In-situ Structural and Thermal Analysis of Dental Restorative Materials

Objectives: The aim of this study was to evaluate in-situ structural and thermal changes of dental restorative materials at periodical time interval. Methods: The commercial materials included zinc oxide eugenol (ZOE:Easydent Tempocav, Densell, Argentine), zinc phosphate type 1 (ZnPO₄:Densell, Argentine), glass ionomer cement type II (GIC:Ketac Molar, 3M ESPE, Germany) and composite (Z350, 3M ESPE, Germany). These materials were processed according to manufacturer's instructions. For structural analysis Fourier Transform Infrared Spectroscopy (FTIR) was used at high resolution. Thermogravimetric Analaysis (TGA) was used to evaluate thermal weight-loss. The FTIR spectra were collected after 60min,24hrs,48hrs,72hrs,96hrs,120hrs and 144hrs. The samples were stored at 37^°C during spectra/thermogram collection time interval. Results: FTIR spectra showed that with time passing all materials exhibited increase in peak intensities and new appearance of shoulders and shifting of peaks e.g. ZnPO₄ (P—O), ZOE (C=O,C=N,C—O—C), GIC (COO-,C—H, Si—OH), composites (C=O,C=C,C=N,C—N –H). The peaks were replaced by bands and these bands became broader with time interval. Resin-based composites showed degree of conversion after light curing; new peaks corresponded to cross-linking of polymer composites, however, insignificant difference was observed with increasing time. TGA analysis showed that significant changes in weight loss of set material were observed after 24hrs, where ZOE showed continuous changes in thermal degradation. The thermal degradation was reduced with time interval. Conclusions: The spectroscopic and thermal analysis of these different dental materials elucidated in-situ setting behavior and understanding of their bonding, compatibility with tooth structure and change in relation to time.