Yah, you brush your teeth because mom (and your dentist) always told you to. Not to mention that plaque, coffee stains and evidence of a midday chocolate break aren’t exactly attractive. Too bad there’s a downside to that minty-fresh feeling: Some toothpaste can actually eat away at the enamel of your teeth.  That’s why researchers in Germany developed a new method to test toothpastes for their levels of abrasiveness. While the existing approach relies on what’s called a radioactive abrasion value (RDA value)—which uses machines to continuously brush radioactive dentin samples, then assesses the damage—some experts say the method is flawed because it’s time consuming and often yields inconsistent results. This new method, however, uses a microscopic friction analysis, which is quicker and more reliable.  Most toothpaste contains abrasives, but you can minimize your exposure: Use a pea-sized amount of paste, and avoid whitening pastes (they tend to be more abrasive) if you’re concerned about enamel damage. Brushing your teeth the right way can also protect enamel—so avoid these other smile-saboteurs to ensure healthy, pearly-white teeth:  You brush too soon after a meal People who brushed their teeth 20 minutes after drinking soda experienced more wear than those who waited 30 to 60 minutes, according to German research. Acid wears down tooth enamel, so brushing right after consuming an acidic beverage can hasten the process.  You only brush horizontally “If you only brush horizontally, you’re not cleaning the surfaces between your teeth well,” says Denis Kinane, PhD, Dean of the School of Dental Medicine at the University of Pennsylvania. Brush in various directions—in circles, horizontally, and vertically—to attack plaque from all angles. Plus, if you’re brushing the same teeth over and over again with the same horizontal motions, you’re sure to wear down the enamel eventually, especially on your canines, he explains. You brush too hard A lot of people brush hard across their teeth and gums, which abrades the necks of the teeth and traumatizes the gums, explains Kinane. A good rule of thumb: “If you need to replace your toothbrush every month, you’re probably over-brushing,” he says. Replacing your brush every 2 or 3 months means you’re striking a better brushing balance.  More from Prevention: 5 Ways Poor Dental Care Makes You Sick