The Study Of Curcumin On The Repair Of Injured Inferior Alveolar Nerve And The Healing Of Tooth Extraction Socket

Objective: The lower lip paresthesia,numbness,and hyperalgesia after inferior alveolar nerve injury,which greatly reduces patient’s quality of life.Curcumin has been shown that possess varieties of pharmacological properties such as anti-oxidation,anti-inflammatory,anti-cancer,antibacterial and neuroprotective effect.It has been demonstrated that curcumin plays a neuroprotective role through inhibiting inflammation,reducing lipid peroxidation and cell apoptosis,anti-oxidation,and promotes the repair of sciatic nerve injury and functional recovery.However,whether curcumin has the same effect on the injured inferior alveolar nerve remains to be confirmed by a large number of studies.Therefore,this study aimed to explore the effect of curcumin on the repair of injured inferior alveolar nerve,and to observe the healing of tooth extraction sockets in the mandible with injured inferior alveolar nerve under curcumin on adult rats.Method: 1.The injured inferior alveolar nerve model on rats was established.Twenty-four wistar rats were randomly divided into normal group,model group,negative control group and curcumin group.The rats were anesthetised by intraperitoneal injection of chloral hydrate(0.3ml/100g).The injured inferior alveolar nerve model on rats was established by clamping nerve with a toothless microscopic vascular forceps.Then,the right lower first to third molars were extracted by use of acutenaculum 2 days after nerve injury.Curcumin at the dose of 100mg/kg was intraperitoneally injected.Then,the rats were sacrificed by cardiac perfusion on the day and 8 weeks after nerve injury,and the specimens of inferior alveolar nerve and mandible were collected.2.The pathological changes of inferior alveolar nerve was observed by HE staining3.LFB staining was used to observe the recovery of myelin sheath of inferior alveolar nerve;4.The expression of S100 protein was detected by use of immunohistochemistry to evaluated the proliferation of Schwann cells;5.The ultrastructural changes of inferior alveolar nerve was observed with transmission electron microscope;6.The formation of new bone of tooth extraction sockets was evaluated by MicroCT scan and analysis;7.HE staining was used to observe the histological changes of tooth extraction socket after intraperitoneal injection of curcumin.Results: 1.The injured inferior alveolar nerve model on rats was successfully established.No animal death during the operation.And the rats were in good condition,actively eating and drinking after operation;2.HE staining results showed that a large number of nerve fibers were broken and disordered.Axons and myelin sheaths were disintegrated after nerve injury.The arrangement of nerve fibers was more orderly and regular with less tissue vacuoles and inflammatory cells.At the same time,the disintegration of axons and myelin were significantly improved after curcumin treatment compared with the negative control group;3.The results of LFB staining showed that the number of myelin sheath was reduced in the model group and negative control group.The degeneration and disintegration of myelin sheath could be seen.The number of myelin sheath was increased in the curcumin group,and myelin sheath was regular in shape,uniform in thickness and clear in boundary,indicating that curcumin could promote the repair of myelin of inferior alveolar nerve;4.The expression of S100 protein was significantly higher in the curcumin group than those of the model group and negative control group,indicating that the proliferation of Schwann cells was significantly increased after curcumin treatment;5.Most of the inferior alveolar nerve fibers are myelinated.The ultrastructure of inferior alveolar nerve showed that the shape of myelin was irregular and shrinking.And the lamina of myelin was loose and fuzzy.Some cracks or small vacuoles in the middle of myelin lamina,demyelination and Wallerian degeneration appeared after nerve injury.The separation of myelin lamina was improved and a few regenerated nerve fibers could be seen in the curcumin group compared with the model group and control group;6.Micro-CT results showed that BV/TV,Tb.Th,Tb.N in the curcumin group were significantly higher than those in the model group and negative control group.BS/BV was significantly lower than negative control group,and the differences were statistically significant(P < 0.05),indicating that the formation of new bone in tooth extraction sockets,and the number and thickness of bone trabeculae were increased;7.The HE staining results showed that there were many fibrous connective tissues,and a small amount of new juvenile bone trabeculae or osteoid matrix could be seen in the negative control group.Compared with the negative group,the bone trabecula was dense,thick,and new blood vessels were visible after curcumin treatment.Conclusion: Curcumin significantly improved the repair of injured inferior alveolar nerve by prompting myelination and the proliferation of Schwann cells.The injury of inferior alveolar nerve was not conducive to the healing of tooth extraction sockets,curcumin accelerated the healing of tooth extraction sockets by facilitating the repair of injured inferior alveolar nerve.