On the Causality Between Dentinal Defects and Root Canal Preparation: A Micro-CT Assessment.

Gustavo De-Deus,Juliana Roter Marins,Marco Aurélio Versiani,Emmanuel João Nogueira Leal Silva,Erick Miranda Souza,Alessandra De Castro Machado,Aline De Almeida Neves,Ricardo Tadeu Lopes,Felipe Gonçalves Belladonna

doi:10.1590/0103-6440201601002

Abstract

This study aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Universal (PTU) system and dentinal defects formation using micro-computed tomography (micro-CT) analysis. Forty mesial canals of mandibular molars with a type II Vertucci's canal configuration were scanned at an isotropic resolution of 14.16 µm. The sample was assigned to an experimental (n = 30) and a control (n = 10) groups, and the mesial canals were prepared with PTU system up to F2 instrument. The specimens from the experimental group were scanned and the cross-section images of the mesial roots, before and after preparation, were screened to identify the presence of dentinal defects. In the control group, the specimens were sectioned perpendicularly to the long axis of the root into 1-mm-thick slices (n = 80) and examined under optical microscope. Once a dentinal defect was detected, the slice was scanned through micro-CT. In the experimental group, dentinal micro-cracks were observed in 4,828 slices (24.04%). In all cross-section images, dentinal defects identified in the postoperative images were already present in the corresponding preoperative image. In the control group, 13 out of 80 slices (16.25%) had at least one dentinal defect visualized under stereomicroscopy, which was identified after a further micro-CT scanning. Micro-CT showed reliability as similar as optical microscopy in detecting dentinal defects, adding the possibility of tracking the dentinal tissue, before and after canal preparation, and providing a clear visualization of micro-cracks. Root canal preparation with PTU system did not induce the formation of new dentinal defects.

Highlights

Over the last two decades, root canal preparation with nickel-titanium (NiTi) rotary instruments became the mainstream approach to mechanically enlarge the root canal space with most of the initial problems being currently overcome
The present study aimed to evaluate the potential cause-effect relationship between root canal preparation performed by a conventional multi-file NiTi rotary system (ProTaper Universal [PTU]; Denstsply Maillefer, Ballaigues, Switzerland) and dentinal defects formation using a micro-CT imaging system
All dentinal defects identified in the postoperative images were already present in the corresponding preoperative image, indicating that cleaning and shaping procedures were not related to the formation of new dentinal micro-cracks (Fig. 1)

Summary

Introduction

Over the last two decades, root canal preparation with nickel-titanium (NiTi) rotary instruments became the mainstream approach to mechanically enlarge the root canal space with most of the initial problems being currently overcome. An important concern has been raised: the creation of dentinal defects after motor-driven rotary NiTi instrumentation Considering that such defects could stand as a trigger point for vertical root fractures [1,2,3], which subsequently affect tooth survival, this issue, undoubtedly, deserves an indepth scientific investigation and consideration. Published studies on this topic always embrace cutting procedures and postoperative observation through optical microscopy technique. It is unlikely that experimental models based on single-moment postoperative microscopic observation would provide the required inputs to create a comprehensive understanding of the complex and multi-factorial phenomenon of micro-crack formation and propagation, as well as its causality by endodontic procedures

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Conclusion