Retrograde peri-implantitis: a case report introducing an approach to its management.

Background: Although several potential etiologic factors associated with retrograde peri-implantitis (RPI) and potential treatment options have been discussed in the literature, the etiology has not been fully investigated and the definitive management methods remain undefined. We propose a decision-making protocol for the treatment of RPI and provide new insight into the etiology of this process based on the findings from two clinical cases.

Methods: The medical and dental histories of two patients who developed RPI were thoroughly reviewed. Both patients were treated according to the treatment guidelines proposed in this manuscript. Fluid from the lesions was collected to examine the presence of 11 bacterial species by molecular-based microbial testing. Biopsies were also obtained for histopathologic examination.

Results: Patient 1, previously diagnosed with human immunodeficiency virus infection, developed RPI 3 months after implant placement. Histopathologic examination revealed a predominantly fibrous connective tissue response with minimal inflammatory infiltrate and bone formation. Patient 2 presented histopathologically with an intense acute inflammatory response. Eikenella corrodens was detected by microbial testing. Three months after surgical intervention, both cases healed uneventfully, and the radiodensity in the lesions significantly increased. The two implants are now functional and free of further complications.

Conclusions: The possible role of bacterial infection from an adjacent tooth may be a potential etiologic factor in the development of RPI. In addition, HIV infection may be associated with RPI and deserves further investigation. A decision-making flowchart was proposed after critically evaluating the currently available relevant literature. Both cases presented in this manuscript were successfully treated by following this protocol.