I learnt a new skill last week - how to clean my teeth properly.

All right, it's not brain surgery and you may think you know all there is to know about using a toothbrush but I bet you a decayed molar to a crowned incisor that you're not doing the job correctly.

At least that's what my dentist reckons.

Which is a shame because once you've perfected the technique you have a better-than-average chance of keeping your pearlies into your old age - and perish the thought of dentures.

Dentures were the stuff of nightmares in my childhood. I had relatives in their 60s and 70s with scarcely a genuine tooth between them.

When they took their false teeth out at night their faces seemed to sink and shrink, as if they were already dead.

To this day I've always associated dentures with old age. I can live with the fact that I really should be wearing bifocals now, that my hair is turning grey and that my joints creak when I stand up in the mornings.

But false teeth? No! Never!

You might as well tattoo the words 'Past Sell By Date' on my forehead as subject me to that indignity.

Which is why I was so attentive when my dentist offered to teach me how to clean my teeth correctly (I think they call it oral hygiene). I was genuinely grateful to be shown how to hang on to a few of my remaining assets.

Of course I didn't remind him that I'd actually been doing the job for more than half a century or ask him if he'd ever taught his grandmother to suck eggs.

But in case I had, he had the very weapon to counter any sarcasm or objections. It was a close-up view, a disturbingly close-up view, of the horrors that can lurk inside the human mouth.

After examining my teeth, he switched on a small screen.

"Ah, this is obviously a new ploy to help patients relax. A little television or movie-watching while he drills and probes," I thought.

But instead of the Teletubbies or Richard and Judy, a mass of hyperactive blobs and dots swirled across the screen.

Obviously the set needed adjusting.

It didn't. What I was watching was exactly what my dentist intended me to see.

"That's a spot of plaque I've put under the microscope," he said.

"Really?" I said. If this were the main feature it was unlikely to win any Oscars.

"What are all those nasty little bug-like blobs jumping about?"

"Bacteria," he said. "Those are the fellows that do all the dental damage. They live in the plaque which collects between your teeth if you don't clean them properly."

"How horrid," I said. "Well, I don't want anything like that inside my mouth."

After a short pause he said: "But they are from inside your mouth . . . whose mouth did you think they were from?"

"Yuck!" I said. "I want them killed!"

"Don't get so upset," he said reassuringly. "We'll give you a lesson in how to really clean your teeth and that will go a long way to solving the problem."

So there I was, fiftysomething going on five, twirling a toothbrush around my mouth as if it was the very first time I'd used one.

"I bet kids love that," I said to my dentist, pointing at the screen where my bacteria were buzzing around like angry wasps.

"Oh, we don't show that to children. It might frighten them," he said. "That s strictly for Adults Only!"