Purpose: The aim of this study was to compare the ability of the bristles of newly developed toothbrushes in removing artificial plaque deposits from the interproximal areas of a jaw model. Materials and Methods: Four toothbrushes were evaluated in this study: A, two differences in level patterns, combination of flat and extremely high-tapered filaments; B, one difference in level pattern, combination of flat and extremely high-tapered filaments; C, rippled pattern and high-tapered filaments; and D, rippled pattern and tapered filaments. The brushing simulator was adjusted to provide a horizontal brushing stroke of 20 mm at a rate of 190 strokes per minute for a duration of 1 min. A 200-g force was applied to the brush head. A plaque-like substrate was placed in the facial and the interproximal sides of the artificial teeth that had the cross-sectional dimensions of mesial face in the maxillary right first molar and distal face in the second premolar. The results were photographed, and the area of penetration and the cleaning effectiveness were calculated for each picture by computer digital image analysis. This test was repeated five times for the toothbrush for each design that was evaluated. The resulting data were analysed using ANOVA and the Scheffe test. Results: The rate of plaque removal was the highest with toothbrush A that gave a significantly greater removal of the artificial plaque than the other three toothbrushes on the maxillary right first molar mesial surface (P 0.05). Conclusion: These results suggest that toothbrush A was more effective in plaque removal in this in vitro model used for determining the interproximal penetration of the four bristle designs. Keywords: interproximal cleaning, jaw model, manual toothbrush