| Objective:ClassⅡmalocclusion is the most common type of dental and jaw deformity in clinical practice.Severe malocclusions cause not only dysfunction in patients,but also the aesthetic problems.Aesthetic problems often cause psychological stress to patients,which will adversely affect their academics,anti-frustration ability and participation in social activities.According to the pathogenesis,classⅡmalocclusions can be divided into:alveolar,osteogenic,mandibular and mixed.If the early mandibular malocclusion is not intervened in time,serious osteogenic malformation may occur.Therefore,early detection and treatment are advocated to reduce its adverse effects on patients’physical and mental health.For patients with mandibular retraction,in clinical practice,functional appliances are often used to guide mandibular advancement to achieve neuromuscular adaptive reconstruction.If the neuromuscular adaptive reconstruction is not completed at the end of the treatment,it will result in the treatment effect being difficult to achieve fully or easy to relapse.Therefore,this study intends to apply medium frequency electrical stimulation to the Jiache acupoints of the masseter muscles in rats to observe changes in rats,seeking the possibility of acupoint medium frequency electrical stimulation to accelerate neuromuscular reconstruction.This study provides a reference for clinical use of medium frequency electrical stimulation to treat patients with functional appliance.Method:Sixty 4-week-old male SD rats were randomly divided into three groups:blank control group,conditioned control group and experimental group,20 per group.1.Establish a rat model of mandibular protrusion:for the blank control group,no treatment;for the condition control group,make and wear a functional appliance;for the experimental group,use medium frequency electrical stimulation of Jiache acupoints while wearing functional appliance.2.Rat’s masseter muscle sections HE staining:According to the group,the rats were sacrificed at 3,7,14,21 d after the corresponding treatment,and the masseter muscle tissue was taken to make paraffin sections,followed by HE staining analysis.3.Immunohistochemical staining of rat masseter muscle sections:The SABC method was used to immunize the rat’s muscle masseter sections of each group.Histochemical staining was used to detect the effects of functional appliance combined with Jiache acupoint medium frequency electrical stimulation on the expression of NT-3 and NGF proteins in the masseter muscle tissue of rats.4.Detection of relative expression of NT-3 mRNA and NGF mRNA:Rats in each group were sacrificed at 3,7,14,21 d after the corresponding treatment.The masseter tissues were taken and the expression levels of NT-3 mRNA and NGF mRNA were detected by qPCR.Using the 3d blank control group mRNA expression as a calibrator,the 2-△△CT value was calculated for statistical analysis to detect the relative expression of NT-3mRNA and NGF mRNA in rat masseter tissues.Results:1.A rat model of functional appliance combined with Jiache acupoint medium frequency electrical stimulation was successfully established.2.Results of HE staining of Rat’s masseter muscle sections:On day 3d,no significant differences in the number and location of nuclei were found in the masseter muscle sections of each group.Inward nucleus shift occurred in the conditional control group and the experimental group on day 7;the number of muscle fibers in each group was basically stable.On the 14th day,the inward nuclear shift phenomenon was more prominent in the experimental group.Until 21d,the inward nuclear shift phenomenon in the condition control group was still obvious,while it was reduced in the experimental group.In the conditional control group and the experimental group,masseter muscle fibers did not appear to break or degenerate.3.Results of immunohistochemical staining:Changes in NT-3 protein expression:compared with the blank control group,the NT-3 protein expression in the conditioned control group and the experimental group increased firstly and then decreased.And the expression of NT-3 protein in the conditioned control group was still higher than that in the blank control group on the 21st day,while the experimental group had returned to normal levels.Changes in NGF protein expression:compared with the blank control group,the expression of NGF protein in the experimental group increased significantly on the 7th day,and the expression of NGF protein was not different from that of the blank conditional group on the 21st day;the expression of NGF protein in the conditioned control group was significantly different on the 14th day,and it was still high at 21 days.4.Results of qPCR:Changes in the relative expression of NT-3 mRNA:compared with the blank control group,the NT-3 mRNA expression in the conditional control group increased on the 14th day,and the relative expression level of the mRNA was still higher than that of the blank control group on the21st day;in the experimental group,the expression of NT-3 mRNA increased on the 7th day,and returned to the pre-treatment level on the 21st day.Changes in the relative expression of NGF mRNA:compared with the blank control group,the expression of NGF mRNA in the experimental group firstly increased and then decreased,while in the conditional control group,the expression of NGF mRNA increased on the 14th day,but there was no trend of decreased expression on the 21st day.Conclusion:Functional orthodontics combined with Jiache acupoint medium frequency electrical stimulation promotes the increase of NT-3 and NGF in masseter muscles of rats.This may promote the switch of masseter muscle fiber types by promoting synaptic maturation and increasing the number of motor neurons.It may accelerate the rate of neuromuscular reconstruction in functional orthodontic rats and shorten the orthodontic time.However,further research is needed to apply functional orthodontics combined with Jiache acupoint medium frequency electrical stimulation to the clinic. |
