Effect of fluoride concentration on rehardening of enamel by a saliva substitute.

An evaluation was made of the effect of different concentrations of F on the ability of OraLube, a saliva substitute developed by the Veterans Administration designed for use by xerostomic patients, to reharden enamel surfaces. Test preparations contained either 0, 1.0, 2.0, 3.0, 4.0 or 5.0 ppm and groups of softened enamel surfaces were treated with these solutions for 30 minutes. Treatment with saliva substitute containing no F did not significantly alter the hardness of enamel surfaces. Including 1.0 ppm F in the formula induced a rehardening of about 5 per cent; 2.0 ppm F solution rehardened at a 12.5 per cent rate. Additional F up to 5.0 ppm did not increase rehardening significantly. The inclusion of 2.0 ppm F in OraLube assures that, in addition to its ability to relieve intraoral soft tissue problems associated with xerostomia, an optimal rehardening potential is provided.