Dentistry is somehow both banal and gruesome, as I was sorely reminded in some of the more orally realistic moments in "Novocaine." This movie makes the most of an unpleasant profession by casting Steve Martin as Fred Sangster, a mild-mannered and only slightly smarmy dentist living the good life. He runs a high-end practice with Jean Noble (Laura Dern) doubling as his perky hygienist and loving fiancée. Sangster's life runs like a well-oiled machine, and even a surprise visit from his sketchy brother Harlan (Elias Koteas) causes him only the slightest discomfort. But enter Susan Ivy (Helena Bonham Carter) as a strung-out yet sexy babe who hustles dentists for drugs, and things start to get complicated. The hapless Sangster makes one mistake and is immediately entangled in a web of lies, crime and sex. The cops, the DEA, and Ivy's ferocious brother Duane (Scott Caan) are pursuing him, and in attempting to set the record straight, Sangster is bounced from seedy motel to car trunk to the slammer.

What could be predictable as a straight-up suspense movie is very funny as a suspense-comedy, especially with the classic Martin voiceover and his deadpan delivery. Of course, you have to assume that the holes in the plot are intentional, sending up those movies in which the innocent hero inexplicably allows himself to be sent further and further up the creek. Because that's exactly what happens to Sangster, and some things are never explained, like his attraction to the drug-addled Ivy and the fact that he never calls the cops.

As the plot becomes more implausible, though, it really does become funnier. The excellent casting helps. Laura Dern is perfect as the impeccably groomed and ambitious Jean, and Elias Koteas plays a fantastic ne'er-do-well, topped only by Scott Caan's borderline-psychotic performance. Everyone knows that Bonham Carter is smashing at playing a lovable druggie, and she does a fine job in "Novocaine," with more of a comic edge than say, her role in "Fight Club." And in case anyone is confused about whether "Novocaine" is a comedy, the presence of Kevin Bacon playing a Hollywood actor following the cops around (doing research for a role) should answer that question.