The effect of using different endomotor files in different working lengths at foraminal deformation: A scanning electron microscope study

The aim of this study was to evaluate the effect of the files on foraminal deformation ex vivo by using scanning electron microscope technique. For this objective, recently developed reciprocal file MicroMega One RECI and the VDW Rotate file systems working with the rotation motion principle are used at different distances of the root canal. In this study, 60 mandibular premolar human teeth that have completed their apical development were used. Roots were removed from their crowns and standardized to be 19±1 mm in length. Before preparation, the teeth were examined with SEM under x300 magnification and images were taken from the apical foramen opening point. Subsequently, divided into four groups according to the files used and the end points of the apical preparation, Group 1: VDW Rotate at the apical foramen (AF); Group 2: 1 mm behind the apical foramen with VDW Rotate (AF-1mm); Group 3: MicroMega One RECI at apical foramen and Group 4: MicroMega One RECI 1 mm behind the apical foramen. Root canal preparation of the teeth in Group 1 and Group 2 was performed using 15/.04, 20/.04, 25/.04 and 35/.04 files of the VDW Rotate (VDW Dental, Germany) NiTi rotary file system. Root canal preparation of the teeth in Group 3 and Group 4 was performed using One G, 20/.04, 25/.04 and 35/.04 files of the One RECI (Micro-Mega®, Besançon, France) NiTi rotary file system. During shaping process, the canals were irrigated with 2 mL of 2.5% NaOCl at each file change. Irrigation was completed by irrigated with each canal a total of 15 mL of NaOCl. The teeth, whose shaping was completed, were fixed in their initial positions and images were taken with SEM again. The SEM images obtained before and after the preparation were compared by calculating the foramen area, circularity and Feret diameter ratio with the help of a software program (Image j), and the presence of foraminal deformation was evaluated according to these measurements. It was determined that the parameters (foramen area, circularity and Feret diameter ratio) were in accordance with the normal distribution with the Shapiro Wilks test of the obtained data, and the homogeneity of variance was examined with the Levene test. Bonferroni test was used for two-way analysis of variance and pairwise comparisons (p=0.05). According to the findings, it was determined that foramen areas increased as a result of the preparation made at different working lengths using two different file systems (p<0.05). The foramen area was found to be significantly higher in the VDW Rotate/AF group compared to the VDW/AF-1mm group (p<0.05). In the One RECI groups, there was no significant difference in terms of foramen area in both study lengths (p>0.05). It was observed that there was no statistically significant difference between circularity and ferret ratios in all groups (p>0.05). Within the limitations of this ex vivo study; it was found that root canal shaping performed both in the apical foramen and 1 mm behind the apical foramen with VDW Rotate and One RECI did not cause apical foramen deformation. Keywords: apical foramen, working length, foraminal deformation, reciprocating movement, rotation movement