Purpose: The aim of the present study was to investigate plaque levels following sonic-powered and manual toothbrushing in subjects with dental implants. Materials and methods: This study included 36 male and 47 female partially edentulous patients (age range 45-78 years, mean age 59.8 years) that were randomly assigned to one of two treatment groups: the sonic toothbrush group (n = 42; Philips Sonicare FlexCare® toothbrush) or the manual toothbrush group (n = 41; Oral-B P40®). Clinical, microbiological and immunological examinations were performed blinded at baseline and after 3, 6, 9 and 12 months. Microbiological analyses were performed by real-time polymerase chain reaction. Immunological analyses (prostaglandin E2) were performed by chromatography-electrospray spectrometry. Results: The plaque index difference between baseline and 12 months at implants showed no significant difference between sonic or manual toothbrushing in a two-sided Mann-Whitney test (W = 773.5, P = 0.426, 95% CI -0.64 to 0.20). At the end of the study, there were no significant changes in plaque index, bleeding on probing, gingival index, pocket probing depth, gingival recession, clinical attachment level or the microbiological and immunological outcomes at implants or teeth in either group. Conclusions: This study uncovered no significant difference between sonic and manual toothbrushing for plaque reduction at implants and teeth. Both toothbrushes maintain healthy peri-implant soft tissue. Keywords: bacterial infection, dental implants, manual toothbrush, PGE2, sonic-powered toothbrush, real-time PCR