Regulation Mechanism Of New Bone Formation And Bone Maintenance Following Tooth Extraction

Objective:The repair and remodeling of bone tissue is closely related to innervation, and there is a certain controversy of whether PRP can promote the regeneration of bone tissue or not. This study aimed to explore the role of innervation and the effect of PRP/PRG on bone healing after tooth extraction by animal model of denervation. Thus it provided evidence for research of animal experiments and clinical application.Methods:1. The unilateral inferior alveolar nerve was sectioned by surgical method to establish an animal denervation model and the modified Eager's method was used to check the degeneration of nerve and confirm the successful establishment of animal model. 2.After completion of modeling, the premolars of denervated side and normal side were extracted and the Beagle dogs were sacrificed at 2,4,8,12 weeks. X-ray, CT scan,hematoxylin-eosin staining were used to detect the possible regulation mechalism of denervation on new bone formation and maintenance after tooth extraction. 3. Filling socket with PRP or PRG, the effect of PRP or PRG on the new bone formation and maintenance after extraction was studied through the same ways. Statistical analyses were performed by one way ANOVA or t-test using SPSS13.0. Results:1.The modified Eager's staining showed thant degenerated nerve fibers were dark- brown and normal nerve fibers were grayish yellow.2.The height,width and CT values of alveolar ridge in denervation group were significantly lower than in control group(P<0.01). There were significant differences between the two groups in the data of alveolar ridge height of the buccal in CT images and histological sections(P<0.05～0.01). The height difference between the buccal and lingual alveolar ridge of the denervation group was significantly higher than the control group(P<0.05～0.01).The quantitative of new bone formation in denervation group was significantly lower than in the control group at 2,4 and 8 weeks(P<0.01), whereas no significant difference was observed at 12 weeks time point(P >0.05).3.The PRG group was observed to have the significantly higher CT values at 2,4 and 8 weeks when compared to PRP and the blank groups (P<0.01), but no significant difference was observed at 12 weeks(P >0.05). The statistical test results of the height difference between the buccal and lingual alveolar ridge were obtained that PRG group had statistical significance when compared with the blank group(P<0.01),or PRP group (P<0.05), and PRP group had significantly larger heigh difference than the blank group(P<0.05) at 2 and 4weeks.There was significant difference between PRG group and PRP/control group(P<0.05), but no significant difference was observed between PRP and control group at 8 and 12 weeks(P>0.05). The new bone quantitative of PRG group was significantly higher than the PRP group at 2 and 4 weeks(P<0.05);and the same between PRP group and the control group. Whereas no significant difference was observed at 12 weeks between the three groups(P >0.05).Conclusion:The method to establish the model with denervation of the inferior alveolar nerve is successful and feasible. Innervaton of bone plays an important role in the regulation of bony healing after tooth extraction. Implantation with PRG in extraction sockets could reduce the extent of alveolar bone absorption, maintain bone mass and promote bone healing in the early stage.