Elsevier

Neuroscience Letters

Volume 690, 18 January 2019, Pages 132-137
Neuroscience Letters

Research article
Response characteristics of the cat somatosensory cortex following the mechanical stimulation to endodontically treated teeth with overextension

https://doi.org/10.1016/j.neulet.2018.10.006Get rights and content

Highlights

  • •

    Hyperesthesia could happen after overextension of canal filling materials.

  • •

    The overfilling of RCT materials causes a higher saturated signal strength level.

  • •

    The overfilling of RCT materials lower the threshold of cortical response.

Abstract

The overextension of filling materials may take place accidentally during an endodontic root canal treatment. Previous studies to understand the correlation between overfilling and paresthesia of teeth were inconsistent. In this study, an intrinsic signal optical imaging technique was employed as the objective tool to compare the response characteristics of the cat somatosensory cortex following mechanical stimulation applied to endodontically treated teeth with overextension (ETTWO) and natural teeth. Based on the evoked cortical response, the signal strength of the ETTWO was found to be significantly higher than that of the natural teeth. However, the tactile threshold of the ETTWO was significantly lower than that of the natural teeth. It was concluded that the tactile function of ETTWO is more sensitive than that of natural teeth, and that the overextension of filling materials can cause hyperesthesia of teeth after root canal treatment.

Introduction

Root canal treatment (RCT) is an effective method to treat pulpitis and apical periodontitis. The overextension of filling materials may take place accidentally through over-instrumentation of the root canals, allowing the passage of these materials into periapical structures. In these cases, some patients complain of hyperesthesia of endodontically treated teeth for a long time after RCT. The findings of previous studies have been inconsistent regarding the correlation between overfilling and paresthesia of teeth. Kim’s clinical study reported that overextension of endodontic filling materials could result in neurologic complications such as paresthesia of teeth [1]. In contrast, Gomes-Filho’s study found that canal-filling materials with both good biocompatibility and antimicrobial activity produced fewer complications from a histological perspective [2,3]. Therefore, a neurophysiological examination is needed to evaluate the tactile sense of endodontically treated teeth with overextension (ETTWO). However, few studies have objectively examined the tactile function of ETTWO.

Intrinsic signal optical imaging enables simultaneous investigation of mapping and functional information in a large area of the cortex containing millions of neurons [[4], [5], [6]]. Our previous studies demonstrated that intrinsic signal optical imaging is a valid tool to investigate the neural response of the tooth-related cortex and could be used to carefully examine the tactile function of teeth at the cortical response level, as well as the possible differences between natural teeth and perfectly root canal-treated teeth [7,8].

The aim of this study was to examine the tactile function of ETTWO at the cortical response level using intrinsic signal optical imaging and evaluate the effect of overextension on the tactile function of endodontically treated teeth.

Section snippets

Animal preparation

Five healthy adult cats weighting between 1.5 and 2.5 kg (Shanghai Yingen Farm) were used in this study. The experimental protocol used in present study was approved by the Animal Experimentation Committee at Fudan University. Animals were treated in accordance with the guidelines for the care and use of experimental animals described by the National Institutes of Health and Fudan University. The preparation for animal experiments was performed as previously reported [7,8]. The root canal

Results

To investigate the functional response of contralateral ETTWO, we compared its responses with those of the ipsilateral natural tooth from the same cat for the following reasons: 1. The response properties of an ipsilateral and contralateral natural tooth are indistinguishable in the cat somatosensory cortex [8]; 2. The normally root canal-treated contralateral tooth (without overfilling) responded similarly to the ipsilateral natural tooth in terms of stimulus-response curve as well as map

Comparison with previous studies

In this study, we found that the response evoked by the contralateral ETTWO tooth was stronger than that evoked by the natural ipsilateral tooth. However, this difference may come from contralateral dominance in a normal cat, the root canal treatment itself, or the overfilling in the root canal.

In our previous studies, the cortical dominance was carefully examined. Intrinsic signal optical imaging was employed to measure population response characteristics of the cat primary somatosensory

Acknowledgements

This study was supported by grants from the National Natural Science Foundation of China (91520203, 31571076, 31171054), and the Shanghai Key Discipline Foundation (B111) to H. Yu. The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article.

1

These authors contributing equally to this work.

View full text
© 2018 Published by Elsevier B.V.