Effect of Early Coronal Flaring on Working Length Change in Curved Canals Using Rotary Nickel-Titanium Versus Stainless Steel Instruments

By Davis R, Marshall J, Baumgartner J

Date: 01/2002
Journal: JOE


Purpose:  to compare pre and post-instrumentation WL in curved root canals prepared by (a) using early coronal flaring (flaring completed before WL determination) versus late coronal flaring (flaring completed after WL determination); and

(b) using either stainless steel or nickel-titanium instruments.

N= 30 extracted human maxillary and mandibular first and second molar teeth.


  • Access cavities were prepared, working length determined using #10 k file by observing the tip of the file at apex under microscope.
  • The teeth were then divided into two groups (G1: Stainless steel (SS) + gates glidden, G2: nickel titanium rotary files).
  • Coronal flaring was accomplished for the SS group using Gates Glidden drills and for the Ni-Ti group using rotary Ni-Ti files.
  • WL determined after preflaring & after complete canal preparation.

Most highlighted Results:

  • WL decreased for all canals after complete canal preparation. The mean decrease in WL was significantly greater for the SS group ( 0.48mm )than for the Ni-Ti group ( 0.22 mm ).
  • Less change in WL occurred in both groups when initial WL was determined after coronal flaring (SS:  -0.36 mm , Ni-Ti: -0.07).

Clinical Significance:

When the canals preflared using gates glidden , WL should be determined after preflaring.