A Radiographic Classification for Retrograde Peri-implantitis.

BACKGROUND: Retrograde peri-implantitis (RPI) is an inflammatory disease that affects the apical part of an osseointegrated implant, while the coronal portion of the implant sustains a normal bone-to-implant interface. It is a diagnostic and therapeutic dilemma for implantologists. There is lack of a standard classification system and a definite treatment algorithm for the same. This article aims to introduce a classification system for RPI based on the radiographic amount of bone loss around an implant apex. MATERIALS AND METHODS: A search of PubMed database was conducted with the keywords "retrograde peri-implantitis" and "implant periapical lesion." Preoperative intraoral periapical (IOPA) radiographs of implants with RPI in case reports/case series were compiled. A total of 54 lOPAs from 36 articles were compiled and were assessed. RESULTS: Three different classes were proposed. The amount of bone loss from the apex of the implant to the most coronal part of radiolucency was calculated as a percentage of the total implant length and classified into one of the three classes: Mild, moderate, and advanced. Treatment options and prognosis have been suggested for each class. CONCLUSION: The proposed classification may allow for an easy and reproducible radiographic assessment of the RPI lesion and may serve as a guideline to prognosis and treatment planning.