摘要：The aim of present study was to use QbD approaches to ev.luate the effect of independent product v.riables and their interaction on particle size of sodium fluoride and then obtain the optimized experimental condition for predefined particle size of sodium fluoride. The sodium fluoride is mainly used in dental preparation for deliv.ring the fluoride ion to the tooth enamel for that nano-particle size is required. Nowadays the milling process is used to reduce the particle size. But that process has some limitations due to crystalline nature of sodium fluoride;for ov.rcoming those limitations, lyophilization method is used. A 43 lev.l full factorial design was used to study the significant influence of process and product v.riables i.e. 1) Concentration of sodium fluoride, 2) Concentration of Pv., 3) Sample v.lume, 4) Drying surface, on particle size of sodium fluoride. The experimental design result shows that independent product v.riables significantly modify the structure and improv. particle size reduction of sodium fluoride.