Ageing of calcium silicate cements for endodontic use in simulated body fluids: a micro-Raman study

To evaluate bioactivity properties, a calcium silicate experimental cement (wTC) and a phosphate-doped wTC cement (wTC-TCP) were aged for different times (1 - 180 days) at 37 degrees C in two simulated body fluids, i.e. Dulbecco's phosphate buffered saline (DPBS) and Hank's balanced salt solution (HBSS). The cements were analyzed by micro-Raman spectroscopy to investigate the presence of calcium phosphate deposits and the composition changes as a function of the storage time (hydration of anhydrite/gypsum and formation of ettringite; hydration of belite/alite and formation of hydrated silicates). After 1 day of ageing in DPBS, the two cements already showed a different behavior: only the surface of wTC-TCP cement showed the band at 965 cm(-1), suggesting the formation of a detectably thick calcium phosphate deposit. The trend of the I(965)/I(990) Raman intensity ratio indicated the formation of a meanly thicker apatite deposit on the wTC-TCP cement until 90 days. After 60 days of ageing in DPBS, the thickness of the apatite deposit on wTC and wTC-TCP was about 200 and 500 mu m, respectively, whereas at 180 days, the two cements did not appear significantly different (thickness of about 900 mu m). The bioactivity of both cements in HBSS was less pronounced than in DPBS, according to the lower phosphate concentration of HBSS; at the same time, higher amounts of calcite were found on the surface of both cements. The wTC-TCP cement showed a higher bioactivity in this medium also; after 180 days, the thickness of the apatite deposit on wTC and wTC-TCP was <50 mu m and about 100 mu m, respectively. Copyright (C) 2009 John Wiley & Sons, Ltd.