Should I be concerned if my dentist has llc after his name?

"LLC" or "llc" means "limited liability company". It is applied to a virtual person a "company or business". Say you dentist was called "Jones" then he could set up a company called "Jones dental practice" and if his practice was set up as a limited liability company, "llc" should be add after the name of the practice.

However if your dentist is using "llc" after their name as a qualification, this is meaningless and if your dentist has no other qualifications then I would suggest you should be concerned - do not go there and ask the authorities in your country to investigate the dentist.