Oval-shaped canal retreatment with self-adjusting file: a micro-CT study

Aims The primary goals of endodontic treatment are to debride and disinfect the root canal space to the greatest possible extent, and to seal the canals as effectively as possible, aiming to establish or maintain healthy periapical tissues. Although initial root canal therapy has been shown to be a predictable procedure with a high degree of success, failure can occur after treatment. Lack of healing is attributed to persistent intraradicular infection residing in uninstrumented canals, dentinal tubules, or in the complex irregularities of the root canal system. Previously treated teeth with persistent infection might be preserved with nonsurgical retreatment, which attempts to re-establish healthy periapical tissues by regaining access to the root canal system through removal of the original canal filling, further cleaning, and re-filling. In oval-shaped canals rotary files have failed to perform adequate cleaning and shaping leaving untouched fins or recesses on the buccal and/or lingual aspects of the central canal area prepared by the instrument. The self-adjusting file system (SAF; ReDentNova, Ra’anana, Israel) has been suggested to eliminate some of the limitations of rotary instruments because of its scraping motion with simultaneous irrigation and its ability to touch a higher percentage of root canal walls. In this way, the SAF is expected to be effective as a second stage in a two-stage procedure for removing remaining root filling material. Earlier ex vivo studies used destructive or two-dimensional methods to determine the amount of remaining filling material after retreatment procedure. However, these conventional methodologies were not able to precisely evaluate the volume of remaining gutta-percha after the retreatment procedures in the entire root canal. In contrast, the nondestructive and non-invasive technique of micro-computed tomography (μCT) allows the reconstruction and volumetric evaluation of tooth tissues as well as the root canal filling, overcoming the limitation of the conventional methods. Thus, the purpose of this study was to assess the removal of gutta-percha from oval-shaped canals with rotary retreatment files with or without the additional use of the SAF.