ABSTRACT
Context: Preparation of the root canal system is recognized as being one of the most important stages in root canal treatment which removes organic debris and microorganisms from the root canal system by means of chemico- mechanical preparation and irrigation of the canals. The use of nickel-titanium instruments has drastically reduced the time and the difficulties that were encountered with traditional hand instruments made up of stainless steel. Utilizing properties of super-elasticity, shape memory and different tapers of these instruments reduces not only the possibility of canal transportation but also affects both the geometry and volume of root canals. This subjects the root dentin to stress and consequently dentinal defects which increases the risk of root fracture during or after root canal treatment. Clinicians now have the opportunity to choose from differently tapered instruments having unique characteristics in their geometry and metallurgy. These are progressively tapered instruments, fixed tapered instruments, and variable tapered instruments, which come with the benefit of conforming to the root canal anatomy as well as removing dentin as little as possible while cleaning and shaping. The aim of this study was to examine the influence of instrument taperAim: on the fracture resistance of endodontically treated roots under in vitro experimental conditions.Conclusion: Under the limitations of this study in in-vitro conditions there were no significant differences between the fracture loads between the different file systems used, however samples prepared with Hyflex EDM recorded the highest fracture resistance, followed by ProTaper NEXT, ProTaper Gold and NeoEndo Flex respectively.
ABSTRACT
Objective: Minor constriction which is the narrowest diameter is considered to be the appropriate apical limit of endodontic treatment. Apex locators provide greater precision, fewer procedural errors, less discomfort to the patient during measurement of working length. The aim of this article is to compare the accuracy of four electronic apex locators in detecting the apical constriction using histological sections as the gold standard. 80Materials and Methods: extracted single-rooted permanent teeth were selected and coronally flattened for stable reference point. Access cavity was prepared and canal patency was checked. Samples were embedded in alginate upto cemento-enamel junction. Working length was determined with the apex locators. A 15 K file adjusted to that reading was placed in the root canal and stabilized with flowable composite. Apical 4 mm of root was longitudinally sectioned and the position of the file in relation to the minor constriction was recorded for each tooth under stereomicroscope at 40X magnification. Chi-square test was carried out to test the difference in accuracy at various levels from the minor foramen. Kruskal Wallis Test was carried out to compare the differences between the study groups for the distance from the tip of the file relative to the minor foramen (P<0.05). Measurements of mean working lengths within ±0.5 mm of minor diameter were 85%Results: acceptable for CanalPro followed by Root ZX Mini (80%) and Propex Pixi (80%) and the least by DPEX V (65%). Conclusion: Accuracy of these instruments for detecting the minor diameter is acceptable for clinical practice