The real-life serial killer dentist, Glennon Engleman (1928-'99), was the inspiration for the story of the film. Corbin Bernsen had previously played Engleman in the 1993 telefilm Beyond Suspicion (1993).
The budget of the film was so low that when the director 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, the producer was not willing to spend any more so he was forced to give his credit card to the art dept who then went to buy the furnishings. Lucky enough they could borrow the products they needed so it didn't cost anything.
(at around 26 mins) The dead dog was actually a dead stuffed goat. They turned the head so the horns are not visible and put some fake blood on it. This was the first day of shooting and they could not find a dead look-a-like dog.
There is one deleted scene; The character of Maria in The Dentist was the housekeeper. There is a scene in which she comes to clean the house and finds the pool boy dying out by the pool (where Corbin slashed him). When he tries to get her help she is scared by his bloody aspect and falls back in the swimming pool and drowns. This scene was cut from the movie.
Anthony C. Ferrante (special make-up effects supervisor); Kevin Yagher was a natural for the oversized mouth. From the Crypt Keeper to Chucky (and some work on Bill & Ted's Excellent Adventure (1989)), he's shown off his amazing talent for bringing life to inanimate objects. He was definitely out of the price range (incredibly out of the price range!), but thankfully he committed to doing the job as a favor.
The movie almost was never made because the studio was not happy with the script. It took more than a year when the studio finally give the movie green lit. In the first version of the script the movie takes place on one day, later this was changed to took over two days. Stuart Gordon was hired later on to write a script. The script was later rewritten by Charles Finch.
Sam Greenmun provided the rotted teeth for a couple of fantasy sequences as well as a severed tongue. Ken Rex (father of Todd Rex, who also helped with the special effects on this movie) hand-crafted all the oversized props and the Goldfarb jawbreaker device.
For the "Brooke effect", which is the horrifying aftermath of Finestone's wife after he has pulled all of her teeth out, the production needed to hire somebody who specializes in character make-ups. Steve Johnson's X/FX was high on the list, but because of his workload he wasn't able to work it into his schedule. Luckily, Christopher Allen Nelson (a Johnson alum), who had done a stunning zombie creation for Brian Yuzna's Return of the Living Dead III (1993), was available and came aboard. Chris had just come off of a horribly abusive situation working on the new "Tales from the Crypt" movie and wanted a chance to prove himself again. The catch with Chris was that he was in the process of moving back to Los Angeles from Canada. He would be able to create the effect in Canada and then fly out to apply it. This would require a lot of long-distance phone calls and a fickle shipping system that had many of the supplies trapped in customs in transit to him.
While this film was in the planning stages, Texas Chainsaw Massacre director Tobe Hooper was developing his own Dentist movie, with a more science-fictional bent. That project never got off the ground.