I can't remember the title of this movie.?

I can't remember the title or the names of any of the actors in this movie. There is this black guy who is in dept to some thugs. He is in an airport running from them when he sees a family looking for a visitor that they haven't seen in years. He pretends to be that guy so he can get away from the bad guys. It turns out he is a dentist and he has to do some lectures. They ask him to pull a tooth and he washes his hands with Novocaine. His hand get all limp and he starts throwing them around. Close to the end of the movie as he is again running from the bad guys he enters a marathon and wins.