S Kaya1,2, M Çifter3, A Çekici4, V Olgaç5, H İşsever6, G Işık4. 1. Department of Periodontology, Okan University Faculty of Dentistry, Gülbahar Mah. Oya Sok. No:23/A Mecidiyeköy/Şişli, TR 34394, Istanbul, Turkey. suheylakaya@msn.com. 2. Department of Periodontology, Istanbul University Faculty of Dentistry, Istanbul, Turkey. suheylakaya@msn.com. 3. Department of Orthodontics, Istanbul University Faculty of Dentistry, Istanbul, Turkey. 4. Department of Periodontology, Istanbul University Faculty of Dentistry, Istanbul, Turkey. 5. Department of Tumor Pathology and Cytology, Istanbul University Institute of Oncology, Istanbul, Turkey. 6. Public Health, Istanbul University, Istanbul, Turkey.
Abstract
PURPOSE: The aim of this study was to evaluate the time course of orthodontic force-induced apoptosis and receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in a rat model under light- and heavy-force conditions. METHODS: Male Wistar rats were divided into light-force (10 cN) and heavy-force (60 cN) groups (N = 28/group). Each group was divided into four time-course subgroups to evaluate all phases of orthodontic tooth movement. Mesialization appliances were placed on three united maxillary molars unilaterally and activated. Tooth movements were calculated, and periodontal ligament (PDL) widths were measured. Expression of Bax, Bcl‑2, caspase 3, caspase 9, and RANK-RANKL were assessed by immunohistochemistry. Expression levels at the PDL-alveolar bone border were compared between experimental and control groups and force groups. RESULTS: The rate of tooth movement did not differ between the force groups. PDL widths were higher on the tension side in the heavy-force group in the post-lag phase. Pro-apoptotic protein Bax expression was elevated in the heavy-force group, whereas anti-apoptotic protein Bcl‑2 expression was elevated in the light-force group. RANK expression on days 7 and 21 and RANKL expression on day 21 differed between the force groups. CONCLUSIONS: Evidence of orthodontic force-induced apoptosis is more robust with stronger forces than with weaker forces. Exuberant RANKL-induced osteoclastogenesis that was seen when applying a low force results from increased RANK and RANKL expression in the post-lag phase.
PURPOSE: The aim of this study was to evaluate the time course of orthodontic force-induced apoptosis and receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in a rat model under light- and heavy-force conditions. METHODS: Male Wistar rats were divided into light-force (10 cN) and heavy-force (60 cN) groups (N = 28/group). Each group was divided into four time-course subgroups to evaluate all phases of orthodontic tooth movement. Mesialization appliances were placed on three united maxillary molars unilaterally and activated. Tooth movements were calculated, and periodontal ligament (PDL) widths were measured. Expression of Bax, Bcl‑2, caspase 3, caspase 9, and RANK-RANKL were assessed by immunohistochemistry. Expression levels at the PDL-alveolar bone border were compared between experimental and control groups and force groups. RESULTS: The rate of tooth movement did not differ between the force groups. PDL widths were higher on the tension side in the heavy-force group in the post-lag phase. Pro-apoptotic protein Bax expression was elevated in the heavy-force group, whereas anti-apoptotic protein Bcl‑2 expression was elevated in the light-force group. RANK expression on days 7 and 21 and RANKL expression on day 21 differed between the force groups. CONCLUSIONS: Evidence of orthodontic force-induced apoptosis is more robust with stronger forces than with weaker forces. Exuberant RANKL-induced osteoclastogenesis that was seen when applying a low force results from increased RANK and RANKL expression in the post-lag phase.