Who do i seek help about jaw bone erosion: a regular dentist or a periodontist?

See a dentist first: The dentist will determine the amount of bone loss present and can treat accordingly. There may be other issues present like cavities or infection. If the gum disease is severe then you will probably be referred to a periodontist. The dentist is the first place to start. Good luck.

General Dentist: See a general dentist first. They can evaluate whether your problem is severe enough to determine whether it needs treatment by a specialist.

Periodontist: I would suggest seeing a periodontist if you are referring to bone loss around your teeth or edentulous ridges where you are missing teeth. Once a diagnosis is made, then the periodontist can refer you to a restorative dentist with whom he can work in implementing a treatment plan appropriate for your situation.