The Experimental Study Of Expression Of MMP-2in The Periodontal Tissues With The Miniscrew For Molar Intrusion With Cyclic Intrusive Force In Dogs

PURPOSE:To observe the expression of MMP-2in the periodontal tissue of molars of dogs afterdifferent time of long-term intrusion in application of miniscrew with cyclic intrusive force, toexplore the reconstruction of periodontal tissue of molar with the miniscrew intruding molar.METHODS:Three mature beagle dogs were used for the experiment. On the buccal and palatal sitesof the left maxillary second and third premolars, a miniscrews was placed at the interradicularsepta separately, intruding the tooth with150g initial force, which reinforced every4weeks.The left side of the teeth as the experimental side, was divided into three groups, respectively,being intruded12,24and36weeks, and the right site as blank control group. Then the dogswere sacrificed, and the second and the third premolars with the surrounding periodontaltissue were cut down, fixed, decalcified, wrapped and cut intoslices. HE and immunohisto-chemical staining with MMP-2was performed. Calculating the average optical density ofMMP-2in the use of IPP software, which represented the expression of MMP-2. SPSS17.0software package was selected and one-way ANOVA (least significant difference, LSD) wasused for statistics analysis.RESULTS:HE staining: Compared with the control side, the experimental side experiencedremarkable histological changes. The periodontal ligament width narrowed down, and thenumber of fibroblasts increased, neither changed obviously with the change of the intrusivetime. The surface of the alveolar bone surface was not serial. In the group of12weeks, a littlebone lacuna primarily at the periapical lesions and alveolar ridge crest, with osteoclasts (0C) in it. In the24-week and36-week groups, bone lacuna was still active with deposition ofnewly formed bone, and osteoblasts (OB) arranged on the surface of new bone. In the24-week group, lacunas appeared in periapical cemental, with new-formed cemental. Up to36-week, the lacunas reached to dentine.Immunohistochemical (IHC) staining revealed that, the expression of MMP-2in controlgroup was low. After tooth intrusion, MMP-2expression increased in the periodontal tissue ofmolars, and reaching the maximum in the group of24weeks, following, MMP-2expressiondecreased in36weeks group, still higher than the control group. There was no significantdifference between experimental groups (P>0.05).CONCLUSION:1.In the process of long-term intrusion, remodeling of alveolar bone occurs in the wholealveolar fossa, the alveolar crest and the periapical region remolding the most active. With theextension of the intrusive time, apical root resorption is aggravating. Which prompting duringthe long-term intrusion of teeth, the resorption of apical root is related to intrusive time;2.MMP-2is mainly expressed in the cytoplasm of fibroblast cells, osteoclasts,osteoblasts and bone cells. Expression of MMP-2increasd obviously in the experimentalgroup. It confirmed that MMP-2is involved in the periodontal tissue remodeling during thelong-term intrusion of teeth;3.In the process of periodically loading, expression of MMP-2in periodontal tissue wasnot significantly increased with extending of intrusion time. It Confirms that with the use ofthe miniscrew intrudes molar with cyclic intrusive force, the periodontal tissue of thelong-term intruded tooth maintances dynamic balance of bone remodeling.