For the purpose of investigating the continuous fluoride releasing from acrylic resin using removable appliances by incorporating fluoride into polymethylmethacrylate during the construction of the appliances, two kinds of fluoride were blended with acrylic powder and devided into five groups as follows. Group 1 : no fluoride (control) Group 2 : NaF 5 wt% Group 3 : NaF 10 wt% Group 4 : $CaF_2$ 5 wt% Group 5 : $CaF_2$ 10 wt% Resin specimens were tested in vitro for fluoride release with fluoride electrode and flexural strength with Instron. The results were as follows ; 1. After 24 hrs, released fluoride concentration(ppm) was the most in group 3($126.5{pm}14.15$) then, next, group 2($49.5{pm}4.92$), group 5($2.67{pm}1.08$), group 4($0.81{pm}0.30$), group 1($0.03{pm}0.01$) in order, but after 28 days, group 3($3.37{pm}0.31$), group 5($1.25{pm}0.25$), group 4($0.74{pm}0.19$), group 2($0.68{pm}0.07$), group 1($0.03{pm}0.01$). 2. Fluoride releasing of NaF groups were faster and more amount than $CaF_2$ groups initially but decreased significantly, later. 3. Flexural strength ($kg/cm^2$) was the biggest in group 1($602.90{pm}69.32$), and then group 4($568.98{pm}20.16$), group 5($556.19{pm}5.26$), group 2($536.12{pm}30.35$), group 3($508.44{pm}26.16$) in order, the differences between control group and NaF groups were statistically significant (p<0.05).