From Trisha's Desk Trisha E. O’Hehir, RDH, MS, Hygienetown Editorial Director

"Brush after meals." That's the message we've heard and repeated for decades. It's not just dentists and hygienists sharing this message, toothpaste companies also tell consumers to brush after meals. But is this idea based on science or simply a tradition that has been repeated so often it's become dogma, without any scientific substance? Research shows that if the meal consists of any high acid foods or beverages brushing right after eating can be detrimental. The acids in orange juice or soda pop will actually soften enamel and dentin enough to make them susceptible to abrasion when brushed with toothpaste. Based on these findings, researchers suggest waiting 60 minutes after eating to brush. Dr. Martin Addy and his research team at the University of Bristol in the U.K. who did the acid testing suggest brushing before eating rather than after to prevent acid production.

Plaque bacteria produce acid right away. According to research published by Dr. John Featherstone of University of San Francisco, acid production occurs within seconds of bacteria's exposure to sucrose or fermentable carbohydrates. This acid production will drop the salivary pH from a neutral of 7 to an acidic level of 4.5 within just five minutes. It then takes 30 minutes to return to a pH of 7. Waiting to remove bacterial plaque biofilm until the meal is over allows the bacteria ample time to produce acid.

Brushing and flossing first thing in the morning to remove the plaque biofilm thoroughly before introducing fermentable carbohydrates prevents acid production. If you wait to brush and floss your teeth until after breakfast, it's too late. Sure, you will now remove both bacterial biofilm and food particles, but if you've had orange juice or other acidic foods, it might cause microscopic damage to the enamel. According to Dr. Addy brushing after the acid is produced is no longer preventive. Preventive interventions occur before the event – in this case, prevention would occur before acid production by Strep mutans, not after.

To consumers, brushing after meals make sense because they equate brushing to removing food particles; however, toothbrushing research focuses on plaque removal, not food removal. We have no research suggesting that toothbrushing is effective for food removal. Food particles generally remain between the teeth, not on the facial and lingual surfaces reached by the toothbrush. Rinsing works to flush out food particles, so using an oral irrigation device after eating makes more sense than brushing after meals.

Another tradition without supporting science suggests that brushing last thing at night is more important than brushing in the morning. When asked, Addy said that, although brushing before going to bed might be convenient, he's not sure what it achieves except to remove acid-softened enamel or dentin. Since soda and alcoholic drink consumption in the evening is a common practice, both in England and the United States, it makes more sense to brush when you get home from work, before having dinner, rather than after softening the enamel with acidic foods and beverages.

It looks like our brushing traditions are just that – traditions. Based on what we do know, however, it makes more sense to brush before eating. That way, plaque is removed before ingesting sugars, and if acidic foods and beverages are ingested, we avoid compounding the erosion with toothpaste abrasion. What about you? Do you brush and floss first thing in the morning or wait until after breakfast? Base your decision on scientific evidence, not tradition.
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