Dental compositions comprising an addition-fragmentation agent having the formula: wherein R 1 , R 2 and R 3 are each independently Z m -Q-, a (hetero)alkyl group or a (hetero)aryl group with the proviso that at least two of R 1 , R 2 and R 3 is Z m -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 X 1 is independently -O- or -NR 4 -, where R 4 is H or C 1 -C 4 alkyl and n 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.
