Ceramicrete is an impervious inorganic binder widely used for encapsulating radioactive and hazardous wastes. This study evaluated the feasibility of using a radiopaque Ceramicrete-based material for root-end fillings. Apical seals of root-end preparations filled with Super EBA (Harry J. Bosworth Co, Skokie, IL), White ProRoot MTA (Dentsply Tulsa Dental Specialties, Tulsa, OK), or Ceramicrete-D were evaluated using a computerized fluid filtration approach after the fillings were immersed in phosphate-containing fluid (PCF). The Ceramicrete-D fillings exhibited significantly (P < 0.05) better seals than the other two commercially available, frequently advocated root-end-filling materials. Scanning electron microscopy and x-ray diffraction of Ceramicrete-D after setting revealed a relatively nonporous KMgPO4.6H2O matrix that binds other incompletely reacted and new reaction phases such as CaHPO4.2H2O. Polished dentin slabs filled with Ceramicrete-D and immersed in PCF for 72 hours revealed depositions of acicular-shaped, apatite-like crystallite clusters on the material surface as the pH of the PCF increased with immersion time. The experimental Ceramicrete-based material is potentially bioactive in the presence of PCF.