Straight line access and coronal flaring: effect on canal length.

By Schroeder KP, Walton RE, Rivera EM.

Date: 01/2002
Journal: JOE


  • Purpose: to determine if canal length is altered significantly after SLA and CF between two groups of teeth: straight versus severely curved. Also, whether the amount of canal length alteration was influenced by tooth type: molars versus premolars.
  • N= 86 intact Max and mand extracted premolars and molars, 49 curved and 37 straight (determind by Schneider ).


  • Access was made, Reference cusp was flattened to facilitate reproducible, accurate measurements.
  • #10 K-file was placed ,excess file protruding from the root-end was viewed and measured before treatemnt with a stereomicroscope.
  • Access was modified with tapered fissure bur, gates glidden (#2,3,4), #10 K-file protrusion was remeasured .
  • The change in canal length was determined by subtracting the length of protrusion of the file (pre – post-TX).

Most highlighted Results:

1.The study showed a measurable statistically significant decrease in WL after SLA and CF with a mean of 0.17mm.

2.Curved canals showed a significant decrease in length compared to straight canals. However, the difference was very small.

3.There was no significant influence between length change and tooth type.

Clinical Significance:

Especially in curved canals, preflaring would reduce the risk of over-instrumenting the canals.

(*SLA: Straight Line Access, CF: Coronal Flaring)