Disclosed is a process for the photopolymerization of vinyl compounds and of photopolymerizable materials containing vinyl compounds and products produced thereby which are especially useful for dental materials. The process utilizes at least one photosensitizer of the formula ##STR1## wherein X is selected from the group consisting of CO, C(R.sup.1)(R.sup.2) and C(R.sup.3)(OR.sup.4); wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 are each selected from the group consisting of hydrogen and a hydrocarbon radical;n is 0 or 1; andA is selected from hydrocarbon radicals which may be substituted and which may be bonded together with the proviso that when n is 1 and X is C(R.sup.1)(R.sup.2), and when n is 0, A is an aromatic radical; andat least one reducing agent of formula (I) or (II) ##STR2## wherein Y is selected from oxygen, sulfur or the group NR.sup.1 where R.sup.1 is a hydrogen atom or an alkyl group having 1-10 carbon atoms, preferably 1-5 carbon atoms;Z is an alkylene group having 2 or 3 carbon atoms where one carbon atom can be substituted with one of the heteroatoms O and S or 2 carbon atoms with the heteroatoms O, S and/or N; andR is a substituted or unsubstituted alkyl group having 1-10 carbon atoms, preferably 1-5 carbon atoms or a substituted or unsubstituted aryl group, preferably a phenyl group, ##STR3## wherein R.sup.5 is selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, aralkyl and substituted aralkyl.