**5. Rotational resistance**

Rotation of the post can be prevented by axial walls.where more coronal tooth structure is present. When most of dentine is destroyed a small groove placed in the canal can serve as an anti rotational element. it should be placed in the bulkiest part of root [usually lingual side]. auxillary pins also acts as anti rotational elements. Alternatively rotation of the threaded post can be prevented by preparing a small cavity, half in the post and half in the root then condensing amalgam in to it after cementation of the post.
