Main Purpose: To evaluate the effect of photodynamic therapy on soft tissue healing after tooth extraction at periodontal infection site, and to compare the effect on pain degree and bone tissue remodeling after tooth extraction.

The aim of this study is to evaluate the effect of photodynamic therapy (PDT) on soft tissue healing and bone remodeling in tooth extraction sockets after tooth extraction. The enrolled patients will be randomized into two groups. The control group used conventional tooth extraction to clean the wound, and the experimental group used photodynamic therapy to help clean the wound. Seven days and 14 days after extraction, the area of extraction socket was measured, the healing rate of extraction socket was calculated, and Landry, Turnbull and Howley soft tissue healing index was measured. The degree of pain was recorded at 6h, 1 day, 2 days and 3 days after tooth extraction. Bone remodeling indexes were measured at 1 month after tooth extraction.

Inclusion Criteria:

• Age range from 18 to 65 years old;
• Patients with extensive periodontitis of the whole mouth;
• There was a deep periodontal pocket with PD≥5mm and at least one adjacent tooth at the extraction site;
• Periodontitis was controlled, and the extraction site and adjacent teeth were not in the acute inflammation or infection stage;
• The extraction site has a hopeless prognosis or no preservation value, and it is the first and second molars or maxillary wisdom teeth that erupt in a positive position

Exclusion Criteria:

• pregnant and lactating women;
• patients with systemic diseases that may affect the ability of postoperative healing (such as patients with radiotherapy and chemotherapy, history of hematological diseases, and uncontrolled disease) Diabetes mellitus, etc.);
• long-term use of drugs known to affect bone metabolism or mucosal healing such as bisphosphonates and non-steroidal anti-inflammatory drugs;
• smoking > 10 cigarettes per day;
• root breakage or gingival tear occurred during tooth extraction.