| Introduction: During the clinical orthodontic treatment,the orthodontic force will adversely affect the tooth and periodontal tissue,clinically gingival retraction,bone cracking and even bone fenestration occurs from time to time.In severe cases,it can cause loosening and loss of teeth.In order to deeply study the mechanism of tissue destruction and seek countermeasures,in this study,an animal model of buccal force produced by the orthodontic appliance bonded to the maxillary molars was established to observe changes in periodontal tissue at different time points of force application,and to discuss the classic Wnt Signaling pathways play a role in this change,and provide experimental basis and ideas for the design of orthodontic treatment plans.METHODS:10-weeks old male Wistar rats were used in this study.The rats were required to have complete teeth and dentition without caries and periodontitis.As per the maxillary morphology of the rat,a personalized impression tray was prepared using a resin sheet.A rat maxillary model was prepared using alginate along with a super-hard plaster for filling in.An orthodontic appliance was fabricated on the plaster model using a round 0.016?? b-titanium wire following a pre-designed model.The orthodontic appliances was bonded to the first molar on the lingual side.The second and third molar adhere the transverse diaphragm to maintain the position of the teeth and minimize the widening of the maxillary bone caused by the orthopedic opening of the middle quilting.All of the rats were randomly divided into 6 groups according to different duration: Group A(control group),Group B(3 d),group C(7 d),group D(14 d),group E(28 d),and group F(56 d),each group had 5 rats.The rats were anesthetized according to their weight by intraperitoneal injection with 10% chloral hydrate(0.35 ml/100 g).According to the experimental design,the maxilla was removed.The left maxillary alveolar bone was stained with HE staining,TRAP staining,Immunohistochemistry and TUNEL(Terminal deoxynucleotidyl transferase dUTP nick end labeling,TUNEL)techniques.The right maxillary alveolar bone was stained with methylene blue under a stereo microscope to measure the degree of alveolar bone resorption.RESULTS:1.After methylene blue staining of rat maxillary specimens,it can be observed that the buccal alveolar crest began to absorb at 3d after force application,and the degree of absorption was significantly higher than the control group at 14 d after force application.The results of HE staining shown that the width of the periodontal ligament on the pressure side was significantly narrowed at 7 d after force application,collagen fibers were arranged disorderly,a large number of bone resorption pockets appeared on the surface of the alveolar bone,and the width of the periodontal ligament on the tension side was widened.By the time the pressure-receiving bone pits were reduced,the periodontal ligament width gradually began to recover,and new bone deposition was observed on the tension-side alveolar bone surface,proving that the orthodontic buccal force rat model was successfully established.2.TRAP staining results showed that the number of positively stained cells in the tissue section of the rat increased significantly after 3 d of force,and the number of positive osteoclasts in the tissue section reached a peak after 7 d of force,and then the number of osteoclasts gradually decreased At the 56 d of afterburning,there was no significant difference from the blank control group(P>0.05);OSX results showed that the expression in the periodontal tissue began to increase at 3-7 d of afterburning,at this time the expression on the stressed side and the tension side The difference was not large.It reached the peak at 14 d of afterburning,and the expression on the tension side was generally stronger than that on the pressure side,and then gradually weakened.By 56 d,there was no significant difference from the control group(P>0.05);PCNA was weakly expressed in the control group,The number of positively stained cells is small,and the expression gradually reaches the peak at 3-7 d of afterburning,and the number of positively stained cells on the tension side is more than that on the pressure side,the time of afterburning is prolonged,and the expression of PCNA gradually shows a downward trend.It tends to be normal;observing the VEGF staining results,there is no significant difference in the expression of VEGF-positive cells between the experimental group and the control group,the pressure side and the tension side of the periodontal tissue at 3 d after force,and the expression gradually increased at 7 d after force It reached a peak at 14 d,and the expression on the pressure side was stronger than the tension side,and then the expression of VEGF gradually weakened;TUNEL staining results showed that the number of apoptotic cells increased rapidly after 3 d of afterburning,and after 7-14 d of afterburning,its change The trend was gradually flattened.After 28 d of afterburning,the number of apoptotic cells had no significant difference with the control group(P>0.05);the test results of ?-catenin showed that it was the first in the periodontal tissue during the afterburning process.After the enhancement,the weakening trend showed that the expression of ?-catenin reached its peak at 7 d of afterburning,and decreased at 56 d,but there was still a significant difference compared with the control group(P<0.05).CONCLUSION: 1.The experimental animal model of rat molar buccal force by making a personalized orthodontic appliances was successfully established.2.The periodontal tissue was in the process of dynamic change during the tooth movement under the action of buccal force,a series of cellular and molecular changes in periodontal tissue occur to adapt to the new position of the teeth.It was mainly destruction in the early period,and in the later period of stress the periodontal tissue mainly remodeling.The Wnt / ?-catenin signaling pathway participated in the process of periodontal tissue remodeling. |
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