IADR Abstract Archives
Characterization of Two Novel Endodontic Cements During Ageing by NMR
Objectives: Purpose of this study was to determine relaxation time of two novel endodontic cements, by means of Time-Domain Nuclear Magnetic Resonance (TD-NMR) of 1H nuclei. Methods: Standard (S) and Fluoridated (F) endodontic cements (TECHBIOSEALER® - ISASAN, Italy), were tested during ageing, from the first hour of mixing up to 30 days. “Solid” signal, coming from low mobility protons, and “Liquid” signal, due to 1H with higher molecular mobility, were evaluated by means of quasi-continuous relaxation time distribution analysis of 1H signals arising from the samples. To get the relaxation time distributions of the longitudinal (T1) and of the transverse (T2) component of nuclear magnetization and to perform the separation between the “Solid” signal and the “Liquid” signal for T1 distributions, we applied our multi-exponential inversion software UpenWin to the experimental data. The method allowed us to determine accurately the amplitudes of the two signals, the relaxation times distributions, and to quantify other important physical properties, e.g. T2FID, an NMR parameter. Results: Strong and rapid changes of the TD-NMR parameters during cement setting are detectable for both samples. The “Solid” component increases at the cost of the “Liquid” one and T1 and T2 distributions of the “Liquid” component shift towards shorter times with different kinetics for the two samples. The evolution of the relaxation time distributions reflects the gradual formation of the nanoporous structure of the quasi-amorphous Calcium Silicate Hydrate C-S-H gel. In figure, it is reported the evolution of T2FID parameter during ageing for the two pastes. Conclusions: TD-NMR results show that parameters obtained by relaxation measurements are clear markers of the rapid changes of the cement pastes, able to distinguish the differences among cement pastes, during the ageing process. Both Tested cements exhibited chemical and physical changes occurring for 30 days after cement preparation.