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Dental Tribune Middle East & Africa Edition July-August 2015

hygiene tribune Dental Tribune Middle East & Africa Edition | July-August 20154B > Page 6B Toothbrush developments. Oral health benefits ByKarenClaire-ZimmetMSBS T oothbrush research and development combines science, technology and art. Optimising toothbrush performance involves several disciplines including an under- standing of mechanical systems, filament properties and physics, production technology, and in addition ergonomics and hu- man behaviour via consumer research. This combination of efforts has yielded toothbrushes that significantly contribute to improvements in the oral health of the population. The modern toothbrush has its origins in primitive designs (Fig- ure1)thathadlargebrushheads with straight, hard and abrasive boar’s hair bristles. In the early 1950s, the first Oral-B manual brush (Figure 2) was developed with multitufted nylon filaments that were flattrimmed, vertical, and end-rounded for safe brush- ing. This was the first modern toothbrush design and similar designs are still in use globally. The full importance of brush head morphology and bristle configurations had yet to be dis- covered. Before that could hap- pen, and more effective designs could be developed, it was nec- essary to fully understand the basic fundamentals and clean- ing mechanisms of the indi- vidual elements that make up a toothbrush. Understanding the fundamen- tals In order to gain a thorough un- derstanding of toothbrushes and what defined toothbrush suc- cess or failure, our team used the power of observation and created a defined problem state- ment: how can we maximise toothbrush bristle contact inter- dentally, for improved cleaning and oral health? By breaking down this problem statement into more basic elements, we were able to gain that under- standing. Although toothbrush- es may appear simple, they are actually quite complicated. As with complex chain molecules that consist of basic chemical elements, at Oral-B we broke down toothbrush mechanisms and design into basic physical elements. We developed our knowledge base by transitioning from what one could call a ‘macroscopic’ perspective to a ‘microscopic’ perspective on the variables that affect toothbrush efficacy and use, first examining brush heads, then tufts of bristles and then individual filaments. Our research needed to address how tufts behaved during use; how individual filaments moved and behaved; what influence usage had on tuft and filament direc- tion and movement, and how this influenced plaque removal efficacy. Other basic elements that re- quired research included dis- covering which factors de- termine the ability of a single bristle/filament to penetrate interproximally, as well as the influence of filament and tuft length, width and shape. I had studied physical chemistry dur- ing my masters degree studies - specifically, polymer dynamics using techniques of light scatter- ing and Fourier transform anal- ysis to understand the time de- pendence of polymer behaviour. The leap from polymer dynam- ics to toothbrush bristle behav- iour, particularly the ability and time dependence of filaments reaching interproximally, is not as large as one might first think. More fundamentally, we further needed to thoroughly under- stand how consumers actually brushed - for instance, we found that a basic horizontal scrubbing motion (rather than a modified Bass technique) was used most often by consumers. All of this was crucial knowledge - only after gaining an under- standing of how consumers re- ally use our products would we be able to improve the design of a toothbrush to work most ef- fectively with common brushing techniques used by consumers. A Journey of Discovery Our basic filament dynamics re- search led to discoveries around the influence of bristle/filament angle and diameter, and the ap- plied brushing load on bristle penetration. I led the filament research, which included creat- ing an experimental setup with a model dentition to enable us to study the ability of filaments to reach interproximally (Figures 3-4). Our hypothesis was that fila- ments bent towards the direc- tion of travel would be more likely to enter the interproximal gap. From our observations, it became clear that when a bris- tle is positioned perpendicular to the tooth surface it tends to bend away from the direction of toothbrush motion and is therefore less likely to penetrate between the teeth. This means that a filament is actually most actively cleaning during direc- tional changes of brushing. As a result, filaments located closest to an interproximal site reach the area most effectively during these directional changes; more distant filaments have already changed their direction of travel by the time they reach the inter- proximal site. Filaments angled at <12º still tend to bend away from the direction of travel and are unable to reach interproxi- mally (Figure 5). However, we were able to demonstrate that filaments at >12º angles are able to effectively maintain their po- sitioning towards interproximal sites, first reaching within the interproximal space before then bending away from the direction of travel while still in the inter- proximal gap (Figure 6). Taking a more macroscopic view of the brush design, including evalu- ating different filament shapes and heights – we found taller, thinner filament tufts are better able to reach interproximally while shorter, thicker filament tufts are superior for flat tooth surfaces. We also discovered that if too much load (brushing pressure) is applied to individual bristles that they collapse and cannot enter the interproximal gap. Conversely, if too little load is ap- plied, the bristles may ‘skip’ over the gap and miss their target. These were key learnings in de- fining what the final tuft density of the CrossAction design would be. Key Learnings - Angled bristles (>12º) are su- perior in reaching interproximal sites - Longer, thinner bristle tufts are more effective interproximally - Shorter, thicker bristle tufts are more effective on accessible sur- faces - Filament packing density influ- ences brushing load on individ- ual filaments and, correspond- ingly, the ability of bristles to contact and clean sites The Outcome: CrossAction The first time we tested an early prototype design of the Cros- sAction toothbrush in our per- formance laboratory we could not believe its cleaning perfor- mance, it was so good. We lit- erally recalibrated the test and analysis equipment, to make sure there were no errors in the analysis and to confirm the cali- bration. We had never seen any- thing that performed so well, the results were off the chart! The result of our research was a shift in the art and science of making toothbrushes, and a novel manual toothbrush de- sign that was based on an un- PPD hears from Procter & Gamble researcher Karen ClaireZimmet about the ground-break- ing advances behind the Oral-B CrossAction toothbrush Figure 1: Primitive brush Figure 2: First Oral-B brush Figure 3: Single filament tester x-y table with stepper motor. A beam balance extends over the table with a filament attached at its end Figure 4: Steel tooth forms mounted on stepper motor oriented buccal surface upward. (Arrow highlights an angled filament being tested) Figure 5: Diagram of bending motion of non-angled bristles perpendicular to the tooth Figure 6: Diagram showing angulation and motion at interproximal gap Longer, thinner bristle tufts are more effective interproximally Shorter, thicker bristle tufts are more effective on accessible surface Angled bristles (>12 degrees) are superior in reaching approximal sites derstanding of the superiority of angled filaments, as well as the importance of filament sizes and shapes, and directional change. The CrossAction toothbrush has bristle tufts with a 16º angle to the brush head in both direc- tions, as well as tall, thin, ellip- tical bristle tufts supported by dense neighbouring tufts that decrease interference between bristles (Figure 7). Its design increases bristle contact with the tooth surface and improves approximal reach during brush- ing, both of which lead to great- er plaque removal efficacy. The effectiveness of CrossAction in interproximal reach, and re- lated approximal plaque remov- al, was initially demonstrated in laboratory studies and the find- ings were confirmed in clini- cal trials. Laboratory research published in 2000 demonstrated significantly greater plaque re- moval for CrossAction relative to 84 manual toothbrushes found in global markets. Subsequent clinical trials, including single- use and long-term studies, cor- roborated the in vitro data. CrossAction was shown in nu- merous clinical trials to pro- vide superior plaque removal and gingivitis benefits versus not only various manual tooth- brushes, but also battery-pow- ered toothbrush models. An important observation and outcome was the response of people testing the CrossAction toothbrush, as well as the reac- tion of dental professionals. People loved the CrossAction - they could feel a difference and intuitively understood that angled bristles would be able to reach between the teeth more effectively. After testing it, they did not want to give it back. At the time of its development, the CrossAction brush design was impossible to make with existing brush-making equip- ment, due to the angled bristle design and very high bristle packing densities. Making the

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