Basic Research
Root Canal Shaping Effect of Instruments with Offset Mass of Rotation in the Mandibular First Molar: A Micro–computed Tomographic Study

https://doi.org/10.1016/j.joen.2017.11.012Get rights and content

Highlights

  • Instruments with offset mass of rotation showed less canal transportation and better centering ability and a comparable amount of dentin removal compared with a system with a conventional centered mass of rotation.

  • The resultant swaggering motion of the systems with offset mass of rotation might have a beneficial effect on dentin removal but not on untouched canal areas.

Abstract

Introduction

The aim of this study was to evaluate the root canal shaping effect of 2 nickel-titanium rotary instruments with offset mass of rotation compared with an instrument with a conventional centered mass of rotation.

Methods

Thirty-six extracted human mandibular first molars with 2 independent mesial canals and 1 oval distal canal were selected and divided equally into 3 groups for instrumentation with ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Revo-S (RS; Micro-Mega, Besançon, France), and ProTaper Universal (PTU, Dentsply Maillefer) systems (n = 12). For apical preparation, PTN X2 (#25/0.06), RS SU (#25/0.06), and PTU F2 (#25/0.08) were used in the mesial canals and PTN X3 (#30/0.07), RS AS30 (#30/0.06), and PTU F3 (#30/0.09) were used in the distal canals. Specimens were scanned before and after instrumentation using a SkyScan 1272 scanner (Bruker micro-CT, Kontich, Belgium) at 10-μm isotropic resolution. Changes in the canal area, volume, structure model index (SMI), and untouched canal area were evaluated. Canal transportation and centering ratio were measured at 1, 3, 5, and 7 mm from the apical foramen. Data were statistically analyzed using 1-way analysis of variance with the Tukey post hoc test.

Results

The PTN and RS systems showed significantly less transportation and better centering ability compared with the PTU system at 1 mm from the apical foramen (P < .05). All instrumentation increased the canal area, volume, and SMI values without significant differences among the 3 groups (P > .05).

Conclusions

Regardless of the differences in the cross-sectional design, alloy type, and taper variation, instruments with offset mass of rotation showed better root canal shaping ability compared with an instrument with a centered mass of rotation.

Section snippets

Materials and Methods

The study was approved by the Ethics Committee of the University of Dental Medicine, Mandalay, Myanmar (#20150202). Thirty-six extracted mandibular first molars with a slight apical binding for a #10 K-file in the 2 independent mesial canals (15°–30° curvature) and a #15 K-file in 1 single oval distal canal (5°–20° curvature) were selected (8). The specimens were scanned before and after root canal instrumentation with the same setting using a SkyScan 1272 scanner (Bruker micro-CT, Kontich,

Results

At 1 mm from the apical foramen, the PTN and RS groups showed significantly less transportation and better centering ability than the PTU group (P < .05). However, no significant differences were noted at other levels from the apical foramen in the mesial canals and at all levels from the apical foramen in the distal canals among the instrument groups (P > .05). Before root canal instrumentation, there was no significant difference among the 3 groups regarding canal area, volume, and SMI value (

Discussion

The present study evaluated the shaping effect on root canal geometry of the mandibular first molar of the 2 file systems with offset masses of rotation compared with 1 conventional file system with a centered mass of rotation using micro-CT analysis. In the present study, both systems with offset mass of rotation showed significantly less transportation and better centering ability than the conventional file system with a centered mass of rotation.

Generally, the shaping effect of NiTi rotary

Acknowledgments

The authors deny any conflicts of interest related to this study.

References (30)

Cited by (16)

  • Micro–computed Evaluation of Canal Transportation and Centering Ability of 5 Rotary and Reciprocating Systems with Different Metallurgical Properties and Surface Treatments in Curved Root Canals

    2021, Journal of Endodontics
    Citation Excerpt :

    The overall results of this study showed that rotary techniques (ie, PTN, TRN, and XPS) caused similar transportation and centering ability in curved canals at all canal levels (3, 5, and 7 mm). The behavior of the PTN instruments in curved canals is well-known from previous studies, which reported their minimal canal transportation that is comparable with other rotary techniques5,15–17. Yuan and Yang18 observed that PTN caused lesser canal transportation compared with the reciprocating system (WaveOne).

  • Cleaning and Shaping Ability of Gentlefile, HyFlex EDM, and ProTaper Next Instruments: A Combined Micro–computed Tomographic and Scanning Electron Microscopic Study

    2020, Journal of Endodontics
    Citation Excerpt :

    In this study, the median percentages of the untouched areas ranged from 6.9%–10.6% and 8.7%–10.2% for the apical and middle regions, respectively (Fig. 1J). This result agrees with previous micro-CT–based studies reporting that portions of canal areas remain untouched after instrumentation of oval-shaped canals4,10–14. In particular, 1 study using mandibular premolars has shown that 17.6% and 34.6% of canal areas remain untouched in the apical 4 mm and 10 mm, respectively, after NiTi rotary instrumentation10.

  • Cone-Beam Computed Tomographic Analysis of Shaping Ability of XP-endo Shaper and ProTaper Next in Large Root Canals

    2020, Journal of Endodontics
    Citation Excerpt :

    However, the mean increase in the prepared dentin area of XPS was more than 100% even in the apical third of the experimental group with the largest canals, which was also statistically significant (P < .05). It was known that rotary instruments with the same tip size and tapers would cause a similar amount of dentin removal, whereas the amount of dentin removed would be higher with larger taper with the same tip size16–18. In the present study, XPS and PTN X3 files had the same tip size, but variable tapers were used.

View all citing articles on Scopus
View full text