Mineral trioxide aggregate (MTA) is a slow setting Portland cement (PC) based dental material for endodontic applications. The present study investigated the effect of adding either CaCl2 or Plaster of Paris (PoP) as setting accelerators on the development of the material properties and microstructure with reaction time for a PC based model system. Mechanical strength, density and relative porosity were measured after 1, 10 and 30days and the microstructure was assessed using scanning electron microscopy (SEM). The strength of all cements increased with time whereas material density and relative porosity decreased due to the progress of the hydration reaction. Cements with 5-10% CaCl2 in the liquid phase had a higher final strength and lower porosity than cements modified with 20wt% PoP in the cement powder, whilst PoP modified cement had a shorter setting time of 15min compared with 60min for 10% CaCl2 addition. The microstructure of the two modifications were noticeably different, with the CaCl2 modified cement having more interconnected needle-like crystals than seen in PoP modified cements, which may explain the higher strength of this cement.
A comparative evaluation of ProRoot mineral trioxide aggregate and Portland cement as a pulpotomy medicament