What foodstuffs are good for the teeth?

DW: Why is sugar in particular bad for the teeth?

Dr. Falk Schwendicke: Sugar is bad because it's metabolized by various microorganisms. These ocurr naturally in the mouth and needn't be a problem. But if we eat too much sugar, they become over-active, multiply and get the upper hand. They produce acids from sugar and these acids then demineralize tooth enamel, and eventually, also the inside layer of the tooth. When microorganisms get inside a tooth and parts of the teeth decay, a hole forms. That's classic caries. So sugar is a catalyst for tooth decay.

DW: Are other carbohydrates also bad for the teeth?

Not to the same extent. These bacteria can metabolize small doses of starch, for example. Microorganisms feed off primarily low-molecular sugar such as beet and cane sugar.

DW: Which other foods are especially bad for the teeth?

Acidic foods such as fruit, juice, coke and so one - everything with an acid PH value. The acid causes erosion, by chemically dissolving tooth enamel. Sugar is the only thing that demineralizes teeth - acid does too. An acidic food also contains sugar makes caries even more likely.

DW: Which foods strengthen the teeth?

Dairy products in particular because they're rich in calcium. Calcium is found in the teeth and is an important factor in keeping them healthy. Food containing fluoride also protect the teeth. I recommend fluoridated salt. Fluoride is added to the water in some countries. But children who are consuming fluoridated salt or water don't need any futher sources of fluoride, such as tablets.

DW: It's impossible to avoid eating foods that are bad for the teeth. Do you have any advice on how to limit teeth decay?

There are three main things one can do. First and foremost, maintaining good dental hygiene. Then it's not disastrous if you eat things that are bad for the teeth now and then. You won't get caries the instant you eat candy. It's a process. Keeping the teeth clean, including flossing, is good protection. Caries only arises after a few weeks if there's plaque build-up that's doesn't get cleaned. It's also important at which time of day you clean your teeth. If you've eatn something acidic then you shouldn't clean your teeth straigth away because the enamel has been softened and can be eroded by teeth-brushing. Ideally you should wait an hour before and after consuming acidic food or drink. Thirdly, take fluoride regularly in the form either of fluoride toothpaste or a fluoride gel that can be bought over the counter and makes enamel more robust. These are good counter-measures for anyone who has a sweet tooth.

Falk Schwendicke is a senior doctor at the Charité Center for Dental, Oral and Maxillary Medicine in Berlin.

Interview: Dorothee Grüner