), was examined.

RESULTS

BAC caused induction of bone-related genes such as sp7, fosl1, alpl, and spp1. In contrast, the expression of runx2, col3a1, and col1a1 was decreased in stem cells treated with BAC with respect to untreated cells.

CONCLUSION

The obtained results are relevant to better understand the molecular mechanism of bone regeneration and as a model for comparing other materials with similar clinical effects.

Thin film composites of nanocrystalline ZrO(2) and diamond-like carbon: Synthesis, structural properties and bone cell proliferation

We report on the synthesis of thin composites of diamond-like carbon (DLC) and nanocrystalline ZrO(2) deposited using pulsed direct current plasma-enhanced chemical vapor deposition at low temperatures (<120 degrees C). Films containing up to 21at.% Zr were prepared (hydrogen was not included in the calculation) and their structural and surface properties were determined using a number of spectroscopic methods and contact angle measurements. Bone cell adhesion to the films was studied using a 3 day cell culture with osteoblasts. These nanocomposites (DLC-ZrO(2)) consist of tetragonal ZrO(2) nanocrystals with an average size of 2-5 nm embedded in an amorphous matrix consisting predominantly of DLC. The surface water contact angle of the films increased from approximately 60 degrees to 80 degrees as the Zr content increased from 0 to 21at.%. The cell culture study revealed that although the cell counts were not significantly different, the morphology of the osteoblasts growing on the DLC-ZrO(2) nanocomposites was markedly different from that of cells growing on DLC alone. Cells growing on the DLC-ZrO(2) surfaces were less spread out and had a smaller cell area in comparison with those growing on DLC surfaces. In some areas on the DLC-ZrO(2) surfaces, large numbers of cells appeared to coalesce. It is postulated that the difference in cell morphology between osteoblasts on DLC-ZrO(2) surfaces and DLC surfaces is related to the presence of very small tetragonal nanocrystals of ZrO(2) in the composite film.

Effects of pulsed electromagnetic fields on human osteoblastlike cells (MG-63): a pilot study

BACKGROUND

Although pulsed electromagnetic fields (PEMFs) are used to treat delayed unions and nonunions, their mechanisms of action are not completely clear. However, PEMFs are known to affect the expression of certain genes.

QUESTIONS/PURPOSES

We asked (1) whether PEMFs affect gene expression in human osteoblastlike cells (MG63) in vitro, and (2) whether and to what extent stimulation by PEMFs induce cell proliferation and differentiation in MG-63 cultures.

METHODS

We cultured two groups of MG63 cells. One group was treated with PEMFs for 18 hours whereas the second was maintained in the same culture condition without PEMFs (control). Gene expression was evaluated throughout cDNA microarray analysis containing 19,000 genes spanning a substantial fraction of the human genome.

RESULTS

PEMFs induced the upregulation of important genes related to bone formation (HOXA10, AKT1), genes at the transductional level (CALM1, P2RX7), genes for cytoskeletal components (FN1, VCL), and collagenous (COL1A2) and noncollagenous (SPARC) matrix components. However, PEMF induced downregulation of genes related to the degradation of extracellular matrix (MMP-11, DUSP4).

CONCLUSIONS AND CLINICAL RELEVANCE

PEMFs appear to induce cell proliferation and differentiation. Furthermore, PEMFs promote extracellular matrix production and mineralization while decreasing matrix degradation and absorption. Our data suggest specific mechanisms of the observed clinical effect of PEMFs, and thus specific approaches for use in regenerative medicine.

Comparison of zirconia and titanium implants after a short healing period. A pilot study in minipigs

The aim of this animal study was to investigate and compare the osseointegration of zirconia and titanium dental implants. 14 one-piece zirconia implants and 7 titanium implants were inserted into the mandibles of 7 minipigs. The zirconia implants were alternately placed submerged and non-submerged. To enable submerged healing, the supraosseous part was removed, using a diamond saw. The titanium implants were all placed submerged. After a healing period of 4 weeks, a histological analysis of the soft and hard tissue and a histomorphometric analysis of the bone-implant contact (BIC) and relative peri-implant bone-volume density (rBVD; relation to bone-volume density of the host bone) was performed. Two zirconia implants were found to be loose. All other implants were available for evaluation. For submerged zirconia and titanium implants, the implant surface showed an intimate connection to the neighbouring bone, with both types achieving a BIC of 53%. For the non-submerged zirconia implants, some crestal epithelial downgrowth could be detected, with a resultant BIC of 48%. Highest rBVD values were found for submerged zirconia (80%), followed by titanium (74%) and non-submerged zirconia (63%). The results suggest that unloaded zirconia and titanium implants osseointegrate comparably, within the healing period studied.

Global gene expression analysis for evaluation and design of biomaterials

Comprehensive gene expression analysis using DNA microarrays has become a widespread technique in molecular biological research. In the biomaterials field, it is used to evaluate the biocompatibility or cellular toxicity of metals, polymers and ceramics. Studies in this field have extracted differentially expressed genes in the context of differences in cellular responses among multiple materials. Based on these genes, the effects of materials on cells at the molecular level have been examined. Expression data ranging from several to tens of thousands of genes can be obtained from DNA microarrays. For this reason, several tens or hundreds of differentially expressed genes are often present in different materials. In this review, we outline the principles of DNA microarrays, and provide an introduction to methods of extracting information which is useful for evaluating and designing biomaterials from comprehensive gene expression data.

Response of osteoblast-like SAOS-2 cells to zirconia ceramics with different surface topographies

OBJECTIVES

Zirconia is a suitable biomaterial for use in medicine (stomatology, orthopaedics) due to its good biocompatibility and outstanding mechanical properties. This study compares the effect of (i) zirconia to the widely used titanium and (ii) zirconia with two different surface topographies (sandblasted and sandblasted/etched) on the adhesion, proliferation and differentiation of SAOS-2 osteoblasts.

METHODS

SAOS-2 cells were cultured on either sandblasted or sandblasted/etched zirconia and compared with sandblasted/etched titanium. 2 and 24 h after plating, cell morphology was investigated by scanning electron microscope (SEM) and fluorescence imaging. At 24 and 48 h, cell number-relevant parameters were determined. Alkaline phosphatase (ALP) activity and mineral accumulation were measured at days 8, 11, 15 and day 22 of culture, respectively.

RESULTS

SEM and fluorescence images revealed a faster spreading as well as higher number of adherent cells after 24 h incubation on zirconia compared with titanium. Also, the cellular metabolic activity after 24 h and the proliferation rate after 48 h is higher with zirconia compared with titanium. Zirconia had a more pronounced effect compared with titanium on the differentiation of SAOS-2 cells: ALP activity, an early differentiation marker increased earlier and mineralization, a late differentiation marker was increased. Only minor differences were found between zirconia with two different surface topographies; etched zirconia promoted slightly greater the differentiation of SAOS-2 cells.

CONCLUSIONS

These data indicate that zirconia mediates a pronounced stronger effect on the adhesion, proliferation and differentiation compared with titanium; and that topographical differences of zirconia have minor effects on osteoblast biology.

Diphenylhydantoin plays a role in gene expression related to cytoskeleton and protein adhesion in human normal palate fibroblasts

AIMS

Morphogenetic processes during palate development are related to extracellular matrix composition. The cell-extracellular matrix relation plays a role in cell activity and in gene expression. We studied the effect of diphenylhydantoin, a teratogen known to induce cleft palate in human newborns, on extracellular matrix production. We investigated whether diphenylhydantoin treatment caused any differences in glycosaminoglycans, collagen synthesis and gene expression in human normal palate fibroblasts.

METHODS

Human palate fibroblasts were maintained for 24 hours in serum-free 199 medium containing 5 microg/mL (3)H-glucosamine or (3)H proline hydrochloride. Collagen and glycosaminoglycan classes were then measured using biochemical methods, gene expression with microarray analysis and cytoskeleton components with immunofluorescent antibodies and computer analysis.

RESULTS

In normal fibroblasts diphenylhydantoin reduced collagen and glycosaminoglycan synthesis with a marked effect on sulphated glycosaminoglycans. There were also substantial decreases in tubulin, vimentin and alpha-actin staining and an increase of vinculin compared to controls. Diphenylhydantoin acted on several genes related to the synthesis of cytoskeleton and adhesion membrane proteins. It inhibited caderin, caveolin, RTK and alpha-actin, and increased nectin, cytoplasmatic FRG vinculin, ITGA, ITGB extracellular matrix ligand and EDG2 gene expression. DNA binding gene expression, which plays a role in cell growth and senescence, was activated.

CONCLUSIONS

Since cell activity is dependent on the cell morphology and extracellular matrix composition, these findings indicate that in human normal palate fibroblasts diphenylhydantoin can modify cytoskeletal components and extracellular matrix-cell adhesion, with consequent effects on gene expression. These changes might be related to anomalous palate development.

In vitro reaction of human osteoblasts on alumina-toughened zirconia

OBJECTIVES

Alumina toughening enhances the mechanical properties of zirconia ceramics but the biocompatibility of this material has rarely been addressed. In this study, we examined the osteoblast response to alumina-toughened zirconia (ATZ) with different surface topographies.

MATERIAL AND METHODS

Human osteoblasts isolated from maxillary biopsies of four patients were cultured and seeded onto disks of the following substrates: ATZ with a machined surface, airborne-particle abraded ATZ, airborne-particle abraded and acid etched ATZ. Airborne-particle abraded and acid etched titanium (SLA) and polystyrene disks served as a reference control. The surface topography of the various substrates was characterized by profilometry (R(a), R(p-v)) and scanning electron microscopy (SEM). Cell proliferation, cell-covered surface area, alkaline phophatase (ALP) and osteocalcin production were determined. The cell morphology was analyzed on SEM images.

RESULTS

The surface roughness of ATZ was increased by airborne-particle abrasion, but with the R(a) and R(p-v) values showing significantly lower values compared with SLA titanium (Mann-Whitney U-test P<0.05). The proliferation assay revealed no statistically significant differences between the ATZ substrates, SLA titanium and polystyrene (Kruskal-Wallis test, P>0.05). All substrates were densely covered by osteoblasts. ALP and osteocalcin production was similar on the examined surfaces. Cell morphology analysis revealed flat-spread osteoblasts with cellular extensions on all substrates.

CONCLUSIONS

These results indicate that ATZ may be a viable substrate for the growth and differentiation of human osteoblasts. Surface modification of ATZ by airborne-particle abrasion alone or in combination with acid etching seems not to interfere with the growth and differentiation of the osteoblasts.

Gene expression, cytoskeletal changes and extracellular matrix synthesis in human osteoblasts treated with cyclosporin A

Cyclosporin A (CyA) is an immunosuppressive agent used to prevent allograft rejection, but unfortunately it causes adverse effects such as bone diseases, osteoporosis and osteomalacia. These pathologies involve an imbalance between synthesis, degradation and mineralization of extracellular matrix. CyA can modify extracellular matrix components such as glycosaminoglycans (GAG) and collagen fibers. In addition, normal cell activity is dependent on cell morphology and substrate cell attachment. We treated normal human osteoblasts with CyA and analyzed: (i) gene expression by a microarray method; (ii) extracellular GAG and collagen after (3)H-glucosamine and Western blot analysis; and (iii) cytoskeletal changes, using actin and tubulin fluorescent antibodies. CyA increased intra- and extracellular GAG and extracellular GAG classes such as hyaluronic acid, chondroitin sulphate, and dermatan sulphate; there was no noteworthy effect on heparan sulphate and the ratio of non-sulphated to sulphated GAG. In osteoblast cultures the drug reduced cytoskeletal actin, while tubulin did not change. In vivo the osteoblasts showed morphological changes with different extracellular matrix synthesis. Microarray analysis indicated the inhibition of gene pathways related to Wnt signaling molecules, and the cytoskeletal and focal adhesion cascade. In in vitro human osteoblasts CyA modified gene expression related to cytoskeletal pattern organization and cell morphology. Since in bone pathologies osteoblasts show different morphology related to cell size, these data suggest that in vivo osteoblast different functions could be dependent on alteration of osteoblast differentiation.

Comparison between genetic portraits of osteoblasts derived from primary cultures and osteoblasts obtained from human pulpar stem cells

Harvesting bone for autologous grafting is a daily problem encountered by craniofacial and oral surgeons. Stem cells derived from human dental pulp are able to differentiate in osteoblasts and are a potential source of autologous bone produced in vitro. However, as stem cells are characterized by self-renewing and commitment in several cellular subtypes (ie, pluripotential differentiation), some concerns may arise as regards their potential uncontrolled proliferation. To screen the behavior of osteoblasts derived from human pulpar stem cells (ODHPSCs), we used microarray techniques to identify genes that are differently regulated in ODHPSC in comparison to normal osteoblasts (NOs). Osteoblasts derived from human pulpar stem cells were obtained from human dental pulp, and cells were selected using a cytometer. The cell profile was c-kit+/CD34+/STRO-1+/CD45-. These cells were capable of differentiation of osteoblasts in vitro. By using DNA microarrays containing 19,200 genes, we identified in ODHPSC some genes whose expression was significantly up- and downregulated compared to NO. The differentially expressed genes have different functional activities: (a) cell differentiation, (b) developmental maturation, (c) cell adhesion, and (d) production of cytoskeleton elements. Thus, some molecular differences exist between NO and ODHPSC, although the previously considered histologic parameters show a normal phenotype.

Zirconium oxide regulates RNA interfering of osteoblast-like cells

Zirconium oxide (ZO) has outstanding mechanical properties, high biocompatibility and high resistance to scratching. Since dental implants are made with ZO and the genetic effects of ZO on osteoblasts are incompletely understood, we used microRNA microarray techniques to investigate the translation process in osteoblasts exposed to ZO. By using miRNA microarrays containing 329 probes designed from Human miRNA sequences, we identified in osteoblast-like cells line (MG-63) cultured on ZO disks several miRNA whose expression was significantly modified. The most notable regulated genes acting on osteoblasts are: NOG, SHOX, IGF1, BMP1 and FGFR1. The data reported below represent the first study on translation regulation in osteoblasts exposed to zirconium and one in which the effect of ZO on bone formation has been detected.

Biological considerations on the use of zirconia for dental devices

Zirconium oxide, known as zirconia, is a ceramic material with optimal esthetical and mechanical properties. Zirconia stabilized with yttrium oxide has the best properties for medical uses. A stress on ZrO2 surface creates a crystalline modification that opposes to propagation of cracks. Zirconia core for fixed partial dentures (FPD) on anterior and posterior teeth and on implants are now available. Clinical evaluations after 3 years report good percentage of success for zirconia fixed partial denture. Zirconia biocompatibility was studied in vivo and in vitro by orthopedic research; no adverse responses were reported on insertion of ZrO2 samples in bone or muscle. In vitro experimentation showed absence of mutation and a good viability of cells cultured on this material.

Genetic effect of zirconium oxide coating on osteoblast-like cells

Zirconium is widely used as material for prosthetic devices because its good mechanical and chemical properties. When exposed to oxygen, zirconium becomes zirconium oxide (ZrO(2)), which is biocompatible. ZrO(2) can be also prepared as a colloidal suspension and then used to coat surfaces. Zirconium oxide coating (ZrO(2)C) can potentially have specific biologic effects, and among them is bone formation related to implant osseointegration. How this biomaterial alters osteoblast activity to promote bone formation is poorly understood. We therefore attempted to address this question by using microarray techniques to identify genes that are differently regulated in osteoblasts exposed to ZrO(2)C. By using DNA microarrays containing 20,000 genes, we identified in osteoblast-like cell lines (MG-63) cultured with ZrO(2)C several genes whose expression was significantly upregulated or downregulated. The differentially expressed genes cover a broad range of functional activities: (a) cell cycle regulation, (b) signal transduction, (c) immunity, and (d) cytoskeleton component. The data reported are, to our knowledge, the first genetic portrait of ZrO(2)C effects. They can be relevant to better understand the molecular mechanism of bone regeneration and as a model for comparing other materials with similar clinical effects.