Soft-tissue response to injectable calcium phosphate cements

In this study, the soft tissue reaction to two newly developed injectable calcium phosphate bone cements (cement D and W) was evaluated after implantation in the back of goats. For one of the cements (cement D) the tissue reaction was also investigated after varying the concentration of accelerator Na 2HPO 4 in the cement liquid (resulting in cement D1 and D2). Eight healthy mature female Saanen goats were used. The cement was applied 10 min after mixing while it was still moldable and plastic. The material was given a standardized cylindrical shape. Thirty-two implants of each cement formulation were inserted and left in place for 1, 2, 4, and 8 weeks. At the end of the study, eight specimens of each material and healing period were available for further analysis. Two specimens were used for X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) and six specimens were used for light microscopical evaluation. XRD and FTIR showed that the cements did set as microcrystalline carbonate apatite with the disappearance of monetite from the cements during implantation. Histological analysis showed that after 8 weeks of implantation around all materials a thin soft-tissue capsule was formed (thickness ranging from 5 to 15 cell layers) with almost complete absence of inflammatory cells. Only in some specimens a slightly higher inflammatory reaction was observed. This was due to cement surface defects and a zone of dispersed particles near the cement–soft tissue interface. There was almost no resorption of the material after 8 weeks of implantation. In a few 4 and 8 weeks samples, small areas of calcification were found in the fibrous capsule surrounding the implants. On the basis of our observations, we conclude that the tested cements were biocompatible and can be used next to soft tissue.