The purpose of this article was to compare the fluoridation effect via individual tray with other professional methods. In oder to compare the fluoridation effect, 40 extracted human teeth was divided into 4 groups(each group was composed of 10 teeth) and the surface hardness of each group was tested in untreated, after fluoridation, after fluoridation and etching by 10% lactic acids. group I: no fluoridation(control) group II : fluoridation with 123%APF group III : fluoridation by iontophoresis with 2% NaF group IV : fluoridation by individual tray with 4% SnF2 gel Surface hardness was measured with Micro hardness tester(Shimadzu Co. Japan), Data analysis was conducted using the repeated measures ANOVA test. The results were as follows: 1. Four tested groups demonstrated nearly the same SMH in extracted state. 2. The SMH after fluoridation showed $330.57{pm}139.09kg/mm^2$ in group IV, $221.79{pm}187.48kg/mm^2$ in group II, $186.43{pm}53.13kg/mm^2$ in group III. So the SMH of group IV, II were was significantly increased(p<0.01). 3. The SMH of group II, III, IV after acid etching was higher than the control group(p<0.01). 4. The SMH between group II, III, and IV after acid etching was not different significantly.