Ethanol-Induced Cervical Sympathetic Ganglion Block Applications for Promoting Canine Inferior Alveolar Nerve Regeneration Using an Artificial Nerve

Summary

We evaluated the effect of cervical sympathetic ganglion block on nerve repair using artificial nerve conduits. Male beagle dogs were each implanted with an artificial nerve across a 10-mm gap in the left inferior alveolar nerve; left cervical sympathetic ganglion was blocked by injecting 99.5% ethanol via lateral thoracotomy.

Abstract

Polyglycolic acid collagen (PGA-C) tubes are bio-absorbable nerve tubes filled with collagen of multi-chamber structure, which consist of thin collagen films. Favorable clinical outcomes have been achieved when using these tubes for the treatment of damaged inferior alveolar nerve (IAN). A critical factor for the successful nerve regeneration using PGA-C tubes is blood supply to the surrounding tissue. Cervical sympathetic ganglion block (CSGB) creates a sympathetic blockade in the head and neck region thus increasing blood flow in the area. To ensure an adequate effect, the blockade must be administered with local anesthetics one to two times a day for several consecutive weeks; this poses a challenge when creating animal models for investigating this technique. To address this limitation, we developed an ethanol-induced CSGB in a canine model of long-term increase in blood flow in the orofacial region. We examined whether IAN regeneration via PGA-C tube implantation can be enhanced by this model. Fourteen Beagles were each implanted with a PGA-C tube across a 10-mm gap in the left IAN. The IAN is located within the mandibular canal surrounded by bone, therefore we chose piezoelectric surgery, consisting of ultrasonic waves, for bone processing, in order to minimize the risk of nerve and vessel injury. A good surgical outcome was obtained with this approach. A week after surgery, seven of these dogs were subjected to left CSGB by injection of ethanol. Ethanol-induced CSGB resulted in improved nerve regeneration, suggesting that the increased blood flow effectively promotes nerve regeneration in IAN defects. This canine model can contribute to further research on the long-term effects of CSGB.

Introduction

In many cases, traumatic injury of the inferior alveolar nerve (IAN) is iatrogenic, being frequently caused by the extraction of the third molar or the placement of dental implants^1,2,3. Injury of the IAN can lead to deficits in thermal and touch sensations as well as paresthesia, dysesthesia, hypoesthesia, and allodynia. Nerve injury is treated not only by conservative therapy but also by other methods, including suturing and autograft placement. However, these methods have drawbacks, which often include the lack of symptom improvement and neurological defects at the donor s....

Protocol

This study was conducted in accordance with the Guiding Principles for the Care and Use of Animals and approved by the Committee for Animal Research of Kyoto University (Kyoto, Japan; authorization number: R-16-16). All efforts were made to minimize animal suffering, and all sections of this report adhere to the ARRIVE (Animal Research: Reporting of in Vivo Experiments) guidelines.

1. Fabrication of the PGA-C tube

1. To fabricate the artificial nerve conduit by means of an absorbable polyglycolic acid (PGA) tube, use a tubular braiding machine equipped with 48 spindles and five PGA fibers, comprised of bundles of 26 filame....

Results

We observed an increase in the facial skin temperature of the blocked side 1 week after the left CSGB (Figure 8).

At 3 months post-reconstruction, the PGA-C tube at the reconstruction area was absorbed and regeneration of the inferior alveolar nerve was observed in the reconstruction-only and reconstruction + CSGB groups (Figure 9A, B)^.......

Discussion

We present an efficient method for IAN regeneration by using a bioabsorbable nerve tube in combination with ethanol-induced CSGB. For this study we used dogs, since other animal models, like mice, rats, and rabbits, have a short life expectancy and small body size, and hence cannot be used to perform the precise surgical procedures. As the IAN is located within the mandibular canal surrounded by bone, a surgical technique is necessary to avoid nerve and blood vessel damage when performing nerve reconstruction. An importa.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
NMP Collagen PS	Nippon Meatpackers	301-84621	Atelocollagen extracted from young porcine skin by enzyme treatment
Surgical clippers	Roboz Surgical Instrument Company	RC-5903
Disposable scalpel (No.15)	Kai medical	219ABBZX00073000
VarioSurg3	Nakanishi	VS3-LED-HPSC, E1133	Piezoelectric surgery for bone processing
4-0 nylon sutures	Ethicon	8881H
8-0 nylon sutures	Ethicon	2775G
Isepamicin sulfate	Nichi-Iko	620005641
Disposable scalpel (No.10)	Kai medical	219ABBZX00073000
30-gauge needle	Nipro	1134
1-0 absorbable stitches	Ethicon	J347H
3-0 Nylon stitches	Ethicon	8872H
Neo Thermo	NEC Avio	TVS-700	Infrared thermography
Neuropack Σ	NIHON KOHDEN	MEB-5504	Orthodromic recorder for electrophysiological recording
Toluidine Blue	Sigma-Aldrich	T3260-5G
Light microscope	Keyence	BZ-9000
Mouse anti-human neurofilament protein monoclonal antibody	DAKO	N1591
Polyclonal rabbit anti-S100 antibody	DAKO	Z0311
Transmission electron microscopy	Hitachi High Technologies	Hitachi H-7000
Dynamic cell count	Keyence	BZ-H1C	Software for morphological evaluation