C‐reactive protein interactive with IL‐6 mediates alveolar bone remodeling imbalance during orthodontic tooth movement with periodontitis

Background Periodontitis (PD) occurring during orthodontic treatment may interfere with the bone remodeling process. This study investigated the impact of PD on bone remodeling during orthodontic tooth movement (OTM) and explored the potential role of C‐reactive protein (CRP) and the IL‐6/JAK2/STAT3 signaling pathway in this process. Methods Models for PD, OTM, and combined PD with OTM (PD+OTM) were created in Sprague–Dawley rats. Alveolar bone loss and activation of the CRP and IL‐6/JAK2/STAT3 signaling pathway in periodontal tissues were observed at 7‐ and 14‐ days post‐modeling. CRP knockout rats and local injection of the tyrosine kinase inhibitor AG490 used to downregulate the IL‐6/JAK2/STAT3 pathway were applied to verify their regulatory roles in bone remodeling during OTM in the presence of PD. Results Alveolar bone resorption was significantly higher in the PD+OTM group than in the PD and OTM groups. Histological analysis revealed increased osteoclast accumulation and a higher RANKL/OPG ratio in the PD+OTM group, along with elevated CRP expression and activation of the IL‐6/JAK2/STAT3 pathway. Both CRP knockout and AG490 treatment led to a reduction in osteoclasts and a decreased RANKL/OPG ratio in the PD+OTM model, as well as decreased expression of IL‐6/JAK2/STAT3‐related molecules. Conclusion PD during OTM impairs bone remodeling, enhancing osteoclastic activity. CRP interactive with IL‐6/JAK2/STAT3 expression in periodontal tissues during OTM, contributing to the imbalance in bone remodeling during OTM with PD. Plain language summary This study explored how periodontitis (PD) affects the way bone adjusts around teeth when the tooth is moving. Researchers used rats to mimic three situations: PD only, tooth movement only, and both conditions together. They found that when PD and tooth movement happened at the same time, it caused significantly more bone loss around the teeth than either condition alone. This was linked to more bone‐removing cells and changes in key signaling molecules in the periodontal tissue, specifically CRP and a pathway involving IL‐6, JAK2, and STAT3. Importantly, when the researchers either removed CRP or blocked the IL‐6/JAK2/STAT3 pathway, they saw less bone loss and fewer bone‐removing cells in the rats experiencing both PD and tooth movement. This shows that active PD disrupts healthy bone remodeling during orthodontic treatment, and that CRP and the IL‐6/JAK2/STAT3 pathway play a key role in causing this extra damage. The findings highlight why treating periodontal disease is crucial before or during tooth movement treatment and point to potential targets for protecting bone health in orthodontic patients with periodontal problems.