The authors have studied on fluoride topical application effect clinically by using of fluoride ion applicator (F-ion) for the purpose of increasing dental caries prevention effect and desensitization efficiency of hypersensitive tooth. We have compared physical components of F-ion to Rivet ion and Pyocure which were made in Japan. And then, we have examined 40 extracted teeth applied 2% NaF solution with F-ion and calculated relative CaF2 production amounts by using of X-ray diffractometer after dividing total samples into 3 parts as control group, one time F-ion application group and 10 times F-ion application group. Otherwise, we have experimented 40 patients who have had hypersensitive teeth applying 10% SnF2 solution with the use of F-ion and found the patient's response for desensitization effects. The obtained results are as follows; 1. There were no obvious differences between F-ion fluoride applicator and other products, Rivet ion or Pyocure in aspect of physical components. 2. CaF2 production amounts were relatively higher in a group of one time 2% NaF application with the use of F-ion than those of control group as only fluoride solution applicated and it were the most in a group of 10 times fluoride application with the use of F-ion, through the examining by X-ray diffractometer, so it was estimated that F-ion technique of fluoride application would increase the fluoride penetration effect. 3. It was estimated that the desensitization effect for several application of 10% SnF2 solution with the use of F-ion would be recognized through the examination by Electro Pulp Tester and patient's response as 85.0% of desensitized persons. 4. The use of F-ion for increasing caries prevention and desensitization effect was recommended to dental clinics.