Effect of Single Versus Multiple Files Retreatment Concepts on Canal Curvature and Surface Topography of the Used Files (An In Vitro Study)

Abstract

A revolutional approach of using single file in root canal instrumentation presented a new perspective for NiTi rotary file usage technique. The introduction of the single file techniques is promising in providing efficient, safe and quick preparation with less time consumption and more comfort to the patient. Also the introduction of rotary NiTi instruments in endodontic retreatment has decreased patient and operator fatigue and reduced time as well.

The study is divided into 2 parts, one dealing with comparison of "OneShape" file with "R-endo" system in terms of canal transportation and the other is dealing with surface topography changes on the "OneShape" file. Sixty Mesio-buccal canals human mandibular molars were divided into 2 equal groups (Oneshape and R-endo) then subdivided into 2 equal sub-groups according to canal curvature. Canals were then cleaned, shaped and obturated. Retreatment was then performed using OneShape and R-endo. The teeth were fixed in position inside a block of acrylic resin during the whole study and then the teeth were scanned using Cone Beam Computed Tomography before and after retreatment. Fusion of the pre-instrumentation and post-instrumentation records was achieved using special software that allows manual and then automatic registration of the primary and secondary images. After retreatment change in canal curvature (transportation) was evaluated. Data were presented as means and standard deviation (SD) values. One Way-ANOVA was used to study the effect of different groups on mean canal curvature and measurements of canal transportation. Also "OneShape" file was evaluated under SEM for defects in its new as well as used conditions to investigate effect of retreatment on the file surface topography and to investigate the type of file fracture.

Conclusion: 1. Single file concept was superior in preserving canal curvature than multiple file system. 2. Degree of canal curvature was found to have no effect on the amount of canal transportation in both single and multiple file systems. 3. File surface topography was highly affected by number of usage.

Recommendations: Further studies are needed to investigate the use of single file concept in retreatment from other prospective as debris extrusion, post-operative pain and its performance in different radii of curvatures, as the single file concept is the future of endodontic instruments.