The effect of preparation procedures on original canal shape and on apical foramen shape.

By Weine FS, Kelly RF, Lio PJ.

Date: 01/1975
Journal: JOE


  • Purpose: To create a simulated canal in a completely transparent system that would provide a vehicle for complete visualization of all the intracanal procedures as they were performed.


  • N=8 simulated curved canals with similar shape were created using clear casting resin.
  • Canals were prepared by 10 different individuals who used the various preparation techniques that they normally used (reaming, quarter-turn filing, rasping, or combinations).
  • Irrigation with 5.25% NaOCl was used
  • After initial examination of the preparations and observations of the apical areas, extracted teeth were selected, macrophotographed, radiographed, and prepared so that the enlarging instruments would go past the apical foramen.

Most highlighted Results:

-All final preparations showed the same general configuration and three specific characteristics:

1-No preparation was completely funnel-shaped from the orifice to the apex.

2-Every file in the canal (precurved or straight) tended to straighten within the canal.

3-the greatest amount of canal preparation at the apical portion was at the expense of the outer portion of the curvature.

-The extracted teeth selected were those in which canal preparation could have easily resulted in overextension of the enlarging instruments because of the early exit of the apical foramen. In these teeth, the teardrop shapes of the zipped apices were clearly demonstrable

Clinical Significance:

Provided insights on the resultant preparation of curved canals.

Certain clinical considerations can be taken (preflaring, removing the outer flutes, rasping) to prevent theses deviations.

weakness: sample size not mentioned, no standardization, the simulated canals do not replicate the actual teeth anatomy