Henri Vahabi

Antibacterial glass-ionomer cement restorative materials: A critical review on the current status of extended release formulations

Glass-ionomer cements (GICs) have been widely used for over forty years, because of their desirable properties in dentistry. The most important advantages of the GICs are associated with their ability to release long-term antimicrobial agents. However, GICs used as restorative materials have still lots of challenges due to their secondary caries and low mechanical properties. Recent studies showed that the fluoride-releasing activity of conventional GICs is inadequate for effectual antibacterial conservation in many cases. Therefore, many efforts have been proposed to modify the antibacterial features of GICs in order to prevent the secondary caries. Particularly, for achieving this goal GICs were incorporated into various biomaterials possessing antibacterial activities. The scope of this review is to assess systematically the extant researches addressing the antibacterial modifications in GICs in order to provide with an authoritative, at the same time in-depth understanding of controlled antibacterial release in this class of biomaterials. It also gives a whole perspective on the future developments of GICs and challenges related to antibacterial GICs.

Chitosan and imide-functional Fe3O4 nanoparticles to prepare new xanthene based poly(ether-imide) nanocomposites

In this work a new series of multifunctional nanocomposites were synthesized based on a soluble poly(ether-imide). The poly(ether-imide) was successfully synthesized via direct polycondensation reaction. A methyl rich diamine containing xanthene group as a new monomer was synthesized and used for polymerization. The xanthene based poly(ether-imide) was characterized using size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR). Fe3O4 nanoparticles were imide-functionalized by a dianhydride, chitosan and phenylalanine. The functional Fe3O4 nanoparticles were incorporated into the new synthesized poly(ether-imide). Effects of the functionalized Fe3O4 nanoparticles on the thermal and combustion properties of the corresponding nanocomposites were investigated. Thermogravimetric analysis (TGA) results indicated that the thermal stability and char yields of the nanocomposites were enhanced compared to the neat poly(ether-imide). Microscale combustion calorimetry (MCC) revealed that the synthesized poly(ether-imide) had low flammability. The incorporation of functional Fe3O4 nanoparticles could further improve the combustion properties of poly(ether-imide). The high interaction between poly(ether-imide) and functional Fe3O4, the presence of an imide group and high hydroxyl content of the functional Fe3O4 nanoparticles seem to be responsible for the improvement of the thermal and combustion properties. Furthermore, the presence of methyl, ether and bulky xanthene groups in the polyimide backbone decreased the glass transition temperature (Tg) and increased the solubility in organic solvents. These properties will be useful for processing and new applications of poly(ether-imide).

High-performance fire-retardant polyamide materials

Abstract This chapter focuses on the thermal degradation and flame retardancy of aliphatic polyamides. A review of past and recent research and developments in the main flame-retardant systems of polyamides is presented. The different mechanisms of action of these flame retardants during combustion of polyamides are described, and original results about glass-fibre-reinforced polyamides are presented. Finally, some issues regarding current developments and future trends are discussed.