Micro-computed tomography assessment of dentinal microcracks after the preparation of curved root canals with rotary and reciprocal systems.

Shiva Shojaeian,Niloofar Mortezapour,Babak Zandi,Yazdan Shantiaee,Fatemeh Soltaninejad

doi:10.17219/dmp/134149

Abstract

Root canal preparation with nickel-titanium (NiTi) instruments may lead to the formation of microcracks in the root canal wall. Vertical root fractures may initiate from dentinal cracks, and eventually necessitate tooth extraction. This study aimed to assess the effect of the instrumentation of curved root canals of mandibular molars with the 2Shape (2S) sequential rotary, EdgeFile® X1 (EFX1) reciprocating and NeoNiTi (NN) rotational single-file systems on the formation of dentinal microcracks with the use of micro-computed tomography (micro-CT). Thirty curved mandibular molar root canals were instrumented with the 2S, EFX1 and NN systems (10 in each group). The teeth underwent micro-CT before and after instrumentation. Next, the pre-instrumentation and post-instrumentation cross-sectional images were evaluated and compared for the detection of dentinal microcracks. The number of microcracks in each group was calculated and reported as percentage. The data was analyzed using the McNemar's test with the IBM SPSS Statistics for Windows software, v. 25.0 (α = 0.05). Out of the 29,280 cross-sectional images evaluated in this study, 11.5% showed dentinal microcracks (n = 3,362). On the post-instrumentation images, the frequency percentage of microcracks was 12.0% (n = 585) in the 2S group, 8.8% (n = 402) in the EFX1 group and 13.3% (n = 694) in the NN group. All of the microcracks detected on the post-instrumentation images were also present on the preinstrumentation images and no new microcracks were formed after root canal instrumentation with the aforementioned systems. Root canal instrumentation with the 2S, EFX1 and NN systems did not result in the formation of new dentinal microcracks.

Highlights

The main goal of the chemomechanical preparation of the root canal system is to eliminate microorganisms, pulpal tissue and debris, and to shape the root canal in order to create adequate space for the root filling material.[1]
All of the microcracks detected on the post-instrumentation images were present on the preinstrumentation images and no new microcracks were formed after root canal instrumentation with the aforementioned systems
Root canal instrumentation with the 2S, EdgeFile® X1 (EFX1) and NN systems did not result in the formation of new dentinal microcracks

Summary

Introduction

The main goal of the chemomechanical preparation of the root canal system is to eliminate microorganisms, pulpal tissue and debris, and to shape the root canal in order to create adequate space for the root filling material.[1]. Root canal preparation with these instruments may lead to the formation of microcracks in the root canal wall.[2,3] Microcracks may occur as a result of the distribution of lateral forces in root canal walls and root surface strain They appear more frequently when high-taper instruments are used or in teeth with curved roots, as the part of the canal with the maximum curvature accumulates the maximum stress.[4] The importance of this topic consists in the fact that vertical root fractures may initiate from dentinal cracks, and eventually necessitate tooth extraction.[5]. Root canal preparation with nickel-titanium (NiTi) instruments may lead to the formation of microcracks in the root canal wall.Vertical root fractures may initiate from dentinal cracks, and eventually necessitate tooth extraction

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