A dental root canal sealing composition curable in the absence of a polymerisation initiator, which comprises: (i) an amino terminated prepolymer having a viscosity at 23<；0>；C of less than 100 Pas, which is obtainable by reacting (a) one mole of a compound of the formula (I) wherein X represents a nitrogen or an oxygen atom； Z represents an n-valent saturated aliphatic C2-16 hydrocarbon group or a divalent saturated cycloaliphatic C3-6 hydrocarbon group, which groups may contain 1 to 6 oxygen atoms, and which may be substituted by 1 to 6 C1-4 alkyl groups； and n represents an integer of from 2 to 6； (b) at least n moles of one or more compounds either of the following formula (II) wherein A represents a divalent saturated aliphatic C2-16 hydrocarbon group or a divalent saturated cycloaliphatic C3-6 hydrocarbon group, which groups may contain 1 to 6 oxygen atoms, and which may be substituted by 1 to 6 C1-4 alkyl groups； Ra and Rb are the same or different and represent a hydrogen atom, a C1-6 alkyl or a C3-14 cycloalkyl group, which may be substituted by one or more members of the group selected from a C1-4 alkyl group, C1-4 alkoxy group, a phenyl group, and a hydroxy group； or of formula (II) in combination with one or more compounds of a formula RNH2, wherein R represents C1-6 alkyl or a C3-14 cycloalkyl group, which may be substituted by one or more members of the group selected from a C1-4 alkyl group, C1-4 alkoxy group, a phenyl group, and a hydroxy group, and/or in combination with a further di- or polyamine compound； (ii) a di- or polyfunctional acrylate compound or a di- or polyfunctional maleimide compound which is capable of undergoing polyaddition with the aminoterminated prepolymer (i)； (iii) 40 to 85 wt.-% of a filler for providing a minimum radioopacity of at least 3mm/mm Al； said compositon being in the form of a two-component composition wherein a first component contains the amino terminated prepolymer (i) and optionally filler (iii) and a secon
