The present invention provides a plurality of positioning area formed on a bristle stem of an interdental brush. Each positioning area has a bottom wall, a side wall formed lateral from the bottom wall, and a capacity area formed by the bottom wall and the side wall. The direction of every adjacent capacity area is disposed differently. Further, the width of the external edges of the bottom side is larger than the outer diameter of the bristle stem, so that the bristle stem is able to be lodged and positioned in the handle firmer. Moreover, the bristle stem will not be loosened or revolved by the external force, which enhances the safety in using.本發明防鬆脫之齒縫刷,其主要在於該齒縫刷之刷桿上成型有複數定位區,而該每一定位區具有一底壁,一位該底壁側邊之側壁,以及一受到該底壁、側壁圈圍之容置空間,同時該相鄰之每一定位區之容置空間設置朝向呈不同,此時若適時再加上該底壁之外緣寬度大於該刷桿外徑變化,將可提供該刷桿與握柄之雙重卡掣定位能力,避免該刷桿受外力作用下而產生鬆脫或轉動等缺失,更增加使用之安全性。3‧‧‧齒縫刷31‧‧‧刷桿32‧‧‧刷毛33‧‧‧握柄310‧‧‧線材331‧‧‧穿孔
