Most sates require you to do what you specialize in once you declared it with the state board. I mean if you want to do a little of everything than just remain a gen dentist. At the monent money wise some speaclty is the way to go. For example pathologist and oral med specialties are not lucrative, your basically going to be teaching. Ortho seems like it will remain lucrative for a long time. Pedo as well and Oral surgery. Gen dentistry income is dropping since many for profit dental schools are pumping out dentist. We already have two in my state and a new one planed for wisc. So dental diploma mills are here and more are coming. Endo is iffy at the moment rotary has hit endo very hard as many general dentist are doing the procedures and many patients are staarting to opt for implants ather than saving the tooth. Pros well most pros I know dont make much bc most general dentist dont refer. Perio is iffy too, some do well some dont. Public health, well here you wont be making much.
Pedo is doing very well (for now)... who knows what the future holds. With so much of their production linked to state funding/state aid and the volume of children they need to see to produce this is a good choice but has a lot of question marks for the future.
Oral surgery is doing incredibly well... and probably will for a long long time. Wisdom teeth aren't going away anytime soon and implants will be here to stay for the forseeable future. Get through your residency and you will make plenty of $$.
Endo is a sleeper choice. So many people discount endo right now because of rotary and implants but these guys are doing fantastic... especially if you choose to move where they are few endodontists. Yes, I know gp's are trained to do rotary well, but many choose to not do it in practice, even the young docs, because of fear/lack of instrumentation (microscope etc). This specialty will be around for a long time and will be very good.
Perio is a question mark. A good periodontist who places mostly implants and does cosmetic perio surgery will do very very well. If you go to a perio school that focuses on "traditional perio", you are making a mistake. Very few people are doing hemi-sections and nobody wants to go to a specialist and get full osseous surgery or SRP (and pay specialist fees for it).
Ortho is a question mark also. Many many ortho's coming out of school right now and is only increasing. Easiest job by far in dentistry, and is more cerebral than physical so is a good choice for some. Good income will always be there, especially the effort vs. reward as compared to GP.
Prostho is in the eye of the beholder. I know many who are doing incredibly well and others who are simply doing general dentistry with 3 years more education. With the right personality and skill set, these guys do incredibly well. Those that rely upon referrals can carve out a really good office, others simply choose to do general type offices but charge more. The focus right now is in implant full arch rehabs.
If you're really unsure, do a couple of years of GP prior to deciding.
Hope this helps.