To provide an interdental cleaning assist capable of being easily inserted when inserting an interdental brush (a twisting brush) into a narrow portion such as a drum-like interdental clearance, by deforming a shaft part without losing its elasticity, well fitted in a three-dimensional shape of the interdental portion, maintaining straightness without causing permanent deformation when the shaft part is bent despite being insertable into the interdental part restricted in the inserting direction, providing less pain and less uncomfortable feeling when coming into contact with teeth and gums during the cleaning operation, and scarcely damaged by repeated bending.

The shaft part of the interdental brush (the twisting brush) is formed of a resin material having shape restorability and elasticity to provide the brush with proper elasticity, shape restorability, and flexibility, and prevent the shaft part from being deformed and broken, and the cross-section of the shaft part is transitionally changed, so that the shaft central part or root part of this deformed fiber resin twisting brush can be prevented from loosing the elasticity.