Enamel Matrix Proteins Induce Periodontal Regeneration On The Orthodontic Tooth Movement In Rats

In recent years,with the raise of people's economy level,the concern of oral health,the orthodontic technique and materials,more and more adults with malocclusion need orthodontic treatment.However,adult oral environment is complex with different degrees of gingivitis,periodontitis,alveolar resorption,tooth loose and tooth displacement,among which periodontitis is the most common.Before orthodontic treatment,periodontitis patients need thorough periodontal treatment.Periodontitis is controlled and periodontal preservation is needed during orthodontic treatment.For the malocclusion patients with periodontal attachment loss and resorption of alveolar bone,attention should be payed to orthodontic force,change of wire and periodontal preservation to avoid more periodontal attachment loss and resorption of alveolar bone. Besides,it is important and difficult that periodontal tissue can acquire certain reconstruction through some methods and technique as well as that reconstructed periodontal tissue can support orthodontic teeth movement for periodontal patients.Purpose:In order to investigate the differences of tooth movement under orthodontic forces in reconstructed and normal periodontal tissue,and explore the effectiveness of Emdogain in orthodontic treatment of periodontitis through animal experiments.Thus.we may provide reference for orthodontic treatment of periodontitis.Methods:Forty-six six-week-old female Sprague-Dawley(SD) rats were chosen for experiment animals,with left maxillary first molar as experimental group and right as control group respectively.Thenφ0.2 mm orthodontic ligation silk was inserted into the cervical part of the experimental maxillary first molar and knotted under anesthesia,with no disposal in the control group.All the rats were fed food with high sugar from the first day of our experiment.Then the periodontal conditions of maxillary first molars were examined six weeks later.The periodontal evaluation criteria:Probing Depth and Bleeding on Probing were regarded as the evaluation criteria of periodontal state, whose examinations were performed by the same experienced periodontal doctor with a special modified periodontal probe.Three rats were killed randomly for histological observation to confirm the establishment of experimental rat model of severe periodontitis.Then enamel matrix proteins were used to induce periodontal regeneration.The rats were anesthetized using 2%Ketamine hydrochloride through intraperitoneal anesthesia.Following successful anesthesia,the surgery were started with minimally invasive microsurgical techniques,the lesions were exposed by improved line of periodontal flap incision,then inflammatory granulation tissues were curetted,and the periodontal pocket walls were trimmed,at last repeated washing with normal saline.The exposed root surfaces were covered by Emdogain (Straumn companies as gifts),and the gingival flap was sutured reset and covered by periodontal treatment agent.Antibiotics were used to prevent infection.Then the periodontal states of the first molar of rats were checked by the same doctor four weeks after periodontal reconstruction.Three rats were killed randomly to make histological slices of reconstruction of periodontal tissues and normal periodontal tissues by HE staining.After confirming the effect of periodontal reconstruction,individual appliances were installed on the maxillary first molars of the remained forty rats in experimental and control groups,while the dental cervix of the molars in the control group were encircled by ligation wire.After anesthesia and fixed,a groove about 0.2mm depth was ground on the two maxillary central incisors at the cervix close to the gingival margin on the lip,tongue and distal surfaces with a pointed diamond bur in the cooling state,where a ligation wire was embedded to ligate the two central incisors as a whole anchorage.Then the bilateral maxillary first molars weared individual appliance were pulled through the NiTi spiral extension spring with a orthodontic force of 0.5N,tne anchorage loss ignored in the whole process.Sterile powder feed were given from the day device installed,and the oral hygiene status in rats and the appliance situations were checked everday to see whether there was missing,deformation or damage.Stressed applications once a week last for a period of 8 weeks,maintaining the force value of 0.5N.Eight weeks after traction, all rats were killed with separated upper jaw.The distances between the distal surface of maxillary first molar and the mesial surface of the second molar were measured by vernier caliper with accuracy of 0.02 mm by the same individual three times and taked average.All the experimental data were analyzed by SPSS10.0,comparing the mesial moving distance of first molar between the two groups.Results:1Six weeks after periodontal ligation,3 rats were selected randomly and with histologic finding:deeper periodontal pocket reaching below CEJ,erosion epithelia of the pocket, infiltrating inflammatory cells,disorder of periodontal membrane fiber and angle absorption of alveolar ridge.All these showed that the establishment of severe periodontitis model of experimental rats succeeded.2.Four weeks after periodontal reconstruction,3 rats were selected randomly with histologic showing:periodontal attachment recovered to CEJ,smooth epithelia,neat periodontal fiber,new bone formation of alveolar ridge with slightly bone density and lotsof osteoblast.It is demonstrated that effective periodontal reconstruction was achieved by the induction of enamel matrix protein.3. After eight weeks,the mesial movement distance of the first molar had no statistical significance in the two groups (P> 0.05).Conclusion:1.Orthodontic ligation on neck of teeth with high sugar soft diet can establish severe periodontitis model of rats.2.Enamel matrix protein can induce periodontal tissue especially non-cell cementum regeneration and achieve effective periodontal reconstruction. 3.The reaction of reconstructed periodontal tissue and normal periodontal tissue to orthodontic force were the same.Regenerated periodontal tissue induced by enamel matrix protein can be reconstructed the same as normal periodontal tissue in orthodontic teeth movement.