Vibrational study of Portland cement-derived materials for dental applications.

Calcium silicate cements have been recently developed as root-end filling materials. They are hydraulic materials able to set in the presence of moisture, allowing their use in oral surgery and in all conditions where blood and fluid contamination hampers the correct use of other materials. Calcium silicate cements, such as mineral trioxide aggregate (MTA) and white portland cements, have shown satisfactory biological properties; moreover, they may induce remineralisation of partially demineralised dentine. Our study was aimed at comparatively investigating the in miro bioactivity of three calcium-silicate cements derived from modified white portland cement: wTC (white tetrasilicate cement), FTC (wTC added with fluoride because of its mitogenic effect on osteoblasts) and Pro-Root MTA, a commercial cement used as reference. Bismuth oxide was included in all cements as radioopacifier. To elucidate the influence of the fluoride doping agent on bioactivity, the cements were aged for different times (from 1 to 28 days), at 37°C, in a phosphate-containing physiological solution, i.e. Dulbecco's Phosphate buffered saline, DPBS. ATR/FT-IR and micro-Raman spectroscopy were used to investigate the presence of deposits on the surface of the cements and the composition changes of the cement as a function of the ageing time. Vibrational spectroscopy allowed to identify the phases present in the unhydrated cement powders (alite, belite, gypsum, anhydrite, calcium carbonate) as well as their different hydration rates (alite > belite; anhydrite > gypsum). Interestingly, the portlandite phase was found only in the interior of the cements, indicating its release into the Storage medium, which consequently increased its pH. After one day of ageing, all the cements showed the presence of a carbonated apatite deposit; both IR and Raman spectroscopy revealed that this deposit was meanly thicker and more homogeneous on FTC. From a quantitative point of view, the Raman I96o(Apatite)/I3II(Bismuth oxide) intensity ratio was identified as marker of the deposit thickness. This ratio attained meanly higher values for FTC especially at short ageing times. At increasing ageing time the maturation of the apatite phase proceeded, as revealed by the progressive decrease in intensity of the Raman band at about 1000 cm-1 (attributable to the HPC42- ion). In the light of these results and of the ability to support cell growth, attachment and cell-surface interactions, these cements appear promising as endodontic sealers and root-end filling materials.