Multi-part dental composition having staged viscosity prior to hardening

A non-aqueous composition comprising:

• a flowable Part A comprising at least one resin and Reactant A;
• and
• a flowable Part B comprising at least one resin and Reactant B;
• wherein at least one of the resins of flowable Part A and flowable Part B further comprise a free radically polymerizable resin;
• wherein at least one of flowable Part A and flowable Part B further comprises a free radical initiator system;
• wherein flowable Part A and flowable Part B are capable of being mixed to provide a flowable mixed composition;
• wherein when flowable Part A and flowable Part B are mixed, Reactant A and Reactant B are capable of interacting to cause a non-free radical reaction within a first staging time to provide a first staged stable consistency for the mixed composition that is lower than the arithmetic mean of the consistency of flowable Part A and the consistency of flowable Part B;
• wherein Reactant A comprises an acid and Reactant B comprises a base, and upon mixing flowable Part A and flowable Part B, the Reactant A acid is capable of reacting with the Reactant B base in an ionic acid-base reaction;
• and,
• wherein the mixed composition having the first staged stable consistency is capable of forming a hardened dental composition upon initiation of free radical polymerization.