Identfying inorganic debris in micro-channels during root canal therapy

Objectives: Root canal therapy involves the internal cleaning of a complex canal network contained within the tooth. The goal is to disinfect the canal and remove any remaining bacteria to prevent further infection prior to root filling. Micro-computed tomography can be used as a non-destructive/non-invasive methodology for mapping out in 3D where inorganic debris accumulates following the internal cleaning process. The aim of this study was to visualise and quantify remaining inorganic debris after instrumentation using syringe irrigation, a commonly used methodology for cleaning.

Methods: Fourteen mandibular permanent molar teeth were selected for the study. Analysis of the entire lengths of all teeth was performed prior to and after preparation using micro-computed tomography. The canals were prepared by an endodontic clinical expert using standard ProTaper instruments. Using image registration and mathematical morphology, two image sets per tooth was obtained for canal space and debris. Three-dimensional models were generated mapping debris to its location. Total amount of debris was quantified via voxel summation.

Results: Debris accumulated in protrusions in the main canal wall and lateral micro-canals. The mean percentage debris which accumulated was 18.5% of the amount of debris produced. However, the amount greatly varied between teeth with a standard deviation of 16.5%

Conclusions: Protrusions, fins and lateral canals create complexities, which should be taken into account when designing instrumentation and evaluating methods for debris removal. Debris accumulated varied with anatomy and a greater understanding of the effect that anatomy has on technique may enable improved methods to be developed enabling debris to be more effectively removed.