The Sonicare sonic toothbrush and a traditional manual toothbrush were compared for efficacy in improving periodontal health in young orthodontic patients with existing gingival inflammation. A 4-week, single-blind clinical trial was employed. Twenty-four subjects, ages 11-17 years, who were fully bonded and banded with fixed orthodontic appliances were selected. Subjects were randomly assigned to use either the manual or the Sonicare toothbrush, instructed in its use, and asked to brush each morning and evening for 2 minutes. Plaque index, gingival index, percentage of sites which bled on probing, pocket depth, and total gram-negative bacteria in a subgingival plaque sample were assessed at baseline and 4 weeks around the banded teeth. The results demonstrate that the Sonicare brush was significantly more effective than the manual brush in all clinical parameters. Sonicare was statistically superior to the manual brush in supragingival plaque reduction (57% vs. 10%, respectively; p < 0.001). Gingival Index scores fell by 29 percent in the Sonicare group, but only 3 percent in the manual group. Reduction of bleeding on probing was significantly greater in the Sonicare group than in the manual group (p < 0.001). The Sonicare group decreased from 78% bleeding sites at baseline to 24.5% after 1 month. In the manual group there was only a slight reduction in bleeding on probing (70% of sites at baseline and 64.6% sites after 1 month). Mean pocket depths were significantly reduced compared to baseline values in both the Sonicare and the manual groups (p < 0.001). Pocket depth reduction in the Sonicare group was, however, significantly greater than in the manual group (28% vs. 6%, respectively: p < 0.001). Total gram-negative bacteria in subgingival plaque samples from banded test teeth of a subset of patients were reduced in the Sonicare group (p < or = 0.05), but increased in the manual group. These results clearly demonstrate that the Sonicare sonic toothbrush is superior to a manual toothbrush in improving periodontal health in adolescent orthodontic patients with existing gingivitis.