The invention relates to a redox initiator system which allows dental formulations to be cured in acidic medium by way of a free-radical polymerization and which ensures a high level of adhesion of the polymerizing composition to the hard substances of the teeth, namely enamel and, in particular, dentine. The redox initiator system comprises the following constituents:

(A) from 14.9 to 50% by weight of a barbituric acid or thiobarbituric acid and/or of a barbituric or thiobarbituric acid derivative,

(B) from 30 to 75% by weight of a peroxodisulfate compound and/or peroxodiphosphate compound,

(C) from 10 to 35% by weight of a sulfinic acid compound, and

(D) from 0.1 to 5% by weight of a copper compound.