Fillers modified superficially with a silane compound (I). Fillers modified superficially with a silane compound (I) of formula ([(PG)-R 1>；-Z] n-SP-[Y 1>；-R 2>；-(AG)] m). A : COOH, -P(=O)(OH) 2, -O-P(=O)(OH) 2, -SO 2OH, -SiR 3>；R 4>；X or a chelatinized group； R 1>；absent or 1-3C -alkylene or cyclopropylene； R 2>；absent or 1-8C alkyl； R 3>；1-8C alkyl, Cl or OR 5>；； R 4>；1-8C alkyl, phenyl, Cl or OR 5>；； R 5>；1-6C alkyl； X : OR 5>； or Cl； Y 1>；O, S, CO-NH, O-CO-NH, NH-CO-NH or absent； Z : O, S, CO-NR 6>；, O-CO-NH, NH-CO-NH or absent； R 6>；H or 1-6C alkyl； PG : radically polymerizable group of formula CH(R 11>；)(H)=CH(R 9>；)-； R 9>；H, 1-3C alkyl, 1-3C hydroxyalkyl or COOR 10>；； R 10>；H, 1-10C alkyl, 1,6-dimethylphenyl or mesityl； R 11>；H or phenyl； m : 1 or 2； n : 1-4； and SP : (n+m)-valued linear or branched aliphatic 1-30C group, in which carbon chain is interrupted by O, S, CO-NH, O-CO-NH or NH-CO-NH, (n+m)-valued aromatic 6-18C group, (n+m)-valued cycloaliphatic 3-18C group or (n+m)-valued heterocyclic 3-18C group (all optionally substituted) or absent. When R 2>； is absent, then Y 1>； is absent； and when AG is silyl group of formula (-SiR 3>；R 4>；X) and PG is a vinyl group of formula (H 2C=CH-), then simultaneously R 1>； and Z are not absent. An independent claim is included for a dental active substance comprising fillers.
