Can you tell me is getting teeth cleaned from a dentist harmful?

Helpful. Regular hygiene visits at your dentist help prevent periodontal disease.
Reverse. Not getting a professional cleaning is harmful, getting a professional cleaning is helpful. Dentist/hygienist reaches places you can' tot remove soft bacterial plaque that produces acids/toxins and hard accretions calculus/tarter that irritate gums. Even if you could reach everywhere you don't have the ability or the instruments to remove accretions or to reduce gum inflammation. Dentist cam.