The SAF was more effective than the ProTaper file system in shaping the walls of C-shaped root canals.

No abstract

The occurrence of more than 1 root canal in central and lateral mandibular incisors is approximately 40% (type III was the predominant canal type). In central and lateral incisors with 1 root canal, long oval canals are common.

The cleaning and shaping of the root canal is a key procedure in root canal treatment. The aim of cleaning is the removal of tissue remnants and bacterial biofilms in order to allow close adaptation of the root filling to the canal walls. In simple straight canals with a round cross‐section, this aim is easily attained by mechanical instrumentation and irrigation. The task of cleaning presents a greater challenge in oval canals, curved canals, and in canal systems that contain an isthmus. In areas that are inaccessible to mechanical instrumentation, the cleaning greatly depends on the action of sodium hypochlorite, which is used to dissolve and remove all of the remaining tissues and bacterial biofilms. Traditional irrigation with syringe and needle is often ineffective in cleaning such inaccessible areas. Newer irrigation methods allow for better cleaning by facilitating a more effective flow of irrigants; nevertheless, adequate, larger, mechanical preparations are required for the effective use of these methods. An alternative approach is to use a hollow file that adapts itself to the cross‐section of the canal, without excessive enlargement of the canal, thus allowing mechanical scrubbing of the walls with a continuous flow of the irrigant through the file. All cleaning methods reach their limit in cases of long narrow isthmuses that are often inaccessible to mechanical instrumentation; adequate instrumentation is, however, a prerequisite for all cleaning methods.

INTRODUCTION: Rotary instruments that are used for retreatment are very effective, but most of them leave root filling residue in the canal. The aim of this study was to evaluate the efficacy of removing gutta-percha-based root fillings with ProTaper retreatment files (Dentsply Maillefer, Ballaigues, Switzerland) followed by F1 and F2 ProTaper instruments and to compare these results with those obtained with a 25 .06 ProFile instrument (Dentsply Maillefer) followed by the Self-Adjusting File (SAF; ReDent, Ra'anana, Israel) using high resolution micro-computed tomography (CT) scanning. METHODS: Twenty-eight mandibular molar teeth with oval distal root canals were divided into 2 equal groups of 14 teeth each. The distal root canals were instrumented with ProTaper files up to an F2 instrument, the roots were subsequently filled, and the root filling was allowed to set fully. Removal of the root canal filling was performed with D1-D3 ProTaper retreatment files followed by F1 and F2 ProTaper instruments or with a 25 .06 ProFile followed by SAFs. Chloroform was used in both groups to assist in the removal of the root filling material. High-resolution micro-CT scans were used to measure the residual quantities of the root filling material after completion of the procedures. Statistical analysis was performed using the Wilcoxon test and the Student t test. RESULTS: The median root filling residue in the ProTaper group was 5.39% (interquartile range [IQR] = 4.71) of the original volume of the root canal filling. In the ProFile and SAF group, the median residue was 0.41% (IQR = 1.64, P < .001). An arbitrarily selected threshold of less than 0.5% residue was defined as "effectively cleaned," and 57% of the teeth treated with the ProFile and the SAF met this threshold, whereas none of the cases in the ProTaper group did. The ProFile and SAF procedure required less time than the ProTaper protocol. CONCLUSIONS: None of the retreatment methods rendered all of the canals completely free of all root filling residue. Under the conditions of this study, the ProFile and SAF procedure was more effective than the ProTaper procedure and left significantly less root filling residue in the root canal.