Design and surface characterization of micropatterned silica coatings for zirconia dental implants

Gallium-doped zirconia coatings modulate microbiological outcomes in dental implant surfaces

Despite the significant recent advances in manufacturing materials supporting advanced dental therapies, peri-implantitis still represents a severe complication in dental implantology. Herein, a sol-gel process is proposed to easily deposit antibacterial zirconia coatings onto bulk zirconia, material, which is becoming very popular for the manufacturing of abutments. The coatings' physicochemical properties were analyzed through x-ray diffraction and scanning electron microscopy-energy-dispersive x-ray spectroscopy investigations, while their stability and wettability were assessed by microscratch testing and static contact angle measurements. Uniform gallium-doped tetragonal zirconia coatings were obtained, featuring optimal mechanical stability and a hydrophilic behavior. The biological investigations pointed out that gallium-doped zirconia coatings: (i) displayed full cytocompatibility toward human gingival fibroblasts; (ii) exhibited significant antimicrobial activity against the Aggregatibacter actinomycetemcomitans pathogen; (iii) were able to preserve the commensal Streptococcus salivarius. Furthermore, the proteomic analyses revealed that the presence of Ga did not impair the normal oral microbiota. Still, interestingly, it decreased by 17% the presence of Fusobacterium nucleatum, a gram-negative, strictly anaerobic bacteria that is naturally present in the gastrointestinal tract. Therefore, this work can provide a valuable starting point for the development of coatings aimed at easily improving zirconia dental implants' performance.

Surface micropatterning of 3D printed PCL scaffolds promotes osteogenic differentiation of BMSCs and regulates macrophage M2 polarization

Micropatterned structures on the surface of materials possessing biomimetic properties to mimic the extracellular matrix and induce cellular behaviors have been widely studied. However, it is still a major challenge to obtain internally stable and controllable micropatterned 3D scaffolds for bone repair and regeneration. In this study, 3D scaffolds with regular grating arrays using polycaprolactone (PCL) as a matrix material were prepared by combining 3D printing and soft lithography, and the effects of grating micropatterning on osteogenic differentiation of BMSCs and M1/M2 polarization of macrophages were investigated. The results showed that compared with the planar group and the 30um grating spacing group, PCL with a grating spacing of 20um significantly promoted the osteogenic differentiation of BMSCs, induced the polarization of RAW264.7 cells toward M2 type, and suppressed the expression of M1-type pro-inflammatory genes and markers. In conclusion, we successfully constructed PCL-based three-dimensional scaffolds with stable and controllable micrographs (grating arrays) inside, which possess excellent osteogenic properties and promote the formation of an immune microenvironment conducive to osteogenesis. This study is a step forward to the exploration of bone-filling materials affecting cell behavior, and makes a new contribution to the provision of high-quality materials.

Hydroxyapatite-Based Coatings on Silicon Wafers and Printed Zirconia

Dental surgery needs a biocompatible implant design that can ensure both osseointegration and soft tissue integration. This study aims to investigate the behavior of a hydroxyapatite-based coating, specifically designed to be deposited onto a zirconia substrate that was intentionally made porous through additive manufacturing for the purpose of reducing the cost of material. Layers were made via sol-gel dip coating by immersing the porous substrates into solutions of hydroxyapatite that were mixed with polyethyleneimine to improve the adhesion of hydroxyapatite to the substrate. The microstructure was determined by using X-ray diffraction, which showed the adhesion of hydroxyapatite; and atomic force microscopy was used to highlight the homogeneity of the coating repartition. Thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy showed successful, selective removal of the polymer and a preserved hydroxyapatite coating. Finally, scanning electron microscopy pictures of the printed zirconia ceramics, which were obtained through the digital light processing additive manufacturing method, revealed that the mixed coating leads to a thicker, more uniform layer in comparison with a pure hydroxyapatite coating. Therefore, homogeneous coatings can be added to porous zirconia by combining polyethyleneimine with hydroxyapatite. This result has implications for improving global access to dental care.

A chlorogenic acid-chitosan complex bifunctional coating for improving osteogenesis differentiation and bactericidal properties of zirconia implants

Poor osteogenesis caused by limited bioactivity and peri-implantitis caused by bacterial colonization are the main challenges affecting the use of zirconia-based materials in dental implants. Accordingly, the development of a surface treatment method with an antibacterial effect and that promotes osteogenesis without damage to cells is crucial for yttrium-stabilized tetragonal zirconia (Y-TZP) implants. Herein, we have developed a functional surface modification strategy whereby a poly (ethylene imine)/hyaluronic acid /chitosan-chlorogenic acid (PEI/HA/CGA-CS) conjugate is deposited on a zirconia surface by the layer-by-layer (LBL) technique, enhancing its osteogenic differentiation and antibacterial activities. The results showed that the PEI/HA/CGA-CS coating improved the wettability of the zirconia surface and maintained stable release of CGA. The PEI/HA/CGA-CS functional coating was found to promote early cell adhesion, proliferation, differentiation, and calcification. The results of bacterial adhesion and activity tests showed that the coating effectively inhibits the proliferation and activity of Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) without impairing the biological activity of osteoblasts. In addition, we found that the PEI/HA/CGA-CS coating enhances the osteogenesis of MC3T3-E1 cells by promoting the protein expression of Nephronectin (NPNT) and activating the Wnt/β-catenin signaling pathway. The above results are of profound significance for the practical application of zirconia-based implants. DATA AVAILABILITY: Data will be made available on request.

Microfabrication approaches for oral research and clinical dentistry

Currently, there is a variety of laboratory tools and strategies that have been developed to investigate in-vivo processes using in-vitro models. Amongst these, microfabrication represents a disruptive technology that is currently enabling next-generation biomedical research through the development of complex laboratory approaches (e.g., microfluidics), engineering of micrometer scale sensors and actuators (micropillars for traction force microscopy), and the creation of environments mimicking cell, tissue, and organ-specific contexts. Although microfabrication has been around for some time, its application in dental and oral research is still incipient. Nevertheless, in recent years multiple lines of research have emerged that use microfabrication-based approaches for the study of oral diseases and conditions with micro- and nano-scale sensitivities. Furthermore, many investigations are aiming to develop clinically relevant microfabrication-based applications for diagnostics, screening, and oral biomaterial manufacturing. Therefore, the objective of this review is to summarize the current application of microfabrication techniques in oral sciences, both in research and clinics, and to discuss possible future applications of these technologies for in-vitro studies and practical patient care. Initially, this review provides an overview of the most employed microfabrication methods utilized in biomedicine and dentistry. Subsequently, the use of micro- and nano-fabrication approaches in relevant fields of dental research such as endodontic and periodontal regeneration, biomaterials research, dental implantology, oral pathology, and biofilms was discussed. Finally, the current and future uses of microfabrication technology for clinical dentistry and how these approaches may soon be widely available in clinics for the diagnosis, prevention, and treatment of relevant pathologies are presented.

The enhanced ZrO2 produced by DLP via a reliable plasticizer and its dental application

Digital light processing (DLP) is considered as one of the most promising additive manufacturing technologies to process ceramics. However, the potential defects produced in the debinding and sintering process extremely restrict ceramic application. In this work, a plasticizer which effectively inhibits defects of the green body in debinding process was investigated. The effects of plasticizer (Polyethylene glycol 200) on the rheological behavior and curing property of the slurry were discussed. In addition, the debinding process and the mechanical of zirconia parts with different PEG200 contents were studied. Adding 20 vol% PEG200 could efficiently suppress the defects in debinding process, and the flexural strength increased from 302 ± 15 to 1210 ± 25 MPa of the ZrO₂ ceramic sintered at 1600 °C. The superior biocompatibility and mechanical property reveal that the DLP zirconia has a promising application prospect of biology dental ceramic prostheses.

Green synthesis and characterization of zirconium nanoparticlefor dental implant applications

Green synthesis is a promising and cost-effective technique to synthesize nanoparticles from plant extract. The present study shows the green synthesis of zirconium nanoparticles using the extract of ginger, garlic, and zirconium nitride. The obtained nanoparticles were studied for potential dental implant applications. The synthesized nanoparticles were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-Ray Spectroscopy (EDX), X-Ray diffraction analysis (XRD), and antibacterial analysis. FTIR analysis confirmed the presence of various organic compounds in the synthesized nanoparticles. The synthesized nanoparticles were spherical, triangular, and irregular, with varying sizes confirmed by FESEM analysis. The nanoparticles synthesized from the combination of garlic and ginger, and zirconium exhibited potent antibacterial activity against S. aureus. Anti-biofilm, anti-microbial activity, biointegration formation, and cell mechanism survival are also mentioned. Thus, the synthesized nanoparticles can be a good candidate for a dental implant because of their excellent antimicrobial properties.