Abstract： Objective To observe the peri-implant osseointegration after the application of exogenous nerve growth factor (NGF)-gelatin sponge(GS) composite.Methods Six beagle dogs were used to establish bi-mandible simultaneous implant model after the first and second premolar extraction.Then the dental implants were implanted into the distal socket while the bone defect was made in the mesial socket of each mandible.Then the NGF-GS was implanted into the defects as NGF-GS group,the gelatin sponge alone was implanted as GS control and the control group was left empty.Two dogs were sacrificed each time at 4 weeks,8 weeks and 12 weeks postoperatively.Specimens were subjected to general observation,radiography,bone histological and histomorphometric analysis for the new bone formation.The data were analyzed with SPSS 11.5 software package.Results The bone density in the defects around implants at 4 and 8 weeks postoperatively was lower than the normal bone.The bone-implant contact ratio in the NGF-GS group[(57.7 ± 6.4)％] was significantly higher than that in the GS control group and the control group [the ratio were(44.2 ± 3.3)％ and(31.2 ± 3.1)％] (P ＜ 0.01) at 4 weeks postoperatively,the bone-implant contact ratio in the GS control group was also significantly higher than that in the control group (P＜0.01) at that time.The bone-implant contact ratio in the NGF-GS group[(94.8 ± 7.7)％] was slightly higher than that in the GS control group and the control group [the ratio were (83.0 ± 4.1) ％ and (86.4 ± 6.3) ％] at 8 weeks postoperatively,but there was no statistical difference (P ＞ 0.05).The bone density in the defects around implants at 12 weeks was almost the same as the normal bone,there was no difference of the bone-implant contact ratio.Conclusions NGF-GS application could increase new bone formation,accelerate maturation of trabecular bone around the implants and shorten the period of osseointegration.