Magnetic motion of superparamagnetic iron oxide nanoparticles- loaded dental adhesives: physicochemical/biological properties, and dentin bonding performance studied through the tooth pulpal pressure model.

The limited durability of dentin bonding harshly shortens the lifespan of resin composites restorations. The controlled, dynamic movement of materials through non-contacting forces provides exciting opportunities in adhesive dentistry. We, herein, describe comprehensive investigations of a new dental adhesive with superparamagnetic iron oxide nanoparticles (SPIONs) sensitive to magnetic fields for bonding optimization. This contribution outlines a roadmap of (1) designing and tuning of an adhesive formulation containing SPIONs to enhance penetrability into etched dentin guided by magnetic-field; (2) employing a clinically relevant model of simulated hydrostatic pulpal pressure on the microtensile bond to dentin; and (3) investigating a potential antibacterial effect of the formulated adhesives, and their biocompatibility. SPION-concentration-dependency chemical and mechanical behavior was shown via the degree of conversion, ultimate tensile strength, and micro shear bond strength to dentin. The effects of SPIONs carried on a dental adhesive on the bonding strength to dentin are studied in depth by combining experiments with in vitro simulated model. The results show that under the guided magnetic field, 0.07 wt.% of SPIONs-doped adhesive increased the bond strength that surpasses the reduction caused by hydrostatic pulpal pressure. Using a magnetic guide workflow during the bonding procedures, SPIONs-doped adhesives improved dentin's adhesion without changing adhesives' physicochemical properties. This outcome addresses the key challenge of poor resin infiltration of dentin's conventional total etching during the bonding procedure. The real-time magnetic motion of dental adhesives may open new paths to enhance resin-based restorations' longevity. STATEMENT OF SIGNIFICANCE: In this study, dental adhesives containing superparamagnetic iron oxide nanoparticles (SPIONs) were developed to enhance penetrability into dentin guided by a magnetic field. The adhesives were screened for physical, chemical, antibacterial properties, and cytotoxicity. For the first time, simulated pulpal pressure was used concurrently with the magnetic field to simulate a clinical setting. This approach showed that it is feasible to overcome pulpal pressure jeopardization on bond strength when SPIONs and a magnetic field are applied. The magnetic-responsive adhesives had great potential to improve bond strength, opening new paths to enhance resin-based restorations' longevity without affecting adhesives' biological properties. The use of magnetic-responsive particles and magnetically assisted motion is a promising strategy to improve the sealing ability of dental adhesives.

Arsenic removal via electrocoagulation from heavy metal contaminated groundwater in La Comarca Lagunera México.

Arsenic contamination is an enormous worldwide problem. A large number of people dwelling in Comarca Lagunera, situated in the central part of northern México, use well water with arsenic in excess of the water standard regulated by the Secretary of Environment and Natural Resources of México (SEMARNAT), to be suitable for human health. Individuals with lifetime exposure to arsenic develop the classic symptoms of arsenic poisoning. Among several options available for removal of arsenic from well water, electrocoagulation (EC) is a very promising electrochemical treatment technique that does not require the addition of chemicals or regeneration. First, this study will provide an introduction to the fundamental concepts of the EC method. In this study, powder X-ray diffraction, scanning electron microscopy, transmission Mössbauer spectroscopy and Fourier transform infrared spectroscopy were used to characterize the solid products formed at iron electrodes during the EC process. The results suggest that magnetite particles and amorphous iron oxyhydroxides present in the EC products remove arsenic(III) and arsenic(V) with an efficiency of more than 99% from groundwater in a field pilot scale study.