Micro–computed Tomography Evaluation of the Preparation of Long Oval Root Canals in Mandibular Molars with the Self-adjusting File

Abstract

INTRODUCTION: The aim of this study was to assess the shaping potential of a novel nickeltitanium instrument, the self-adjusting file (SAF), in long oval root canals in distal roots in mandibular molars. METHODS: Twenty mandibular molars with long oval distal root canals were selected and scanned preoperatively and postoperatively by using micro-computed tomography at an original resolution of 20 m. Canals were shaped with the SAF, three-dimensionally reconstructed, and evaluated for volume, surface area, canal transportation, and prepared surface. Data were statistically contrasted by using paired t tests and regression analysis. RESULTS: Preoperatively, canal volume was 7.73 ± 2.13 mm(3), and canal area was 42.83 ± 8.14 mm(2). Volumes and surface areas increased significantly (P < .001) by 4.84 ± 1.73 mm(3) and 3.34 ± 1.73 mm(2), respectively, and no gross preparation errors were detected. Unprepared canal surface varied between individual canals, and mean unprepared surface was 23.5% ± 8.9%. Prepared areas were significantly larger compared with rotary canal preparation done in a previous study. Canal transportation scores were higher in the coronal root canal third (106 ± 50 m) compared with the apical third (81 ± 49 m). CONCLUSIONS: In vitro, preparation of long oval-shaped root canals in mandibular molars with the SAF was effective and safe. Moreover, shapes generated with the SAF were more complete compared with rotary canal preparation.

Root Canal Morphology and Configuration of 118 Mandibular First Molars by Means of Micro–Computed Tomography: An Ex Vivo Study

“…Due to the great anatomical variations, in both mesial and distal roots, and a high frequency of accessory canals, we are also (5) of the opinion that endodontic instruments and treatment techniques should be carefully selected in order to avoid mishaps; thus, compromising success during endodontic treatment (5). With the morphology knowledge reported in this and other micro-computer tomography investigations (5,7,11,13,(16)(17)(18)(23)(24)(25), the importance of appropriate root canal preparation systems and irrigating solution selection becomes evident when considering the three dimensionality of the root canal system.…”

“…The teeth were scanned at an isotropic resolution of 20 µm in a desktop micro-computed tomography unit (µCT 40; Scanco Medical, Brüttisellen, Switzerland) by means of a previ-ously established method (16)(17)(18) at settings of 70 kV and 114 µA resulting in 800 to 1200 slices per tooth.…”

Micro-CT Evaluation of Non-instrumented Canal Areas with Different Enlargements Performed by NiTi Systems

“…Essentially, "shaping ability" refers to the dentinal surface area that is mechanically removed during the canal preparation procedures and may be regarded as a suitable outcome parameter to compare different instrumentation techniques. In general, micro-CT results revealed that more than half of the dentinal walls (ranging from 59.6% to 79.9%) remained unprepared in oval-shaped canals, regardless of the instrumentation technique (7,16,17). Thus,…”

“…This non-invasive scientific tool allows visualization of morphological characteristics of the tooth in a detailed and accurate manner (12)(13)(14)(15). Moreover, micro-CT imaging technology has been also used to evaluate the shaping ability of current instruments and techniques (6)(7)(8)(16)(17)(18). Essentially, "shaping ability" refers to the dentinal surface area that is mechanically removed during the canal preparation procedures and may be regarded as a suitable outcome parameter to compare different instrumentation techniques.…”

Properties of Mechanical Endodontic Instruments and the Quality of the Simulated Canal Preparation

“…Its widening to larger sizes in order to remove infected dentin seems to be reasonable. Furthermore, due to the fact that 59.6% ± 14.9% of oval canal walls remain intact despite widening them to the size of ProTaper # 4, the use of larger files should be considered [22]. According to the principle of saving tissues and protecting the root structure against fracture, the canal preparation to the size of 25 or 30 seems to be worth considering.…”