A temporary root canal sealer dispersion having a pH of at least 9 and comprising: (i) an aqueous dispersion medium comprising - an oligomer and/or polymer having Lewis basic groups, and - optionally a hydroxide of an alkali metal and/or a hydroxide of an alkaline earth metal, and (ii) a dispersed phase comprising a radio-opaque filler, wherein the weight ratio of oligomer and/or polymer having Lewis basic groups to hydroxide of an alkali metal and/or hydroxide of an alkaline earth metal is at least 0.5 when said aqueous dispersion medium comprises a hydroxide of an alkali metal and/or a hydroxide of an alkaline earth metal.
