Expression And Correlation Of PTHrP And C-fos During Rat Experimental Tooth Movement

BackgroundAs s ociety progresses, people on the aesthetic and functional requirements has also been a greatdevelopment. Orthodontic tooth movement is that Periodontal Tissues produce series ofpathological and physical reactions under the focus which the orthodontic devices produce.bone remodeling during orthodontic treatment is the key. Therefore, the research in this fieldhave its research and clinical value.ObjectiveDuring the orthodontic tooth movement, many factors participate in bone formation and haveimportant adjustment functions. PTHrP, a promoting factor of osteogenic growth , has animportant and complex function that it adjusts not only calcium and phosphorus metabolism,but also cell proliferation, differentiation, and death. In recent years it can be found that PTHrPplays an important role in stomatology especially the bone formation of orthodontic teeth. Theresearch probes preliminarily the correlation between alveolar bone formation and PTHrP and itsdownstream signal molecule, c-fos protein during the orthodontic tooth movement. Themechanism of tooth movement is known deeply, which may provide oral orthodontic work withnew targets that promotes or inhibits the tooth movement .MethodsForty-two male wistar rats ( age:6-8 weeks , weight : 200 to 220g) were classified into sevengroups randomly , the control group(0 day group)and the experiment group ( 1, 3, 5,7, 14, 21days group), each of which consisted of 6 rats . After 1 week , the rats underwent lateral toothmovement. Each group was injected with the anaesthesia composed of 3% Nembutal and 3%kessodrate. In the groups, thrust augmentation device was placed between the left maxillary firstmolar and the left maxillary first incisor and 50g mesial force was applied to pull the leftmaxillary first molar in the rats. The rats in the experiment groups were sacrificed after 1, 3, 5, 7,and 14 days respectively. The specimens were infiltrated in 4%citroment 4℃for 72 hours. After decalcification in 7% EDTA 4℃for about 2 months, histological sections were made by routinemethod. The left 40 rats were only injected with citrate buffer and served as the control group.Precise upper jaw models were made before and after exerting the mesial force . Measure thedistance between first molar mesiolingual groove and third molar mesiolingual groove for threetimes by sliding caliper and caculate the distance of orthodontic tooth movement of each group.The rats in the experiment groups were sacrificed after 1, 3, 5, 7, and 14 days respectively. Thespecimens were infiltrated in 4%citroment 4℃for 72 hours. After decalcification in 7% EDTA4℃for about 2 months, histological sections were made by routine method. By the way of HEstain, histologic changes of periodontal tissue during rat orthodontic tooth movement wereobserved. Two-step immunohistochemical method was applied to localize and examine theexpression of PTHrP and c-fos in periodontal tissues. Image analysis system was applied tomeasure the express area and the average gray scale to calculate the integrated opticaldensity(IOD). In addition, SPSS17.0 software was used to carry out statistical treatment.Results1.The number of osteoblasts on the tension side of rat alveolar bone show that the properdistraction forces can promote osteocytes proliferation up to weak on the 7th day.2.Immunohistochemical analysis demonstrates that PTHrP in normal periodontal tissues of thecontrol group is mainly distributed in the osteoclasts, fibroblasts mesenchymal cells and thepositive staining is not obvious. The tension sides of the experiment group is stained deeper thanthat of the control group and bone formation area is stained obviously , which is up to the peakon 5th day, parallel to the documents. It shows that PTHrP participates in bone formation duringorthodomntic tooth movement.3.In the control group , the expression of c-fos protein in osteoclasts and fibroblasts of alveolarbone appears positively but the expression rate is low .In the experiment groups , c-fos protein inbone formation area (on the tension sides) is stained deeper than the control group, up to thepeak on 5th day, which indicates that c-fos protein plays a role in bone formation area. But thespecific mechanism need study further still.4 There is a correlation between the expressions of c-fos protein and PTHrP on the tension sideof rat alveolar bone .Conclusions 1. The proper distraction force can promote osteoblasts proliferation .2. The proper distraction force may promote bone formation through raising the expression ofPTHrP.3. The process that PTHrP promotes osteoblasts proliferation may has the correlation with that ofc-fos protein.