Dental compositions comprising an addition-fragmentation agent having the formula:whereinR1, R2 and R3 are each independently Zm-Q-, a (hetero)alkyl group or a (hetero)aryl group with the proviso that at least two of R1, R2 and R3 is Zm-Q-；Q is a linking group have a valence of m +1；Z is an ethylenically unsaturated polymerizable group；m is 1 to 6；each X1 is independently -O- or -NR4-, where R4 is H or C1-C4 alkyl； andn is 0 or 1；at least one multifunctional monomer comprising at least two ethylenically unsaturated group； optionally an inorganic filler； and a redox initiator system； and the use thereof are described.
