The purpose of this study was to evaluate the efficacy of the Sonicare $Elite^{(R)}$ power toothbrush in plaque removal and reduction of gingivitis from hard-to-reach sites of the moderate periodontitis compared to regular manual toothbrush in 12 week follow-up. 82 subjects with incipient to moderate periodontitis were randomly assigned to use either the manual or sonic brush, instructed in its use, and asked to brush 2 times a day for 2 minutes. Plaque scores were taken at baseline, 1, 4, 12 weeks using Silness & $Lddot{o}e$ plaque index and gingival inflammation was assessed by the $Lddot{o}e$ & Silness gingival index. The results were as follows. 1. The Sonicare $Elite^{(R)}$ power toothbrush showed a significant reduction(p<0.0001) of the plaque(Silness & $Lddot{o}e$) and gingival inflammation(Loe & Silness). 2. The Sonicare $Elite^{(R)}$ power toothbrush showed a significant better reduction of plaque and gingivitis(p<0.05) than the manual toothbrush after 1, 4, and 12 weeks. 3. The Sonicare $Elite^{(R)}$ power toothbrush demonstrated a significant reduction(p<0.0001) of the plaque in interproximal sites(p<0.0001), buccal sites(p<0.0001) and the lingual sites(p=0.00l8) of the teeth. 4. The Sonicare $Elite^{(R)}$ power toothbrush demonstrated a significant reduction(p<0.0001) of the gingival inflammation in the interproximal sites(p<0.0001), the buccal sites(p<0.0001) and the lingual sites(p<0.0001) of the teeth. The results of this study support the findings that Sonicare $Elite^{(R)}$ power toothbrush has a great potential to remove the plaque and resolve the gingival inflammation during the period of 12 week.