Composition comprising: (a) a filler system consisting of or comprising inorganic filler particles surface-modified by means of organic structural elements, in which the organic structural elements are convertible with an organic bonding system with formation of covalent bonds, in which the filler particles of the composition have a mean particle size in the range between 1 nm and 150 nm, (b) an organic bonding system comprising one or more polymerizable monomers, in which the filler system is dispersed in the organic bonding system (b), for use in a process for the infiltration and/or sealing of hard tooth substance and for the detection, by means of fluorescence, of caries in the infiltrated region or under the sealing, in which the total amount of the organic bonding system (b) comprises one, two or more monomers chosen from the group consisting of compounds (monomers) of the structure Q(Y x G e) b, in which the following applies: - Q represents a saturated or olefinically unsaturated polyalicyclic structural element chosen from the group consisting of bicyclic, tricyclic, tetracyclic, pentacyclic and hexacyclic hydrocarbon radicals, in which one, two or more of the hydrogen atoms of this polyalicyclic structural element Q not substituted by substituents Y x Z e are optionally substituted by alkyl groups, alkoxy groups, halogen atoms or trifluoromethyl groups, - b is a natural number chosen from the group of the natural numbers 1, 2, 3 and 4, - each Z represents a structural element which, independently of possible additional structural elements Z, is chosen from the group consisting of -O-(C=O)-CH=CH 2, -O-(C=O)-C(CH 3)=CH 2, -(C=O)-CH=CH 2, -(C=O)-C(CH 3)=CH 2 -CH=CH 2, -C(C H 3)=CH 2 and -O-CH=CH 2, - each index e is a natural number which, independently of possible additional indices e, is chosen from the group of the natural numbers 1, 2, 3 and 4, - each index x represents, independently of possible additional indices x, 0 or 1, - each Y represents, in the structure Q(Y x Z e) b with x = 1, a structural element which bonds the polyalicyclic structural element Q with e structural elements Z, in which each Y is chosen independently of possible additional structural elements Y. (a) a filler system consisting of or comprising inorganic filler particles surface-modified by means of organic structural elements, in which the organic structural elements are convertible with an organic bonding system with formation of covalent bonds, in which the filler particles of the composition have a mean particle size in the range between 1 nm and 150 nm, (b) an organic bonding system comprising one or more polymerizable monomers, - Q represents a saturated or olefinically unsaturated polyalicyclic structural element chosen from the group consisting of bicyclic, tricyclic, tetracyclic, pentacyclic and hexacyclic hydrocarbon radicals, in which one, two or more of the hydrogen atoms of this polyalicyclic structural element Q not substituted by substituents Y x Z e are optionally substituted by alkyl groups, alkoxy groups, halogen atoms or trifluoromethyl groups, - b is a natural number chosen from the group of the natural numbers 1, 2, 3 and 4, - each Z represents a structural element which, independently of possible additional structural elements Z, is chosen from the group consisting of -O-(C=O)-CH=CH 2, -O-(C=O)-C(CH 3)=CH 2, -(C=O)-CH=CH 2, -(C=O)-C(CH 3)=CH 2 -CH=CH 2, -C(C H 3)=CH 2 and -O-CH=CH 2, - each index e is a natural number which, independently of possible additional indices e, is chosen from the group of the natural numbers 1, 2, 3 and 4, - each index x represents, independently of possible additional indices x, 0 or 1, - each Y represents, in the structure Q(Y x Z e) b with x = 1, a structural element which bonds the polyalicyclic structural element Q with e structural elements Z, in which each Y is chosen independently of possible additional structural elements Y.