Dentinal Micro-crack Formation during Root Canal Preparation by Ni-Ti Rotary File

—Analysis of Root-crack by Single Ni-Ti Rotary File—

Abstract

 Purpose: The aim of this study was to compare the incidence of root cracks observed at the apex in the canal wall after canal instrumentation with two single reciprocating files (WaveOne and Reciproc), and a multiple rotary file (ProTaper).
 Methods: Forty maxillary premolars with two independent canals were selected. The teeth were divided into four groups (n=20) of 10 teeth with 20 canals according to the Ni-Ti rotary file type used: WaveOne (Dentsply Maillefer, Switzerland), Reciproc (VDW, Germany), and ProTaper (Dentsply Maillefer), and then instrumented with Glide (Dentsply Maillefer). The apical root surface and horizontal sections 1, 3, 5 mm from the apex were observed under a microscope. The presence of cracks was counted and the significance level was set at 0.05.
 Results: No cracks were found in the control. Root canal cracks were found in both the single reciprocating file (WaveOne and Reciproc) and multiple file (ProTaper) groups, but no significant difference was found in the total value of all cross sections (p>0.05). On the other hand, the number of root crack lines on the 1-mm cross section was significantly less than in the 3- and 5-mm sections in all experimental groups.
 Conclusions: Root canal preparation with both reciprocating and rotary file instruments resulted in root cracks at 1－5 mm from the apex, although there was no significant difference between the file systems.