Esberg A, et al. - Researchers sought for the peri-implant crevicular fluid (PICF) protein pattern that could be associated with the active peri-implantitis process. They conducted a proteomic analysis of peri-implant crevicular fluid from 25 peri-implantitis sites using liquid chromatography–tandem mass spectrometry before and at 3, 6 and 12 months after treatment. Based on their 3–12 months PICF proteomic profiles, two major clusters of the subjects were defined. Cluster 2 differed from cluster 3 by 52 proteins. Cases belonging to cluster 2 had implant loss and bleeding on probing. Cluster 3 was associated with implant survival and enamel matrix derivative treatment. These findings suggest the association of a specific PICF proteomic profile with active peri-implantitis process and implant loss.