The mechanisms by which fluoride increases caries resistance include all of the following except-

The benefits of fluoride in the reduction of dental caries have been known for years, but  its  exact  mechanism  of  action  is not completely understood. The mechanisms by which fluoride increases caries resistance may arise from both systemic and topical applications  of  fluoride. A  number  of proposed mechanisms have been identified which are assumed to work simultaneously and can be grouped as follows;  1. Increase enamel resistance (or) Reduction in enamel solubility  2. Increased rate of post-eruptive maturation  3. Remineralization of incipient lesions  4. Interference with plaque microorganisms  5. Modification in tooth morphology.