Orthodontic Force Increases Interleukin‐1β and Tumor Necrosis Factor‐α Expression and Alveolar Bone Loss in Periodontitis

Background: The present study aims to evaluate the effects of orthodontic movement (OM) on the periodontal tissues of rats with ligature‐induced periodontal disease. Methods: Eighty‐eight rats were divided into four groups: 1) negative control (sham operated); 2) periodontal disease; 3) OM; and 4) periodontal disease followed by OM (OMP). Rats were sacrificed 3 hours or 1, 3, or 7 days after OM commencement. Bone volume fraction (BVF) and bone mineral density (BMD) were assessed in hemimaxillae by microcomputed tomography analysis. Expression of the proinflammatory cytokines interleukin (IL)‐1β and tumor necrosis factor (TNF)‐α were evaluated in gingival samples by quantitative polymerase chain reaction and enzyme‐linked immunosorbent assay, and in the furcation region by immunohistochemistry analysis (IHC). Results: The OMP group had lower BVF and BMD levels compared to the other groups at day 7 ( P <0.05). Maximum messenger ribonucleic acid expression of both cytokines was observed in the OMP group at day 1 ( P <0.05). In the same period, all proteins were expressed in high levels for all test groups compared to the control group. The number of cells positive for IL‐1β and TNF‐α by IHC was highest in the OMP group at day 1, with progressive reduction thereafter. Conclusion: The results suggest that OM acts synergistically with periodontal disease in periodontal breakdown through upregulation of proinflammatory cytokines.