p 8 How teeth decay.

The mechanisms of tooth decay and erosion are very complicated and not for the faint-hearted erst-while discoverer of the whole truth (sic!).

However I have devised a modified, simple version which has allowed hundreds of my patients to understand sufficient for them to gain a healthy enjoyable diet which suits the availability of food/drink wherever they are: in their own home, at secondary school, in work canteens, on holiday, at motorway service stations, in the pub, out with the boys or girls, or for pack lunch, school trips, holiday camp, kids parties or a night in front of the box when there's a box of chocolate biscuits and a slab of Black Bun given to you by some inebriated stranger who visited your house in the wee small hours of the first of January. (For a greater understanding of the last bit here starting at 'or a night', please come to Scotland for a wonderful night at Hogmanay.)

Teeth are made of a calcium compound blended with organic compounds. The outer layer (enamel) is tougher than the inner (dentine).

Dental decay is caused by an acid which is produced by the action of certain bacteria on simple sugar. If we put sugar into our stomachs, our complex bodies break it down into energy, carbon dioxide and water. Bacteria cannot do this. Certain bacteria in our mouths break sugar down into energy and a particular acid. This acid dissolves the calcium compound of teeth. When the compound dissolves (dental decay), the tooth substance just falls apart.

At first a very small hole is dissolved through the tough enamel; then a much bigger hole is dissolved inside the tooth dentine. At this time, only a dentist can identify the presence of the decay (sometimes with the help of x-rays - radiographs). When the hole inside the tooth gets bigger, the outer wall of enamel collapses so that there seems to be a sudden big hole. Then, anyone can see the hole!

This decaying process does not progress in an even way. The most vulnerable teeth show the first open holes, but by then many other teeth have holes in dentine where the enamel has not yet collapsed.

That's enough of that, then.

How does it all happen?

There are lots of different acids in the mouth and in foods we put into the mouth but we need only to know of two types.

Type 1. Sugar-produced acid which decays teeth.

Type 2. Any other acid from any source and none of which decay teeth (they can corrode teeth but that's another subject!).

Then there is saliva. Very complex stuff but here we just need to know two things.

1. It dilutes anything in the mouth.
2. It has substances in it which reduce the effects of acids and alkalis (called buffering) - not stops but reduces.

So, with a small amount of acid or alkali, there is little or no change,but the more acid or alkali present, the less the buffering effect of saliva.

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