The Scoop on Prosthodontics
If you wanted to become a prosthodontist first you'd have to know what Prosthodontics is.
What in the World Does a Prosthodontist Do?
If you go to a Prosthodontist for treatment they will have to take x-rays, makes molds of your mouth and teeth and prescribe fixtures (crowns, dentures, bridges, you get the drift) for your mouth. If you were working as a Prosthodontist you would also have to perform what amounts to Oral Surgery to implant the crowns or bridges. This would involve prepping a patient for surgery and making sure they know how to care for their mouth after surgery.
Also, please remember that if you are a Prosthodontist you're really - a Dentist, which means that you can perform all the normal duties of a General Dentist, so you don't have to devote your WHOLE career to dentures if you don't want to. I would estimate that most people have never heard the word Prosthodontist because they just got a crown or a bridge and they went to a Dentist to get it done. (Honestly, why would a Dentist confuse you by calling themselves a Prosthodontist when they can just say "Hi, I'm a Dentist!"?
What Kind of Training do I need (A.K.A. - Will I have to go to School?)
Prosthodontics, like all other areas of dentistry, requires a Bachelor's Degree (typically in Biology or Chemistry as Dental School prefer you to have taken lots of Science classes) then you have to pass the DAT (the standardized test for Dental School admission) and then complete a 4 year program at a Dental School. You would go to Dental School to become a "Doctor of Medical Dentistry" or a "Doctor of Oral Surgery" before you went into Prosthodontics. There are 56 Accredited Dental Schools in the U.S. so going to Dental School might be hard for you if you can't just up and move on a whim. But, if you can make it to Dental School then you're on the right track.
After Dental School you would have to complete another couple years of training solely in Prosthodontics before you could get a license from the State Dental Board to practice in this Specialty area. Getting your license would involve an additional written exam (after you already did one in General Dentistry) and an additional "skills exam". Plus, your License will require continuing education to renew just like a regular Dentist. (It might even be a good idea to work as a General Dentist or Oral Surgeon while you work on your specialization in Prosthodontics.)
How Do I get One of These Jobs Anyways?
As I said, Prosthodontists are also Dentists, so it might be best to open your own practice as a General Dentist or Oral Surgeon because you would have been trained to do that in Dental School. It would be a shame to put that all to waste. You could open your own practice and ALSO offer Prosthodontic services to your patients (basically you're referring yourself to yourself) and you might have an easier time building a client base because people will know they can come to you for lots of things instead of driving all over town.
I might be to your advantage, depending on where you live, to work at a larger Dental Practice as "The Prosthodontist" or alongside another Dentist in a two-way practice where you are "The Prosthodontist" and the Dentist just sends their people over to you for your services. Once again, you keep people from having to drive all over town.
Advancement would look similar to that of any other Dental Professional. If you wanted to become a Professor of Prosthodontics you could get a few more years of advanced training and teach at a Dental School or you could conduct research. These are good options for folks who are retired or thinking of retiring.