Aim of the study was to evaluate apatite forming ability and ion dissolution of bioactive glass-ceramic (BGC) particles from novel polydimethylsiloxane (PDMS) based endodontic sealer Guttaflow Bioseal. Firstly, water sorption and solubility were determined for Guttaflow 2 and Guttaflow Bioseal (GB), the latter containing BGC filler particles. Mineral precipitations in simulated body fluid (SBF) were observed with SEM/EDX. Ion-release from the sealer was determined with inductively coupled plasma optical emission spectrometry (ICP-OES) in Tris-buffer solution. Change in pH was also measured. The obtained data was statistically analyzed with Tukey's HSD test (p<0.05). GB exhibited significantly higher water sorption and solubility in comparison with Guttaflow 2. Surface structure exposed particles of BGC in the PDMS matrix. The BGC particles (size of 20-40 μm) indicated to consist of CaO-SiO2-Na2O-ZrO2-P2O5. Morphologically spherical Ca/P precipitation formed after 3 days in the SBF on the sealer surface. Ca/P ratio of the precipitation ranged in 1.20-1.65 indicating transformation to hydroxyapatite (HA). The pH of the immersion solution rose gradually.