Nanoclay addition to a conventional glass ionomer cements: Influence on physical properties
Objective: The objective of the present study is to investigate the reinforcement effect of  polymer-grade montmorillonite (PGN nanoclay) on physical properties of glass ionomer cement (GIC). Materials and Methods: The PGN nanoclay was dispersed in the liquid portion of GIC (HiFi, Advanced Healthcare, Kent, UK) at 1%, 2% and 4% (w/w). Fourier-transform infrared (FTIR) spectroscopy was used to quantify the polymer liquid of GICs after dispersion of nanoclay. The molecular weight (M w ) of HiFi liquid was determined by gel permeation chromatography. The compressive strength (CS), diametral-tensile strength, flexural strength (FS) and flexural modulus (E f ) of cements (n = 20) were measured after storage for 1 day, 1 week and 1 month. Fractured surface was analyzed by scanning electron microscopy. The working and setting time (WT and ST) of cements was measured by a modified Wilson′s rheometer. Results: The FTIR results showed a new peak at 1041 cm−1 which increased in intensity with an increase in the nanoclay content and was related to the Si-O stretching mode in PGN nanoclay. The M w of poly (acrylic acid) used to form cement was in the range of 53,000 g/mol. The nanoclay reinforced GICs containing <2% nanoclays exhibited higher CS and FS. The E f cement with 1% nanoclays was significantly higher. The WT and ST of 1% nanoclay reinforced cement were similar to the control cement but were reduced with 2% and 4% nanoclay addition. Conclusion: The dispersion of nanoclays in GICs was achieved, and GIC containing 2 wt% nanoclay is a promising restorative materials with improved physical properties.
Milestones in adhesion: glass-ionomer cements.
The glass-ionomer cements (GIC), when introduced in the 1970s, were initially welcomed as the first chemically-adhesive esthetic restorative materials. However, the clinical results were disappointing, as these early products were brittle and were particularly susceptible to early water loss and uptake, and to long-term water loss. Continued development, notably the addition of resin polymerization components, has made the GIC an increasingly important part of clinical practice.
Magnetic properties of Lu2Fe17 crystals
Abstract We present the results of crystal structure and magnetization studies of three single crystals grown from melts of different nominal compositions in the vicinity of the Lu2Fe17 stoichiometry. The ferromagnetic state of the crystals is strongly dependent on the real sample composition and the local atomic ordering. A drastic difference is observed in the behaviour of the ferro–antiferromagnetic transition, even in crystals for which almost identical composition and crystal parameters were determined by microprobe and X-ray analysis.