Authors: Allison DA, Weber CR, Walton RE.
Title: The influence of the method of canal preparation on the quality of apical and coronal obturation.
Journal: J Endod
Date: Oct 1979
Citation: 5(10):298-304
Category: Obturation
Evidence-based Ranking: 5
Purpose/Objectives: 1. to compare two different methods of canal enlargement as to their effect on the apical seal. 2. To evaluate whether the depth of spreader penetration during obturation relates directly to the distance that microleakage can occur from the apical area. 3. To determine if the method of canal preparation affects the coronal seal.

Materials and Methods: All teeth were accessed with round burs and GG burs. Instrumentation was done with K files and 5.25% NaOCl irrigation. 2 techniques were utilized, the first was the standardized taper (Ingle), which shapes 2-3 sizes past the first file that binds at working length (usually 35-50). The second was a step back technique (Weine and Walton), to a size 25, with larger files backed out .5 mm. The degree of taper was determined by a D-11 that extended 1mm from WL. All teeth were obturated with lateral condensation. Positive and negative controls were used, and then the teeth were sealed with nail polish everywhere except the coronal and apical segments. The teeth were then submerged in radioactive Ca for 48 hrs, and then transversely sectioned. The sections were then evaluated for “fogging” in the canal to determine the presence and extent of Ca 45 leakage. Results: The negative control showed no leakage, and the positive control showed leakage throughout the canal. The standardized taper group showed significant leakage occurred in all these teeth, except for those which allowed the spreader penetration to be 2.0 mm or less from the apex. Most teeth showed extent of leakage greater than 3.6mm. In regards to the step back technique, the teeth that allowed spreader penetration within 1mm of the apex, no significant microleakage was shown. Only two teeth showed an extent greater than 1mm.

Author’s Conclusions: The method of canal preparation which permitted deeper penetration of the spreader resulted in a seal closer to the prepared length. Microleakage generally extended close to the point where the tip of spreader had penetrated. The coronal seal was not affect by either method. Reviewer’s comments: Results showed the importance of spreader depth in lateral condensation, excellent study.