The budget of the film was so low, that when Director Brian Yuzna wasn't satisfied with the cabinets in the set of the "heaven" room, or the toys for the children to play with in the waiting room, and the producer was not willing to spend any more, Brian was forced to give his credit card to the art department, who then went to buy the furnishings. Luckily enough, they could borrow the products they needed, so it didn't cost anything.
There was only one oversize mouth available for the movie, so they changed out the teeth for the different characters.
The real-life serial killer dentist, Glennon Engleman (1928-1999), was not the inspiration for the story of the film. The idea for the movie came from Mark Amin, and was written by Charles Finch, Stuart Gordon and Dennis Paoli. However, Corbin Bernsen had played a character inspired by Engleman in Beyond Suspicion (1993), which has nothing to do with this movie.
Stuart Gordon was originally set to direct (and retains a writing credit) before Brian Yuzna took over.
The oversized mouth for the kid Jody was made in just two days by J.M. Logan, after they realized they needed one oversized mouth for this shots.
Brian Yuzna: (At around one hour and twenty-eight minutes) Attendant who pushes Dr. Feinstone in the chair at the end of the movie.