Expression of matrix metalloproteinase-8 [MMP-8] gene in patients with fixed orthodontic appliances

Orthodontic treatment with fixed appliance produces structural and biochemical changes and breaking the balance between the synthesis and the breakdown of the collagen in the periodontium. MMP-8 plays an important role in the remodeling of periodontal ligament during orthodontic movement. The purpose of this study was to observe the expression of MMP-8 gene in the gingival crevicular fluid [GCF] of fixed orthodontic patients. It is expected that the result can be used as a reference to decide the proper time for elastomeric chain to be reactivated. Orthodontic fixed appliances were placed on 8 patients and elastomeric chains exerting a force of 75 grams were attached to produce canine distalization. GCF samples were collected from the distal side of upper canines before force application, 1-, 2-, 3-and 4 weeks after application consecutively. The samples were analyzed by using RT-PCR. Statistical analyses used were univariate analysis and Mann-Whitney U test. The expression of MMP-8 in the GCF at t0 was 31.3% but the force application elevated its expression of 65.6% at t1, and then decreased continuously at t2, t3, and t4. There was no statistically difference of MMP-8 gene expression between to and t3. The highest level of MMP-8 gene expression due to orthodontic forces happened in the first week, but it declined continuously in the following weeks. The proper time to reactivate an elastomeric chain was 3 weeks after application