For the treatment procedure of flap surgery, the surgical area is disinfected with iodophor and injected with lidocaine or articaine for blocking or local infiltration anesthesia. The gingiva is incised along the proximal and distal middle of the affected tooth to reach the bone surface, the soft tissue is separated using a stripper, the mucoperiosteal flap is lifted to expose the root surface, and the diseased bone and granulation tissue are scraped away with a scraper. The gingival residual epithelial tissue is removed using surgical scissors, and the gingival flap is trimmed so that the gingival papillae on the buccolingual side can dock and cover the exposed root bone surface, and periodontal plugging agents are placed after suspension suturing to promote healing, and the sutures are removed in about 7-10 days.