Effect of different surgical repair modalities on regeneration of the rabbit mandibular nerve

Atypical trigeminal neuralgia of the mental nerve: a case study

Any division or branch of the trigeminal nerve can exhibit signs and symptoms of neuralgia. Those who treat patients suffering with craniofacial pain are frequently charged with determining the cause of illusive pain complaints and if objective signs are not discovered, the patient may not be treated and may be forced to seek help elsewhere. Trigeminal neuralgia-like pain is often seen in the mental nerve region of the mandible, but frequently, there is no radiographic evidence for the source of such pain. In the current case report, it was discovered that the patient's mental nerve pain was cause by an irregular surface of the anterior portion of the mental foramen. Successful treatment was provided by surgically recontouring the edge or lip of the mental foramen without injury to the mental nerve.

Low-level laser effect on neural regeneration in Gore-Tex tubes

PURPOSE

The purpose of this investigation was to determine the effects of low-level laser (LLL) irradiation on neural regeneration in surgically created defects in the rabbit inferior alveolar nerve.

STUDY DESIGN

Five adult female New Zealand White rabbits underwent bilateral exposure of the inferior alveolar nerve. A 6-mm segment of nerve was resected, and the nerve gap was repaired via entubulation by using a Gore-Tex conduit. The experimental side received 10 postoperative LLL treatments with a 70-mW gallium-aluminum-arsenide diode at 4 sites per treatment. At 15 weeks after surgery, the nerve segments were harvested bilaterally and prepared for light microscopy. Basic fuchsin and toluidine blue were used to highlight myelinated axons. The segments were examined histomorphometrically by using computer analysis to determine mean axonal diameter, total fascicular surface area, and axonal density along the repair sites.

RESULTS

Gross examination of all nerves showed intact neural bundles with variable degrees of osseous remodeling. Light microscopic evaluation revealed organized regenerated neural tissue in both groups with more intrafascicular perineural tissue in the control group. Histomorphometric evaluation revealed increased axonal density in the laser treated group as compared with the control.

CONCLUSIONS

LLL irradiation may be a useful noninvasive adjunct to promote neuronal wound healing in surgically created defects repaired with expanded polytetrafluoroethylene entubulation.

Facial nerve repair with expanded polytetrafluoroethylene and collagen conduits: an experimental study in the rabbit

PURPOSE

This study evaluated autogenous nerve grafts and expanded polytetrafluoroethylene (e-PTFE) and collagen tubes as conduits for the repair of continuity defects in the facial nerve of rabbits.

MATERIALS AND METHODS

The buccal division of 24 facial nerves was isolated, transected, and separated 10 mm. The gap between the 2 nerve ends was then repaired with an autologous nerve graft or an e-PTFE or collagen conduit. Fifteen days and 1, 2, and 4 months after the procedure, the animals were subjected to electrophysiologic tests, killed, and the nerves were removed for histologic examination.

RESULTS

At 15 days postsurgery, no regeneration was observed through the e-PTFE and collagen tubes or across the autologous nerve grafts at the midpoint of the specimens. However, regeneration across the chambers and autologous nerve grafts was seen in the following 4 months, although the number of axons regenerated was small.

CONCLUSIONS

The results of the study indicate that e-PTFE and collagen tubing may be effective in the repair of continuity defects in peripheral nerves. However, further research will be necessary for generalization of this procedure.

Nerve regeneration: basic and applied aspects

Increased knowledge is shedding new light on our understanding of central and peripheral nerve anatomy and molecular biology and function. New tools and methods provide important methods for the study of the behavior of cells, axons, and receptors. This review discusses the current state of that knowledge, with particular regard to the efficacy of the Seddon classification of nerve injury. The correlation of that new information to damage and repair of the peripheral sensory nerve, especially the inferior alveolar and lingual nerves, serves to highlight the progress and problems that exist.

Critical time of exposure of the rabbit inferior alveolar nerve to Carnoy's solution

To reduce the recurrence of keratocysts, tanning of the epithelial lining with modified Carnoy's solution has been advocated as an ancillary procedure. This agent has occasionally been reported to induce long-lasting local neurotoxicity, when the inferior alveolar nerve (IAN) was located within the bony cavity of larger cysts. As the severity of the neurologic damage depends on the tissue penetration of the solution, a critical exposure time must be assumed. To substantiate this hypothesis, rabbit IANs were decorticated over an approximate length of 1 cm and soaked with modified Carnoy's solution for periods from 30 seconds to 10 minutes. Sensory nerve function was monitored using somatosensory evoked potentials. Exposures up to 2 minutes did not result in any electrophysiologic abnormality. Exposure for 3 minutes led to either normal or rudimentary evoked potentials. After exposure of 5 minutes, and invariably after 10 minutes, the evoked potentials from the IAN were absent. Nerve segments were removed for histologic examination and the penetration depth of the Carnoy's solution was identified by staining with the Berlin-blue reaction. The involved areas were morphometrically evaluated and they reflected the electrophysiological findings. Transmission electron microscopy showed morphologic changes confined to the outer nerve sheaths (epineurium and perineurium) after exposure of 3 minutes. Exposure of 5 minutes and longer resulted in involvement of both the nerve sheaths and their axonal contents, with disruption and disintegration of the neural tissue. This study clearly supports the hypothesis that contact of a peripheral nerve (ie, IAN) with Carnoy's solution carries a time-related risk to produce acute sensory impairment.(ABSTRACT TRUNCATED AT 250 WORDS)

Conduction velocity of the human inferior alveolar nerve: a preliminary report

This preliminary report describes a technique to consistently record electrophysiological signals from the uninjured inferior alveolar nerves of human subjects. Bilateral recordings were obtained from 15 consecutive human volunteers. The mean conduction velocity was 67.6 m/s, with no differences shown for right or left sides or gender. Conduction velocity testing could offer a new objectivity in the clinical study of the inferior alveolar nerve, aiding in the documentation, diagnosis, management, and follow-up of the sometimes complex neural lesions that oral and maxillofacial surgeons routinely see.

Electrophysiological assessment of human inferior alveolar nerve function

This study describes a technique for making electrophysiological recordings from the inferior alveolar nerve of conscious human subjects. Recordings were obtained from 6 of 10 subjects, with consistent waveform latencies and amplitudes across subjects. The neurogenic origin of the responses was verified by blocking the nerve with 2% xylocaine, resulting in a loss of the waveform. The method is relatively simple, tolerated well by patients, and yields consistent electrophysiological information. Proposed refinements of the technique could result in a clinically useful method of objectively assessing the functional state of the inferior alveolar nerve following injury or surgical intervention.

Risks and benefits of removal of impacted third molars. A critical review of the literature

A critical review of the literature about risks and benefits of the removal of impacted 3rd molar teeth is presented in 4 categories: risk of non-intervention, risk of intervention, benefit of non-intervention and benefit of intervention. There are well-defined criteria for removal of impacted 3rd molar teeth. Absolute indications and contra-indications for the removal of asymptomatic 3rd molar teeth cannot be established because no long-term studies exist which validate the benefit to the patient either of early removal or of deliberate retention of these teeth. The prudent course of action for the clinician to follow is based on rational clinical decision-making using traditional methods of evaluation to effect the optimal outcome, keeping the interests of the individual patient above all else.

Efficacy of nerve growth factor in regeneration of the mandibular nerve: a preliminary report

An experimental study evaluating the potential utility of nerve growth factor (NGF) on sensory nerve regeneration was conducted in a rabbit mandibular nerve model. In 10 animals, bilateral 7-mm nerve gaps were created and repaired with the placement of 10-mm Silastic (American Scientific Products, McGaw Park, IL) conduits into which NGF (left side) and a control solution (cytochrome C, right side) was instilled. After 90 days, the nerve repairs were removed and the two sides compared by clinical appearance, and histologic and electrophysiologic assessment. The conduits instilled with control solution failed to result in nerve regeneration in any of the animals. The conduits with NGF solution, however, consistently displayed neural connections between the proximal and distal ends with the presence of slowed, but recordable, conduction velocities. The axonal numbers in the NGF repairs were significantly less than those of the normal nerve, but when adjusted for fascicular size, the axonal densities were comparable. In addition, osteoid tissue was observed around many of the NGF-induced nerve regenerates, but not on the control solution side, suggesting a possible influence of this protein on bone formation.

Electrodiagnostic evaluation of the uninjured rabbit inferior alveolar nerve

This investigation describes the electrophysiology of the uninjured rabbit inferior alveolar nerve. There were no differences in the measured waveform parameters between animals nor between the two sides of each animal. The model is reliable and could be applied to basic studies of inferior alveolar nerve regeneration and the effects of pharmacologic or surgical intervention.