Background: Infection and inflammation in tissues adjacent to dental implants are common. There are few controlled studies assessing interventions. We assessed if mechanical debridement with titanium curettes, is equally effective as an ultrasonic device in reducing clinical signs of inflammation and the total bacterial load. Materials and methods: Thrity two subjects (mean age 62.5 S.D ± 11.7) with one implant each demonstrating peri-implantitis were randomized in two intervention groups. Clinical and microbiological data were obtained before and during 6 months. Group one received debridement using titanium hand-instruments and group two received ultrasonic treatment using a coated working end. Results: At the different time-points, data analysis by independent t–test, or Mann–Whitney U tests failed to demonstrate group differences. Comparing baseline data with results at 6 months (merged groups) demonstrated that overall PI scores and at implants decreased (mean diff: 20.2%, S.E ± 6.3, 95%CI: 7.0 to 32.7, P < 0.002) and (mean diff: 27.2% S.E ± 7.9, 95%CI: 11.3 to 43.1, P < 0.001). Bleeding scores at implants improved (P < 0.01). PPD scores at implants did not improve (P = 0.30). Conclusions: No differences in treatment outcomes between the two treatment methods studied were found. While PI and BOP scores improved no effects in PPD were identified.