Simultaneous Inferior Alveolar Nerve Regeneration and Osseointegration With a Nerve Growth Factor-Supplying Implant: A Preliminary Study  Jin-Yong Lee, DDS, PhD, Jeong-Won Jahng, PhD, Soung-Min Kim, DDS, PhD, Myung-Jin Kim, DDS, PhD, Jong-Ho Lee, DDS, PhD  Journal of Oral and Maxillofacial Surgery  Volume 73, Issue 3, Pages 410-423 (March 2015) DOI: 10.1016/j.joms.2014.07.009 Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 1 Design of the NGF-supplying dental implant and diagrammatic and intraoperative views of animal surgery. A, Design and cross-sectional diagram of NGF-supplying dental implant. Body diameter and platform diameter were 3.4 and 4.8 mm, respectively. The fixture was 8 mm long and the gingival height of the collar was 2.2 mm. The collar has a Morse taper internal design with an 8° angle and octagonal shape. B, Photograph of NGF-supplying dental implant with an internal lumen. C, Scheme of animal surgery, NGF delivery, and electrode positioning. D, Completed repair of transection injury and microcatheter and mini-osmotic pump connected to the IAN transection site. IAN, inferior alveolar nerve; NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 1 Design of the NGF-supplying dental implant and diagrammatic and intraoperative views of animal surgery. A, Design and cross-sectional diagram of NGF-supplying dental implant. Body diameter and platform diameter were 3.4 and 4.8 mm, respectively. The fixture was 8 mm long and the gingival height of the collar was 2.2 mm. The collar has a Morse taper internal design with an 8° angle and octagonal shape. B, Photograph of NGF-supplying dental implant with an internal lumen. C, Scheme of animal surgery, NGF delivery, and electrode positioning. D, Completed repair of transection injury and microcatheter and mini-osmotic pump connected to the IAN transection site. IAN, inferior alveolar nerve; NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 2 Comparison of compound nerve action potential amplitude by interval and group. A, Consecutive comparison of average amplitude for the NGF and PBS groups using repeated measured analysis of variance. The NGF group showed improved recovery, although this finding was not statistically important. B, Comparison of the relative ratio of average amplitude using paired t test. Baseline was set as the average value measured on the day of surgery. At 3 and 6 weeks after surgery, the average amplitude of the NGF group had increased slightly, but there were no changes to the average amplitude in the PBS group. NGF, nerve growth factor; PBS, phosphate buffered saline; Post 3W, 3 weeks after surgery; Post 6W, 6 weeks after surgery. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 3 Comparison of compound nerve action potential latency by interval and group. A, Consecutive comparison of the average latency of the NGF and PBS groups using repeated measured analysis of variance. In the 2 groups, average latencies had increased slightly after 3 weeks and decreased at 6 weeks after surgery, but these changes were not statistically important. B, Comparison of relative ratio of average latency with paired t test. Baseline was set as the average value measured on the day of surgery. The average amplitude gradually decreased in the 2 groups, although this change was not statistically meaningful. NGF, nerve growth factor; PBS, phosphate buffered saline; Post 3W, 3 weeks after surgery; Post 6W, 6 weeks after surgery. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 4 Comparison of conduction velocity between groups. A, Consecutive comparison of average conduction velocity of the NGF and PBS groups using the Friedman test. After transection, the 2 groups exhibited a decreased conduction velocity, which then increased by 6 weeks after surgery. At 6 weeks, the average conduction velocity of the NGF group was significantly higher than that of the PBS group (**P < .01). B, Comparison of relative ratio of average conduction velocity with Wilcoxon signed rank test. Baseline was set as the average value measured on the day of surgery. In the 2 groups, average conduction velocity gradually increased. The average conduction velocity of the NGF group was close to preoperative values. NGF, nerve growth factor; PBS, phosphate buffered saline; Post-Op 6W, 6 weeks after surgery. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 5 Comparison of peak voltage between groups. A, Consecutive comparison of average peak voltage for the NGF and PBS groups using the Friedman test. Decreased peak voltage in the NGF group had increased by 6 weeks and was significantly higher than in the PBS group (**P < .01). There were no noticeable changes in the PBS group at 6 weeks. B, Comparison of relative ratio of average latency with the Wilcoxon signed rank test. Baseline was set as the average value measured on the day of surgery. Average peak voltage increased considerably in the NGF group, but not in the PBS group. NGF, nerve growth factor; PBS, phosphate buffered saline; Post-Op 6W, 6 weeks after surgery. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 6 Histomorphometric analysis of axons (toluidine blue stain; magnification, ×100). Microscopic images show a 1-μm-thick specimen from the A, NGF and B, PBS groups. These images were digitally converted and analyzed to determine axon count and density. Comparison of C, axon count and D, density was performed with the Student t test. Axon count and density in the NGF group were significantly higher than those in the PBS group (***P < .001). NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 7 Histomorphometric analysis of myelin (magnification, ×5,000). Transmission microscope images of an 80-nm-thick specimen from the A, NGF and B, PBS groups. Comparison of C, myelin thickness and D, G-ratio was performed using the Student t test. Myelin from the NGF group was significantly thicker than myelin from the PBS group (**P < .01). The average G-ratio was slightly lower in the NGF group than in the PBS group, although this difference was not important. G-ratio, ratio of axon diameter to fiber diameter; NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 8 Histologic findings from a non-decalcified specimen (hematoxylin and eosin staining; magnification ×40). Microscopic images of the A, NGF-supplying implant in the alveolar bone and B, tissue response around the implant apical hole in the NGF group. Bone formation in the C, PBS group was significantly less prominent than in the NGF group, which was obviously noticeable around D, the implant apical hole in the PBS group. NGF, nerve growth factor; PBS, phosphate buffered saline. Arrows indicate the magnified area around implant apical hole. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 9 Histologic findings of decalcified specimens (Masson trichrome stain; magnification, ×40). Microscopic images of the A, NGF-supplying implant in the alveolar bone and B, tissue response around the implant apical hole in the NGF group. New bone formation in the C, PBS group, was less prominent than NGF group, especially noticeable around D, the implant apical hole in the PBS group. The implant in the alveolar bone was removed during the decalcification procedure (block arrows). NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 10 Comparison of BIC and BA between groups. A, The BIC was higher in the NGF group (46.609 ± 18.445%) than the PBS group (42.884 ± 17.168%), but this difference was not important. B, The BA was higher in the NGF group (36.993 ± 19.923%) than the PBS group (33.327 ± 17.332 %), but this difference was not important. BA, ratio of bone area inside thread area; BIC, bone-to-implant contact ratio; NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions

Figure 11 Comparison of implant stability quotient at 6 weeks in the NGF and PBS groups. The average implant stability quotient of the NGF group (42.375 ± 8.535) was slightly higher than that of the PBS group (38.714 ± 6.701), but there was no significant difference between the 2 groups. NGF, nerve growth factor; PBS, phosphate buffered saline. Journal of Oral and Maxillofacial Surgery 2015 73, 410-423DOI: (10.1016/j.joms.2014.07.009) Copyright © 2015 American Association of Oral and Maxillofacial Surgeons Terms and Conditions