The barbed broach is formed from a tapered round shaft by lifting up portions of metal of the shaft almost at a right angle to the shaft.
These elevated barbs will engage the pulp tissue and remove it from the canal.
In its use, the largest size broach which will fit freely – loosely – in the canal is selected.
A broach must not engage the canal walls as it is advanced, or the pressure on the barbs will flatten them against the shaft; as the instrument is withdrawn, the barbs will then embed themselves in the walls, making it difficult or impossible to remove the broach.
Because the barbs are “nicked” out of the shaft this is an extremely fragile instrument and will break easily if misused. It must fit loosely.