In an editorial voice-over, the cuckolded dentist, played by Campbell Scott, does his best to make us feel good about our oral cemetery; he is, after all, an American, so he dispenses therapy while installing crowns and busily flossing. 'Teeth outlast everything,' he says. 'Death is nothing to a tooth.' The obtuse slabs last for thousands of years, even when buried in acidic soil; like our hair and our fingernails, which continue to sprout in the coffin, they appear immortal.
This message, I think, is supposed to be cheering, although I don't care if my molars and incisors outlive me (which is hardly likely, since a few of them have already predeceased me).

Eventually, overcome by gloom as he stares into yet another dank, carious abyss, Scott reflects: 'You can't grieve for every mouth.' Meanwhile, his nurse treats her privileged view of our primary orifice as an aid to sexual selection. When a patient flirts with her, she sassily replies: 'I'm waiting for a man who takes really good care of his teeth - which I can see that you don't.' She then rolls back her ripe lips to show off that most vainglorious of American merit badges - an orthodontically perfected smile.

Only in the US could a story about dentistry be turned into a psychodrama about marital and mental breakdown. Over here, where we are less surprised to learn about mortality and less inclined to imagine that cosmetic treatments will save us from it, the profession is likelier to produce low farce. In a 1961 film called Dentist on the Job, Bob Monkhouse earnestly attempts to flog a new kind of toothpaste; the endeavour is an excuse for sexual innuendo as nubile patients are asked to open wide. Our sniggering covers our embarrassment, which, in turn, covers our dread.

The hero of Iris Murdoch's novel, The Black Prince, a tax inspector, reflects that his is one of two jobs that are socially unmentionable, bound to kill conversation. The other, inevitably, is dentistry. His reasons are depressingly moralistic. The taxman reminds us that as we earn, so we must pay; the dentist tells us that as we grow, we die. The end of the financial year is a precursor of judgment day, and a dental check-up is a memento mori, delivered, if we're really pious, every six months. The Catholic church, shrewdly exploiting our distress, long ago nominated a dental martyr, who became the patron saint of dentists. St Apollonia was an Alexandrian deaconess who, in the fifth century, leapt on to a funeral pyre rather than renounce Christ. Her persecutors had previously smashed her teeth with pincers; represented in religious art, she usually grips one of the gory fragments in a pair of pliers. Her story does little to bolster the faith; if you ask me, what it demonstrates is that death is preferable to toothache.

Religion is supposed to be a healing agency, but what if God is a sadist, designing faulty creatures so he can watch them decay, suffer and die? In that case, the deity is very much like a dentist. In Rudolph's film, Scott treats an obnoxious jazz trumpeter who is worried about his embrochure. Scott sends him on his way, predicting that he will lose every tooth in his head: 'I've never seen a worse case of gum disease.' That dismissal is a reminder that satirists, who envy the executive powers of a ruthless God, love to peer inside the mouths of their victims.

A poem by Swift describes an elderly harlot who decomposes every night before she goes to bed. She removes her wig, her glass eye and her straw-filled breasts, along with the padding that fills out her concave cheeks and the wire that anchors her artificial choppers. In another poem about Armageddon, Swift mimics God as he dooms the human race, and terminates our pitiful history with a brutal rhyme:

I to such blockheads set my wit!
I damn such fools! - Go, go, you're bit!

'Wit' and 'bit' belong together, like a jaw snapped shut to slice through a tasty morsel. No wonder Martin Amis spent so much money on dental repairs a few years ago. It wasn't his smile but his bite that he worried about. If your business is to snarl and snap at mankind and to gnaw any bit of flesh you can prise off, you must keep your tools in good working order.

The Nazis demeaned the millions they killed by tugging gold fillings from the mouths of gassed corpses. Laurence Olivier, as the Nazi doctor in Marathon Man, applies similar procedures to a live, squirming, unanaesthetised patient, and interrogates Dustin Hoffman with the aid of a dental drill.

Although Alan Rudolph quixotically imagines that we can be made to sympathise with the hero of Secret Lives, we are happier to see the dentist as a villain - Dr Evil, armed with a battery of stabbing needles and torturing picks. Hence the wickedly satisfactory revenge on the entire profession engineered by Hitchcock in his first version of The Man Who Knew Too Much, made in 1934. Leslie Banks, tracking down a gang of terrorists in Wapping, visits the dental surgery which it uses as a front. A set of dinosaur-sized dentures in a grimy street advertises the place; they look like the gates of hell. Screams can be heard from within. But Banks exchanges roles with the malevolent dentist. He plugs the gas mask to the man's face to dope him and, stripping off his white surgical coat, gives him a taste of his own vicious medicine. When the reluctant patient stirs to life, Banks treats him to an extra dose of hissing anaesthetic and leaves him for dead.

The dental metaphor can be made to anatomise a social malaise. Ezra Pound, railing against the First World War, called England 'an old bitch gone in teeth', and lamented the loss of the young men who had been sent off to die for this defanged civilisation. The same image was recently applied to multicultural Britain in Zadie Smith's novel, White Teeth. We all have white teeth, despite the colour of our skins; but Smith, investigating the backgrounds of her immigrant characters, delves into what she calls their root canals, which lead her by a snaky subterranean route from Cricklewood and Brixton back to India and Jamaica. Her verdict on the body politic employs the rhetoric of oral hygiene: 'The first sign of loose teeth is something degenerate, deep within the gums. Roots were what saved, the ropes one throws out to rescue drowning men.'

The very idea of teeth induces a twinge. But we shouldn't forget that they can also be a source of pleasure. Kissing requires their collaboration; they are one of the body's defences against invasion, and when a tongue finds it way through them it's as if a portcullis had been raised. Yet teeth are seldom eroticised (except by that snooty nurse in Rudolph's film). Revealingly, Herod in Oscar Wilde's Salome emphasises his lascivious stepdaughter's bite, not her kiss. 'I love to see in a fruit the mark of thy little white teeth,' he says. When Salome makes love to the severed head of John the Baptist, she gnaws and nibbles it, rather than amorously slobbering. She intends, she tells the head, 'to bite thy mouth with my teeth as one bites a ripe fruit'. What difference is there between sex and cannibalism?

Wilde's imagery is a salutary reminder that teeth are weapons, first given to us so that we could kill our prey and tear apart its bleeding flesh. Dogs, which only smile when they intend to do you harm, know what they were meant for. Teeth are remnants of the naked ape, which is why they cause such discomfort to the pampered Americans in The Secret Lives of Dentists. I once spent a day in Los Angeles in the company of the elfin coiffeur Vidal Sassoon (on assignment for The Observer, I hasten to add). His girlfriend Ronnie, a plastic goddess with a smile like the fender of a 1950s Cadillac, told me about their first date. Vidal had taken her to a symphony concert; when Ronnie asked him if they were going to eat afterwards, he said: 'Oh, I'll just blend us a health drink. Then we won't have to chew.' Californians are squeamish, dainty creatures: for them, to mobilise your teeth when you're eating is as uncivilised as using your knife and fork simultaneously.

At least Freud ensured, by a series of symbolic transferences, that we could have fun in the dental chair. Sedated by gas, we are allowed to sleep through the bloody struggle; meanwhile the fantasy can convert anguish into an orgy. One of Freud's patients, a closeted young homosexual, reported a dream about a night at the opera when, having spied a potential partner, he 'suddenly flew through the air right across the stalls, put his hand in his mouth, and pulled out two of his teeth'. The analysis notes that there has been a sneaky transposition between the upper and lower parts of the body. The man, Freud concluded, had hurried home and masturbated not once but twice. If only all such extractions were so simple and so painless!