Does the first file to bind correspond to the diameter of the canal in the apical region?

By Wu MK, Barkis D, Roris A, Wesselink PR.

Date: 01/2002
Journal: IEJ


Purpose:  To determine whether the first file that binds reflects the diameter of apical canal

N=   20 mandibular premolars with curved canals and an apical foramen at the apex were selected.


    • Teeth were divided into 2 groups : K file & Lightspeed (n=10)
    • Coronal flaring was done using GG drills (#1-4).
    • One investigator inserted files into the canals starting with #10; until binding occurred and reported to a second investigator who recorded the length.
    • The apical 1 mm of each root was removed horizontally to expose the canal and instrument at the WL level.
    • Root surface was observed under a microscope.

Most highlighted Results: 

1.In (90%) 18 canals (9 canals /group), the diameter of the instrument was smaller than the diameter of the apical canal

2.The discrepancy was up to 0.19 mm in the( K-file) group and 0.14 mm in the (Lightspeed) group.

3.In (25%) canals (1 K-file Gp & 4 Lightspeed Gp) the instrument did not touch the wall at the WL. whereas in the (75%) canals the instrument was found binding at one part of the wall.

4.The first file to bind did not reflect the apical diameter and that the size of the file was noticeably smaller than the size of root canal at the WL .

Clinical Significance:

 Using the first binding file for gauging the diameter of the apical canal and as guidance for apical enlargement is not reliable .