The design of the modern conventional manual toothbrush can be attributed to Dr. Robert Hutson, a Californian periodontist, who in the early 1950s developed the multitufted, flattrimmed, end-rounded nylon filament brush that became known as the Oral-B manual toothbrush. The trademark Oral-B emphasized that this was an oral brush, designed to clean all parts of the oral cavity, not merely a toothbrush. Flat-trimmed conventional toothbrushes based on the original Oral-B design have good plaque-removing capability when used carefully. However, limitations in terms of patients' brushing technique and brushing time necessitated a radical change in bristle pattern to improve performance, especially at approximal sites and along the gumline.

Rationale for Product Development
Detailed studies of the tooth-brushing process, using advanced scientific and ergonomic research methods, led to new toothbrush designs intended to maximize the efficacy of brushing efforts. These studies showed that the point of greatest interproximal penetration occurs when the direction of brushing changes; bristles angle back into the interproximal space, moving down and back up the adjoining approximal surface. These mechanics were further optimized on the basis of standardized evaluations of brush-design characteristics, including combinations of tuft lengths, insertion angles and tuft layout. With conventional vertical bristles these improvements yield limited benefits because only a few bristles are correctly positioned at the interproximal junction when the brush changes direction. Ultimately, a design with bristle tufts arranged at 16º from vertical along the horizontal brush head axis was identified, in which the maximum number of bristles operated at the optimum angle throughout the brushing cycle. This design was significantly more effective (p < 0.001) than others in terms of penetration (by 9.6%) and cleaning effectiveness per brush stroke (by 15.5%).

Effectiveness
This discovery paved the way for a new toothbrush design with a unique patented array of tufts, which became known as the Oral-B CrossAction brush. This design was selected for extensive independent studies designed to evaluate plaque removal at the gingival margins and in the approximal areas and longer-term control of gingivitis, relative to current standard designs. In a series of studies (published in 2000), 14 single-brushing comparisons and 2 longer-term studies demonstrated the consistent superiority of the Oral-B CrossAction brush over the equivalent commercial standards. Since then, several additional studies have contributed further positive performance data for the CrossAction brush. Two of the studies demonstrated that plaque removal by this brush was superior to that of 15 other manual toothbrushes, and further investigations contributed similarly positive data. Longer-term data have confirmed superior CrossAction performance and the long-term benefits of improved efficacy, particularly for gingivitis.

Discussion
Novel approaches to toothbrush design have produced a toothbrush that, when tested in a large number of clinical studies, has consistently met or exceeded established standards of efficacy. The literature contains a wealth of performance data on various toothbrush designs, but none of these designs shows the year-on-year consistency and reproducibility of the Oral-B CrossAction.