Alpha-TCP improves the apatite-formation ability of calcium-silicate hydraulic cement soaked in phosphate solutions

Abstract

The in vitro apatite-forming ability of experimental calcium-silicate hydraulic cements designed for dentistry was investigated. Two cements containing di- and tricalcium-silicate (wTC and wTC-TCP, i.e. wTC added with alpha-TCP) were soaked in different phosphate-containing solutions, namely Dulbecco's Phosphate Buffered Saline (DPBS) or Hank's Balanced Salt Solution (HBSS), at 37 °C and investigated over time (from 24 h to 6 months) by SEM/EDX, micro-Raman and ATR-FTIR. The early formation (24 h) of an aragonite/calcite layer onto both cements in both media was observed. Calcium phosphate deposits precipitated within 1–3 days in DPBS; spherical particles (spherulites) of apatite appeared after 3–7 days. wTC-TCP cement showed earlier, thicker and more homogeneous calcium phosphate deposits than wTC. In HBSS calcite deposits were mainly noticed, while phosphate bands appeared only after 7 days; the presence of globular deposits after 14–28 days was mostly detected on wTC-TCP. After 6 months, an approx. 900 micron carbonated apatite layer formed in DPBS whilst a 150–350 micron thick calcite/apatite layer generated in HBSS. Also in HBSS the carbonated apatite coating was earlier and thicker on wTC-TCP than wTC. Calcium-silicate cements showed the formation of a bone-like apatite layer, depending on the medium composition and ageing time. The addition of alpha-TCP increases the apatite-forming ability of calcium-silicate cements. Calcium-silicate hydraulic cements doped with alfa-TCP represent attractive materials to improve apical bone healing.