Captives has Tim Roth as a guy in prison, and Julia Ormond is the prison dentist. So there is quite a steep power gradient, with him cast into a powerless position. I don't at all consider dentistry itself to be sexy BTW (yuck, see 'Marathon Man': no thanks). I was thinking more about how the depiction of the power-relationship in this film is more satisfying to me than in most films, regardless of its (hem hem) oral trappings.
Obviously power relations are of interest to both male and female writers and directors. However, I feel that in most mainstream heterosexual stories it is a bit one-sided. Either the man or the woman is submissive or needy, and then usually gets to suffer for it. And that kind of takes the fun out of it in my eyes. Whereas in the films I like the underdog is more likely to put up a bit of a fight, and to be sufficient unto themselves. I much prefer that.
Perhaps this is why I am more interested in the relationships between men in films, because they are less likely to give way to each other. In this one, I find the heterosexual relationship quite satisfying. Or I did ten years ago. It may turn out to be rubbish on repeat viewing.