| Objective: By establishing orthodontic tooth movement model in SD rats,the effects of bovine lactoferrin on tooth displacement and recurrence distance and periodontal remodeling at different time points after orthodontic tooth movement in rats were studied.Methods: Thirty-six male SD rats aged 8 to 10 weeks,weighing 225 to 250 g,were randomly divided into experimental group(n=18)and negative control group(n=18).All rats had two maxillary anterior teeth as anchorage.NiTi tension spring device was installed between maxillary first molars and anterior teeth,and the maxillary first molars were moved near the middle.The traction force value was 40g/ side,and the loading device was removed after 21 days of continuous stress.The experimental group and the negative control group did not apply any orthodontic force after the force device was removed,allowing it to recur.The rats were perfused with bovine lactoferrin(85mg/kg/d)and 0.9%normal saline(1ml/100g/d)respectively one day before the removal of Bovine lactoferrin(Bovine lactoferrin).The rats were killed 7,14 and 21 days later,and6 rats in each group were killed each time.The maxillary impression was made when the force device was removed and the rats were killed,and the plastermodel was perfused.The recurrence and displacement distance of maxillary first molar before and after intragastric administration was measured and calculated.After the rats were killed,the complete maxillary first molars and their periodontal tissues were taken,fixed,decalcified and embedded to prepare paraffin sections.The morphological changes of proximal and distal periodontal tissue and root of maxillary first molar were analyzed by hematoxylin-eosin staining;Tartrate-resistant phosphatase staining was used to analyze the expression of osteoclasts in the proximal,middle and distal sides;expression of osteopontin and bone sialoproteinin in proximal and distal periodontal tissues of maxillary first molars were observed by immunohistochemical staining.Semi-quantitative analysis was carried out by using Image-pro-plus6.0 image analysis system.The experimental results were analyzed and processed by SPSS16.0 statistical software.Results:(1)Establish the orthodontic tooth movement model induced by mechanical force: the maxillary first molars of each group moved in varying degrees after 21 days of loading.(2)The distance of recurrent movement of the first molar:(1)The recurrence distance of maxillary first molars in the experimental group and the negative control group increased with the prolongation of time.After 7 days,14 days and 21 days of gavage,the recurrence movement distance of the experimental group was shorter than that of the control group(P < 0.05).(2)In the first week after the removal of the loading device,the amount of tooth recurrence was the most,the average recurrence movement of maxillary first molars was 0.07±0.02 mm in the experimental group and 0.13±0.03 mm in the negative control group.In the 2nd and 3rd week,the moving averagerecurrence distance was less than that in the first week.(3)HE staining:In the proximal side,the osteogenic repair activity was dominant in the experimental group and the negative control group,but the alveolar bone formation in the lactoferrin group was faster and the new bone formation was more obvious than that in the control group,and in the distal side,the alveolar bone formation in the experimental group was faster than that in the negative control group.The formation of new bone was obvious,and the number of osteoclasts decreased with the prolongation of holding time.(4)TRAP staining:On both sides of the proximal and distal sides,the number of osteoclasts in the experimental group and the negative control group decreased gradually with the prolongation of intragastric administration,and the number of osteoclasts in the experimental group was less than that in the control group(P < 0.05).The difference between the two groups was statistically significant on the 21 st day(P< 0.05),and on the distal side,the number of osteoclasts was statistically significant on the 14 th and 21 st day(P < 0.05).(5)Immunohistochemical staining of OPN:In the proximal and middle side,the expression of OPN in the periodontal ligament of the experimental group and the negative control group increased gradually,and the expression of OPN in the experimental group was higher than that in the control group,the difference of expression was statistically significant at 14 d and 21 d(P < 0.05).The expression of OPN in the periodontal ligament of the experimental group and the negative control group decreased gradually,and the expression of OPN in the experimental group was lower than that in the control group,the difference was statistically significant at 7 days and 14 days(P < 0.05).(6)Immunohistochemical staining of BSP:In the proximal and distal sides,the expression of BSP in the periodontal ligament of the experimental group and the negative control group increased gradually.In the proximal side,the difference was statistically significant at 7days and 21 days(P < 0.05),and in the distal side,the difference was statistically significant at 21 days(P < 0.05).Conclusion: Intragastric administration of bovine lactoferrin can reduce the recurrence and movement distance of orthodontic teeth in rats,promote proximal and distal osteogenic activity,and promote the remodeling of proximal and distal periodontal tissue. |
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