Sugar and acid
Ten small snacks do more harm than one large piece of cake.
Sugar and acid harm the teeth in two different ways. Sugar is the raw material for the bacteria that turn it into acid. Acid from food does not need this detour — it attacks the enamel directly. The two together are more common than it seems: most soft drinks contain both.
Frequency is the factor that matters
After every contact with sugar the pH value at the tooth surface falls into the acidic range and needs about 30 minutes before the saliva has neutralised it again. During that time the tooth loses minerals; afterwards it can regain them.
From this follows a calculation that is unknown to many: a piece of cake in the afternoon is half an hour of acid. Ten sweets spread across the day are five hours. The amount of sugar may be smaller in the second case, the damage considerably greater.
The practical conclusion is therefore not abstinence but bundling: sweet things with a meal rather than in between, and afterwards a pause in which nothing follows.
Where sugar hides where you would not suspect it
- Fruit yoghurt, muesli bars and breakfast cereals
- Fruit juices and smoothies — they contain fruit sugar in dissolved form and fruit acid as well
- Ketchup, ready-made sauces, salad dressings, coleslaw
- Cough sweets and many liquid medicines, especially for children
- Drinks advertised as having “no added sugar” that nevertheless contain fruit sugar
In lists of ingredients, sugar appears under many names: glucose, fructose, sucrose, maltose, dextrose, maltodextrin, syrup, fruit concentrate. For the bacteria in the mouth the difference is small; honey and cane sugar are no kinder to the teeth than household sugar.
Sugar substitutes are a real alternative. Xylitol and erythritol cannot be used by the caries bacteria; xylitol even inhibits their metabolism. Sugar-free chewing gum with xylitol after eating is one of the simplest effective measures there is — it stimulates the flow of saliva and thereby shortens the acidic phase.
Erosion: when acid attacks directly
Erosion is not a caries process and has nothing to do with bacteria. Acid dissolves the enamel across a surface. The result looks different from caries: the tooth does not become holey but thinner. Chewing surfaces become flatter and develop bowl-shaped hollows, the edges of front teeth look translucent, and the teeth become more sensitive overall.
Where the acid comes from
- Soft drinks, cola and energy drinks — often very acidic, regardless of the sugar content
- Citrus fruit, juices and smoothies
- Vinegar and acidic dressings
- Wine, especially white wine
- Frequent vomiting, for instance with eating disorders or during pregnancy
- Heartburn and reflux — here stomach acid acts, above all at night, usually on the inner surfaces of the upper front teeth
What helps
- Do not drink acidic drinks spread across the day but with a meal. With a straw there is less contact with the front teeth.
- Afterwards rinse the mouth with water or drink milk — it neutralises.
- Do not brush straight away. After contact with acid the enamel is softer for a short time; the brush then removes it as well. Wait about half an hour.
- Use fluoride — it hardens the surface.
- With recurring heartburn, have the cause clarified medically. Dentistry can only limit the damage here.
The essentials at a glance
- What matters is how often sugar enters the mouth — not how much. Every contact starts an acid attack of about 30 minutes.
- Acid from drinks and fruit attacks the enamel directly, without any bacteria at all. That is called erosion and is something other than caries.
- After something acidic, do not brush for half an hour — the enamel is then soft and is additionally worn away by the brush.
- Sugar-free chewing gum after eating stimulates saliva and shortens the acidic phase.
Answered briefly