New Ceramic Multi-Unit Dental Abutments with an Antimicrobial Glassy Coating

The choice of suitable materials and new designs in oral implantology and the subsequent enhancement of the characteristics of the dental implant developed is an important research topic with wide scope. The present work aims to develop a new multifunctional zirconia-ceria/alumina (Ce-TZP/Al₂O₃) composite with an antimicrobial glass-based coating to be used in multi-unit abutments compatible with commercially available Ti implants for peri-implantitis prevention. An airbrush spraying technique was effectively applied to coat the sintered ceramic composite starting from a glass powder suspension. This deposition technique was appropriate for obtaining continuous antimicrobial glass-based coatings with homogenous thickness (~35 µm) on ceramic dental implant components. The dental implant systems with the antimicrobial glassy coating were subjected to a mechanical integrity test following ISO 14801 to determine their long-term stability. The tested implant-coating structure seems to be stable under in vitro conditions with ultimate applied forces exceeding the maximum physiological occlusal loading force. This paper also presents a pilot clinical case report that shows peri-implant tissue around the mechanically stable glass coating with no signs of inflammation 1 year after implant insertion. This result is a preliminary probe of the durability and biological tolerance of the glassy material by the gingiva, as well as the antimicrobial effect on the peri-implant microbiota displayed by the coating.

Broad virus inactivation using inorganic micro/nano-particulate materials

Inorganic materials can provide a set of tools to decontaminate solid, liquid or air containing viral particles. The use of disinfectants can be limited or not practical in scenarios where continuous cleaning is not feasible. Physicochemical differences between viruses raise the need for effective formulations for all kind of viruses. In the present work we describe two types of antimicrobial inorganic materials: i) a novel soda-lime glass (G3), and ii) kaolin containing metals nanoparticles (Ag or CuO), as materials to disable virus infectivity. Strong antiviral properties can be observed in G3 glass, and kaolin-containing nanoparticle materials showing a reduction of viral infectivity close to 99%. in the first 10 ​min of contact of vesicular stomatitis virus (VSV). A potent virucidal activity is also present in G3 and kaolin containing Ag or CuO nanoparticles against all kinds of viruses tested, reducing more than 99% the amount of HSV-1, Adenovirus, VSV, Influenza virus and SARS-CoV-2 exposed to them. Virucidal properties could be explained by a direct interaction of materials with viruses as well as inactivation by the presence of virucidal elements in the material lixiviates. Kaolin-based materials guarantee a controlled release of active nanoparticles with antiviral activity. Current coronavirus crisis highlights the need for new strategies to remove viruses from contaminated areas. We propose these low-cost inorganic materials as useful disinfecting antivirals in the actual or future pandemic threats.

Adding Two Antimicrobial Glasses to an Endodontic Sealer to Prevent Bacterial Root Canal Reinfection: An In Vivo Pilot Study in Dogs

Current endodontic procedures continue to be unsuccessful for completely removing pathogens present inside the root canal system, which can lead to recurrent infections. In this study, we aimed to assess the antimicrobial capacity and tissue response of two inorganic bactericidal additives incorporated into a paste root canal sealer on contaminated root dentin in vivo. An experimental study was performed in 30 teeth of five Beagle dogs. After inducing microbiological contamination, root canal systems were treated by randomly incorporating one of two antimicrobial additives into a commercial epoxy-amine resin sealer (AH Plus), i.e., G3T glass-ceramic (n = 10) and ZnO-enriched glass (n = 10); 10 samples were randomized as a control group. After having sacrificed the animals, microbiological, radiological, and histological analyses were performed, which were complemented with an in vitro bactericidal test and characterization by field emission scanning electron microscopy. The tested groups demonstrated a non-significant microbiological reduction in the postmortem periapical index values between the control group and the bactericidal glass-ceramic group (p = 0.885), and between the control group and the ZnO-enriched glass group (p = 0.169). The histological results showed low values of inflammatory infiltrate, and a healing pattern characterized by fibrosis in 44.4% of the G3T glass-ceramic and 60.0% of ZnO-enriched glass. Bactericidal glassy additives incorporated in this root canal sealer are safe and effective in bacterial reduction.

Novel antimicrobial phosphate-free glass-ceramic scaffolds for bone tissue regeneration

In this study a phosphate-free glass-ceramic porous scaffold was synthesized by a three-step methodology involving slurry preparation, induction of porosity by surfactant-assisted foaming following by freeze-drying and sintering. This inorganic scaffold was characterized by X-ray diffraction, scanning electron microscope (SEM), degradation and bioactivity. Thermal treatment at 750 °C showed two new crystalline phases, combeite and nepheline, into the glassy matrix responsible for its properties. The cell response of the scaffold was also evaluated for using as a bone graft substitute. A commercial Biphasic Calcium Phosphate, BCP, scaffold was assessed in parallel as reference material. Microstructures obtained by SEM showed the presence of macro, meso and microporosity. The glass-ceramic scaffold possesses an interconnected porosity around 31% with a crack-pore system that promote the protein adsorption and cell attachment. Glass-ceramic scaffold with high concentration of calcium ions shows an antimicrobial behavior against Escherichia coli after 24 h of contact. Nepheline phase present in the glass-ceramic structure is responsible for its high mechanical properties being around 87 MPa. Glass-ceramic scaffold promotes greater protein adsorption and therefore the attachment, spreading and osteodifferentiation of Adipose Derived Stem Cells than BCP scaffold. A higher calcification was induced by glass-ceramic scaffold compared to reference BCP material.

Effect of the Medium Composition on the Zn2+ Lixiviation and the Antifouling Properties of a Glass with a High ZnO Content

The dissolution of an antimicrobial ZnO-glass in the form of powder and in the form of sintered pellets were studied in water, artificial seawater, biological complex media such as common bacterial/yeast growth media (Luria Bertani (LB), yeast extract, tryptone), and human serum. It has been established that the media containing amino acids and proteins produce a high lixiviation of Zn²⁺ from the glass due to the ability of zinc and zinc oxide to react with amino acids and proteins to form complex organic compounds. The process of Zn²⁺ lixiviation from the glass network has been studied by X-ray photoelectron spectroscopy (XPS). From these results we can state that the process of lixiviation of Zn²⁺ from the glass network is similar to the one observed in sodalime glasses, where Na⁺ is lixiviated to the media first and the fraction of Zn that acts as modifiers (~2/3) is lixiviated in second place. After the subsequent collapse of the outer surface glass layer (about 200-300 nm thick layer) the dissolution process starts again. Antifouling properties against different bacteria (S. epidermidis, S. aureus, P. aeruginosa, E. coli, and M. lutea) have also been established for the glass pellets.

Histological response of soda-lime glass-ceramic bactericidal rods implanted in the jaws of beagle dogs

Bacterial and fungal infections remain a major clinical challenge. Implant infections very often require complicated revision procedures that are troublesome to patients and costly to the healthcare system. Innovative approaches to tackle infections are urgently needed. We investigated the histological response of novel free P₂O₅ glass-ceramic rods implanted in the jaws of beagle dogs. Due to the particular percolated morphology of this glass-ceramic, the dissolution of the rods in the animal body environment and the immature bone formation during the fourth months of implantation maintained the integrity of the glass-ceramic rod. No clinical signs of inflammation took place in any of the beagle dogs during the four months of implantation. This new glass-ceramic biomaterial with inherent bactericidal and fungicidal properties can be considered as an appealing candidate for bone tissue engineering.

Bone loss at implant with titanium abutments coated by soda lime glass containing silver nanoparticles: a histological study in the dog

The aim of the present study was to evaluate bone loss at implants connected to abutments coated with a soda-lime glass containing silver nanoparticles, subjected to experimental peri-implantitis. Also the aging and erosion of the coating in mouth was studied. Five beagle dogs were used in the experiments. Three implants were placed in each mandible quadrant: in 2 of them, Glass/n-Ag coated abutments were connected to implant platform, 1 was covered with a Ti-mechanized abutment. Experimental peri-implantitis was induced in all implants after the submarginal placement of cotton ligatures, and three months after animals were euthanatized. Thickness and morphology of coating was studied in abutment cross-sections by SEM. Histology and histo-morphometric studies were carried on in undecalfied ground slides. After the induced peri-implantitis: 1.The abutment coating shown losing of thickness and cracking. 2. The histometry showed a significant less bone loss in the implants with glass/n-Ag coated abutments. A more symmetric cone of bone resorption was observed in the coated group. There were no significant differences in the peri-implantitis histological characteristics between both groups of implants. Within the limits of this in-vivo study, it could be affirmed that abutments coated with biocide soda-lime-glass-silver nanoparticles can reduce bone loss in experimental peri-implantitis. This achievement makes this coating a suggestive material to control peri-implantitis development and progression.

Radiologic evaluation of bone loss at implants with biocide coated titanium abutments: a study in the dog

The objective of the present study is to evaluate bone loss at implant abutments coated with a soda-lime glass containing silver nanoparticles subjected to experimental peri-implantitis. Five beagle dogs were used in the experiments, 3 implants were installed in each quadrant of the mandibles. Glass/n-Ag coted abutments were connected to implant platform. Cotton floss ligatures were placed in a submarginal position around the abutment necks and the animals were subject to a diet which allowed plaque accumulation, and after 15 weeks the dogs were sacrificed. Radiographs of all implant sites were obtained at the beginning and at the end of the experimentally induced peri-implantitis. The radiographic examination indicated that significant amounts of additional bone loss occurred in implants without biocide coating, considering both absolute and relative values of bone loss. Percentages of additional bone loss observed in implants dressed with a biocide coated abutment were about 3 times lower (p<0.006 distal aspect; and p<0.031 at mesial aspect) than the control ones. Within the limits of the present study it seems promising the use of soda-lime glass/nAg coatings on abutments to prevent peri-implant diseases.

Management of odontogenic infection of pulpal and periodontal origin

The dental biofilm is a complex bacterial ecosystem that undergoes evolution, maturing and development, and thus leads to odontogenic infection. The infection is normally located in the tissues of the dental organ itself, and follows a chronic course of evolution. However, bacterial pathogens express virulence factors in the biofilm, and this together with changes in host immunity, may cause clinical exacerbations and spread of infection to other areas of the body. Odontogenic infection management should take into consideration the fact that therapeutic success lies in the control of the infectious aetiologic agent, using mechanical-surgical debridement and/or antimicrobial therapy. Debridement techniques have a fundamentally quantitative effect (by reducing the size of the inoculum) and therefore if these techniques are used alone to control infection, despite an initial clinical improvement that is sometimes prematurely considered as therapeutic success, odontopathogens may persist and the process may recur or become chronic. Microbiological examination may be helpful in defining therapeutic success in a more reliable way, it could define the prognosis of recurrence more precisely, and could enable the most appropriate antibiotic to be selected, thus increasing therapeutic efficacy. Antimicrobial therapy brings about a quantitative and qualitative change in the bacterial composition of the biofilm, in addition to being able to act on sites that are inaccessible through mechanical debridement. However, incorrect antimicrobial use can lead to a selection of resistant bacterial species in the biofilm, in addition to side effects and ecological alterations in the host. In order to minimise this risk, and obtain maximum antimicrobial effect, we need to know in which clinical situations their use is indicated, and the efficacy of different antibiotics with regard to bacteria isolated in odontogenic infection.