Abstract: Objective: To compare the clinical effects of different treatment techniques of ridge preservation following tooth extraction in patients with severe periodontitis. Methods: A total of 21 hopeless teeth diagnosed with severe periodontitis at our institution were included. Tooth extraction and ridge preservation were operated in each socket. All sockets were grafted with Bio-Oss after tooth extraction. They were divided into three groups by covering different membranes: Bio-Gide group, PRF group, and Bio-Gide+PRF group. Clinical and radiographic examinations were carried out pre operation, 3 and 6 months post-operation. Keratinized tissue width (KTW) and gingival recession (GR) of adjacent tooth were measured. Adjacent bone height (ABH) and socket depth (SD) were measured using parallel projection of apical radiographs. Buccal-lingual bone width (BLW) was measured using CBCT. Results: There was no significant difference at GR and ABH among three groups 6 months post-operation (P>0.05). Compared to pre-operative parameters, after 6 months, SD values of 3 groups had significant change (P＜0.05). Only BLW result of PRF group became worse after surgery (P<0.05). After surgery, the values of KTW from high to low were as follows: Bio-Oss+PRF group, Bio-Oss+Bio-Gide+PRF group, and Bio-Oss+Bio-Gide group. Conclusion: All techniques following tooth extraction in advanced periodontitis patients can effectively maintain the adjacent alveolar bone height and reduce the further recession of soft tissue. Covering Bio-Gide+PRF membrane after Bio-Oss grafting is more beneficial to maintain the width of buccal-lingual alveolar bone and has advantages of promoting soft tissue healing and preserving sufficient keratinized gingiva.

Key words: severe periodontitis, alveolar ridge preservation, PRF, CBCT