Endodontic retreatment in small and large curved canals

This study used a special jig system, photography, and a sonic digitizer to evaluate the change in canal size and location after retreatment in 20 teeth with small or large curved canals (greater than 23 degrees). During initial instrumentation, small canals enlarged twice as much as large canals in the coronal and middle areas. During retreatment, small and large canals showed 30 to 85% enlargement compared with that of the initial instrumentation. There was a trend, primarily during retreatment, for small canals to deviate more than large canals away from the original canal location.