The present invention relates to a kit of parts comprising Part A and Part B, Part A comprising: ascorbic acid, component(s) comprising an ascorbic acid moiety or derivative(s) thereof, optionally polymerizable component(s) without acidic moieties, optionally polymerizable component(s) with acidic moieties, and optionally filler(s), Part B comprising polymerizable component(s) without acidic moieties, polymerizable component(s) with acidic moieties, transition metal component(s), organic peroxide(s), and optionally filler(s), The invention is also directed to a redox initiator system comprising ascorbic acid, component(s) comprising an ascorbic acid moiety or derivative(s) thereof, transition metal component(s), preferably comprising a copper or iron ion containing salt, organic peroxide(s), preferably comprising a hydroperoxide or di-peroxide. The kit of parts and redox initiator system are particularly useful in the dental field.