For filling and forming teeth, novel (meth)acrylic acid derivatives of triisocyanates of the formula ##STR1## wherein R.sup.1 and R.sup.2 are identical or different and stand for hydrogen or a lower alkyl radical,R.sup.3, R.sup.4 and R.sup.5 are identical or different and denote hydrogen or methyl,Y.sup.1 to Y.sup.3 are identical or different and denote divalent straight-chain or branched hydrocarbon radicals of 2 to 15 carbon atoms which may optionally include 1 to 3 oxygen bridges and which may be unsubstituted or substituted by 1 to 4 additional (meth)acryloyloxy radicals,X.sup.1 to X.sup.3 are identical or different and denote --NR.sup.1 -- or --O--, at least one of the radicals X.sup.1 to X.sup.3 denoting --NR.sup.1 --, and the ringsA and B are identical or different and may be aromatic or saturated.