A method using an Orion combination electrode (96–09) was developed for determining the total fluoride content of soft tooth deposits. The samples were collected by plastic sealers and dried at 105° C. After weighing, the sample was dissolved in a small polypropylene tube, positioned inside a larger tube. The dissolution was carried out in 0.2 ml of a mixture of HClO4 and HNO3 at 60° C for 2 h. The outer tube contained 0.3 ml NaOH and 1 ml Na3-citrate. After the soft deposit was dissolved, the contents of the tubes were mixed without opening the sealed outer tube. The final mixture had a pH of 5.8 and the F–– was determined directly. The recovery was found to be satisfactory. Known amounts of F added to dried deposits of Streptococcus salivarius and to Ca3(PO4)2 indicated no F- binding in the solubilized material. Deposits collected from a group of children 5–6 days after mouthrinsing with 0.2 % NaF had an average fluoride concentration of 85 ppm F (on dry weight) as compared to 52 ppm F in the cont