Effect of Prolonged Stretching of the Nerve in vitro

The extensive resorption of the posterior mandible may inhibit implant installation and infrerior alveolar nerve repositioning is usually implemented, resulting in a possible stretching of the nerve causing ischemia and anoxia. Objectives: To investigate the effects of stretching of nerve in its electrophysiogical properties in vitro. Methods: Twenty-four male Wistar rats of 300 gr. of weight were anesthetized and a portion of the sciatic nerve, was removed and placed in a nerve bath with three compartments. The compartments were filled with a physiological solution of adjustable pH at the value of 7.4. The nerve bath temperature was maintained at 30 degrees C. One end of the isolated nerve was stimulated electrically, so that maximal compound action potentials (CAPs) were evoked. The application of the force was achieved by placing a metal rode of 0.96 g (n=8) and 1.76 g (n=8 under anoxia and n=8 under oxygenation) on the part of the nerve in the perfusion chamber. The one end of the rode was attached to the bottom of the perfusion chamber and the other was attached on the nerve and the applied force was measured using a isometric tension transducer. Under these recording conditions the viability curve was estimated to have an inhibitory time IT50 (time required to reduce the CAP to 50 % of its initial value. Results: Regarding the force of 0.96 g and oxygenation there was no statistical significant difference with the control, while regarding the force of 1.76 g there were statistically significant differences between the IT50 times (1.76 g with oxygenation 13.828±2.223 h – control 22.086±1.241 h, 1.76 g under anoxia 6.066±1.727 h – control 12.047±1.013 h) Conclusions: Except from the proper manipulation of the nerve during repositioning procedures the degree of the tension and the subsequent anoxia is of great importance in the possible neurosensory disturbances.