Friends with periodontal disease must have this doubt, “I have periodontal disease, my teeth are already loose, and if I undergo orthodontic treatment, won’t my teeth fall out?” To better answer the doubts of periodontal disease patients, we must first understand the bite condition of periodontal disease patients. Periodontal disease is a chronic progressive disease caused by multiple factors, when our gums and alveolar bone resorption due to periodontal disease is reduced to half of the length of the root, teeth will appear to varying degrees of loosening, followed by displacement and elongation and loss, after the displacement of teeth, may cause secondary malocclusion and occlusal trauma, then the looseness of the teeth will increase, aggravating the resorption of the alveolar bone and displacement of teeth, so forming a vicious circle. How can we get out of this vicious circle? First of all, we have to carry out systematic periodontal treatment for the affected teeth, and after the periodontal condition is stabilized, orthodontic treatment will be carried out, that is, the misaligned teeth will be moved to normal position by light orthodontic force, and normal occlusal relationship will be established, so as to eliminate the joint trauma. Orthodontic treatment has become a part of periodontal treatment and is important in promoting the patient’s periodontal health and improving the occlusion. Studies have shown that after periodontal inflammation is controlled, improving the occlusal relationship can reduce periodontal trauma and facilitate recovery from periodontal disease. The orthodontically aligned teeth, which are easy to clean, also play a role in promoting the maintenance of the healing effect after periodontal treatment. Because the affected teeth are loose and difficult to stabilize in their new position, we often use permanent retention after treatment is completed to stabilize the healing process.