In some circumstances, the canal must be retreated. As much of the root filling material as possible must therefor be removed before retreatment itself can begin.
D-Race instruments are used to remove most of the old root-filling material, such as Gutta-Percha, obturators or resin-based material, from the canals.
The D-Race set consists of two NiTi files – DR1 and DR2. The first instrument, DR1, has an active tip for handling the root-filling material and is used in the first millimetres of the coronal and straight part of the canal. Once access is cleared with the DR1, the second instrument, DR2, is used to reach the WL. As this work puts a lot of strain on the instrument, it is intended for single use. The final shape is achieved using the BT-Race, iRace or BioRace sequences.