The Expression And Significance Of VEGF During Experimental Traumatic Occlusion And Periodontitis In The Periodontium Of Rats

Objective: To study the changes of expression of vascular endothelialgrowth factor (VEGF) in periodontal tissue with Immunohistochemicalmethod after establishing animal models of experimental occlusal trauma andperiodontitis. To speculate and analysis the mechanisms of damage and repairprocess in periodontal tissue. Provide better methods for the early detectionand treatment of the clinical work for treating disease.Methods: Choosing120healthy Wistar rats,3months old, weighing250to280g. Oral health is in good condition and no oral disease, occlusalrelationship is good. They were randomly divided into four groups:①Controlgroup (n=30);②Occlusal trauma group (n=30);③Periodontitis group(n=30);④: Occlusal trauma+periodontitis group. Every group was randomlydivided into six groups again:1day group,3day group,7day group,2weekgroup,4week group and6week group. For general anesthesia, rats wereinjected100g/L chloralic hydras intraperitoneally in accordance with3ml/kgper injection before they were fixed lying on back on the operating floor.Bilateral mouth mucosa were disinfect with1%iodine tincture and75%alcohol. For occlusal trauma group, first maxillary molars were choserandomly in rats of occlusal trauma group as experimental molars. Theocclusal surface of the experimental molar was polished with carborundumround bur and embrocate light-cured acid etch for30seconds and washed withwater. After it dry, embrocate binder and light-cured. Edgewise,0.6mm indiameter and length in2mm, was bound to occlusal surface with compositeresin and light-cured. For periodontitis group, first mandibular molars werechose randomly in rats of periodontitis group as experimental molars. Ligaturewire,0.2mm in diameter, was ligtured on the cervical region of first mandibular molar locating in the gingival crevice. For occlusal trauma+periodontitis group, first ipsilateral mandibular molars and maxillary molarswere chose randomly in rats of occlusal trauma+periodontitis group asexperimental molars in accordance with above methods.At every experimental period, for general anesthesia, rats were injected100g/L chloralic hydras intraperitoneally in accordance with3ml/kg perinjection before transcardial perfusion with4%paraformaldehyde.Immediately stripped the regions of the molar tissue and dissection,post-fixation at4℃for48h, and decalcification at4℃in10%EDTA.Removing composite resin and ligature wire before the tissue were paraffinembedding, section tissue into5μm slices. Respectively, HE staining andVEGF immunohistochemistry were performed.Positive cells using specialized image analysis software Image-Pro Plus6.0counting VEGF-positive vessels and total vessels and get the dates ofVEGF-positive vessels propotion. SSPS13.0software analyse measurementdates in accordance relevant method. As a=0.05, P≤0.05was consideredsignificant difference.Results:1HE staining1.1Control groupCoronary sections of control animals showed the periodontal ligamentline in order. Apical periodontal ligament was jointed closely with alveolarbone. Demarcation was clear. Bone resorption pits distribute uniformly andtheir size was right. A few bone resorption pits include VEGF positive cells.Around the vessels inner alveolar bone, there were a few VEGF positive cells.1.2Experimental groupThe number of fibroblasts in the periodontal ligament increase a little.The fibers disorderly arrange. The size and the number of some boneabsorption pits enlarge. The number of VEGF positive cells in bone resorptionpits were increased and become climax at2week group.2Immunohistochemistry 2.1Control groupVEGF positive cells were not located in the vessels of dental crown ofmandibular molar and in the bone resorption pits around apical. A little VEGFpositive cells were located in a few large vessels of alveolar bone.2.2Experimental groupDistribution of VEGF positive cells had some characters:(1) In theexperimental groups, the number of VGEF positive vessels and VEGFpositive cells that were started to appear in bone resorpotion pits wasincreased gradually, appearing climax at2week group and showing decline at4week and6week group.(2) VEGF positive cells that were found in boneresorpotion pits and VEGF positive vessels that were found in alveolar boneconcentrating apical were located in periodontium of all molars contain first,second and third molar. However, VEGF positive cells were not found in theperiodontium of dental crown and adjacent teeth of molars.(3) In differentexperimental group, compare the number of VGEF positive vessels and VEGFpositive cells that were in bone resorpotion pits, control group<periodontitisgroup<occlusal truma group<occlusal truma+periodontitis group.Conclusions:1The changes of VEGF in the periodontal tissue indicate that it wasinvolved in periodontal tissue injury and repair process. In the occlusaltrauma+periodontitis group, VEGF expresses stronger than the other twoguoups in positive cells, which mean that VEGF could enhance the effect ofVEGF positive cells and promote the alveolar bone absorption.2Osslusal trauma could promote the process of periodontitis.