Bicyclic cyclopropane derivatives of the general Formula (I) in which n+m is 0 to 8; r is 1 to 4; R1 is absent or is a C1-C20 alkylene radical which can be interrupted by O or S, a cycloaliphatic C4-C12 radical, a bicyclic C4-C12 radical, a C6-C14 arylene or C7-C20 alkylenearylene radical; R2 is for r=1 a C1-C20 alkyl radical which can be interrupted by O or S, a cycloaliphatic C4-C12 radical, a bicyclic C4-C12 radical, a C6-C14 aryl or a C7-C20 alkylaryl radical; is for r>1 an r-times substituted aliphatic C1 to C20 radical which can be interrupted by O or S, a cycloaliphatic C4-C12 radical, an aromatic C6-C14 radical or aliphatic-aromatic C7-C20 radical; X is absent or is —CO—O—, —CO—NH— or —O—CO—NH—, and Y is CH2, O or S which is suitable in particular for the preparation of dental materials.