Retrievability of Calcium Silicate-based Root Canal Sealers During Retreatment: An Ex Vivo Study.

INTRODUCTION: The retrievability of calcium silicate-based sealers (CSSs) during nonsurgical retreatment has been equivocal. This study compared the retrievability of 3 different CSSs using 1 of 3 different solutions or no solution. METHODS: A total of 130 extracted teeth with a straight canal were decoronated to a standardized root length. The canals were instrumented to 35/.04 and divided into 3 groups (BC: EndoSequence BC sealer; EBC: EdgeBioceramic; NEO: NeoSEALERFlo), and each group was further divided into 4 subgroups (6% sodium hypochlorite; 5% acetic acid; carbonated water; no solution). After sealer placement, each master gutta-percha cone was placed intentionally 2 mm short of the working length (WL) to ensure the apical 2 mm was filled only with sealer. After storage for 21 days at 37°C and 100% humidity, retreatment was performed until apical patency was obtained. The operator was blinded to the CSS and solution used. Data were analyzed using analysis of variance to compare apical patency rates and the mock chair-times. RESULTS: Overall success rates for apical patency in BC, EBC, and NEO were 63.64%, 69.77%, and 100%, respectively. There was significantly higher apical patency rate in NEO than BC and EBC. The chair-time for NEO was significantly shorter than BC (P < .05) and EBC sealer (P < .001). There was no significant difference in the chair-time between BC and EBC sealer groups. CONCLUSION: BC, EBC, and NEO sealers in a straight canal were consistently retrievable when no solution was used. Compared with no solution, the retrievability of BC, EBC, and NEO decreased when solutions were used.

Double emulsions for the compatibilization of hydrophilic nanocellulose with non-polar polymers and validation in the synthesis of composite fibers.

A route for the compatibilization of aqueous dispersions of cellulose nanofibrils (CNFs) with a non-polar polymer matrix is proposed to overcome a major challenge in CNF-based material synthesis. Non-ionic surfactants were used in CNF aqueous dispersions equilibrated with an organic phase (for demonstration, a polystyrene solution, PS, was used). Stable water-in-oil-in-water (W/O/W) double emulsions were produced as a result of the compromise between composition and formulation variables. Most remarkably, the proposed route for CNF integration with hydrophobic polymers removed the need for drying or solvent-exchange of the CNF aqueous dispersion prior to processing. The rheological behavior of the double emulsions showed strong shear thinning behavior and facilitated CNF-PS co-mixing in solid nanofibers upon electrospinning. The morphology and thermal properties of the resultant nanofibers revealed that CNFs were efficiently integrated in the hydrophobic matrix which was consistent with the high interfacial area of the precursor double emulsion. In addition, the morphology and quality of the composite nanofibers can be controlled by the conductivity (ionic strength) of the CNF dispersion. Overall, double emulsion systems are proposed as a novel, efficient and scalable platform for CNF co-processing with non-polar systems and they open up the possibility for the redispersion of CNFs after removal of the organic phase.

Cellulose nanofibrils for one-step stabilization of multiple emulsions (W/O/W) based on soybean oil.

Cellulose nanofibrils (CNF) were incorporated in water-in-oil (W/O) microemulsions and emulsions, as well as water-in-oil-in-water (W/O/W) multiple emulsions using soybean oil. The addition of CNF to the aqueous phase expanded the composition range to obtain W/O/W emulsions. CNF also increased the viscosity of the continuous phase and reduced the drop size both of which increased the stability and effective viscosity of the emulsions. The effects of oil type and polarity on the properties of the W/O/W emulsions were tested with limonene and octane, which compared to soybean oil produced a smaller emulsion drop size, and thus a higher emulsion viscosity. Overall, CNF are a feasible alternative to conventional polysaccharides as stability enhancers for normal and multiple emulsions that exhibit strong shear thinning behavior.

Lignin supracolloids synthesized from (W/O) microemulsions: use in the interfacial stabilization of Pickering systems and organic carriers for silver metal.

Taking advantage of the aromatic and cross-linking tendency of lignin macromolecules extracted from plants, we present a novel method for their assembly into supracolloidal structures. Specifically, spherical particles with controllable size (∼90 nm to 1 µm) were obtained from water-in-oil (W/O) microemulsions formulated with a mixture of nonionic surfactants and a colloidal dispersion of a low molecular weight alkali lignin. After spontaneous emulsification, the internal lignin-rich phase was cross-linked to produce the solid particles that could be easily separated by removal of the organic, continuous phase. The efficiency of the fractionated lignin particles to stabilize hexadecane-in-water Pickering emulsions was demonstrated and their properties were compared against those obtained by using traditional inorganic particles. The effect of the particle size of lignin on the emulsion structure is discussed. As a proof of concept we further introduce the use of related emulsions to enable in situ reduction of silver and loading of silver nanoparticles in lignin carriers.

Microemulsion systems for fiber deconstruction into cellulose nanofibrils.

A new method to produce cellulose nanofibrils (CNF) is proposed to reduce the energy demand during deconstruction of precursor fibers suspended in aqueous media. Microemulsions were formulated with aqueous solutions of urea or ethylenediamine and applied to disrupt interfibril hydrogen bonding. Compared to typical fibrillation of lignin-containing and lignin-free fibers, pretreatment with microemulsion systems allowed energy savings during microfluidization of 55 and 32%, respectively. Moreover, microemulsion processing facilitated smaller-scale CNF structures (higher degrees of deconstruction), with higher water retention value (WRV) and surface area. Urea-containing microemulsions were found to be most effective in reducing energy consumption and in weakening the cellulosic matrix. Films prepared from CNF processed after pretreatment with urea-containing microemulsions presented a more uniform fiber network and produced films with smoother surfaces compared to those based on ethylenediamine. The lignin-containing CNF (LCNF) produced denser films than those obtained from lignin-free CNF. The mechanical properties of films obtained after application of microemulsion pretreatment were compared, and the benefits of the proposed approach were further confirmed. Overall, fiber deconstruction after microemulsion treatment is a step toward energy-efficient production of nanocellulose.

Capillary flooding of wood with microemulsions from Winsor I systems.

A new approach based on microemulsions formulated with at least 85% water and minority components consisting of oil (limonene) and surfactant (anionic and nonionic) is demonstrated for the first time to be effective for flooding wood's complex capillary structure. The formulation of the microemulsion was based on phase behavior scans of Surfactant-Oil-Water systems (SOWs) and the construction of pseudo-ternary diagrams to localize thermodynamically stable one-phase emulsion systems with different composition, salinity and water-to-oil ratios. Wicking and fluid penetration isotherms followed different kinetic regimes and indicated enhanced performance relative to that of the base fluids (water, oil or surfactant solutions). The key properties of microemulsions to effectively penetrate the solid structure are discussed; microemulsion formulation and resultant viscosity are found to have a determining effect in the extent of fluid uptake. The solubilization of cell wall components is observed after microemulsion impregnation. Thus, the microemulsion can be tuned not only to effectively penetrate the void spaces but also to solubilize hydrophobic and hydrophilic components. The concept proposed in this research is expected to open opportunities in fluid sorption in fiber systems for biomass pretreatment, and delivery of hydrophilic or lipophilic moieties in porous, lignocellulosics.