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Aim: The study was designed to quantitatively evaluate the quality of root canal preparation and root canal obturation in canals treated with either rotary or self adjusting files, using three-dimensional micro-computed tomographic (CT) analysis., Methodology: Pair-matched root canals were instrumented with either rotary nickel-titanium files or self-adjusting files following the manufacturers' instructions. The area of the canal wall unaffected by the preparation procedure was analyzed using before and after micro-CT images. Root canal obturation was done using lateral compaction with gutta-percha and AH26 (Dentsply-DeTrey, Konstanz, Germany). Teeth were scanned a third time, and the adaptation of the filling material to the canal walls was evaluated three-dimensionally by micro-CT analysis and the area of canal wall untouched by the filling was determined. The correlation between these two parameters within each of the groups was studied using the Pearson correlation test., Results: A high percentage of unaffected root canal walls (60% +/-14%) and areas untouched by the root canal filling (45% +/- 15%) were found in canals treated with rotary files. Both parameters were significantly smaller in canals treated with self-adjusting files (17% +/- 9% and 17% +/- 11%, respectively) (p < 0.01). No correlation was found between these parameters within each of the groups., Conclusion: Within the limitations of the present study, the self-adjusting files allowed better cleaning and shaping and better adaptation of the root canal filling than those allowed by rotary files., (Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Aim: To introduce a new concept, the self-adjusting file (SAF), and discuss its unique features compared with current rotary nickel-titanium file systems., The New Concept: The SAF file is hollow and designed as a thin cylindrical nickel-titanium lattice that adapts to the cross-section of the root canal. A single file is used throughout the procedure. It is inserted into a path initially prepared by a # 20 K-file and operated with a transline- (in-and-out) vibration. The resulting circumferential pressure allows the file's abrasive surface to gradually remove a thin uniform hard-tissue layer from the entire root canal surface, resulting in a canal with a similar cross-section but of larger dimensions. This holds also for canals with an oval or flat cross-section, which will be enlarged to a flat or oval cross-section of larger dimensions. The straightening of curved canals is also reduced because of the high pliability of the file and the absence of a rigid metal core. Thus, the original shape of the root canal is respected both longitudinally and in cross-section. The hollow SAF file is operated with a constant flow of irrigant that enters the full length of the canal and that is activated by the vibration and is replaced continuously throughout the procedure. This results in effective cleaning even at the cul de sac apical part of the canal. The SAF has high mechanical endurance; file separation does not occur; and mechanical failure, if it occurs, is limited to small tears in the latticework., Conclusion: The SAF represents a new step forward in endodontic file development that may overcome many of the shortcomings of current rotary nickel-titanium file systems., (Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Aim: The aim of this study was to evaluate the cleaning ability of the Self-Adjusting File (SAF) system in terms of removal of debris and smear layer., Methodology: Root canal preparations were performed in 20 root canals using an SAF operated with a continuous irrigation device. The glide path was initially established using a size 20 K-file followed by the SAF file that was operated in the root canal via a vibrating motion for a total of 4 minutes. Sodium hypochlorite (3%) and EDTA (17%) were used as continuous irrigants and were alternated every minute during this initial 4-minute period. This was followed by a 30-second rinse using EDTA applied through a nonactivated SAF and a final flush with sodium hypochlorite. The roots were split longitudinally and subjected to scanning electron microscopy (SEM). The presence of debris and a smear layer in the coronal, middle, and apical thirds of the canal were evaluated through the analysis of the SEM images using five-score evaluation systems based on reference photographs., Results: The SAF operation with continuous irrigation, using alternating irrigants, resulted in root canal walls that were free of debris in all thirds of the canal in all (100%) of the samples. In addition, smear layer-free surfaces were observed in 100% and 80% of the coronal and middle thirds of the canal, respectively. In the apical third of the canal, smear layer-free surfaces were found in 65% of the root canals., Conclusions: The operation of the SAF system with continuous irrigation coupled with alternating sodium hypochlorite and EDTA treatment resulted in a clean and mostly smear layer-free dentinal surface in all parts of the root canal., (Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)