Two single-blind clinical studies investigated the stain removal properties of Sonicare, a new electronic toothbrush that combines sonic vibrations and dynamic fluid activity with mechanical scrubbing to clean tooth surfaces. In one study, 30 subjects used a 0.12% chlorhexidine mouthrinse (Peridex) for two weeks to accumulate stain, and then were assigned to either Sonicare or a manual toothbrush (Oral-B P-35). The subjects brushed with their assigned device for 2 minutes twice a day. In a second study, 19 subjects with extrinsic stain due to coffee, tea, or tobacco (CTT) causes were randomly assigned to either Sonicare or a manual toothbrush (Crest Complete). These subjects also brushed for 2 minutes twice a day, with additional brushing on the stained areas. Stain on the labial surfaces of the subjects' anterior teeth was evaluated with the Lobene index at the pretrial, 2-week, and 4-week periods. Clinical analysis indicated that use of Sonicare resulted in Peridex stain reductions of 54% and 50% after 2 and 4 weeks, respectively, and reductions in CTT stain of 39% and 82% at similar time points. The manual toothbrush resulted in stain increases of 4% and 24% in the Peridex study and CTT stain decreases of 41% and 39% after 2- and 4-week brushing periods. Computer image analysis was performed on photographic records from the CTT stain study and showed a high correlation with the Lobene index (r = 0.82). The results of these two independent studies indicate that Sonicare is superior to the manual toothbrushes studied in removing both Peridex and CTT stains.(ABSTRACT TRUNCATED AT 250 WORDS)