[Retrospective analysis of the etiology and treatment of 20 cases of retrograde peri-implantitis].

Objective: To retrospectively analyze the pathogenic factors of retrograde peri-implantitis (RPI) and assess the effectiveness of treatment, and to provide clinicians evidence for the prevention and treatment of RPI. Methods: A total of 2 731 patients with missing teeth (4 016 implants) who underwent implant restoration in the Department of Stomatology, The First Affiliated Hospital of Wenzhou Medical University between January 2004 and December 2022 were included in the study. According to the diagnostic criteria of RPI, a total of 20 cases (23 implants) of RPI were collected, including 4 female (5 implants) and 16 male (18 implants), and the treatment medical records, intraoral photos and cone beam CT or oral panoramic radiographs records of each patient were collected. Each patient with RPI was treated accordingly and followed up regularly to evaluate its efficacy. Results: After treatment, the follow-up time for 20 patients with clinical symptoms of RPI was 13 (6, 40) months (1 month to 13 years), and the survival rate of the treated implants was 91% (21/23). There were 7 patients (8 implants) with inactive RPI, no clinical symptoms, no loosening of the implant, with normal occlusal load, and the disease was at the inactive stage and was not treated. The pulp vitality of the natural tooth adjacent to the implant was normal, and the implant could function normally. There were 13 patients (15 implants) with infected RPI, 1 patient (1 implant) had no loosening of the implant, and the periapical radiolucency of the implant disappeared after endodontic treatment of the natural tooth adjacent to the implant; 12 patients (14 implants) had clinical symptoms such as implant loosening, pus discharge, etc. Among them, 10 patients (12 implants) were successfully implanted in situ or in adjacent sites after removing the implants, and were successfully implanted after 3 to 20 months. Two patients(2 implants) were removed and no further implants were placed. Among them, 2 implants with infected RPI had cystic lesions, which was similar to natural root apex cysts. Conclusions: The etiology of RPI is related to inflammation of adjacent tooth root tips or bacterial residues from inflammatory lesions in the alveolar bone and bone augmentation. RPI can be treated by perfect root canal treatment of adjacent teeth, removal of inflammatory tissue, or simultaneous guided bone regeneration techniques.