Goodness me! Of all the things you'd expect of a Killer Vagina film, "classy" isn't one of them. I must admit that I'd been viewing Teeth as little more than the one between Sexual Parasite: Killer Pussy and the new Frank Henenlotter. I'd put it in the queue, but without expectations.

We're back in the Killer Vagina genre, by the way. I've found other landmarks of taste since I embarked upon this academic study, one being a 2003 British low-budget schlocker called Penetration Angst and another being a 1996 effort from Germany called Killer Condom. The latter is technically a different category of deviancy (title = clue), but it's still a closer cousin than more mainstream fare like Hard Candy, Lady Vengeance and Virgin Spring. Anyway, that's the cinematic company we're in. Any film standing next to Henenlotter could be said to have a public relations problem.

That said though, Teeth confounds expectations by being excellent. It's a proper film with themes, character development and the minimum of nudity. Obviously it's chosen to tackle outrageously schlocky subject matter, but having made that decision it's doing it in a realistic, restrained style and using its fantastical element to tackle some big themes and tell a coming-of-age story. Personally I loved it. Like the very best genre movies, it's telling an extreme but emotionally honest story that couldn't be told any other way. This film has things to say about sexual awakening, self-denial, morality and more. In its own way, it gave me a new perspective on how we all feel when discovering sex for the first time. The boys don't listen to the girls, except when they think they've heard something they think they can use to get them into bed. If the girl says she doesn't want to and it's wrong, they'll brush it aside. We all know that. However I suspect we've never seen it demonstrated under circumstances quite this eye-watering.

Our heroine is played by Jess Weixler. Hilariously, at the start of the film, she's an abstinence pledger. As far as I can tell this is a real movement in American schools, in which boys and girls attend religious meetings, wear "Promise Rings" and swear never to indulge in sex before marriage. Yeah, that's going to work. Leaving aside real-world practicalities like the divorce rates among people who marry young, the heart bleeds (as will certain other places) for whatever unlucky man ended up unknowingly marrying our heroine. Imagine it. You and your wife have been saving yourselves. Let's say you're twenty-five and so have been suppressing your sexuality for the past decade, but more importantly with luck maybe you're now mature enough that your friends won't be openly holding a divorce sweepstake. You have the big day, you get into your long-awaited marital bed together on the wedding night and... ouch. Obviously the precise gory details are fantastical, but I think there's a moral to be had here.

Even more classic are their school's sex education lessons. The state school board has ordered that big stickers be placed over the diagrams of female genitalia in everyone's textbooks, which Weixler defends. "Girls have a natural modesty." This is true. They do indeed. Nevertheless she's still supporting censorship of education, which might sound like a fairly abstract cause to get indignant about except that here it's about to have extreme consequences. She doesn't know what she's meant to look like down there! In a Killer Vagina film, this is not an academic consideration.

Anyway, this is all a hoot. Among all the other things it's doing, this film is a black comedy. It's not gutbuster stuff, but there's a lot of very delicate wit in these performances that makes me want to follow these actors and see what they're doing in ten or twenty years time. I'm not surprised to see that the writer-director Mitchell Lichtenstein is an actor himself. The most important cast member obviously is Weixler, who covers a huge range and is never less than outstanding. At the beginning she's a prissy church girl who probably deserves slapping, yet Weixler's so innocent and sweet that no matter what she does, we're on her side. We're talking here about a girl whose bedroom fantasies involve church music and a wedding dress. That's only the starting point, though. Weixler has quite an emotional journey lying ahead and some debatable decisions, but she never falters and never loses us. Make no mistake, this was a challenging role. It's a huge opportunity for an actress, but Weixler always seems so natural that you never stop to think how dumb and schlocky the film could have seemed had she been less assured with it. This role won her the Dramatic Special Jury Prize at the Sundance Festival and she earned it.

This isn't a one-girl show, though. John Hensley is a joy to watch as her appalling brother, Brad. He's a dick, but also somehow cool and really entertaining. I could have watched him all day. Then you've got the freak to whom she's attracted, played fascinatingly by Hale Appleman. It's a very dry comic performance as a character without a shred of humour or self-awareness. "I'm a virgin... in His eyes. It was just once, a year and a half ago. I'm still dealing with the guilt." The film's got things to say with him too. You've got to love the conversation where they agree that they mustn't see each other again because they like each other.

The only downside is that the film feels a little insubstantial. It's got that problem one got all the time with British films about ten years ago, in that the script feels as if it's stretching a little to be a full-length movie. What we have is truthful to itself and wonderful as far as it goes, but I'd have liked it even more with a more fully developed story.

I like how they handle the schlocky elements. The first gore shot contains barely any blood at all, being just a cut finger, but this makes it realistic and thus helps keep you nervous for pretty much the entire film. Not seeing the vagina dentata itself is also scarier. If you can't see what those fingers are doing down there, there's more room for your imagination to get to work. All these reasons meant I'd be cringing all the more in anticipation and then to my surprise laughing my head off when Weixler's lower mouth chomped. There are money shots, yes, but they're done in a controlled way. Mind you, for the finale Lichtenstein does at last allow himself a set-piece of relatively flamboyant bad taste, which I have to say was one of the funniest things I've seen all year. Oh, and the crab was hysterical too. Is Lichenstein a Troma fan? I ask partly because those reactor towers we keep seeing are reminiscent of and serving the same cinematic purpose as the nuclear reactor in Tromaville. They're never mentioned in dialogue and one could perhaps argue that they're just a visual throwaway, but this is also a film that includes symbolism like phallic rocks and a cave and a classroom lecture on sudden evolutionary mutation.

When I put on this film, I hadn't been expecting anything even half this good. It's intelligent, satirical and even feminist, which again is a surprise for an idea that sounds as if it should be pure exploitation cinema. It's examining all kinds of familiar teenage dilemmas and making them fresh and scary by overturning all our expectations, so for instance the notion of a sexual predator acquires new meaning. "It's not you." We know what the boy's thinking when he hears that, but he's 110% wrong. There's even a subtle introduction of parenthood into this story of sexuality, in the way that the Mum and Dad figures become more important towards the end. Personally the only criticism I can even imagine of this film is that earlier one that it's a little lightweight in the plot department, although it has to be said that some people have reacted strongly against it. This isn't even remotely a trashy film, but it's borrowing toys from Mr Trashy's playpen. Not everyone will be able to get past that.

This is a thoroughly impressive little film. It's in absolute control of its tone and its director is getting pitch-perfect performances from a talented cast, walking a delicate middle ground between truth, satire and "oh my God, I can't believe they did that". It knows when to be subtle. It's intelligent and funny. And in case that wasn't enough, it even includes a clip of Peter Cushing in The Gorgon (1964) and for a brief moment becomes perfect.