I can't say I've ever thought about dentits ("doctor of dental services," or DDS, is the proper title, at least in the U.S.) in Trek; however, I think the last three are pretty much spot on. Given the level of Starfleet technology in the 23rd and 24th centuries, there are probably fewer dental specialists in the medical community, as most dental work is likely done with regenerators (and, quite likely, protective enzymes in replicated food and drink).
The protective and regenerative technologies also probably means that there is little requirement for more invasive procedures, as the vast majority of people will never need to have teeth extracted/replaced. Broken or evulsed teeth are reinserted/regenerated (easily done by a competent general physician or surgeon).
Cosmetic work may be the only true dental practice left in Trekdom, as children are probably sent to the DDS to have their teeth adjusted and properly aligned (wisdom teeth may actually never need be removed, given the level of technology to properly correct genetic flaws with little extraction).
Now, other species may have different needs. For example, I could see Caitians/Regulans with specific dental practitioners to ensure that their teeth are in prime hunting shape. I guess it all depends on how important teeth are to the more ritual side of their culture. For my take on Caitians, hunting is an almost-spiritual experience in their modern culture, partly as a rite of passage into adulthood and a connection to their spiritual mastery of the planet.
Davy Jones
"Frightened? My dear, you are looking at a man who has laughed in the face of death, sneered at doom, and chuckled at catastrophe! I was petrified."
-- The Wizard of Oz