Here's how it works. Everybody has bacteria (germs) in their mouths. Decay happens when certain types of these germs turn sugar into acid. This acid causes decay. The good guy is your saliva. The saliva neutralises the acid produced by the germs (stick around, this will get more interesting). It takes 2 hours however after having anything with sugar for your teeth to stop dissolving. So, your teeth are dissolving for two hours after you have anything with sugar. If you have two meals a day with sweets and nothing in between, your teeth dissolve for four hours a day. Most people seem to cope OK with this.

Graph of decay activity with low sugar exposure

Every sugary snack between meals adds an extra two hours to your dissolving time. If you've got enough fingers count up how many meals or snacks or drinks with sugar you have a day. Multiply by two (use toes as necessary) and you get how much of the day your teeth spend decaying. If it's 10 hours or more, you may as well reserve a seat in our chair for lots of fillings.

Some people take much longer than others to neutralize the acid, and these folks need to be extra careful as they are much more cavity-prone than others. See our Cavity Prevention page for the extra protection and treatments we can use.

Graph of decay activity with frequent sugar exposure


Example of teeth with high sugar exposure

Public enemy number one, the sugary snacks are the obvious ones like candies, lozenges, cookies and cakes, but this also includes drinks with sugar such as soft drinks, fruit juice, coffee or tea with sugar. Did you know that a large McDonalds Coke has 22 teaspoons of sugar? It's full of acid too, which really wrecks the teeth. A cup of juice is healthier, but still has 6-8 teaspoons. It has all the sugar and acid from the 6-8 fruits it was made from.

The worst snacks are those you suck on for a long time, especially sour candies which have built-in acid. Even "healthy" snacks like granola bars and dried fruit are loaded with sugar. Before all you chocoholics jump out the window, there is a simple solution. All you have to do is bundle up all your snacks and juice and include them with the three major meals. Presto! No more decay. (See the first graph, above)

If you must gobble or nibble between meals some things are OK. Most dairy products, fresh fruit (not dried) and vegetables are fine to have as snacks. Meat, cheese and the like are good too. You can drink water, milk, coffee or tea unsweetened or with sugar substitute, and watered-down juices in moderation. Juice with soda water tastes good, and has a lot less sugar and calories. There are fruit and berry flavoured herbal teas available that make good iced tea without any sugar. Diet soft drinks contain  artificial sweetners and acid which can damage your teeth, so use moderation.  Some surgarless gums sweetened with Xylitol can actually  reduce decay.

It sounds easy and it is. The rest is up to you. With thanks to Dr. Brett Taylor, Sydney, Australia, for his assistance.

Link to the ODA's page on nutrition