I remember being terrified of movie blood when I was younger, and gradually getting less so, until getting jaded enough, as I'm sure many other viewers have become, so that the barrage of gory films produced in last few years have entertained me but not scared me or made me squirm. "The Dentist" turned that around.
The setup seems simple: a mentally unstable dentist wreaks havoc on the insides of mouths, and perhaps bodies as well. A clever twist, though, is that the dentist is the film's protagonist, so instead of being some one-dimensional bad guy with no clear motivation, his development is the most extensive of any character and he is very human and believable. The viewer thus feels sympathy for him as well as his victims, and instead of hoping for justice to come to him, I found myself hoping he would somehow find a way to cover up his tracks and return to a normal life.
What really "makes" a horror movie is the violence. And "The Dentist" does it better than any other film I can think of. First off, the film has tons of tension, which is something that modern gore films tend to lack. In one scene (), the dentist is emotionally distraught and has to see a young child patient for the first time. As he reaches into the child's mouth, you hope that, for the dentist's and the child's sake, the encounter ends without injury. I won't spoil what happens. Second, when the gore does come, it hits all the worst, squirmy nerves. Once again, I won't give anything away.
Of course, being a movie that you've never heard of, it does have flaws. Most importantly, it's exclusively for horror fans. Also, as another reviewer mentioned, by taking place over a span of just a few days, we don't really get any background on the characters. And the tension drops a little bit during the very end. But really, the fact that we would even want to know background about the characters is evidence to how good it is, and the bulk of the film is solid enough that any small lapses in tension can be forgiven.
It's strange, after years of being accustomed to movie gore, to suddenly want to cover my eyes at the sight of blood. "The Dentist" made me scared and thoroughly uncomfortable, and for this it earns my full approval.