Long-term Effects of Titanium Implant Surfaces on Nerve Action Potentials

The extensive resorption of the posterior mandible for implant placement and subsequent inferior alveolar nerve repositioning results in possible neurosensory dysfunction. Objectives: To investigate the long-term effects of various titanium implant surfaces on the nerve conduction in vitro. Methods: Thirty male Wistar rats of 300 gr. of weight were anesthetized,a portion of the sciatic nerve, was removed and placed in a nerve bath with three compartments. The nerve lay across two electrodes in the stimulating compartment of the bath, and two recording electrodes. The three 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 using a circulator. One end of the isolated nerve was stimulated electrically, so that maximal compound action potentials (CAPs) were evoked. The mean amplitude was read on a digital oscilloscope. The signal from the oscilloscope was recorded every 10 minutes by a computer through a special interface. Readings were taken at 10 min intervals right after each implant was placed into the middle compartment of the nerve bath and in firm contact with the nerve. A total of 30 sciatic nerves were divided equally into five groups. Machined titanium, hydroxylapatite-coated, TCP-blasted and thermal double acid etched titanium surfaces were compared in this study. Nerves with no contacting implant have been used as a control. An intimate contact between each implant surface and nerve was maintained for a 180 minute testing period. Results: The long-term reduction of CAPs amplitude for hydroxylapatite-coated implants was negligible as compared to the control group, while the other implant surfaces presented a more complex behaviour, either enhancing or reducing nerve conductivity. Conclusions: HA-coated implants might be more suitable during repositioning of the inferior alveolar procedures.