Anatomical Science International

, Volume 94, Issue 1, pp 136–143 | Cite as

Contribution of capsaicin-sensitive innervation to the continuous eruption of the rat mandibular incisors

  • Jose Johann ChidiacEmail author
  • Ammar Kassab
  • Khaldoun Rifai
  • Elie D. Al-Chaer
  • Nayef E. Saadé
Original Article


A major component of tooth innervation is made of capsaicin-sensitive primary afferents (CSPA). These fibers play a key role in tooth pain and inflammation; little is known, however, about the role of CSPA in tooth eruption. The aim of this study was to examine the role of the capsaicin-sensitive afferents in the process of eruption of intact rat incisors. CSPA fibers in several rat groups, were subjected to one of the following experimental procedures: systemic chemical ablation, systemic ablation followed by chemical sympathectomy and localized activation. The observed effects on incisor eruption were compared to those made on controls. The total amount of eruption in control/naïve rats, measured over a total period of 144 h, was 3.18 ± 0.07 mm and decreased to 2.43 ± 0.08 mm (n = 7; p < 0.001) following systemic ablation of CSPA. Further decrease to 2.24 ± 0.08 mm (n = 7; p < 0.001) was noticed when chemical sympathectomy was added to CSPA ablation. The average rate of eruption was 1.7 ± 0.25 mm following CSPA activation, compared to an average of 0.8 ± 0.07 mm for controls (n = 7; p < 0.001). Capsaicin sensitive fibers play an important role in tooth homeostasis, and intact neural supply is required for tooth growth under normal conditions.


Rat incisor Capsaicin Guanethidine Sympathectomy Tooth eruption Tooth innervation 



Capsaicin-sensitive primary afferents


Inferior alveolar nerve


Substance P


Calcitonin gene-related peptide



Prs. Nada Naaman and Nadim Mokbel (St Joseph University, School of Dental Medicine, Department of Periodontics, Beirut-Lebanon) are thanked for their help in cutting the incisors and using the microscope to take the pictures. The authors thank Bassem Najm and Sawsan Zeidan for their technical assistance. This project was supported by a Grant from the Lebanese National Council for Scientific Research (no. O/651).

Compliance with ethical standards

Animal welfare

All experiments have been reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) of the American University of Beirut under a written protocol and in accordance with the Policy on Human Care and Use of Laboratory Animals and the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health in the USA.

Ethics approval

The animal experimental protocol in this study was approved by the Institutional Animal Care Committee, number IACUC # 16-03-466, approved on 31 March 2016.

Consent for publication

All authors have approved the manuscript and given their consent for their data to be published in the report.

Conflict of interest

The authors declare that they have no competing interests.

Availability of data

The dataset supporting the conclusions of this article is included within the article.


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Copyright information

© Japanese Association of Anatomists 2018

Authors and Affiliations

  1. 1.School of DentistryLebanese UniversityBeirutLebanon
  2. 2.Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of MedicineAmerican University of BeirutBeirutLebanon

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