A dental composition comprising: an addition-fragmentation agent of 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 one 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 selected from and wherein R 4 is H or C 1 -C 4 alkyl; 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; and Q is selected from -O-, -S-, -NR 4 -, -SO 2 -, -PO 2 -, -CO-, -OCO-, -R 6 -, -NR 4 -CO-NR 4 -, NR 4 -COO-, NR 4 -CO-NR 4 --CO-O-R 6 -, -CO-NR 4 -R 6 -, -R 6 -CO-O-R 6 -, -O-R 6 -. -S-R 6 - -, -NR 4 -R 6 -, -SO 2 -R 6 -, -PO 2 -R 6 -, -CO-R 6 -, -OCO-R 6 -, -NR 4 -CO-R 6 -, NR 4 -R 6 -CO-O-, and NR 4 -CO-NR 4 -, wherein each R 4 is hydrogen, a C 1 to C 4 alkyl group, or aryl group, each R 6 is an alkylene group having 1 to 6 carbon atoms, a 5- or 6-membered cycloalkylene group having 5 to 10 carbon atoms, or a divalent arylene group having 6 to 16 carbon atoms, with the proviso that Q-Z does not contain peroxidic linkages, or Q is selected from an alkylene or a hydroxyl-substituted alkylene or an aryloxy-substituted alkylene or an alkoxy-substituted alkylene; at least one monomer comprising at least two ethylenically unsaturated groups; and inorganic oxide filler. an addition-fragmentation agent of 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 one 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 selected from and wherein R 4 is H or C 1 -C 4 alkyl; 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; and Q is selected from -O-, -S-, -NR 4 -, -SO 2 -, -PO 2 -, -CO-, -OCO-, -R 6 -, -NR 4 -CO-NR 4 -, NR 4 -COO-, NR 4 -CO-NR 4 --CO-O-R 6 -, -CO-NR 4 -R 6 -, -R 6 -CO-O-R 6 -, -O-R 6 -. -S-R 6 - -, -NR 4 -R 6 -, -SO 2 -R 6 -, -PO 2 -R 6 -, -CO-R 6 -, -OCO-R 6 -, -NR 4 -CO-R 6 -, NR 4 -R 6 -CO-O-, and NR 4 -CO-NR 4 -, wherein each R 4 is hydrogen, a C 1 to C 4 alkyl group, or aryl group, each R 6 is an alkylene group having 1 to 6 carbon atoms, a 5- or 6-membered cycloalkylene group having 5 to 10 carbon atoms, or a divalent arylene group having 6 to 16 carbon atoms, with the proviso that Q-Z does not contain peroxidic linkages, or Q is selected from an alkylene or a hydroxyl-substituted alkylene or an aryloxy-substituted alkylene or an alkoxy-substituted alkylene; 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 one 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 selected from and wherein R 4 is H or C 1 -C 4 alkyl; 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; and Q is selected from -O-, -S-, -NR 4 -, -SO 2 -, -PO 2 -, -CO-, -OCO-, -R 6 -, -NR 4 -CO-NR 4 -, NR 4 -COO-, NR 4 -CO-NR 4 --CO-O-R 6 -, -CO-NR 4 -R 6 -, -R 6 -CO-O-R 6 -, -O-R 6 -. -S-R 6 - -, -NR 4 -R 6 -, -SO 2 -R 6 -, -PO 2 -R 6 -, -CO-R 6 -, -OCO-R 6 -, -NR 4 -CO-R 6 -, NR 4 -R 6 -CO-O-, and NR 4 -CO-NR 4 -, wherein each R 4 is hydrogen, a C 1 to C 4 alkyl group, or aryl group, each R 6 is an alkylene group having 1 to 6 carbon atoms, a 5- or 6-membered cycloalkylene group having 5 to 10 carbon atoms, or a divalent arylene group having 6 to 16 carbon atoms, with the proviso that Q-Z does not contain peroxidic linkages, or Q is selected from an alkylene or a hydroxyl-substituted alkylene or an aryloxy-substituted alkylene or an alkoxy-substituted alkylene; at least one monomer comprising at least two ethylenically unsaturated groups; and inorganic oxide filler.