Final answer:
The amount of widening in a Root Canal Therapy procedure can vary and is not strictly 1mm as it depends on the initial and required final size of the canal.
Step-by-step explanation:
The statement that canal walls are widened 1mm during an RCT procedure (Root Canal Therapy) is too specific and may not always hold true. The actual amount of widening or enlargement of the canal will depend on the initial size of the canal and the final size needed to properly clean, shape, and fill the canal. During an RCT, endodontic files are used to remove the damaged tissue and bacteria, and to shape the canal walls for filling. The objective is to widen the canals enough to provide adequate cleaning while maintaining the structural integrity of the tooth.