Forty-seven adult orthodontic patients with fixed orthodontic appliances were divided into three study groups: (1) oral irrigation with automatic toothbrush, (n = 16); (2) oral irrigation with manual toothbrushing, (n = 16); (3) control group with continued normal toothbrushing only, (n = 15). Gingival and plaque indices, bleeding after probing, and gingival sulcus depths were assessed at baseline, 1-month, and 2-month periods. Marked and significant gingival and plaque improvements from baseline were measured in all three study groups. After 1 to 2 months use of the automatic toothbrush and/or the oral irrigation device, there was a significant reduction in plaque when compared with the control group who used only the manual toothbrush (p = 0.026). Also, there was a significant reduction in gingival inflammation (p = 0.045) and evidence for reducing bleeding after probing (p = 0.037). No significant differences were found in probe depths among the three study groups, however, use of both devices reduced the pocket depth significantly from baseline by 0.5 mm (p < 0.0002). For this population of orthodontic patients, significant reductions in plaque, gingival inflammation, and a tendency for reduced bleeding after probing occurred in both groups with the power device. These improvements were most attributable to the effect of the oral irrigation device.