A family of magnesium phosphate cements was explored as candidate biomaterials for hard tissue applications. These cements were prepared by mixing magnesium oxide with either sodium dihydrogen phosphate, ammonium dihydrogen phosphate or an equimolar mixture of both. The exothermia and the setting kinetics of the cement formulations were tailored. The ammonium-containing magnesium phosphate cements resulted in struvite, whereas the cement prepared with sodium dihydrogen phosphate resulted in an amorphous product. The magnesium phosphate cements studied had an early compressive strength and antimicrobial properties. These properties make magnesium phosphate cements good candidates for endodontic applications. It is with this latter point in mind that their radiopacity was enhanced. The sealing efficiency of the magnesium phosphate cements and their adhesion to dentin were shown to be comparable or even higher than those presented by other inorganic cements used for endodontic treatments.