Simultaneous Inferior Alveolar Nerve Regeneration and Osseointegration With a Nerve Growth Factor-Supplying Implant: A Preliminary Study

Abstract

Although nerve growth factor (NGF) has been proved to enhance inferior alveolar nerve (IAN) regeneration, its clinical application remains a challenging issue. This study investigated the functional regeneration of IAN injury by supplying NGF using an NGF-supplying implant and its effect on the osseointegration. In canine IAN transection-and-repair models (n = 9), NGF-supplying implants connected to osmotic pumps were installed just above the transection site. In the right IAN, NGF 300 μg in phosphate buffered saline (PBS) 2 mL was loaded in the pump and pure PBS 2 mL was loaded in the left IAN. The gross clinical finding was evaluated by wound healing, inflammation, implant exposure, and loss of fixture. To evaluate IAN regeneration, electrophysiologic (amplitude, latency, conduction velocity, and peak voltage) and histomorphometric (axon count and density, myelin thickness, and ratio of axon diameter to fiber diameter) analyses were performed. Implant stability quotient, bone-to-implant contact ratio, and new bone area were measured to assess the osseointegration of the NGF-supplying implant. The conduction velocity (2.675 m/second) and peak voltage (1.940 μV) of the NGF group at 6 weeks were considerably higher than those of the PBS group (1.892 m/second and 1.300 μV, respectively). The same results were observed for axon count (NGF vs PBS, 4,576.107 ± 270.413 vs 3,606.972 ± 242.876), axon density (10,707.458 ± 638.835 vs 7,899.781 ± 1,063.625/mm(2)), and myelin thickness (1.670 ± 0.555 vs 1.173 ± 0.388 μm). There were no meaningful differences for the other parameters. Supplying NGF with specially designed dental implants can be a new therapeutic approach to enable IAN regeneration and osseointegration simultaneously.