Factors affecting retention of Cu in the human oral cavity after mouth rinses.

Retention of Cu in the mouth after rinses with aqueous solutions of CuSO4 was measured by atomic absorption spectrophotometry. The retained amount of Cu exhibited a linear relationship against the concentration of the rinsing solution in the range tested. Approximately one third of the Cu retained after a 60 s rinse was retained within the first 15 s, and about 75% within 30 s. Retention of Cu was only little affected by the pH of the rinsing solution in the range from 2.0 to 5.7, being reduced by about 50% at pH 9.0. However, variations in cupric ion activity rather than pH per se could explain these effects. A mutual reduction in retention of either metals was seen when Cu and Zn were applied simultaneously.