Figure 1 - The shape of the prepared root canal should be a gradual, even taper, with the widest part coronally and the narrowest part 1.
From the following article
Verifiable CPD Paper:
Endodontics: Part 7 Preparing the root canal
P Carrotte
British Dental Journal 197, 603 - 613 (2004) Published online: 27 November 2004
doi:10.1038/sj.bdj.4811823
0 mm from the root apex.
