Analysis of forces developed during root canal preparation with the balanced force technique

Abstract

The aim of this study was to examine the forces and torque developed during root canal preparation with the balanced force technique using a recently described force-analyser device. A tooth was placed in a holder within the Endograph and forces and torques exerted were recorded. These parameters, which can be studied during preparation (on-line) or stored and examinated subsequently (off-line) generated endograms, which showed the forces generated with time. In addition, the endograms of preparations performed by students and endodontists, as well as deliberately induced failures in preparation technique (broken instruments), were compared. The values for the forces and torques depended on the size of the instruments and were related to the phase of the preparation. For the endodontists, the vertical and horizontal forces varied, respectively, from 0.08 +/- 0.01 kg for a size 15 to 0.65 +/- 0.10 kg for a size 45, and from 0.01 +/- 0.005 kg for a size 15 to 0.4 +/- 0.1 kg for a size 40. The torque varied from 0.08 +/- 1 kg mm-1 for a size 15 to 1.6 +/- 0.4 kg mm-1 for a size 45. With the endograms used as a reference, the relation between the developed vertical forces and the torque became more similar between the groups of endodontists and students. The Endograph provides a new approach to the analysis of preparation technique because it depicts the relationships between the different parameters of the preparation.

The Effect of Root Preparation Technique and Instrumentation Length on the Development of Apical Root Cracks

“…Then, a counterclockwise movement of 120 to 180 , under apical-directed pressure, cuts the dentin. The instrumentation sequence followed an incremental size increase (15,20,25,30,35,40,45, and 60), and all canals were irrigated with 1% sodium hypochlorite solution followed by recapitulation with a size 15 file after each file change. The instrumentation length of groups A and B were RCL and 1 mm short of RCL (RCL À 1 mm), respectively.…”

Comparison of ProTaper, RaCe and Safesider instruments in the induction of dentinal microcracks: a micro‐CT study

“…Improvements in the design concepts and kinematics of rotary NiTi instruments have provided easier and better root canal shaping (Blum et al . , Gianluca , Tasdemir et al . , Franco et al .…”

A Novel Platform for In Vitro Analysis of Torque, Forces, and Three-dimensional File Displacements During Root Canal Preparations: Application to ProTaper Rotary Files

“…Some authors performed static and fatigue tests on files (7)(8)(9)(10)(11)(12)(13); others analyzed the involved apical force and file torque during the preparation of synthetic blocks or extracted teeth (1)(2)(3)(4)(5)(6). These last studies analyzing the files working conditions in terms of involved loads could be helpful in the assessment of the files' separation risks by comparison between the involved loads and the failure loads of the file (the ratio between the applied load and the failure load has been defined as the safety quotient by some authors [2]).…”

“…In particular, those analyzing the files' working conditions in terms of involved loads and displacements could be helpful in the assessment of the files' separation risks (by comparison between the involved loads and the strength of the file). Different experimental setup and protocols have been proposed to study the forces developed during a root canal preparation on extracted teeth or synthetic blocks (1)(2)(3)(4)(5)(6). Nevertheless, in some of them (4,6), the displacement or the torque imposed to the file were only along a fixed axis relative to the tooth, which was not able to reproduce completely the actual clinical hand motion.…”

“…Nevertheless, in some of them (4,6), the displacement or the torque imposed to the file were only along a fixed axis relative to the tooth, which was not able to reproduce completely the actual clinical hand motion. In others, an actual clinical hand motion was performed (1)(2)(3), but only the force and the torque according to the apical direction were analyzed. We are aware of no study including a free clinical hand motion and a multidirectional measurement of involved efforts (forces and torque) and file displacements; this seems important to us in an advanced analysis of the biomechanical behavior of the rotary endodontic files.…”