I screamed so loudly, the hygienist swivelled off her chair and I grabbed my dentist's hand like he was Leo DiCaprio in the last scene of Titanic. What was happening was this: when the bottom tooth with a gold filling met the top tooth with a silver filling, the different metals created an electric current. But the intensity of it perplexed him.

"I promise you," I mumbled defensively, "I'm not lying! I can't close my mouth. I'm not making it up. It's real. Why would I make this up?" He looked confused. "I'm not saying you're making it up," he said. "I believe you. I'm just not sure what to do." He kept saying he'd never experienced anyone having such a severe reaction before. Oh. I felt much better after that. I was a medical phenomenon.

At this point, the tears were rolling down my cheeks and I was afraid to close my mouth. It was getting late and I could tell the hygienist was growing impatient; the last thing she wanted was to spend her Friday night holding a saliva tube.

My dentist told me the options, starting with what I couldn't get: a white enamel filling, because the cavity was too large and would take a week to make; a gold filling was too expensive. He said she could pull the filling out and replace it with a temporary one, but I stopped listening because all I could think about was how it could be that I am the only one in the history of his practice - maybe in the history of the world - that this has ever happened to.

"Sometimes you can't explain these things," he said. "You're an unusual case." How many times have I heard that one before? He decided I should sit quietly to see if the shock disappeared. How could I not sit quietly? I couldn't close my mouth. I was frozen in a perpetual state of surprise.

The hygienist, obviously bored, asked if I'd been flossing. I nodded. It amused me to think that I was lying through my teeth.

Thirty minutes later, he told me to "bite down". I was tentative. Very slowly I began to close my mouth. Very slowly. So slowly, he repeated "bite down" a dozen times, and every time he said it, I'd have to open my mouth and start again. "Stop pressuring me," I said. The anticipation was too much.

But in the end it was, in fact, better. My dentist told me it would take a few days for it to fully go away, and every so often I might get a shock, but that I should go home and eat lots of eggs because the sulphur would help.

How great it would be if only I could get a metallic shock for other things. Cognitive filling therapy. The way dogs have shock treatment in their collars to change their behaviour, I'd have my fillings. For instance, every time I began flirting with someone who was wrong for me, I'd get zapped. Or just as I was about to press "send" on an e- mail that should be deleted. Or buying a $600 pair of shoes. As I opened the door to the shop, I'd be stopped in my tracks. I would be at the dentist every day.